Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Organische mestkwaliteit beïnvloedt bodemmicroben en bodemfuncties
    Heijboer, A. ; Berge, H.F.M. ten; Ruiter, P.C. de; Kowalchuk, G.A. ; Jorgensen, H.B. ; Bloem, J. - \ 2016
    Landschap : tijdschrift voor landschapsecologie en milieukunde 27-29 (2016). - ISSN 0169-6300 - p. 27 - 29.
    agro-ecosystemen - bemesting - bodembiologie - micro-organismen - bodemmicrobiologie - stikstofkringloop - fosfolipiden - veldproeven - brassica oleracea var. gemmifera - agroecosystems - fertilizer application - soil biology - microorganisms - soil microbiology - nitrogen cycle - phospholipids - field tests - brassica oleracea var. gemmifera
    Micro-organismen spelen een sleutelrol in bodemfuncties zoals de kringlopen van koolstof en stikstof. Voor een duurzame landbouw is het van belang dat deze kringlopen optimaal functioneren om verliezen van nutriënten zoveel mogelijk te voorkomen. Dit onderzoek geeft inzicht in de rol van bodemmicroben bij optimalisatie van de stikstofkringloop door toevoeging van zowel minerale kunstmest als verschillende kwaliteiten organisch materiaal.
    Functionele diversiteit mycorrhizaschimmels onder druk door stikstofdepositie
    Ozinga, W.A. ; Kuijper, Thomas - \ 2015
    Vakblad Natuur Bos Landschap 12 (2015)117. - ISSN 1572-7610 - p. 20 - 22.
    mycorrhizaschimmels - functionele biodiversiteit - stikstof - stikstofkringloop - depositie - ecosystemen - bosgebieden - mycorrhizal fungi - functional biodiversity - nitrogen - nitrogen cycle - deposition - ecosystems - woodlands
    Bosbodems kunnen veel verschillende ectomycorrhiza-vormende schimmels herbergen. In de herfst is een glimp van deze ondergrondse rijkdom te zien via de vorming van vruchtlichamen (‘paddenstoelen’). De ectomycorrhizaschimmels spelen een belangrijke rol bij onder andere de nutriëntenkringloop, de vastlegging van koolstof en de natuurlijke regeneratie van bomen. Hoge stikstofgehaltes in de bodem leiden echter tot een sterke afname van de abundantie en diversiteit aan mycorrhizaschimmels en dit kan doorwerken in het hele ecosysteem.
    KringloopWijzer moet inspireren
    Haan, M.H.A. de; Aarts, H.F.M. - \ 2015
    Grondig : vakblad voor de cumelasector, specialisten in groen, grond en infra (2015)5. - ISSN 2210-3260 - p. 40 - 41.
    akkerbouw - kringlopen - stikstofkringloop - veehouderij - milieueffect - gewasopbrengst - mineralenopname - bemesting - fosfaat - koolstof - arable farming - cycling - nitrogen cycle - livestock farming - environmental impact - crop yield - mineral uptake - fertilizer application - phosphate - carbon
    De komende jaren moeten melkveehouders verplicht gaan werken met de KringloopWijzer. Dat heeft als doel ze bewuster te maken van hun bedrijfsprestaties en de manier waarop ze de mineralenstroom kunnen sturen. In dit artikel leggen de grondleggers van het systeem uit hoe de KringloopWijzer werkt en waarom dit voor loonbedrijven van belang is.
    NPK balans, N-verlies en beddingsamenstelling van vrijloopstal Hoogland in 2014
    Boer, H.C. de - \ 2015
    Wageningen : Wageningen UR Livestock Research (Livestock Research rapport 886) - 24
    rundvee - huisvesting van koeien - loopstallen - dierenwelzijn - stikstofkringloop - stikstof - vervluchtiging - bemesting - vergelijkingen - landbouw en milieu - stikstofverliezen - dierlijke productie - melkvee - milieu - cattle - cow housing - loose housing - animal welfare - nitrogen cycle - nitrogen - volatilization - fertilizer application - comparisons - agriculture and environment - nitrogen losses - animal production - dairy cattle - environment
    Een aantal Nederlandse melkveehouders stapt de laatste jaren over van een ligboxenstal met roostervloer naar een vrijloopstal zonder boxen en met een organische bedding. Een belangrijke reden voor deze overstap is het realiseren van een beter dierenwelzijn in de stal. Naast een beter dierenwelzijn heeft de overstap ook andere effecten, waaronder op de stikstofkringloop op het bedrijf. Stikstof (N) verdwijnt uit deze kringloop onder andere door vervluchtiging uit de stal, uit de mestopslag en na het uitrijden van mest op het land. N kan vervluchtigen in de vorm van ammoniak (NH3), lachgas (N2O), stikstofgas (N2) en overige stikstofoxiden (NOx). De vervluchtiging van ammoniak kan bijdragen aan verzuring en eutrofiëring van de natuur en vervluchtiging van lachgas aan opwarming van de aarde. De vervluchtiging van stikstofgas heeft geen directe negatieve effecten op de omgeving. Echter, door het verdwijnen van N uit de bedrijfskringloop moet er wel meer N op het bedrijf aangevoerd worden om de productiviteit van de bodem, de gewassen en de koeien op niveau te houden. Gebeurt dit met dierlijke mest of kunstmest, dan leidt dit alsnog tot een hogere milieubelasting. Gezien de bovenstaande consequenties is het wenselijk om de N-vervluchtiging op het melkveebedrijf zo laag mogelijk te houden. Om inzicht te krijgen in milieu- en productiviteitseffecten van de omschakeling van een ligboxenstal naar een vrijloopstal is het dus nodig om inzicht te krijgen in de hoeveelheid N die vervluchtigt uit de vrijloopstal en deze te vergelijken met de ligboxenstal. N vervluchtigt niet alleen uit de stal maar ook na het uitrijden van mest uit de stal op het land. Een stalsysteem met een relatief lage Nvervluchtiging direct uit de stal kan een relatief hoge N-vervluchtiging na mesttoediening hebben, en omgekeerd. Bij de ligboxenstal met productie van drijfmest wordt bijna de helft van de totale Nvervluchtiging (stal + land) na het emissiearm uitrijden van de mest op het land gerealiseerd (zie paragraaf 2.4). Om een meer volledig en betrouwbaar beeld te hebben van de N-vervluchtiging van een stalsysteem is het daarom gewenst om de N-vervluchtiging direct uit de stal en na mestaanwending gezamenlijk te beoordelen.
    Ontwikkeling van de N-balans, het N-verlies en de beddingsamenstelling van vrijloopstal Hartman in 2013/2014
    Boer, H.C. de - \ 2015
    Wageningen : Wageningen UR Livestock Research (Livestock Research rapport 885) - 43
    stikstofbalans - stikstofverliezen - stallen - landbouwschuren - huisvesting van koeien - stikstofkringloop - melkveehouderij - duurzame veehouderij - mest - landbouw en milieu - rundveehouderij - dierenwelzijn - loopstallen - nitrogen balance - nitrogen losses - stalls - barns - cow housing - nitrogen cycle - dairy farming - sustainable animal husbandry - manures - agriculture and environment - cattle husbandry - animal welfare - loose housing
    Een aantal Nederlandse melkveehouders stapt de laatste jaren over van een ligboxenstal met een roostervloer naar een vrijloopstal met een organische bedding. Deze overstap heeft meerdere effecten, waaronder op de stikstofkringloop op het melkveebedrijf. Stikstof (N) verdwijnt uit deze kringloop onder andere door vervluchtiging uit de stal, uit de mestopslag en na het uitrijden van mest op het land. N-vervluchtiging kan negatieve effecten hebben op de milieukwaliteit en leiden tot verlies van productiviteit. Daarom is het wenselijk om het N-verlies door vervluchtiging op het melkveebedrijf zo laag mogelijk te houden. Het onderzoek in dit rapport richtte zich op het vaststellen van het totale N-verlies door vervluchtiging uit de vrijloopstal van de familie Hartman in Heibloem (Limburg).
    Ontwikkeling van de N-balans, het N-verlies en de beddingsamenstelling van vrijloopstal Ottema-Wiersma in 2013/2014
    Boer, H.C. de - \ 2015
    Wageningen : Wageningen UR Livestock Research (Livestock Research rapport 881)
    huisvesting van koeien - melkveehouderij - stikstofbalans - stikstofverliezen - stikstofkringloop - vervluchtiging - rundveemest - stalinrichting - loopstallen - rundveeteelt - dierenwelzijn - landbouw en milieu - cow housing - dairy farming - nitrogen balance - nitrogen losses - nitrogen cycle - volatilization - cattle manure - animal housing design - loose housing - cattle farming - animal welfare - agriculture and environment
    Een aantal Nederlandse melkveehouders stapt de laatste jaren over van een ligboxenstal met een roostervloer naar een vrijloopstal met een organische bedding. Deze overstap heeft meerdere effecten, waaronder op de stikstofkringloop op het melkveebedrijf. Het onderzoek in dit rapport richtte zich op het vaststellen van het N-verlies door vervluchtiging uit de vrijloopstal van de VOF Ottema-Wiersma in Midwolde (Groningen).
    Nitrogen : too much of a vital resource : Science Brief
    Erisman, J.W. ; Galloway, J.N. ; Dise, N.B. ; Sutton, M.A. ; Bleeker, A. ; Grizzetti, B. ; Leach, A.M. ; Vries, W. de - \ 2015
    Zeist, The Netherlands : WWF Netherlands (WWF science brief NL ) - ISBN 9789074595223 - 27
    stikstofkringloop - waterverontreiniging - eutrofiëring - emissiereductie - broeikasgassen - terrestrische ecosystemen - wetenschappelijk onderzoek - milieubeleid - nitrogen cycle - water pollution - eutrophication - emission reduction - greenhouse gases - terrestrial ecosystems - scientific research - environmental policy
    It is now clear that the nitrogen problem is one of the most pressing environmental issues that we face. But in spite of the enormity of our influence on the N cycle and consequent implications for the environment and for human well-being, there is surprisingly little attention paid to the issue. While biodiversity loss and climate change have spawned huge budgets to create national and multidisciplinary programs, global organizations, political and media attention, the N challenge remains much less apparent in our thinking and actions. This is because we are educated with the important role that N plays with regard to food security. This paper aims to contribute to the understanding of the N challenge, and to provide options for decreasing the negative impacts of excess N.
    Invloed bedrijfsvoering akkerbouwers op financieel resultaat en stikstofhuishouding
    Prins, H. ; Daatselaar, C.H.G. - \ 2013
    Wageningen : LEI, onderdeel van Wageningen UR (LEI report 2013-065) - ISBN 9789086156603 - 78
    akkerbouw - bedrijfsresultaten in de landbouw - stikstofkringloop - waterkwaliteit - monitoring - bodemtypen - zandgronden - zware kleigronden - arable farming - farm results - nitrogen cycle - water quality - monitoring - soil types - sandy soils - clay soils
    Onder de vlag van het Landelijk Meetnet effecten Mestbeleid (LMM) heeft het LEI de invloed onderzocht van de bedrijfsstructuur en de bedrijfsvoering van akkerbouwbedrijven op het stikstofoverschot, de waterkwaliteit en de financiële bedrijfsresultaten. Met behulp van regressieanalyse met paneldata is nagegaan hoe groot de invloed is van de bedrijfsstructuur en die van de bedrijfsvoering. Het onderzoek betrof de periode 1991-2009, waarbij onderscheid is gemaakt tussen de grondsoorten zand, klei en löss.
    Soil biota and nitrogen cycling in production grasslands with different fertilisation histories
    Rashid, M.I. - \ 2013
    Wageningen University. Promotor(en): Lijbert Brussaard, co-promotor(en): Egbert Lantinga; Ron de Goede. - S.l. : s.n. - ISBN 9789461735485 - 192
    stikstofkringloop - bodemfauna - mineralisatie - rundveemest - decompositie - bodeminvertebraten - bodem ph - aardwormen - graslanden - bodembiologie - nitrogen cycle - soil fauna - mineralization - cattle manure - decomposition - soil invertebrates - soil ph - earthworms - grasslands - soil biology
    Our nutrient world. The challenge to produce more food & energy with less pollution
    Sutton, M.A. ; Bleeker, A. ; Howard, C.M. ; Erisman, J.W. ; Abrol, Y.P. ; Bekunda, M. ; Datta, A. ; Davidson, E. ; Vries, W. de; Oenema, O. ; Zhang, F.S. - \ 2013
    Edinburgh : Centre for Ecology & Hydrology (Key messages for Rio+20 ) - 114
    nutrientenbeheer - kringlopen - stikstofkringloop - fosfor - voedselzekerheid - milieubeleid - duurzaamheid (sustainability) - nutrient management - cycling - nitrogen cycle - phosphorus - food security - environmental policy - sustainability
    The message of this overview is that everyone stands to benefit from nutrients and that everyone can make a contribution to promote sustainable production and use of nutrients. Whether we live in a part of the world with too much or too little nutrients, our daily decisions can make a difference. Without swift and collective action, the next generation will inherit a world where many millions may suffer from food insecurity caused by too few nutrients, where the nutrient pollution threats from too much will become more extreme, and where unsustainable use of nutrients will contribute even more to biodiversity loss and accelerating climate change. Conversely with more sustainable management of nutrients, economies can play a role in a transition to a Green Economy in the context of sustainable development and poverty eradication. The Global Overview develops these essential themes, to prepare societies to take the next steps.
    Implementing water protection policy at farm level in the European Union: lessons from the N-Toolbox case studies
    Cooper, J. ; Burgt, G.J.H.M. van der; Kristensen, H. ; Quemada, M. ; Carmichael, A. ; Gascoyne, K. ; Timmermans, B.G.H. ; Rietberg, P.I. - \ 2012
    Newcastle : Newcastle University - 21 p.
    waterkwaliteit - oppervlaktewaterkwaliteit - grondwaterkwaliteit - stikstofkringloop - nitraatuitspoeling - stikstofverliezen - landbouwbedrijven - bemesting - strategisch management - water quality - surface water quality - groundwater quality - nitrogen cycle - nitrate leaching - nitrogen losses - farms - fertilizer application - strategic management
    In 2008 the European Commission released a call for proposals under the workprogramme topic: novel approaches for reducing nitrogen losses. The objective of the programme was to improve uptake of the Nitrates Directive at the farm level. The consortium (Newcastle University, Louis Bolk Institute, Technical University of Madrid, and Aarhus University) responded to the call by developing a project that combined a review of the state of the art in technologies to reduce losses of N to water, with the upgrading of a user-friendly software package for simulating field-scale N dynamics, and the testing of strategies with farmers. N-Toolbox will lay the foundations for improved implementation of water protection policy at the farm level throughout the EU. This document is a short summary of key findings and experiences from the on-farm case study component of the project in Spain, United Kingdom, The Netherlands and Denmark.
    PlantyOrganic: design and results 2012
    Burgt, G.J.H.M. van der; Bus, M. - \ 2012
    Driebergen : Louis Bolk Instituut (Publicatie / Louis Bolk Instituut 2012-048 LbP) - 37 p.
    bemesting - biologische landbouw - akkerbouw - groenbemesters - teeltsystemen - stikstofkringloop - veldproeven - rotaties - fertilizer application - organic farming - arable farming - green manures - cropping systems - nitrogen cycle - field tests - rotations
    Increasingly strict legislation about fertilizer inputs and developing organic regulations are a strong stimulation to optimize the internal nutrient dynamics of organic arable farms. In the project ' PlantyOrganic', initialized by Biowad and realized at SPNA location Kollumerwaard, a challenging arable system is developed and tested: 100% internal nitrogen supply without input of nutrients from outside. In this report the design of the rotation and fertilizer scheme is presented and discussed, and the starting conditions in spring 2012 are documented. The NDICEA nitrogen model is used to explore the nitrogen dynamics. It is concluded that a 100% farm-own nitrogen supply can be achieved with good production levels. The 2012 results gave no reason to reconsider the rotation and fertilizer design, but since this was the first year of this experiment none of the crops had the pre-crop as foreseen in the design and the fertilizer used was only partly cut-and-carry fertilizer
    PlantyOrganic - Onderzoeksverslag 2012: Onderzoek naar het innovatieve landbousysteem dat zichzelf voorziet van (plantaardige) stikstof en daarmee 100% zelfvoorzienend is
    Burgt, G.J.H.M. van der; Werkman, D. ; Bus, M. - \ 2012
    Biowad - 35 p.
    akkerbouw - groenteteelt - veldgewassen - biologische landbouw - groenbemesters - bemesting - agrarische bedrijfsvoering - duurzaamheid (sustainability) - veldproeven - stikstofgehalte - stikstofkringloop - aardappelen - grasklaver - penen - bloemkolen - tarwe - arable farming - vegetable growing - field crops - organic farming - green manures - fertilizer application - farm management - sustainability - field tests - nitrogen content - nitrogen cycle - potatoes - grass-clover swards - carrots - cauliflowers - wheat
    Onderzoek naar het innovatieve landbouwsysteem dat zichzelf voorziet van (plantaardige) stikstof en daarmee 100% zelfvoorzienend is. In dit rapport worden alle projectactiviteiten in 2012 beschreven en komen de eerste resultaten aan de orde. Aangezien het een meerjarig project is – er wordt verwacht ten minste een volledige rotatie van zes jaar te kunnen onderzoeken – en in dit eerste jaar de meeste gewassen nog niet de voorvrucht hadden die ze in het ontwerp hebben, zijn de resultaten nog bescheiden.
    Explorative research on innovative nitrogen recovery
    Eekert, M.H.A. van; Weijma, J. ; Verdoes, N. ; Buisonje, F.E. de; Reitsma, B.A.H. ; Bulk, J. van den - \ 2012
    Amersfoort : Stichting Toegepast Onderzoek Waterbeheer (Rapport / STOWA 2012-51) - ISBN 9789057735851 - 56
    afvalwaterbehandeling - rioolwaterzuivering - zuiveringsinstallaties - stikstof - terugwinning - stikstofmeststoffen - stikstofkringloop - waste water treatment - sewage treatment - purification plants - nitrogen - recovery - nitrogen fertilizers - nitrogen cycle
    This report comprises the results of an explorative study on innovative nitrogen recovery from side streams of wastewater treatment plants (WWTPs) in the Netherlands. The main objective of the study was to identify promising new technologies for recovery of nitrogen which can be subsequently used as an artificial fertilizer. This shortcircuits the global nitrogen cycle and thereby reduces the environmental impact of the nitrogen cycle that has been distorted by human influence (eutrophication, greenhouse gases).
    Evaluation of the NDICEA model
    Rietberg, P.I. ; Burgt, G.J.H.M. van der - \ 2012
    Driebergen : Louis Bolk Institute (Publication 2012-026 LbP) - 39 p.
    bemesting - modellen - beslissingsmodellen - stikstof - stikstofmeststoffen - stikstofkringloop - voedingsstoffenbeschikbaarheid - fertilizer application - models - decision models - nitrogen - nitrogen fertilizers - nitrogen cycle - nutrient availability
    Within the N-Toolbox project the NDICEA nitrogen model, one of the key tools in the virtual Toolbox, has been improved and tested in England, Denmark and Spain. The model performance was evaluated on datasets from these three countries by means of visual observation, RMSE and RSR from the soil nitrogen dynamics. In England the scenarios with organic fertilizer performed better than those with artificial fertilizer, leading to the suggestion that the calculated nitrogen release out of fertilizer could be improved. Timing of the soil sampling on soil inorganic nitrogen is important to realize a good model evaluation; two samples only, before sowing and after harvest, is not enough. When soil mineral nitrogen samples were taken during crop growth, model calculation and measured values showed sometimes big differences. It is suggested to improve the plant nitrogen uptake sub-model.
    Nutrient flows in urban and peri-urban agroecosystems in three West African cities
    Abdulkadir, A. - \ 2012
    Wageningen University. Promotor(en): Herman van Keulen, co-promotor(en): J.O. Agbenin; Peter Leffelaar. - [S.l.] : s.n. - ISBN 9789461730039 - 217
    stikstofkringloop - kringlopen - voedingsstoffen - stadslandbouw - bedrijfssystemen - west-afrika - nitrogen cycle - cycling - nutrients - urban agriculture - farming systems - west africa

    Key words: Sustainability, CATPCA, two-step cluster analysis, farm types, nutrient balances, West Africa, gross margin, NUTMON/MONQI.

    Urban and peri-urban agriculture (UPA) is defined as the cultivation of crops and keeping livestock within and around cities. In addition to providing the cities’ demand of fresh vegetables, crops and livestock products, it plays an important role in the livelihoods of the urban farmers. With the rapid urbanization in sub-Saharan Africa, UPA provides food and jobs for many urban dwellers. UPA makes use of a diverse range of urban resources such as labour, waste and wastewater to produce food and raise livestock, and it is characterized by large nutrient imports into farms or gardens, often accompanied by environmental and human health risks. In view of the complexity and diversity of the UPA systems, there is a need to understand the socio-economic characteristics of UPA as drivers to farm management practices. This research was conducted in three secondary West African cities with important UPA activities: Kano (Nigeria), Bobo Dioulasso (Burkina Faso) and Sikasso (Mali). From principal component analysis of categorical variables (CATPCA) and two-step cluster analysis, six major farm types were identified based on production systems and market orientation, of which three are common in the three cities and one farm type is unique to each city. The six farm types are commercial gardening plus field crop-livestock (cGCL); commercial gardening plus semi-commercial cropping (cGscC); commercial livestock plus subsistence field cropping (cLsC); commercial gardening plus semi-commercial livestock (cGscL); commercial cropping (cC); and commercial gardening (cG). The former three are common for the three cities, the latter three farm types are unique for one city, each. The diverse activities in these farm types contributed differently to household income. Nutrient balance studies are useful indicators to assess the sustainability of farming systems. From the identified farm types, in-depth assessment of nutrient flows and balances as well as the economic performance of the different production systems was conducted in Kano (Nigeria) using the nutrient monitoring toolbox (NUTMON/MONQI). Farm nitrogen (N) balance was positive at 56.6, 67.4 and 56.4 kg farm−1 yr−1 for cGCL, cGscL and cLsC farm types, respectively. The same trend was observed for phosphorus (P) and potassium (K) in all the farm types except for cGCL where an annual negative K balance of 16 kg farm−1 was found. Commercially-oriented livestock keeping (cLsC) was economically more viable than the other farm types with average annual positive gross margin (GM) and net cash flow (NCF) of 033 and 35, respectively. Cropping activities within cGCL and cGscL had positive GMs (059 and 94) and NCFs (57 and 06), but livestock activities in both farm types incurred financial losses. Using the same MONQI approach across vegetable production systems of the three cities, large amounts of nutrients were observed to be applied with large positive nutrient balances. Average annual N balances were positive for all gardens in the three cities: 279, 1127 and 74 kg N ha–1 in Kano, Bobo Dioulassoand Sikasso, respectively. Phosphorus balance was positive in all cities except annual K deficits of 222 and 187 kg ha–1 in Kano and Sikasso, respectively. Efficiencies were 63%, 51% and 87% for N; with poor P use efficiencies due to excess application in all three cities. K efficiency of 85% was observed in Bobo Dioulassowhile in Kano and Sikasso’s gardens, it was 120% and 110% respectively, indicating K mining. The average annual gross margins/benefits from gardening indicate a higher return of .83 m–2 in Bobo Dioulasso and differs statistically (P<0.05) from returns obtained in Kano (conv2.info.92 m–2) and Sikasso (.37 m–2). Results show that UPA is an important economic livelihood strategy for urban and peri-urban farmers because of positive economic returns but with huge environmental trade-offs as a consequence of excess nutrient application. Efforts to better integrate resource management with measures to improve environmental and food safety are required of UPA stakeholders. Achieving this will require the formal recognition of the UPA sector by city officials, along with formulating realistic strategies for effective nutrient and water management for a more sustainable UPA operation in West Africa. The consistent and replicable typology developed in this study provides a basis to target system-specific technologies and appropriate recommendations to improve use efficiencies of resources as a whole.

    Denitrification in ditches, streams and shallow lakes
    Veraart, A.J. - \ 2012
    Wageningen University. Promotor(en): Marten Scheffer, co-promotor(en): Jeroen de Klein. - S.l. : s.n. - ISBN 9789461733115 - 208
    denitrificatie - sloten - meren - waterlopen - zoetwaterecologie - milieufactoren - stikstofkringloop - waterplanten - opwarming van de aarde - denitrification - ditches - lakes - streams - freshwater ecology - environmental factors - nitrogen cycle - aquatic plants - global warming
    Het Nederlandse oppervlaktewater wordt sterk belast met stikstof. Dit is afkomstig uit de landbouw, maar ook van industrie, verkeer en huishoudens. Door het teveel aan stikstof verslechtert de waterkwaliteit. In ondiepe meren leidt dit bijvoorbeeld tot overmatige algengroei met zuurstofloosheid en vissterfte tot gevolg. Denitrificatie, de omzetting van de stikstofverbinding nitraat naar stikstofgas, is een natuurlijk proces dat stikstof uit oppervlaktewater verwijdert.
    The nitrogen cycle and its influence on the European greenhouse gas balance
    Sutton, M.A. ; Nemitz, E. ; Skiba, U. ; Beier, C. ; Butterbach-Bahl, K. ; Cellier, P. ; Vries, W. de; Kros, J. ; Veldkamp, A. ; Reinds, G.J. - \ 2011
    Edinburgh : Centre for Ecology & Hydrology - ISBN 9781906698218 - 44
    klimaatverandering - broeikasgassen - stikstof - stikstofkringloop - europa - climatic change - greenhouse gases - nitrogen - nitrogen cycle - europe
    Newcomers in plant communities : interactions with soil and climate change
    Meisner, A. - \ 2011
    Wageningen University. Promotor(en): Wim van der Putten, co-promotor(en): W. de Boer. - [S.l.] : S.n. - ISBN 9789085859826 - 136
    plantengemeenschappen - invasieve soorten - stikstofkringloop - planten - klimaatverandering - bodem - geïntroduceerde soorten - stikstof - ecosystemen - interacties - plant communities - invasive species - nitrogen cycle - plants - climatic change - soil - introduced species - nitrogen - ecosystems - interactions

    Soil infertility undermines the agriculture-based livelihoods in Malawi, where it is blamed for poor crop yields and the creation of cycles of poverty. Although technologies and management strategies have been developed to reverse the decline in soil fertility, they are under-used by smallholder farmers. This study was conducted to assess with farmers the performance of a range of maize-legume technologies and their benefits on soil fertility management in central Malawi. Farmer participatory experimentation was a focus of the study. The aim was to facilitate learning and the interpretation of experiences, improve the communication of information about the concepts and technologies to farmers, and provide insights for researchers.

     Using a combination of survey and participatory methods, 136 smallholder farmers from Chisepo were grouped into four resource groups, comprising of better-resourced (RG 1 with 6 farmers), medium resourced (RG 2, 14 farmers), less well-resourced (RG 3, 64 farmers) and least-resourced groups (RG 4, 52 farmers). Analysing their livelihoods for their effects on soil fertility revealed that soil fertility management is a complex activity which is influenced by ownership of assets. Farmers from RG 1 and RG 2 owned more resources including cattle, had larger fields, hired-in labour for timely farm operations, earned more income and invested far more in soil fertility improvement. Farmers from RG 3 and 4 (who are in the large majority) were resource constrained and did not invest adequately in improving soil fertility. They had large food deficits due to poor crop yields. Ganyu labour (casual work done for other farmers for food or cash) was their main strategy to reduce food deficits. Farmers from all the four RGs were interested in working with research to explore strategies to improve soil fertility. They tested various grain- and green-manure-legumes, and mineral N and P fertiliser on maize and the legumes for effects on crop productivity and soil fertility. Associated production risk and interest in technology adoption were assessed.

     On-farm evaluation was done on maize (cv. MH18) in rotation with pigeonpea cv. ICP 9145,intercropped with groundnut (cv. CG 7), (Mz/Pp+Gn); intercropped with tephrosia (Mz+Tv); intercropped with pigeonpea (Mz+Pp) and in rotation with mucuna (Mz/Mp). These technologies were compared with sole crop maize without fertiliser (Mz−Ft) or with 35 kg N ha-1(Mz+Ft) in experiments with 32 farmers from the four RGs over four years. Economic and risk assessments were made. Maize grain yields (accumulated over the four years) were greater for farmers from RG 1 and 2 than RGs 3 and 4. Mz+Pp and Mz+Tv gave greater cumulative yields than Mz/Pp+Gn and Mz/Mp. The legumes improved maize grain yields by between 0.2 and 4 t ha-1(P < 0.001) over Mz-Ft and additionally they gave legume grain to the household.Mz+Pp was less risky to all RGs, and applying 35 kg N ha-1to the legumes resulted in Mz+Tv, Mz/Pp+Gn and Mz/Mp being least risky to RG 1, RG2 and RG 3. Farmers in RG 1 had the highest returns to labour (USconv2.info.8 day-1with Mz-Ft and US.1 day-1with Mz+Pp) and these increased to 1.9 and 1.7 respectively with 35 kg N ha-1. Mz+Pp intercrop gave consistent positive returns across the RGs and was the only technology to provide positive returns to labour in RG 4. Use of pigeonpea was overall the least risky option, and was especially suited to least-resourced farmers.

     Application of phosphorus fertiliser (0, 20 kg P ha-1) to legumes significantly (P = 0.05) increased grain and biomass yields for mucuna, groundnut, soyabean, Bambara groundnut and cowpea by 1.0, 0.8, 0.5, 1.0 and 0.3 t ha-1compared with unfertilised plots. Cowpea and fertilised groundnut had larger yields in the home fields than middle fields, but other legumes performed better (P = 0.05) in the middle fields.

     Maize responses to small amounts of fertiliser (0, 15, and 30 kg N ha-1and 0, 20 kg P ha-1) in two weeding regimes showed that weeding twice significantly (P < 0.001) raised maize yields by 0.4 t ha-1over weeding once (0.9 t ha-1). Stover yields (significant at P < 0.001) were 2.3 and 1.6 t ha-1respectively. Mean grain N kg ha-1was 17.1 and 9.8 for plots weeded twice and once respectively while that of stover were 10.1 and 5.6 kg N ha-1. Applying N at 15 kg N ha-1increased maize yields, but the 30 kg N ha-1increased yield only on more clay soils due to the effects of mid-season dry spells on sandy soils. Except for the physiological efficiency of N (PEN), all agronomic indices of N use showed significant differences due to weeding (agronomic efficiency of applied fertiliser N (AEN) at P < 0.001, recovery efficiency of applied N (REN) and partial factor productivity for N (PFPN) at P < 0.01). The average PENof 40.7and PFPNof 78.8 in plots weeded twice were within the ranges of 40–60 kg grain kg-1N and 40–80 kg grain kg-1N applied respectively. AENand REN values of 38.7 and 0.9 respectively were above the common range of 10-30 kg grain kg-1 N applied and 0.3-0.5 or 0.5–0.8 kg N kg-1. Mean indices from plots weeded just once were all within the ranges stated above but lower than indices from plots weeded twice; suggesting the unsustainability of the use of fertiliser without means to raise its efficiency through better management or combination with organic resources. Weeding twice gave higher returns to labour (USconv2.info.30 day-1) than weeding once (USconv2.info.05 day-1) and gross margins of US5.00 and US.00 with labour taken into account respectively.Farmers need to ensure timely weeding to get decent efficiencies and returns from the fertiliser, especially in drier cropping seasons.

     Using surveys, focus group discussions and the analytical hierarchy process (AHP), adoption of the ten legumes introduced to farmers in Chisepo was assessed among 136 farmers in 2004 and 84 farmers in 2007. Thirty-five percent of the farmers in 2004 and 22% in 2007 had adopted at least one of the legumes, with food grain legumes predominantly soyabean, groundnut, pigeonpea and to a lesser extent Bambara groundnut and cowpea being most adopted. Mucuna and tephrosia were adopted by few farmers while sunnhemp and grahamiana were not adopted at all. Farmers from RGs 1 and 2 adopted more of the legumes than those from RG 3 and 4. Lack of consistent markets, a lack of seed for planting, as well as land and labour shortages were cited for weak adoption.

     Soil fertility management by smallholder farmers is influenced by ownership of assets and the majority poorer farmers fail to invest adequately in improving soil fertility. In the absence of such resources, grain legumes will play an important role as a source of both food and organic matter to improve soil fertility. The participatory methods used in the study helped farmers better understand some of the soil fertility concepts and options, including the legumes. There is need to focus on how to assist farmers with practical knowledge to help them best combine organic and mineral fertiliser resources for improving soil fertility, and to develop and promote new dual-purpose legume options that feed humans and the soil.

     Key words: Adoption, analytical hierarchy process, crop yield, financial returns, food security, household assets, legume integration, livelihoods, NP fertiliser, nitrogen use efficiency, production risk, resource groups, smallholder, soil fertility, weeding. 

    Effecten van verzuring op bodemleven en stikstofstromen in bossen : verkenning van mogelijkheden voor herstelmaatregelen
    Kemmers, R.H. - \ 2011
    Wageningen : Alterra (Alterra-rapport 2204) - 42
    verzuring - bodemchemie - bodembiodiversiteit - bosgronden - stikstofbalans - stikstofkringloop - ecologisch herstel - acidification - soil chemistry - soil biodiversity - forest soils - nitrogen balance - nitrogen cycle - ecological restoration
    Dit rapport geeft een samenvatting van de resultaten van de analyses van het bodemleven, de stikstofstromen en bodemcondities over een brede range van bosgronden. In dit rapport staat de vraag centraal of door verzuring de relatie tussen ondergrondse en bovengrondse biodiversiteit via de N-kringloop is beinvloed. De conclusie is dat door verzuring de activiteit van bacterien (protozoa) en regenwormen is afgenomen en die van schimmels, nematoden en potwormen is toegenomen. Hierdoor is een verschuiving opgetreden in de stikstofbalans van N-immobilisatie naar netto N-mineralisatie. Hiervan profiteren opportunistische soorten in de ondergroei door het extra N-aanbod om te zetten in biomassa waardoor kritischer soorten worden benadeeld. Herstelmaatregelen moeten gericht zijn op herstel van de N-balans tussen bovengronds en ondergronds leven in de richting van een grotere N-retentie door het bodemleven. Hierin kan via het beheer worden gestuurd.
    Surface-atmosphere exchange of ammonia : measurements and modeling over non-fertilized grassland in the Netherlands
    Wichink Kruit, R.J. - \ 2010
    Wageningen University. Promotor(en): Bert Holtslag; Maarten Krol, co-promotor(en): W.A.J. van Pul. - [S.l. : S.n. - ISBN 9789085856429 - 175
    graslanden - landbouw - ammoniak - emissie - kringlopen - stikstofkringloop - modellen - nederland - ammoniakemissie - grasslands - agriculture - ammonia - emission - cycling - nitrogen cycle - models - netherlands - ammonia emission
    In dit proefschrift wordt de oppervlakte-atmosfeer uitwisseling van ammoniak boven agrarisch grasland in Nederland bestudeerd. De belangrijkste doelstellingen van dit proefschrift zijn om een beter begrip van het oppervlakte-atmosfeer uitwisselingsproces van ammoniak te krijgen, vooral boven agrarische grasland in Nederland, en om de modelbeschrijving van het oppervlakte-atmosfeer uitwisselingsproces van ammoniak te verbeteren.
    Stikstofbemesting: klaar voor de toekomst? Minder afhankelijk worden van dierlijke mest
    Scholberg, J.M.S. ; Staps, J.J.M. - \ 2010
    Ekoland 2010 (2010)3. - ISSN 0926-9142 - p. 11 - 13.
    stikstofkringloop - groenbemesters - kostenanalyse - biologisch-dynamische landbouw - bemesting - nitrogen cycle - green manures - cost analysis - biodynamic farming - fertilizer application
    Aanscherping van fosfaatnormen en strengere normen voor gebruik van bio-mest vormen een uitdaging voor de bedrijfsvoering. Biodynamisch akkerbouwer Joost van Strien speelt hierop in, in samenwerking met het Louis Bolk Instituut. Centraal staat dan het sluiten van kringlopen, door gebruik van vlinderbloemige maaimeststoffen
    Vergelijking van luzerne en gras-klaver, inclusief effect op aanwezige aaltjes en de volgteelt prei
    Geel, W.C.A. van; Visser, J.H.M. ; Verstegen, H.A.G. ; Haan, J.J. de - \ 2009
    Lelystad : PPO AGV (PPO-AGV / Rapport ) - 32
    biologische landbouw - ziektebestrijdende teeltmaatregelen - rotaties - organische stikstof - stikstofkringloop - bodemvruchtbaarheid - weidevlinderbloemigen - luzerne - meloidogyne hapla - trichodoridae - gewasbescherming - akkerbouw - grasklaver - organic farming - cultural control - rotations - organic nitrogen - nitrogen cycle - soil fertility - pasture legumes - lucerne - meloidogyne hapla - trichodoridae - plant protection - arable farming - grass-clover swards
    In het biologisch bedrijfssysteem op proefboerderij Vredepeel (zuidoostelijk zand) is een tweejarige teelt van een vlinderbloemig hoofdgewas in de rotatie opgenomen om extra stikstof in het systeem te brengen. De vlinderbloemige wordt begin augustus gezaaid, na voorvrucht aardappel en fungeert dan tevens als stikstofvanggewas voor de minerale stikstof die na de aardappeloogst in de bodem achterblijft en de stikstof die later in de zomer en herfst nog mineraliseert. De vraag was of luzerne of gras-klaver het meeste geschikt zou zijn als vlinderbloemige in de rotatie, gelet op drogestofproductie, geschiktheid voor latere zaai en vermeerdering van aanwezige probleemaaltjes. Er is voor luzerne gekozen, omdat het een iets slechtere waard is voor enkele specifieke aaltjes. Om beter uitsluitsel te verkrijgen over de geschiktheid van luzerne versus gras-klaver, is tevens een vergelijking tussen beide gewassen aangelegd
    Soil fungi and nitrogen cycling : causes and consequences of changing fungal biomass in grasslands
    Vries, F.T. de - \ 2009
    Wageningen University. Promotor(en): Lijbert Brussaard, co-promotor(en): Jaap Bloem; Ellis Hoffland. - [S.l. : S.n. - ISBN 9789085853251 - 126
    bodemschimmels - stikstof - stikstofkringloop - graslanden - kunstmeststoffen - vesiculair-arbusculaire mycorrhizae - uitspoelen - peulgewassen - stikstofverliezen - soil fungi - nitrogen - nitrogen cycle - grasslands - fertilizers - vesicular arbuscular mycorrhizas - leaching - legumes - nitrogen losses
    This thesis focuses on the interaction between fungi and the nitrogen cycle in grassland soils, and attempts to unravel causes and consequences of changing fungal biomass.
    Msimu wa Kupanda : targeting resources within diverse, heterogenous and dynamic farming systemes of East Africa
    Tittonell, P.A. - \ 2008
    Wageningen University. Promotor(en): Ken Giller, co-promotor(en): B. Vanlauwe; Mark van Wijk. - [S.l.] : s.n. - ISBN 9789085048077 - 320
    bedrijfssystemen - bodemvruchtbaarheid - middelentoewijzing - systeemanalyse - simulatiemodellen - kringlopen - voedingsstoffen - stikstofkringloop - organisch bodemmateriaal - kenya - uganda - afrika ten zuiden van de sahara - bodemvruchtbaarheidsbeheer - farming systems - soil fertility - resource allocation - systems analysis - simulation models - cycling - nutrients - nitrogen cycle - soil organic matter - kenya - uganda - africa south of sahara - soil fertility management - cum laude
    cum laude graduation (with distinction)
    Is het ammoniakprobleem opgelost als alle veehouders handelen als Koeien & Kansen?
    Aarts, H.F.M. - \ 2007
    Nieuwsbrief Koeien & Kansen 2007 (2007)25. - p. 3 - 3.
    melkveehouderij - ammoniakemissie - stikstofkringloop - excretie - reductie - agrarische bedrijfsvoering - opinies - dairy farming - ammonia emission - nitrogen cycle - excretion - reduction - farm management - opinions
    Voor 2010 moet de Nederlandse melkveehouderij ten minste 15% minder ammoniak uitstoten. Op verzoek van het Milieu- en Natuurplanbureau (MNP) is verkend hoe groot het ammoniakverlies is als alle veehouders de aanpak van Koeien & Kansen volgen. Een verslag daarvan verschijnt binnenkort, maar het meest opmerkelijke willen we u niet zolang onthouden.
    Grassland renovation in the Netherlands; agronomic, environmetal and economic issues
    Schils, R.L.M. ; Aarts, H.F.M. ; Bussink, D.W. ; Conijn, J.G. ; Corre, V.J. ; Dam, A.M. van; Hoving, I.E. ; Meer, H.G. van der; Velthof, G.L. - \ 2007
    In: Grassland resowing and grass-arable crops rotations / Conijn, J.G., Velthof, G.L., Taube, F., Wageningen : PRI (Report / Plant Research International 47) - p. 9 - 24.
    graslandverbetering - grasmatverbetering - kosten-batenanalyse - economie - milieueffect - stikstofkringloop - nederland - grassland improvement - sward renovation - cost benefit analysis - economics - environmental impact - nitrogen cycle - netherlands
    Experimental studies into the effects of grassland renovation on environmental and agronomic parameters are scarce in the Netherlands. The effects of grassland renovation have been estimated for the three cases of permanent grassland on sand, clay and peat soil, and an additional case for a grass-maize rotation on dry sandy soil. There is need for a futher quantification of the effects of grassland renovation on N cycling in the plant-soil system, with respect to soil type, renovation strategy and crop management
    Gebruiksnormen van meststoffen in de praktijk, getoetst in 2004 en 2005
    Oenema, J. ; Assinck, F.B.T. ; Verloop, J. ; Velthof, G.L. ; Aarts, F. - \ 2007
    Lelystad : Animal Sciences Group (Koeien & kansen rapport 38) - 78
    stikstofgehalte - nitraatreductie - organische stikstof - stikstofkringloop - mestgiften - agrarische bedrijfsvoering - melkveehouderij - stikstofverliezen - bemesting - nitrogen content - nitrate reduction - organic nitrogen - nitrogen cycle - dressings - farm management - dairy farming - nitrogen losses - fertilizer application
    Het doel van dit onderzoek is het toetsen van de voor 2009 geldende gebruiksnormen voor meststoffen (dierlijke mest en kunstmest) in praktijksituaties. De gebruiksnormen voldoen in theorie aan de milieueisen van de EU-nitraatrichtlijn en zijn gebaseerd op veronderstellingen over i) de verdeling van aangevoerde nutriënten over bodem en gewas en ii) het lot van N in de bodem. De toetsing richt zich op deze veronderstellingen. De volgende onderzoeksvragen worden beantwoord: 1. Leidt strikte toepassing van de gebruiksnormen 2009 op perceelsniveau tot in de wet veronderstelde benutting van meststoffen (gewasopbrengsten)?; 2. Hoeveel minerale stikstof blijft in de bodem in het najaar achter? ; 3. Wat is het lot van N in de bodem? Welk deel komt in het grondwater terecht?; 4. Wat is de invloed van waterhuishouding, grondgebruik, bemesting en graslandgebruik op de nitraatconcentraties in het bovenste grondwater? Dit rapport doet verslag van de resultaten van de eerste 2 meetseizoenen. Per onderzoeksvraag worden voorlopige conclusies getrokken. Voor hardere conclusies zijn meer meetjaren nodig. Het onderzoek wordt voortgezet
    Chemical characterization of manure in relation to manure quality as a contribution to a reduced nitrogen emission to the environment
    Stelt, B. van der - \ 2007
    Wageningen University. Promotor(en): Willem van Riemsdijk, co-promotor(en): Erwin Temminghoff. - [S.l.] : S.n. - ISBN 9789085046301 - 152
    dierlijke meststoffen - ammoniak - vervluchtiging - dieet - stikstofkringloop - graslandgronden - organisch bodemmateriaal - samenstelling - voer - animal manures - ammonia - volatilization - diet - nitrogen cycle - grassland soils - soil organic matter - composition - feeds
    Keywords:manure composition, ammonia volatilization, free ions, Donnan Membrane Technique, manure additives, dietary changes, nitrogen dynamics,grasslandsoils.

    More insight in manure composition, ammonia (NH 3 ) volatilization, and into relationships between soil organic matter (SOM) content and nitrogen (N) flows in grasslands is needed to improve the nutrient use efficiency of manure as fertilizer for plants and concomitantly to reduce the environmental impact of agricultural activities.

    Additives are often added to improve manure quality ( e.g. reduce NH 3 volatilization). Laboratory studies showed that additives used in this study did in general not affect manure characteristics or NH 3 volatilization, when manure was incubated at three temperatures and either regular mixed or not mixed. Only when Agri-mest ® and Effective Micro-organisms ® were both added and the manure was incubated at 4 °C without mixing, NH 3 volatilization was reduced by 34%.

    To study manure composition in more detail, a DMT-manure cell was developed, which either measures 'free' dissolved cation or anion concentrations in manure. Dilution studies showed that total nutrient concentrations and monovalent 'free' dissolved cation concentrations decreased proportionately with increasing dilution, whereas 'free' dissolved divalent cation concentrations were buffered upon dilution. The buffering of divalent cation concentrations is probably the result of the release of these ions from organic matter, or it is the result of the dissolution of certain phosphate minerals ( e.g. struvite and whitlockite). Only a small part of the total phosphorus (P) content (<1%) and the total sulphur content (<13%) was present in a 'free' dissolved ionic form.

    A feeding trial with non-lactating cows showed that the total N and P content and the total ammoniacal nitrogen (TAN= NH 3,aq + NH 4+ ) content of manure increased when the dietary protein or energy content was raised, whereas the 'free'-to-total ratios of Ca and Mg in the manures were not affected by dietary changes. Ammoniavolatilization from manure increased with an increase in dietary protein content and decreased with an increase in dietary energy content, although the TAN content of manures produced from diets with a higher dietary energy content werehigher.

    A field trial, in combination with incubation studies, was carried out in the VEL-VANLA area to study how N dynamics was affected by SOM content. Incubation studies showed that potential N mineralization rates (measured at 20 °C and 60% water holding capacity) of eighteen grassland soils were related to the initial dissolved organic nitrogen content and to the dissolved organic carbon content of the soil, as measured in 0.01M CaCl 2 extracts. During the growing season, two peaks in total soluble N content were observed, which could not be related to the time of manure application, but were both preceded by a period of draught. Maximum total soluble N and nitrate content were higher in soils with a lower SOM content. This is probably caused by faster water depletion of soils with a lower SOM content during drought periods, which will hamper N uptake by plants.

    Concluding, adjusting diets seems to be a more promising way to reduce NH 3 volatilization than the use of manure additives, especially since adjusting the diet will reduce NH 3 volatilization at any time of manure handling (housing, storage, and during manure application), which is not always the case for other NH 3 volatilization reduction techniques. A proper estimation of N mineralization during the growing season can help to improve the nutrient gift (via manure) in order for plants to grow with limited risks to the environment. Dissolved organic N might be a promising parameter to estimate N mineralization.

    Rapport studiedag procesonderzoek mineralisatie en bemesting: lessen uit de stikstofkringloop, 28 mei 2002, Meterik
    Langeveld, H. ; Haan, J.J. de - \ 2004
    Wageningen : Plant Research International (Telen met toekomst ) - 16
    mineralisatie - stikstof - bevruchting - stikstofkringloop - kunstmeststoffen - mestbehoeftebepaling - veldgewassen - proefbedrijven - nederland - mineralization - nitrogen - fertilization - nitrogen cycle - fertilizers - fertilizer requirement determination - field crops - pilot farms - netherlands
    Stikstofstromen op het kernbedrijf Meterik : modelberekeningen met FUSSIM2 en MOTOR
    Assinck, F.B.T. ; Willigen, P. de - \ 2004
    Wageningen : Plant Research International (Telen met toekomst OV0405) - 42
    stikstofkringloop - stikstofbalans - simulatiemodellen - systeemanalyse - uitspoelen - nitraat - waterverontreiniging - groenbemesters - oogstresten - akkerbouw - nederland - nitrogen cycle - nitrogen balance - simulation models - systems analysis - leaching - nitrate - water pollution - green manures - crop residues - arable farming - netherlands
    Nitrogen Cycling in Agroforestry Systems of Sub-humid Zimbabwe: Closing the loop
    Chikowo, R. - \ 2004
    Wageningen University. Promotor(en): Ken Giller, co-promotor(en): Peter Leffelaar; P. Mapfumo. - Wageningen : S.n. - ISBN 9789058089861 - 116
    agroforestrysystemen - stikstofkringloop - braaksystemen - verbeterde braak - stikstoffixatie - uitspoelen - mineralisatie - stikstof - zimbabwe - agro-ecosystemen - agroforestry systems - nitrogen cycle - fallow systems - improved fallow - nitrogen fixation - leaching - mineralization - nitrogen - zimbabwe - agroecosystems
    Keywords: improved fallows, biological N 2 -fixation, nitrogen cycling, nitrate leaching, oxide emissions, N mineralization -immobilization, granitic sands

    This thesis focuses on nitrogen: its acquisition in cropping systems through biological N 2 -fixation and subsoil capture, its release by legume prunings and litter, its use by maize and its loss through leaching and as nitrous oxide gas. The context of the study is improved fallows using leguminous trees/shrubs on a sandy clay loam soil under sub-humid conditions inZimbabwe.

    Two-year legume fallows of Sesbania Sesban, Acacia angustissima and Cajanuscajan were evaluated for their residual N effects on two subsequent maize crops under minimum and conventional tillage management. The proportion of N 2 -fixed in litter was 56, 55, 84 and 58 % for Acacia, Sesbania , Cajanus, and cowpea, respectively, resulting in inputs of biologically fixed N of 122, 84, 97 and 28 kg N ha -1 . Maize growth following the legumes for two subsequent cropping seasons was in most cases not directly related to the N inputs due to pest infestation and drought. On a sandy soil, these legumes adapted poorly and did not improve N cycling.

    Soil samples for mineral N determination in profiles were taken at fallow termination and every two weeks during maize cropping with an auger in 0.2 m sections to 1.2 m depth. Pre-season NH 4+ amounts were > 12 kg N ha -1 in the 0-0.2 m layer for treatments that had a large litter layer. There was a flush of NO 3- -N in the Sesbania and Acacia plots with the first rains. Topsoil NO 3- had increased to >29 kg N ha -1 by the time of establishing the maize crop. NO 3- -N amounts decreased rapidly within three weeks of maize planting to 9 and 11 kg N ha -1 for the Sesbania and Acacia plots, respectively. Total NO 3- -N leaching losses from the 0-0.4mlayer ranged from 29-40 kg ha -1 for Sesbania and Acacia plots within two weeks when 104 mm rainfall was received to an already fully recharged soil profile. NO 3- -N then increased below the 0.4 m depth during early season when the maize had not developed a sufficient root length density to effectively capture nutrients. Nitrous oxide emissions were small, with a peak of 12 g N 2 O-N ha -1 day -1 from Sesbania plots and near background fluxes in maize monoculture plots. The decrease of mineral N concentration in the topsoil resulted in reduced N 2 O fluxes, despite very high soil moisture conditions. N 2 O-N emissions were greatest for Sesbania plots with only 0.3 kg ha -1 lost in 56 days.

    The effects of improved fallows on rainfall partitioning and associated soil loss were investigated using simulated rainfall at 35 mm h -1 . Immediately after fallow clearance, infiltration rates were greater than water application rate for the Acacia and natural fallow treatments, but steady state infiltration rates were 24 mm h -1 in Sesban and 5 mm h -1 in continuous maize. The estimated runoff losses after 30 minutes of rainfall were 44% from continuous maize compared with 22% from Sesbania and none from Acacia and natural fallow plots. After one post-fallow crop, water infiltration was still greater than 35 mm h -1 in the Acacia plots. Steady state infiltration rates after 30 minutes of rainfall were 8 and 5 mm h -1 for Sesbania and continuous maize systems, respectively. Planted tree fallows increase infiltration rates, but the effect markedly decrease after one year of maize cropping in non-coppicing tree fallows.

    In a field litterbag decomposition experiment, the course of the decomposition could be adequately described by the function Y = (Y0-Q)e -kt + Q, and the relative decomposition constants for Sesbania and Acacia litters were 0.053 and 0.039 d -1 , respectively. Under laboratory incubation conditions, N mineralized from fresh Sesbania prunings was 55% after 120 days compared with 27% only for the Sesbania litter. During the same period, fresh prunings of Acacia released only 12 % of the added N while Acacia litter released 9 %. N mineralization from Acacia fresh prunings was depressed by the high protein binding capacity of its polyphenols. Except for Sesbania litter, the rest of the senesced legume materials showed N immobilization up to 60 days. 

    The study showed that Sesbania, Acacia and Cajanus produced useful amounts of biomass on soils of at least loamy texture and improved N cycling significantly, but adapted poorly in lighter soils. Under conditions of severe texture constraints, mucuna showed robustness but has the disadvantage of having no direct food value. Gaseous N losses after incorporating legume materials were small, and the reduction of NO 3- leaching is the single largest challenge to increased N recovery in the highly porous soils.

    Stikstofstromen op het kernbedrijf Vredepeel : modelberekeningen met FUSSIM2 en MOTOR
    Assinck, F.B.T. ; Willigen, P. de - \ 2004
    Wageningen : Plant Research International (Telen met toekomst / Alterra, Praktijkonderzoek Plant en Omgeving, Plant Research International, DLV Adviesgroep nv OV0402) - 40
    stikstof - stikstofkringloop - grondwaterstroming - waterkwaliteit - transport - bevruchting - simulatie - modellen - nederland - de peel - nitrogen - nitrogen cycle - groundwater flow - water quality - transport - fertilization - simulation - models - netherlands - de peel
    Uit de mest- en mineralenprogramma's : Verkenningen van stikstof- en fosfaatemissies uit de landbouw in vier regio's
    Velthof, G.L. - \ 2003
    Wageningen : Alterra (Informatieblad / Alterra 398.37) - 2
    bodemchemie - modellen - stikstofgehalte - stikstofkringloop - fosfaat - waterkwaliteit - landbouw - soil chemistry - models - nitrogen content - nitrogen cycle - phosphate - water quality - agriculture
    Er is behoefte aan een methodiek waarbij op eenvoudige wijze de interactie tussen landbouw-, milieu- en natuurrandvoorwaarden in kaart kan worden gebracht. In het project Milieugebruiksruimte (programma 398-III) wordt samen met andere programma's een beslissingsondersteunend syteem ontwikkeld voor integrale analyses van milieudruk uit de landbouw (zie informatieblad 398.6). Het integraal stikstofmodel INITIATOR vormt hiervoor de basis. Begin 2003 is INITIATOR uitgebreid met fosfaat. INITIATOR richt zich op de langere termijn effecten van ingrepen in het milieu. De met INITIATOR berekende milieukwaliteit betreft de toestand die na 30 jaar is bereikt. Dit in tegenstelling tot het model STONE dat wel dynamisch rekent. In dit infoblad worden resultaten weergegeven van de N- en P-emissies in vier regio's met behulp van INITIATOR
    Uncertainties in the fate of nitrogen I: An overview of sources of uncertainty illustrated with a Dutch case study
    Kroeze, C. ; Aerts, R. ; Breemen, N. van; Dam, D. van; Hoek, K. van der; Hofschreuder, P. ; Hoosbeek, M.R. ; Klein, J. de; Kros, H. ; Oene, H. van; Oenema, O. ; Tietema, A. ; Veeren, R. van der; Verhoeven, H. ; Vries, W. de - \ 2003
    Nutrient Cycling in Agroecosystems 66 (2003)1. - ISSN 1385-1314 - p. 43 - 69.
    nitraten - milieueffect - monitoring - stikstofkringloop - onzekerheid - bronnen - nederland - bodemchemie - emissie - uitspoelen - soil chemistry - nitrates - emission - leaching - environmental impact - monitoring - nitrogen cycle - uncertainty - sources - netherlands - organic-matter accumulation - coastal marine ecosystems - forest ecosystems - oxide production - river-basins - managed grasslands - atlantic-ocean - dry deposition - n2o emission - world rivers
    This study focuses on the uncertainties in the fate of nitrogen (N) in the Netherlands. Nitrogen inputs into the Netherlands in products, by rivers, and by atmospheric deposition, and microbial and industrial fixation of atmospheric N2 amount to about 4450 Gg N y¿1. About 60% of this N is transported out of the Netherlands in products. The fate of the remaining 40%, however, is less clear. We discuss uncertainties in losses to the atmosphere (as ammonia or through denitrification), by leaching and runoff, and in N accumulation in biomass and soils. These processes may account for the fate of about 40% of the N in the Netherlands, and for the fate of about 60% of the N in Dutch agricultural soils. Reducing uncertainties in the estimates of these fluxes is necessary for reducing the impact of excess N in the environment. In particular, monitoring the environmental effects of ammonia emissions and nitrate leaching to groundwater and aquatic systems requires an increased understanding of the fate of N. Uncertainties arise because (1) some N fluxes cannot be measured directly and are usually quantified indirectly as the balance in N budgets, (2) direct measurements of N fluxes have inevitable inaccuracies, (3) lack of experimental data and other information (e.g. statistics) needed for upscaling, (4) large spatial and temporal variability of fluxes, and (5) poor understanding of the processes involved. These uncertainties can be reduced by additional experimental studies and by further development of process-based models and N budget studies. We prioritize these future research needs according to a range of different criteria
    Exploring the potential for improved internal nutrient cycling in dairy farming systems, using an eco-mathematical model
    Groot, J.C.J. ; Rossing, W.A.H. ; Lantinga, E.A. ; Keulen, H. van - \ 2003
    Netherlands Journal of Agricultural Science 51 (2003)1-2. - ISSN 0028-2928 - p. 165 - 194.
    melkveehouderij - voedingsstoffen - kringlopen - stikstofkringloop - gebruiksefficiëntie - emissie - mineralisatie - simulatiemodellen - dairy farming - nutrients - cycling - nitrogen cycle - use efficiency - emission - mineralization - simulation models - grass-silage diets - ammonia volatilization - cattle slurry - nitrogen-utilization - ecosystem processes - surface application - animal production - grazing systems - herbage yields - soil
    Nutrient management at Dutch dairy farms is changing rapidly from strong reliance on external inputs to more prudent utilization of internal resources. This paper explores opportunities and constraints arising from this shift towards eco-technological management. A mathematical model of inorganic and organic nitrogen (N) flows in a dairy farming system was formulated based on ecological concepts, integrating processes of nutrient input, recycling, immobilization and mineralization. Recycling is defined as the mineralization of N within the year of its incorporation into herbage, which occurs through release from faeces, animal urine and non-harvested biomass. We simulated changes in inorganic and organic N per hectare, and the consequent emission (E), mineralization (MS) and recycling (R) of N for different initial amounts of inorganic and organic N. Results demonstrate that in the long term, the system evolves to equilibrium amounts of inorganic and organic N, which are strongly determined by the imposed management practices, such as fertilizer input and grassland management. In the short term, moving away from the equilibrium is possible for particular initial amounts of inorganic and organic N. In the equilibrium state, E was reduced by lowering inorganic fertilizer input rate, increasing grassland productivity and improving animal N conversion efficiency, i.e., only by production-related parameters. Only in the short term E was affected by adjustments in quality-related parameters: lower N content, lower digestibility of herbage, reduced degradability of non-harvested biomass and faeces, and parameters determining the functioning of soil biota (degradation rate, efficiency, C/N ratio). Qualityrelated parameters had no effect on internal nutrient cycling in the equilibrium state, because adjustments in MS were completely compensated by changes in R. A comparison of farming systems demonstrated that farming systems can be designed in such a way that improvement of internal nutrient cycling supports the same production with lower inputs and lower emissions.
    Prospects for Sphagnum bogs subject to high nitrogen deposition
    Limpens, J. - \ 2003
    Wageningen University. Promotor(en): Frank Berendse. - [S.l.] : S.n. - ISBN 9789058087850 - 143
    veenmoerassen - sphagnum - plantenecologie - depositie - plantenvoeding - voedingsstoffenbalans - stikstofkringloop - ecosystemen - bogs - sphagnum - plant ecology - deposition - plant nutrition - nutrient balance - nitrogen cycle - ecosystems

    S phagnum bogs harbour a wealth of rare vascular plant and bryophyte species, preserve an amazing pollen record and are long-term sinks for atmospheric carbon. Unfortunately, the relatively low production and decomposition rates, that make these bogs such important environments, also make them vulnerable to changes in atmospheric nitrogen (N) input. The research presented in this thesis had as its aim to investigate to what extent N deposition could affect bogs, and explore whether its influence could render initially successful restoration efforts futile.

    We conducted a set of field and greenhouse experiments, aimed at delineating the effects of N and P on the interactions between Sphagnum and vascular plants, epiphytic algae, fungi and other Sphagnum species. In addition, we paid attention to the physiological effects of a high N supply on Sphagnum , and we studied the impact of an elevated N supply on litter quality and decomposition rate, to get an impression of its long-term effects on bog vegetation.

    Our results unambiguously showed that a simulated increase in N deposition depressed Sphagnum growth. How this decreased vitality came about is not so straightforward, however. We can distinguish two types of negative N effects on Sphagnum . A direct toxic effect that seems to be linked to the N metabolism of Sphagnum and an indirect effect brought about by intensified interactions with other organisms. Additionally, our results showed that Sphagnum originating from sites with a high N deposition decomposed faster than Sphagnum from a site with intermediate N deposition. This combination of decreased Sphagnum production and increased decomposition nudges the carbon balance of these systems towards the negative, and thus challenges the survival of bogs.

    A considerable part of the effects mentioned above depends on the amount of deposited N that Sphagnum can incorporate in its tissue and on the resulting tissue N concentration. As such, the impact of a high N supply is not so much determined by the level of N deposition per se than by the balance between the negative effects of N on the one hand and the supply of potentially growth-limiting factors such as water, P, CO 2 , light and temperature on the other hand. Thus, it seems possible to circumvent an important part of the negative N effects by optimising the overall growing conditions of Sphagnum . However, we must realise that the resilience of the bog ecosystem and the range of conditions under which Sphagnum bogs can survive decrease with N deposition, and thus are limited.

    Stikstofstromen op de kernbedrijven Meterik en Vredepeel; mineralisatie van bodem en gewasresten
    Smit, A. ; Zwart, K.B. - \ 2003
    Wageningen : Plant Research International (Telen met toekomst OVO304) - 25
    mineralisatie - stikstof - stikstofmetabolisme - stikstofkringloop - organisch bodemmateriaal - oogstresten - nederland - mineralization - nitrogen - nitrogen metabolism - nitrogen cycle - soil organic matter - crop residues - netherlands
    Uncertainties in the fate of nitrogen: II. a quantitative assessment of the uncertainties in major nitrogen fluxes in the Netherlands
    Vries, W. de; Kros, J. ; Oenema, O. ; Klein, J.J.M. de - \ 2003
    Nutrient Cycling in Agroecosystems 66 (2003)1. - ISSN 1385-1314 - p. 71 - 102.
    nitraten - monitoring - milieueffect - stikstofkringloop - onzekerheid - nederland - bodemchemie - emissie - uitspoelen - soil chemistry - nitrates - emission - leaching - monitoring - environmental impact - nitrogen cycle - uncertainty - netherlands - soil type - oxide production - grassland soil - peat soils - denitrification - ecosystem - model - cycle - input - nitrification
    Enhanced levels of nitrogen in the environment may have several adverse effects, including decreased plant species diversity in (semi) natural terrestrial ecosystems, eutrophication of surface waters, pollution of groundwater due to nitrate leaching and global warming due to nitrous and nitrogen oxide emissions. To determine the effectiveness of policies aimed at the reduction of emission of ammonia, nitrous and nitrogen oxide, nitrate leaching and nitrogen runoff, it is essential to have information on the fate of nitrogen in both agricultural and non-agricultural soils on a regional and national scale and its inherent uncertainties. In this paper, the authors quantified the uncertainties in the emission, uptake, accumulation, denitrification, leaching and runoff of nitrogen at a national scale and for specific land use–soil type combinations. Furthermore, they identified which parameters contribute most to the overall uncertainty in the emission of ammonia to the atmosphere and the leaching / runoff to groundwater and surface water. To gain quantitative insight into the propagation of the uncertainty, a model was developed representing all crucial processes in the nitrogen chain by simple process descriptions. Uncertainties were quantified for the Netherlands as a whole, including terrestrial systems, both agricultural and non-agricultural land, and aquatic systems
    Enhanced levels of nitrogen in the environment may have several adverse effects, including decreased plant species diversity in ( semi) natural terrestrial ecosystems, eutrophication of surface waters, pollution of ground-water due to nitrate leaching and global warming due to nitrous and nitrogen oxide (N2O and NOx) emissions. To determine the effectiveness of policies aimed at the reduction of emission of ammonia (NH3), N2O and NOx, nitrate (NO3) leaching and nitrogen (N) runoff, it is essential to have information on the fate of nitrogen in both agricultural and non-agricultural soils on a regional and national scale and its inherent uncertainties. In this paper, we quantified the uncertainties in the emission, uptake, accumulation, denitrification, leaching and runoff of nitrogen at a national scale and for specific land use-soil type combinations. Furthermore, we identified which parameters contribute most to the overall uncertainty in the emission of ammonia to the atmosphere and the leaching/runoff to groundwater and surface water. To gain quantitative insight into the propagation of the uncertainty, a model was developed representing all crucial processes in the N chain by simple process descriptions. Uncertainties were quantified for the Netherlands as a whole, including terrestrial systems, both agricultural and non-agricultural land, and aquatic systems. For agricultural and non-agricultural land, plots were distinguished, consisting of a multiple of 500 3 500 m and of 250 3 250 m grid cells, respectively, with unique combinations of soil use, soil type and groundwater table class that were derived from existing digital maps. Model parameters were assigned by using relationships with soil type, groundwater level class and land use. The uncertainty was quantified by means of a Monte Carlo analysis, whereas statistical approaches were used to identify which parameters contribute most to the overall uncertainty of the fate of nitrogen. The 90% confidence interval for the fluxes of N compounds to air, groundwater and surface water (in Gg N.yr(-1)) ranged between 102 and 194 for ammonia emission, between 18 and 51 for N2O emissions, between 32 and 108 for NO3 inflow to groundwater and between 2 and 38 for N inflow to surface water. The uncertainty in NH3 emission was mainly caused by the uncertainty in the NH3 emission fractions for animal manure, whereas the uncertainty in N2O emission was mainly due to the uncertainty in the fractions relating total nitrification and denitrification to N2O emissions. The uncertainty in inflow to groundwater and runoff to surface water was mainly caused by the uncertainty in denitrification in the soil and in upper groundwater and in non-agricultural soils also by the N accumulation in the soil. In view of the need to monitor and evaluate the impact of N reduction policies and measures, it is essential to put more effort in activities yielding a reduction of these large uncertainties, such as additional data gathering and process research under field circumstances.
    Biologisch boeren is samen produceren
    Zonderland, J. ; Enting, I. ; Visser, M. de; Spruijt-Verkerke, J. - \ 2002
    Praktijkkompas. Varkens 16 (2002)4. - ISSN 1570-8578 - p. 20 - 21.
    biologische landbouw - agrarische bedrijfsvoering - samenwerking - landbouwbedrijven - stikstof - stikstofkringloop - producentengroepen - input van landbouwbedrijf - input-output analyse - mest - stro - voer - voedergewassen - veevoeder - mineralen - kringlopen - gelderland - organic farming - farm management - cooperation - farms - nitrogen - nitrogen cycle - producer groups - farm inputs - input output analysis - manures - straw - feeds - fodder crops - fodder - minerals - cycling - gelderland
    Biologische mest, voer en stro zijn onvoldoende beschikbaar. Bovendien zijn deze biologische 'grondstoffen' in de regel duurder dan gangbare.
    Biologisch boeren, is samen produceren
    Zonderland, J. ; Enting, I. ; Visser, M. de; Spruijt-Verkerke, J. - \ 2002
    Praktijkkompas. Rundvee 16 (2002)4. - ISSN 1570-8586 - p. 6 - 7.
    biologische landbouw - agrarische bedrijfsvoering - landbouwbedrijven - samenwerking - stikstof - stikstofkringloop - mineralen - kringlopen - producentengroepen - input van landbouwbedrijf - input-output analyse - mest - stro - voer - voedergewassen - veevoeding - gelderland - organic farming - farm management - farms - cooperation - nitrogen - nitrogen cycle - minerals - cycling - producer groups - farm inputs - input output analysis - manures - straw - feeds - fodder crops - livestock feeding - gelderland
    Voor het sluiten van de mineralenkringlopen moet meer voer en mest worden uitgewisseld.
    A review of potential indicators for nitrate loss from cropping and farming systems in the Netherlands
    Berge, H.F.M. ten - \ 2002
    Wageningen : Plant Research International - 144
    nitraten - stikstof - stikstofbalans - stikstofkringloop - emissie - nitraatreductie - reductie - gegevensanalyse - bedrijfssystemen - grondwaterverontreiniging - bodemwater - nederland - milieuwetenschappen - nitrates - nitrogen - nitrogen balance - nitrogen cycle - emission - nitrate reduction - reduction - data analysis - farming systems - groundwater pollution - soil water - netherlands - environmental sciences
    Improvements of nitrification, denitrification and N20 emission module NITDEN
    Conijn, J.G. - \ 2002
    Wageningen : Plant Research International - 22
    nitrificatie - denitrificatie - stikstofkringloop - stikstofoxide - simulatiemodellen - nitrification - denitrification - nitrogen cycle - nitric oxide - simulation models
    Relationships between soil nitrogen availability indices, yield, and nitrogen accumulation of wheat
    Walley, F. ; Yates, T. ; Groenigen, J.W. van; Kessel, C. van - \ 2002
    Soil Science Society of America Journal 66 (2002)4. - ISSN 0361-5995 - p. 1549 - 1561.
    Canada - bemesting - bodemvruchtbaarheid - gewasproductie - nutriënten - stikstofkringloop - Canada
    Factors affecting N immobilisation/mineralisation kinetics for cellulose-, glucose- and straw-amended sandy soils
    Vinten, A.J.A. ; Whitmore, A.P. ; Bloem, J. ; Howard, R. ; Wright, F. - \ 2002
    Biology and Fertility of Soils 36 (2002)3. - ISSN 0178-2762 - p. 190 - 199.
    bodembiologie - bodemvruchtbaarheid - nutriënten - stikstofkringloop
    The kinetics of nitrogen immobilization/mineralization for cellulose-, glucose- and straw-amended sandy soils were investigated in a series of laboratory incubations. Three Scottish soils expected to exhibit a range of biological activity were used: aloamy sand, intensively cropped horticultural soil subject to large inputs of inorganic fertilizers and pesticides (Balmalcolm - pH 7.2, organic matter 3.3%); a sandy loam soil highly enriched with organic manures and used for organic vegetable production (Strathmiglo - pH 7.1, organic matter 7.3%); and a loamy sand soil of low fertility in a zero-grazing, low intensity organic ley-arable rotation (Aldrochty - pH 6.0, organic matter 5.0%). Incubations of soils with 1000 mg cellulose-C per kg soil at 8 °C, showed peak N immobilization of 71 6, 92 6 and 65 15 mg N per g added C for the Balmalcolm (after 34 d), Strathmiglo (after 34 d) and Aldrochty soils (after 63 d). The N remineralization by the end of the incubation (>300 d) was 0, 50 and 22 mg N per g cellulose-C in the Balmalcolm, Strathmiglo soil and Aldrochty soils, respectively. Only about 30% of the N immobilization could be explained by soil microbial biomass N accumulation (much less than expected from model simulations). The C/N ratio of theextra microbial biomass was quite wide (19). Bacterial, protozoan and nematode biomass accounted for only 18%, 0.1% and 0.5% of the extra C immobilization, respectively. These data suggest that fungal biomass growth and deposition of recalcitrant fungal metabolites are the main sinks for the N immobilized. With 1000 mg glucose-C per kg added to the Balmalcolm soil, about 75 mg N per g added C were immobilized after 6 d. Under less well aerated conditions at 15 °C, immobilization of only 10-20 mg N per gadded cellulose-C took place in 2-4 weeks, but soluble organic C increased greatly. The N remineralized after 4-6 weeks.
    Efficiency improvement for a sustainable agriculture : the integration of agronomic and farm economics approaches
    Koeijer, T.J. de - \ 2002
    Wageningen University. Promotor(en): J.A. Renkema; P.C. Struik; G.A.A. Wossink. - S.l. : S.n. - ISBN 9789058085542 - 143
    beta vulgaris var. saccharifera - suikerbieten - duurzaamheid (sustainability) - agrarische economie - gewasteelt - landbouwplantenteelt - cultuurmethoden - systeemanalyse - gebruiksefficiëntie - efficiëntie - weer - variatie - stikstofkringloop - stikstofbalans - nederland - beta vulgaris var. saccharifera - sugarbeet - sustainability - agricultural economics - crop management - crop husbandry - cultural methods - systems analysis - use efficiency - efficiency - weather - variation - nitrogen cycle - nitrogen balance - netherlands
    Keywords: Sustainable farming systems, Agronomic efficiency, Economic efficiency, Environmental efficiency, Sustainability index, Interdisciplinary analysis.

    The objective of the research described in this thesis was to determine what role improved agronomic efficiency can play in the transition towards more sustainable production systems. Agronomic efficiency measures the technical performance. If it could be improved, environmental damage could be reduced while, at the same time, economic performance could be improved. The latter is an important condition for a successful transition to sustainable agriculture.

    Because economists and agronomists use different concepts and assumptions, they disagree about the efficiency that should be feasible in practice. Therefore, first a conceptual model integrating agronomic and economic concepts was developed. The model presents a division into production levels and accompanying production restricting factors. The hypothesis that improved agronomic efficiency also improves sustainability was tested empirically for sugar beet growing. A positive correlation was indeed found between agronomic efficiency and sustainability. Next, the effect of some production restricting factors on the agronomic efficiency was assessed, using a model that simulated crop growth and water and nitrate processes in the soil to assess the effect of annual variation in weather on the efficiency. It was found that efficiency decreased by 13% due to variation in weather (including indirect weather effects). When the effect of differences in management was measured in an experiment using an interactive simulation model, socio-psychological factors were found to restrict the efficiency by 50-70%. Finally, using these results, the conceptual model was completed quantitatively. The refined conceptual model suggests that the differences between the theoretically-assessed efficiency levels are considerably smaller than the differences between 'average' and 'best practice'. The general conclusion is that normative economic models seem to be a valuable tool for the development of sustainable production systems, as they incorporate not only knowledge derived from practice but also new technological findings.

    Stable nitrogen isotopes : study about its use in the assessment of denitrification and N fixation
    Carratala Sanchez, C. - \ 2001
    Wageningen : Plant Research International (Note / Plant Research International 145) - 19
    stikstof - stikstofkringloop - stabiele isotopen - stikstoffixatie - denitrificatie - meting - methodologie - nitrogen - nitrogen cycle - stable isotopes - nitrogen fixation - denitrification - measurement - methodology
    Synthesis and conclusions
    Dolman, A.J. ; Ierland, E. van; Hutjes, R.W.A. ; Maat, H.W. ter; Haarsma, R. ; Dorland, C. ; Leemans, R. - \ 2001
    In: Land use, climate and biogeochemical cycles: feedbacks and options for emission reduction / Hutjes, R.W.A., Dolman, A.J., Nabuurs, G.J., Schelhaas, M.J., ter Maat, H.W., Kabat, P., Moors, E., Huygen, J., Haarsma, R., Ronda, R., Schaeffer, M., Opsteegh, J.D., Leemans, R., Bouwman, L., Busch, G., Eickhout, B., Kreileman, E., Strengers, B., de Vries, B., Verhagen, A., Vleeshouwers, L., Corre, W.J., Jongschaap, R.E.E., Kruseman, G., van Ierland, E., Holtslag, A.A.M., Willemsen, F., Dorland, C., van Tol, R.S.J., - p. 211 - 221.
    atmosfeer - biogeochemie - broeikaseffect - koolstofkringloop - landgebruik - klimaat - milieu - stikstofkringloop
    Land use, climate and biogeochemical cycles: feedbacks and options for emission reduction
    Dolman, A.J. - \ 2001
    In: Land use, climate and biogeochemical cycles: feedbacks and options for emission reduction / Hutjes, R.W.A., Dolman, A.J., Nabuurs, G.J., Schelhaas, M.J., ter Maat, H.W., Kabat, P., Moors, E., Huygen, J., Haarsma, R., Ronda, R., Schaeffer, M., Opsteegh, J.D., Leemans, R., Bouwman, L., Busch, G., Eickhout, B., Kreileman, E., Strengers, B., de Vries, B., Verhagen, A., Vleeshouwers, L., Corre, W.J., Jongschaap, R.E.E., Kruseman, G., van Ierland, E., Holtslag, A.A.M., Willemsen, F., Dorland, C., van Tol, R.S.J., - p. 1 - 8.
    atmosfeer - biogeochemie - broeikaseffect - koolstofkringloop - landgebruik - klimaat - milieu - stikstofkringloop
    Land use, climate and biogeochemical cycles: feedbacks and options for emission reduction
    Hutjes, R.W.A. ; Dolman, A.J. ; Nabuurs, G.J. ; Schelhaas, M.J. ; Maat, H.W. ter; Kabat, P. ; Moors, E.J. ; Huygen, J. ; Haarsma, R. ; Ronda, R. ; Schaeffer, M. ; Opsteegh, J.D. ; Leemans, R. ; Bouwman, L. ; Busch, G. ; Eickhout, B. ; Kreileman, E. ; Strengers, B. ; Vries, B. de; Verhagen, A. ; Vleeshouwers, L. ; Corre, W.J. ; Jongschaap, R.E.E. ; Kruseman, G. ; Ierland, E. van; Holtslag, A.A.M. ; Willemsen, F. ; Dorland, C. ; Tol, R.S.J. van - \ 2001
    Bilthoven : RIVM (Dutch nat. Res. Programme global Air Pollut. Climate Change Rep. 410200107) - ISBN 9789058510815 - 230
    luchtverontreiniging - emissie - broeikaseffect - klimaatverandering - klimaat - landgebruik - kringlopen - biogeochemie - milieuwetenschappen - atmosfeer - koolstofkringloop - milieu - stikstofkringloop - air pollution - emission - greenhouse effect - climatic change - climate - land use - cycling - biogeochemistry - environmental sciences
    Nutrient management legislation in European countries
    Clercq, P. de; Hofman, G. ; Jarvis, S.C. ; Neeteson, J.J. ; Sinabel, F. ; Gertsis, A. - \ 2001
    Wageningen : Wageningen Pers - ISBN 9789080653726 - 347
    voedingsstoffen - kringlopen - stikstofkringloop - voedingsstoffenbalans - bedrijfsvoering - boekhouden - fosfor - dierlijke meststoffen - bedrijfssystemen - wetgeving - landbouwbeleid - milieuwetgeving - europa - nutrients - cycling - nitrogen cycle - nutrient balance - management - book-keeping - phosphorus - animal manures - farming systems - legislation - agricultural policy - environmental legislation - europe
    Het nitraatbeleid: de wetenschap, de sector en het beleid. Nationaal symposium over normen, onderzoeksresultaten en praktijk, met spreciale aandacht voor melkveehouderij op zand
    Keulen, H. van; Oenema, J. - \ 2001
    Wageningen [etc.] : Plant Research International [etc.] - 144
    melkveehouderij - nitraat - stikstofkringloop - stikstof - landbouwbeleid - rundveemest - bedrijfsvoering - grondwaterverontreiniging - landgebruik - zandgronden - milieubeleid - nitraatreductie - proefbedrijven - nederland - dairy farming - nitrate - nitrogen cycle - nitrogen - agricultural policy - cattle manure - management - groundwater pollution - land use - sandy soils - environmental policy - nitrate reduction - pilot farms - netherlands
    Het mineralenbeleid in Nederland en het nitraatbeleid binnen de EU De mestproblematiek staat al vele jaren op de politieke agenda. Daarbij zijn zwaarwegende maatschappelijke belangen in het geding. Sedert 1984 worden in Nederland maatregelen getroffen om de belasting van het milieu door mest terug te dringen, om te kunnen voldoen aan de nationale en internationale milieudoelstellingen. Daarbij is steeds gekozen voor een gefaseerde aanpak, om de landbouwsector de gelegenheid te geven in te spelen op de strenger wordende milieueisen en te groeien naar een milieuverantwoorde wijze van produceren. Er zijn grote stappen in de goede richting gezet en de sector heeft daartoe behoorlijke inspanningen geleverd. Recente ontwikkelingen maken echter duidelijk dat, om te voldoen aan de internationale milieudoelstellingen - en in het bijzonder aan de EU-Nitraatrichtlijn -, een ingrijpende bijstelling van het mestbeleid onontkoombaar is
    Een relationele database "op afstand" gekoppeld aan dynamische simulatiemodellen
    Kroes, J.G. ; Timmerman, A. - \ 2001
    Agro Informatica 14 (2001)2. - ISSN 0925-4455 - p. 28 - 30.
    milieubescherming - stikstofkringloop - waterbeheer - databanken - simulatiemodellen - belgië - nederland - automatisering - bemesting - database - informatietechnologie - nutriënten - simulatiemodel - stikstof - environmental protection - nitrogen cycle - water management - databases - simulation models - belgium - netherlands - database
    Als onderdeel van een samenwerkingsproject tussen Belgische en Nederlandse onderzoeksinstituten is een simulatieonderzoek uitgevoerd om de relatie tussen de water- en nutriëntenstromen en de invloed hiervan op de gewasproductie en het milieu te bepalen
    De fysiologische basis voor de minimale onbestedig eiwit balans in melkveerantsoenen
    Vuuren, A.M. van; Tamminga, S. - \ 2001
    CVB - 22
    melkveehouderij - melkkoeien - melkveevoeding - stikstof - stikstofmetabolisme - pensmicro-organismen - pensvertering - stikstofkringloop - ureum - pens - dairy farming - dairy cows - dairy cattle nutrition - nitrogen - nitrogen metabolism - rumen microorganisms - rumen digestion - nitrogen cycle - urea - rumen
    In dit rapport komen de volgende onderwerpen aan de orde: - systematisch inzicht in de stikstofstromen, die van belang zijn voor een adequate stikstofvoorziening van pensmicroben; - beschrijving van deze factoren en van de kwantitatieve rol, die zij spelen bij de stikstofvoorziening van pensmicroben. Hierbij zal met name de recycling van stikstof naar de pens aandacht krijgen; - fluctuaties in stikstofvoorziening over de dag.
    Nitrogen transformations and fluxes in fish ponds: a modelling approach
    Jiménez-Montealegre, R.A. - \ 2001
    Wageningen University. Promotor(en): E.A. Huisman; J.A.J. Verreth; M.C.J. Verdegem. - S.l. : S.n. - ISBN 9789058084019 - 185
    visteelt - aquacultuur - visvijvers - stikstof - stikstofretentie - stikstofkringloop - stikstofmetabolisme - visvoeding - modellen - fish culture - aquaculture - fish ponds - nitrogen - nitrogen retention - nitrogen cycle - nitrogen metabolism - fish feeding - models

    Nitrogen is a key element in aquatic environments, and in Aquaculture it is an important pond management variable. In current aquaculture research two important goals are to maintain the water quality within the system, and to improve the retention of nutrients applied to the system in order to minimize the discharge. The principal objectives of this study were to integrate the information available of nitrogen processes in fish ponds into a predictive model, and to investigate further the nitrogen dynamics between the water, the sediments and the biota present in this systems. First, a nitrogen balance in fish ponds was followed along a growing cycle; by combining estimates of the deposition rates of uneaten feed, faeces and dead phytoplankton with measurements of nitrogen accumulation in the sediment, the rate of decomposition of organic matter in the sediment was evaluated. The cumulative recovery at the end of the experiment was almost 100%, meaning that the nitrogen budget in the system studied can be fully explained without any consideration of nitrogen volatilisation, due to either denitrification or ammonia volatilisation. The interactions between various N-species are complex and difficult to integrate. A model that calculates the amounts of various N-compounds in the water column and in the sediment was constructed, and used to gain insight into the relative importance of transformation processes between the various N-compounds. The model was divided into three modules: fish, phytoplankton and sediment-water.

    All concentrations of the various N-species present were simulated well except the N retained in organic matter in the sediment. To improve our understanding of the bottom organic matter dynamics, and make the model a more comprehensive predictive tool, an estimation of the principal sources of organic matter that accumulate in fish pond bottoms was assessed. Organic matter accumulation in fish ponds was quantified, and the data was used to construct, to calibrate and to validate a dynamic simulation model of organic matter deposition/decomposition in fish ponds. Besides, the rates of sedimentation and resuspension were measured along a growing cycle, following the influence of nutrient input, water parameters, fish biomass and fish size on these processes. Using a dilution analysis method to differentiate between sedimented and resuspended particles, sedimentation and resuspension rates were calculated. The rate of material collected in sediment traps increased from 88.5 to 330 g/m 2 per day along the growing cycle, but the relative resuspension did not change significantly, being always in the range of 42 to 47% of the total collected material. The processes of sedimentation of organic matter and resuspension were included in the original model. The proportion of three principal sources of organic matter that accumulate in the pond bottom were also included as parameters of the sedimentation process. A logistic equation relating the rate of resuspension and the fish biomass was calculated; and seepage, as a potential loss of nitrogen from the system, was also considered. The additions to the model represented a substantial improvement to model simulations.

    Application of nutrient balance sheets in analysis and design of agricultural systems: examples from the Netherlands and Poland : paper presented at the seminar "Scientific basis to mitigate the nutrient dispersion into the environment", held at Falenty-Nadarzyn, 13-14 December 1999
    Langeveld, J.W.A. - \ 2000
    Wageningen : Plant Research International (Note / Plant Research International 27) - 13
    plantenvoeding - stikstofkringloop - input-output analyse - polen - nederland - milieubescherming - plant nutrition - nitrogen cycle - input output analysis - poland - netherlands - environmental protection
    Duurzame melkveehouderij en stikstofmanagement
    Keulen, H. van - \ 2000
    Wageningen : Plant Research International (Rapport / De Marke 21) - 136
    dierlijke productie - duurzaamheid (sustainability) - stikstofkringloop - kringlopen - verontreiniging - verontreinigingsbeheersing - milieueffect - grondwaterverontreiniging - animal production - sustainability - nitrogen cycle - cycling - pollution - pollution control - environmental impact - groundwater pollution
    Mest, stro en voer : Het gemengde bedrijf op afstand als optie voor een zelfstandige biologische landbouw in de regio West- en Midden-Nederland : Samenvatting
    Hendriks, K. ; Oomen, G. - \ 2000
    Wageningen : Wetenschapswinkel (Rapport / Wetenschapswinkel 159) - ISBN 9789067545891 - 10
    biologische landbouw - stalmest - stro - plantenresten - diervoedering - voer - ruwvoer (roughage) - mengvoer - bedrijfssystemen - stikstofkringloop - gemengde landbouw - nederland - zuid-holland - organic farming - farmyard manure - straw - plant residues - animal feeding - feeds - roughage - compound feeds - farming systems - nitrogen cycle - mixed farming - netherlands - zuid-holland
    Mest, stro en voer : het gemengde bedrijf op afstand als optie voor een zelfstandige biologische landbouw in de regio West- en Midden-Nederland
    Hendriks, K. ; Oomen, G. - \ 2000
    Wageningen : Wetenschapswinkel (Rapport / Wetenschapswinkel 158) - ISBN 9789067545884 - 94
    biologische landbouw - stalmest - stro - plantenresten - diervoedering - voer - ruwvoer (roughage) - mengvoer - bedrijfssystemen - stikstofkringloop - gemengde landbouw - nederland - zuid-holland - organic farming - farmyard manure - straw - plant residues - animal feeding - feeds - roughage - compound feeds - farming systems - nitrogen cycle - mixed farming - netherlands - zuid-holland
    Resource management in a 'De Marke' dairy farming system = Het benutten van grondstoffen op een "De Marke' melkveebedrijf
    Aarts, H.F.M. - \ 2000
    Agricultural University. Promotor(en): H. van Keulen; J.A.C. Meijs. - S.l. : S.n. - ISBN 9789058082176 - 222
    melkveehouderij - bedrijfssystemen - hulpbronnenbeheer - stikstof - nitraten - fosfor - milieu - zandgronden - grondwater - uitspoelen - voedingsstoffenbalans - stikstofbalans - stikstofkringloop - melkproductie - melkopbrengst - nederland - gelderland - dairy farming - farming systems - resource management - nitrogen - nitrates - phosphorus - environment - sandy soils - groundwater - leaching - nutrient balance - nitrogen balance - nitrogen cycle - milk production - milk yield - netherlands - gelderland

    Sandy soils in the Netherlands are mainly used for dairy farming. As a result of intensification in the recent past, valued functions of sandy regions now are threatened by high emissions of nitrogen (N) and phosphorus (P) and by increased water consumption by forage crops. Dairy farms could probably meet environmental standards by expanding farm size to reduce milk production intensity per hectare. However, land is very expensive and therefore extensive farming probably will not be sustainable from an economic point of view. Moreover, a societal demand exists for alternative use of available land, like expanding nature reserves. Export of slurry, to increase farm output of nutrients, is also expensive and may lead to environmental problems elsewhere. Improved utilisation efficiency of fertilisers, feeds and water is proposed as a strategy to realise environmental targets in an economically attractive way. Experimental results of the prototype system 'De Marke' indicate that an average intensive commercial farm can halve inputs of fertilisers and feeds at least, without the need to reduce milk production per hectare or to export slurry. Besides, water consumption of crops can be reduced by 13%, leading to an increase in groundwater recharge by 570 m 3ha -1. Nitrate concentration in the upper groundwater decreased from 200 to 50 mg l -1. Until so far, changes in soil fertility did not lead to serious agricultural problems but costs of milk production increased by 5%. However, additional costs probably can be compensated if the extra groundwater is 'harvested' by water companies, because of high cost of purification of surface water. In 1999, the examined strategy of improved resource management was implemented on 12 commercial farms, representing the full range of conditions for dairy farming in the Netherlands.

    Stikstofbenutting van maïs; theorie en praktijk : themadag AB-DLO, in samenwerking met LUW, gehouden op 8 april 1998 te Wageningen
    Oenema, O. ; Schröder, J.J. ; Struik, P.C. - \ 1999
    Wageningen : DLO Instituut voor Agrobiologisch en Bodemvruchtbaarheidsonderzoek (AB-DLO Thema,s 7) - 70
    maïs - kunstmeststoffen - stikstof - stikstofkringloop - voedingsstoffen - gewasproductie - plantenveredeling - plantenfysiologie - nederland - belgië - uitspoelen - verontreinigingsbeheersing - maize - fertilizers - nitrogen - nitrogen cycle - nutrients - crop production - plant breeding - plant physiology - netherlands - belgium - leaching - pollution control
    Afstemming van de organische bemesting op variatie in ruimte en tijd
    Vos, J.A. de; Heinen, M. - \ 1999
    Wageningen : AB - 44
    organische meststoffen - mest - biologische landbouw - proefstations - nederland - modellen - simulatiemodellen - stikstofkringloop - bemesting - organic fertilizers - manures - organic farming - experimental stations - netherlands - models - simulation models - nitrogen cycle - fertilizer application
    Evaluating the nitrogen-supplying power of soils in field cropping systems
    Whitmore, A.P. - \ 1999
    Wageningen : AB-DLO - 23
    mestbehoeftebepaling - stikstof - methodologie - onderzoek - stikstofkringloop - bodem - aanbod - verliezen - fertilizer requirement determination - nitrogen - methodology - research - nitrogen cycle - soil - supply - losses
    ANIMO 3.5; user's guide for the ANIMO version 3.5 nutrient leaching model
    Kroes, J.G. ; Roelsma, J. - \ 1998
    Wageningen : DLO Winand Staring Centre (Technical document / DLO-Staring Centrum 46) - 98
    bodem - uitspoelen - stikstof - stikstofkringloop - bacteriën - rivieren - waterlopen - kanalen - water - oppervlaktewater - waterverontreiniging - waterkwaliteit - modellen - onderzoek - soil - leaching - nitrogen - nitrogen cycle - bacteria - rivers - streams - canals - water - surface water - water pollution - water quality - models - research
    Bodembelasting (N en P205) in de periode 1972-1993; Uitgangspunten voor berekeningen met ANIMO
    Oudendag, D.A. ; Boers, G.J. ; Luesink, H.H. - \ 1996
    Den Haag : LEI-DLO (Mededeling / Landbouw-Economisch Instituut (LEI-DLO) 557) - ISBN 9789052423395 - 57
    bodem - stikstof - stikstofkringloop - bacteriën - fosfor - uitspoelen - modellen - onderzoek - drijfmest - stalmest - soil - nitrogen - nitrogen cycle - bacteria - phosphorus - leaching - models - research - slurries - farmyard manure
    Biological sulphate reduction with synthesis gas
    Houten, R.T. van - \ 1996
    Agricultural University. Promotor(en): G. Lettinga. - S.l. : Van Houten - 125
    micro-organismen - biochemie - metabolisme - synthese - microbiologie - stikstofkringloop - reductie - sulfaten - microorganisms - biochemistry - metabolism - synthesis - microbiology - nitrogen cycle - reduction - sulfates

    The objectives of this thesis are (1) to study the feasibility of using synthesis gas as electron donor and carbon source for biological sulphate reduction and (2) to develop criteria for design and operation of gas- lift bioreactors for sulphate reduction using immobilized biomass.

    At appeared that sulphate-reducing bacteria, grown on H 2 /CO 2 , formed stable biofilms on pumice particles. Biofilm formation was not observed when basalt particles were used. However, use of basalt particles led to the formation of aggregates of sulphate-reducing biomass. The sulphate-reducing bacteria grown on pumice particles easily adapted to free H 2 S concentrations up to 450 mg/L. These high free H 2 S concentrations caused reversible inhibition rather than acute toxicity. When free H 2 S concentrations were kept below 450 mg/L. a maximum sulphate conversion rate of 30 g SO42-/L.d could be achieved after only 10 days of operation. Gas to liquid mass transfer capacity of the reactor determined this maximum sulphate conversion rate.

    Furthermore, biological sulphate reduction appeared to be applicable within a pH range of 5.5 to 8.0, with an optimum near pH 7.5. The pH affected aggregate configuration and diameter. At pH 7.0, the average Sauter mean diameter of the aggregates was 1.5 mm. Moreover, phase-contrast and SEM microscopy showed highly branched aggregate surfaces. A pH increase led to increased surface irregularity without affecting the particle diameter. A pH decrease caused a decreased surface irregularity and changed the aggregate Sauter mean diameter from 1.50 mm at pH 7.0 to 2.26 at pH 5.5. However, the pH did not have a significant effect on the biomass composition. Examination of the bacterial composition of the aggregates by phase-contrast microscopy, SEM microscopy as well as enrichments showed that at all pHs Desulfovibrio sp. and Acetobacterium sp. were the most abundant micro-organisms.

    When sulphate reduction was carried out with synthesis gas as electron donor and carbon source, the reactor performance was strongly affected. Addition of 5% CO negatively affected the overall sulphate conversion rate, i.e. it dropped from 12 - 14 g SO42-/L per day to 6 - 8 g SO42-/L per day. However, a further increase of CO to 10 and 20% did not further deteriorate the process. With external biomass recycling the sulphate conversion rate could be improved to 10 g SO42-/L per day. Therefore biomass retention clearly could be regarded as the rate limiting step. Furthermore, CO affected the aggregate shape and diameter. SEM photographs showed that rough aggregates, pre-grown on H 2 /CO 2 , changed into smooth aggregates upon addition of CO. Addition of CO also changed the aggregate Sauter mean diameter (d32) from 1.7 mm. at 5% CO to 2.1 mm at 20% CO. After addition of CO, a layered biomass structure developed. Acetobacterium sp. were mainly located at the outside of the aggregates, whereas Desulfovibrio sp. were located inside the aggregates.

    Additionally, thermophilic (55 °C) sulphate and sulphite reduction was studied. The results of the experiments clearly demonstrated that sulphate conversion rates up to 7.5 g SO42-/Lper day can be achieved. With sulphite a reduction rate of 3.7 g S/L per day was obtained, which equals a sulphate conversion rate of 11.1 g SO42-/L per day. Under the applied conditions, a strong competition for hydrogen between hydrogenotrophic sulphate-reducers, designated as Desulfotomaculum sp., and hydrogenotrophic methanogens was observed. Growth of the mixed culture was totally inhibited at a H 2 S concentration of 250 mg/L. Poor attachment of sulphate-reducing bacteria was observed in all experiments. The biomass concentration did not exceed 1.2 g/L, despite the presence of 50 g/L of pumice.

    Based in the abovementioned results it is concluded that both aims of the thesis are attained. First, biological sulphate reduction appears to be feasible. Additionally, a number of criteria for design and operation of gas-lift bioreactors for sulphate reduction were developed and discussed. Finally, several recommendations for future research are given.

    Invloed van plantverdeling, zaaitijdstip en koude - tolerantie op de stikstofbenutting door mais tijdens de jeugdgroei = Influence of plant spacing sowing time and cold tolerance on nitrogen efficiency of maize during juvenil stage
    Schans, D.A. van der; Dijk, W. van; Dolstra, O. - \ 1995
    Lelystad : PAGV (Verslag / Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond nr. 191) - 105
    bacteriën - klimaatfactoren - kouderesistentie - oogstschade - droogteresistentie - bodemfactoren - beschadigingen door vorst - maïs - stikstof - stikstofkringloop - plantenveredeling - plantdichtheid - planttijd - rijenafstanden - zouttolerantie - bodem - zaaitijd - temperatuurresistentie - zea mays - bacteria - climatic factors - cold resistance - crop damage - drought resistance - edaphic factors - frost injury - maize - nitrogen - nitrogen cycle - plant breeding - plant density - planting date - row spacing - salt tolerance - soil - sowing date - temperature resistance - zea mays
    Denitrificatie in poldergronden : verslag van een onderzoek naar het belang van denitrificatie in de stikstofhuishouding van poldergronden en het mogelijke effect van peilverhoging op de denitrificatie, uitgevoerd in opdracht van de Provincie Zeeland
    Corre, W.J. - \ 1995
    Haren Gr. : AB-DLO (Rapport / AB-DLO 41) - 28
    bacteriën - kanalen - zware kleigronden - denitrificatie - stikstofkringloop - polders - regulatie - rivieren - waterlopen - oppervlaktewater - water - waterverontreiniging - waterkwaliteit - wetlands - waterstand - bacteria - canals - clay soils - denitrification - nitrogen cycle - polders - regulation - rivers - streams - surface water - water - water pollution - water quality - wetlands - water level
    Nitraatverliezen bij gras en witte klaver
    Schils, R.L.M. - \ 1995
    Praktijkonderzoek / Praktijkonderzoek Rundvee, Schapen en Paarden (PR), Waiboerhoeve 8 (1995)2. - ISSN 0921-8874 - p. 18 - 21.
    bacteriën - drainage - graslanden - uitspoelen - stikstofkringloop - bodem - trifolium repens - bacteria - drainage - grasslands - leaching - nitrogen cycle - soil - trifolium repens
    In dit artikel ligt de nadruk op de stikstofverliezen via het drainwater.
    Short-term and long-term effects of bacterivorous nematodes and nematophagous fungi on carbon and nitrogen mineralization in microcosms
    Bouwman, L.A. ; Bloem, J. ; Boogert, P.H.J.F. van den; Bremer, F. ; Hoenderboom, G.H.J. ; Ruiter, P.C. de - \ 1994
    Biology and Fertility of Soils 17 (1994). - ISSN 0178-2762 - p. 249 - 256.
    bacteriën - koolstof - mineralisatie - nematoda - stikstofkringloop - bodem - bodemschimmels - bacteria - carbon - mineralization - nematoda - nitrogen cycle - soil - soil fungi
    A microcosm experiment was carried out to quantify the effects of organisms at various trophic levels on C and N mineralization after the addition of crop residues to arable soil. The effects of the bacterivorous nematodes Rhabditis sp. and Acrobeloides bütschlii and of the nematophagous fungi Arthrobotrys oligospora und Drechmeria coniospora on soil respiration and N mineralization were measured over 6 months at 20°C. In the presence of nematodes, C mineralization was increased during the first month and subsequently reduced; N mineralization was increased during the first 2 months and then reduced. The results support the assumption that nematodes influence C mineralization mainly indirectly by affecting bacterial activity, and N mineralization mainly directly by mineralizing bacterial biomass. A. oligospora contributed directly to C mineralization. The effect of both fungi on N mineralization was indirect and resulted from the reduction in the numbers of nematodes. The results showed that the effects of nematodes and nematophagous fungi and the mechanisms behind the effects may vary strongly in time, and are correlated with the type of organic matter decomposed.
    A comparative study of nitrogen flows in two similar meadows affected by different groundwater levels
    Berendse, F. ; Oomes, M.J.M. ; Altena, H.J. ; Visser, W. de - \ 1994
    Journal of Applied Ecology 31 (1994). - ISSN 0021-8901 - p. 40 - 48.
    bacteriën - graslanden - hydraulisch geleidingsvermogen - infiltratie - stikstof - stikstofkringloop - kwel - grondwaterspiegel - bacteria - grasslands - hydraulic conductivity - infiltration - nitrogen - nitrogen cycle - seepage - water table
    1. A comparative study was carried out on nitrogen flows in two meadow ecosystems that were similar at the beginning of the experiment. In the wet meadow, groundwater levels had been raised and in the dry meadow no changes in the original groundwater levels had been imposed. 2. Annual nitrogen mineralization and nitrogen accumulation in above-ground biomass were reduced by c. 20in the wet meadow as compared with the dry meadow. In the dry compartment the peak in nitrogen mineralization was reached in spring, whereas in the wet compartment the peak was reached in summer. 3. In the wet compartment a smaller fraction of the ammonium produced was oxidized to nitrate than in the dry compartment (60losses through denitrification were similar (about 17 kg N ha -1 year -1 ). During the summer, however, denitrification was greater in the wet compartment. During the winter denitrification increased sharply, because of nitrate accumulation in the soil at the end of the growing period and was greater in the dry compartment. 5. The nitrogen balance of the two meadow ecosystems shows that the inputs through atmospheric deposition and the outputs through hay removal are quantitatively the most important components of the nitrogen balance. Raising groundwater levels led to less nitrogen accumulation in the aboveground biomass and, thus, to smaller nitrogen outputs through hay removal.
    Uitbreiding van het graslandbeheersmodel GRASMOD: invloed van de opfok van jongvee voor de melkveehouderij op stikstofstromen in grasland
    Boons - Prins, E.R. ; Ven, G.W.J. van de - \ 1993
    Wageningen : CABO-DLO (Verslag / CABO-DLO 171) - 38
    bacteriën - kalveren - melkvee - melkveehouderij - graslanden - uitspoelen - wiskundige modellen - microbiologie - nederland - nitraten - nitrieten - stikstof - stikstofkringloop - weiden - onderzoek - bodem - voedergrassen - bacteria - calves - dairy cattle - dairy farming - grasslands - leaching - mathematical models - microbiology - netherlands - nitrates - nitrites - nitrogen - nitrogen cycle - pastures - research - soil - fodder grasses
    De kringloop van nutrienten bij enkele graslandbeheersvormen op "de Veenkampen"
    Altena, H.J. - \ 1993
    Wageningen : CABO-DLO (Verslag / CABO-DLO 190) - 22
    bacteriën - graslanden - stikstofkringloop - bacteria - grasslands - nitrogen cycle
    Naar een optimale stikstofbemesting van consumptie- en zetmeelaardappelen.
    Vos, J. - \ 1993
    In: Themadag aardappelen : teelt van consumptie- en zetmeelaardappelen in relatie tot kwaliteits- en milieu-eisen / van Loon, C.D., Bosch, H., Zwanepol, S., - p. 30 - 39.
    assimilatie - mestbehoeftebepaling - groei - microbiologie - stikstof - stikstofkringloop - stikstofmeststoffen - aardappelen - bodem - solanum tuberosum - duurzaamheid (sustainability) - fabrieksaardappelen - assimilation - fertilizer requirement determination - growth - microbiology - nitrogen - nitrogen cycle - nitrogen fertilizers - potatoes - soil - sustainability - starch potatoes
    De stikstofkringloop: samenspel van organismen en tegenspel vanuit het milieu.
    Brussaard, L. ; Laanbroek, H.J. ; Verhoef, H.A. - \ 1993
    Bodem 4 (1993). - ISSN 0925-1650 - p. 184 - 187.
    bacteriën - microbiologie - stikstofkringloop - onderzoek - rizosfeer - grondanalyse - wetenschap - wetenschappelijk onderzoek - bacteria - microbiology - nitrogen cycle - research - rhizosphere - soil analysis - science - scientific research
    Stikstofstromen in agro-ecosystemen
    Meer, H.G. van der; Spiertz, J.H.J. - \ 1992
    Wageningen : CABO-DLO (Agrobiologische thema's 6) - ISBN 9789073384149 - 107
    bodemchemie - stikstof - mineralisatie - stikstofkringloop - stikstofbalans - waterkwaliteit - agro-ecosystemen - stikstofverliezen - soil chemistry - nitrogen - mineralization - nitrogen cycle - nitrogen balance - water quality - agroecosystems - nitrogen losses
    The publication consists of six chapters: Simulation of nitrogen mineralization on the basis of food chain interactions in different soil ecosystems; The nitrogen cycle in an unfertilized grassland ecosystem: effects of measures in hydrology and management; Nitrogen utilization and losses in production grassland; Physiology of nitrogen uptake and utilization: crop and root characteristics; Nitrogen utilization and losses in maize cropping systems; Modelling of nitrogen utilization and losses.
    Food web modeling of C and N mineralization in four grassland soils
    Neutel, A.M. - \ 1992
    Haren (Gr.) : DLO-Instituut voor Bodemvruchtbaarheid (Nota / DLO-Instituut voor Bodemvruchtbaarheid 264) - 23
    graslanden - bodem - koolstof-stikstofverhouding - mineralisatie - stikstofkringloop - bacteriën - computersimulatie - simulatie - simulatiemodellen - grasslands - soil - carbon-nitrogen ratio - mineralization - nitrogen cycle - bacteria - computer simulation - simulation - simulation models
    De stikstofkringloop in een niet bemest graslandoecosysteem:effecten van ingrepen in hydrologie en natuurbeheer
    Best, E.P.H. ; Oomes, M.J.M. ; Berendse, F. - \ 1992
    In: Stikstofstromen in agro-ecosystemen / van der Meer, H.G., Spiertz, J.H.J., Wageningen : CABO (Agrobiologische Thema's ) - p. 19 - 32.
    landbouw - landbouw bedrijven - graslanden - natuurbescherming - stikstofkringloop - grondwaterspiegel - agro-ecosystemen - agrarisch natuurbeheer - gelderse vallei - agriculture - farming - grasslands - nature conservation - nitrogen cycle - water table - agroecosystems - agri-environment schemes - gelderse vallei
    4. Decomposition: the roles of various functional groups of organisms
    Brussaard, L. - \ 1991
    In: Decomposition and accumulation of organic matter in terrestrial ecosystems : research priorities and approaches : proceedings of a workshop, Doorwerth, The Netherlands, September 2 - 4, 1991 / van Breemen, N., CEC (Ecosystem research report no. 1) - ISBN 9782872630769 - p. 27 - 34.
    bacteriën - stikstofkringloop - bodemfauna - bacteria - nitrogen cycle - soil fauna
    Old tree root channels in acid soils in the humid tropics: Important for crop root penetration, water infiltration and nitrogen management
    Noordwijk, M. van; Widianto, ; Heinen, M. - \ 1991
    In: Plant-soil interactions at low pH - p. 423 - 430.
    bacteriën - bosbouw - uitspoelen - stikstof - stikstofkringloop - plantenontwikkeling - plantenfysiologie - wortels - bodem - bodemaciditeit - bodem ph - subtropen - tropen - bacteria - forestry - leaching - nitrogen - nitrogen cycle - plant development - plant physiology - roots - soil - soil acidity - soil ph - subtropics - tropics
    Root nodulation : the twelfth hypothesis (agroforestry and soil fertility)
    Noordwijk, M. van; Dommergues, Y.R. - \ 1990
    Agroforestry today 2 (1990)2. - ISSN 1013-9591 - p. 9 - 10.
    agroforestry - bacteriën - bosbouw - stikstofkringloop - knobbelvorming - wortelknolletjes - bacteria - forestry - nitrogen cycle - nodulation - root nodules
    Nitrogen cycling in high-input versus reduced-input arable farming
    Faassen, H.G. van; Lebbink, G. - \ 1990
    Netherlands Journal of Agricultural Science 38 (1990)3A. - ISSN 0028-2928 - p. 265 - 282.
    toedieningshoeveelheden - extensieve landbouw - bedrijfssystemen - kunstmeststoffen - intensieve landbouw - microbiologie - stikstof - stikstofkringloop - application rates - extensive farming - farming systems - fertilizers - intensive farming - microbiology - nitrogen - nitrogen cycle
    Onderzoek naar de potentieele niveau's van stikstofkringloopprocessen met het doel om de invloeden van veranderingen in teeltintensiteit te beoordelen. Research into the levels of nitrogen cycling processes with the purpose of examining the influences of changes in cultivation intensity
    Decomposition and nitrogen mineralization in natural and agro-ecosystems: the contribution of soil animals.
    Verhoef, H.A. ; Brussaard, L. - \ 1990
    Biogeochemistry 11 (1990). - ISSN 0168-2563 - p. 175 - 211.
    bacteriën - stikstofkringloop - bodemfauna - agro-ecosystemen - bacteria - nitrogen cycle - soil fauna - agroecosystems
    Protozoan predation and the turnover of soil organic carbon and nitrogen in the presence of plants.
    Kuikman, P.J. ; Jansen, A.G. ; Veen, J.A. van; Zehnder, A.J.B. - \ 1990
    Biology and Fertility of Soils 10 (1990). - ISSN 0178-2762 - p. 22 - 28.
    bacteriën - koolstof-stikstofverhouding - micro-organismen - stikstofkringloop - protozoa - bodem - bodemfauna - bacteria - carbon-nitrogen ratio - microorganisms - nitrogen cycle - protozoa - soil - soil fauna
    N-management in the humid tropics : report of field visits to Ketapang (Lampung, Sumatera, Indonesia) in August 1988 and January 1989, including observations on roots and water infiltration
    Noordwijk, M. van - \ 1989
    Haren (Gr.) : IB (Nota / Instituut voor Bodemvruchtbaarheid 208) - 28
    bacteriën - indonesië - stikstof - stikstofkringloop - rizosfeer - bodem - bodemwater - subtropen - tropen - sumatra - bacteria - indonesia - nitrogen - nitrogen cycle - rhizosphere - soil - soil water - subtropics - tropics - sumatra
    Nitrificatieremmers en nitraatuitspoeling bij toediening van dierlijke mest : verslag van een door het Financieringsoverleg Mestonderzoek mede gefinancierd literatuuronderzoek naar het belang van nitrificatieremmers ter beperking van nitraatuitspoeling als gevolg van toediening van dierlijke mest in de landbouw
    Enckevort, P. van - \ 1988
    Haren (Gr.) : IB (Nota / Instituut voor Bodemvruchtbaarheid 191,192,193,194)
    dierlijke meststoffen - bacteriën - stalmest - uitspoelen - nitraten - nitrificatieremmers - nitrieten - stikstof - stikstofkringloop - drijfmest - bodem - animal manures - bacteria - farmyard manure - leaching - nitrates - nitrification inhibitors - nitrites - nitrogen - nitrogen cycle - slurries - soil
    ANIMO : user's guide, version 2
    Kroes, J.G. - \ 1988
    Wageningen : ICW (ICW nota 1848) - 112
    bodemchemie - grondwaterverontreiniging - uitspoelen - stikstof - stikstofkringloop - verontreinigingsbeheersing - modellen - soil chemistry - groundwater pollution - leaching - nitrogen - nitrogen cycle - pollution control - models
    The groundwater quality model ANIMO describes the nitrogen and carbon cycle and its interrelation. With as main purpose the prediction of nitrate leaching to ground and surface water
    ANIMO : user's guide, version 1
    Kroes, J.G. - \ 1988
    Wageningen : ICW (Nota / Instituut voor Cultuurtechniek en Waterhuishouding 1848) - 60
    bacteriën - grondwaterverontreiniging - uitspoelen - modellen - stikstof - stikstofkringloop - verontreinigingsbeheersing - bescherming - onderzoek - bodem - waterkwaliteit - bacteria - groundwater pollution - leaching - models - nitrogen - nitrogen cycle - pollution control - protection - research - soil - water quality
    Nitraatimmissie en Nederlandse ecosystemen : een globale risico-analyse
    Denneman, W.D. ; Torenbeek, R. - \ 1987
    Arnhem : RIN (RIN-rapport 87/23) - 164
    luchtverontreiniging - milieu - schade - milieueffect - neerslag - chemische eigenschappen - zuurgraad - zure regen - stikstofkringloop - bacteriën - dierlijke meststoffen - besluitvorming - analyse van besluiten - nederland - air pollution - environment - damage - environmental impact - precipitation - chemical properties - acidity - acid rain - nitrogen cycle - bacteria - animal manures - decision making - decision analysis - netherlands
    Nitrogen fixation (Acetylene reduction) in the sediments of the pluss-see : with special attention to the role of sedimentation
    Blauw, T.S. - \ 1987
    Agricultural University. Promotor(en): E.G. Mulder, co-promotor(en): H.J. Overbeek. - S.l. : Blauw - 199
    meren - reservoirs - plassen - water - sediment - microbiologie - stikstofkringloop - nitrificatie - gramnegatieve bacteriën - bondsrepubliek duitsland - acetyleenreductie - lakes - reservoirs - ponds - water - sediment - microbiology - nitrogen cycle - nitrification - gram negative bacteria - german federal republic - acetylene reduction

    Sediments of productive lakes are usually rich in organic matter and, except for a thin surficial layer, anaerobic. These conditions seem to be favourable for heterotrophic nitrogen fixation. However, these sediments also contain relatively high ammonium concentrations. Ammonium represses the synthesis of the enzyme nitrogenase. Moreover, ammonium inhibits the activity of the enzyme in aerobic nitrogen fixers. These effects of ammonium seem to be functional. Nitrogen fixation is a highly endergonic process. Therefore it is more economic to use combined nitrogen (e.g. ammonium) than atmospheric nitrogen as a nitrogen source. Nevertheless, a number of workers have detected nitrogen fixing activity in ammonium rich sediments.

    In the present investigation the significance of heterotrophic nitrogen fixation in the sediments or the nitrogen economy of the Pluss-See has been studied. Special attention has been paid to the role of organic matter supply and ammonium.

    The surface area of the lake is 14 ha, the maximum depth is 29 m. Every year a stable thermal stratification develops in the lake, usually with an anaerobic hypolimnion.

    The problem of nitrogen fixation in lake sediments has been approached in three ways:
    1. Nitrogen fixation in the sediments was studied under controlled conditions in the laboratory;
    2. The relation between nitrogen fixation and some properties of the sediments was studied under natural conditions;
    3. The relation between nitrogen fixation in the sediments and processes within the lake was studied under natural conditions.

    Laboratory studies (chapters 3, 4 and 5).

    Nitrogen fixating activity was measured with the acetylene reduction assay. One of the requirements for this assay, the saturation of nitrogenase with acetylene, was not met (figure 5), because nitrogen fixation apparently occured in protected microsites with poor accessibility for acetylene (3.2.2). This protection may have also consequences for the measurement of nitrogen fixation with 15N 2 (3.2.3).

    Nitrogenase activity of the sediments was stimulated by the addition of organic substrates, as mannitol, glucose, fructose etc., suggesting that the activity of nitrogenase in situ in these sediments was limited by the availability of organic substrate (4-2). This suggestion is affirmed by the absence of a discontinuity in the Arrhenius plot (figure 17b).

    Upon addition of organic substrate to the sediments two phases could be observed (figure 9). In the first phase acetylene reducing activity is constant, but higher than in control sediments. In this phase the activity of the already present nitrogenase is stimulated (increase of the actual activity). In the second phase, after the interstitial ammonium concentration has dropped below a certain threshold-value, the synthesis of nitrogenase is derepressed and an exponential increase of nitrogenase activity can be observed (increase of the potential activity). Because nitrogenase synthesis in situ had to be assumed above the derepression threshold, the conclusion was drawn that the dissolved ammonium concentration within the protected microsites was lower than in the bulk of the sediments (4.3). Apparently nitrogen fixation occures in ammonium rich sediments, because nitrogen fixers are not in contact with these high concentrations.

    Field observations; relation between the nitrogenase activity and some other properties of the sediments (chapters 6 and 7).

    During a year nitrogenase activity and some other characteristics of the sediments were measured at three stations in the lake: in the littoral sediments at 5 m water depth and in the profundal sediments at 15 and 29 m water depth. Highest nitrogenase activity was measured at the sediment surface at the deepest part of the lake (figure 27). Especially in the winter period very high rates were observed (figure 28). In the sediments at the deepest part of the lake the yearly fixed amount of nitrogen was estimated to be 0.24-1.10 g.m -2, depending on the conversion factor used. In the shallower regions this amount was estimated to be 0.15-0.77 g N.m -2.

    Acetylene reduction in the littoral sediments was correlated with temperature (table II). In the profundal sediments no significant temperature variation could be observed. Acetylene reducing activity in the profundal sediments was correlated with the C/N ratio (figure 33), which could be shown to be an index for substrate availability in these sediments. In both littoral and profundal sediments acetylene reducing activity was highly significantly correlated with the maximum glucose uptake velocity (V m ) of the heterotrophic population in the sediments (figure 41). The repression-derepression threshold of the interstitial ammonium concentration could be observed under natural conditions (figure 33). Acetylene reducing rates were higher at ammonium concentrations below this threshold. The ammonium adsorption coefficient (Ke) of the sediments seemed to be more important for the acetylene reducing activity than the ammonium concentration it self (table II). This finding suggests that the dissolved ammonium concentration in the protected microsites is lowered by adsorption.

    Field observations; the relation between nitrogen fixation in the sediments and the sedimentation of suspended matter (chapters 8, 9 and 10).

    Sedimentation of particulate organic matter was measured at the three stations. The measured rates were corrected for resuspension using the differences in carbon content between the settling particulate material and the carbon content of the surficial sediments (8.4; figure 47). Eight percent of the primary production reached the bottom at the deepest part of the lake (table VI). Redistribution of sediments resulting in sediment focusing is important in the lake. Both intermittent complete mixing and sliding of sediments on slopes are important for the focusing process. A correlation between sedimentation and acetylene reducing activity could be observed in the littoral sediments and at the deepest part of the lake (figure 63). No correlation was found at 15 m water depth. Only at the deepest part of the lake a correlation was found between the sedimentation and both the C/N ratio and Ke of the sediments (figure 61 and 62). These correlations and non- correlations could be explained by the transport of sediments within the lake, described by a simple focusing model (8.7). Using this model the efficiency of nitrogen fixation under natural conditions could be estimated to be high compared to the efficiency measured in pure and enrichment cultures (8.10).

    Also using this model it could be shown (10) that nitrogen fixation may be important to the nitrogen economy of the sediments but not for the nitrogen economy of the whole lake. Nitrogen fixation is expected to be more important in lakes with a larger proportion of the primary production reaching the bottom.

    Root studies on a tropical ultisol in relation to nitrogen management : report of field work at IITA's high rainfall substation at Onne (Port Harcourt, Nigeria) in 1985
    Hairiah, K. ; Noordwijk, M. van - \ 1986
    Haren (Gr.) : I.B. (Rapport / Instituut voor Bodemvruchtbaarheid no. 7-86) - 121
    akkerbouw - bacteriën - veldgewassen - stikstof - stikstofkringloop - stikstofmeststoffen - plantenontwikkeling - plantenfysiologie - wortels - bodem - subtropen - tropen - ultisols - arable farming - bacteria - field crops - nitrogen - nitrogen cycle - nitrogen fertilizers - plant development - plant physiology - roots - soil - subtropics - tropics - ultisols
    The relation between nitrogen fertilization and root development is studied for several crop types. Also the root development in intercropping of maize and cassave is studied
    Simulatie van de stikstofhuishouding van de grond in voor- en najaar
    Zandt, P.A. ; Willigen, P. de; Neeteson, J.J. - \ 1986
    Haren (Gr.) : I.B. (Rapport / Instituut voor Bodemvruchtbaarheid 9-86) - 57
    herfst - bacteriën - computersimulatie - wiskundige modellen - nitrificatie - stikstof - stikstofkringloop - onderzoek - simulatie - simulatiemodellen - bodem - lente - autumn - bacteria - computer simulation - mathematical models - nitrification - nitrogen - nitrogen cycle - research - simulation - simulation models - soil - spring
    Het verloop van minerale stikstof in de grond wordt berekend met een eenvoudig simulatiemodel dat uitspoeling en mineralisatie van stikstof kan berekenen. Het model berekent de mineralisatie volgens 2 methoden: volgens de ene methode wordt de mineralisatiesnelheid gerelateerd aan het humusgehalte en oogstresten, bij de andere wordt de mineralisatiesnelheid geacht een constante te zijn bij een bepaalde temperatuur
    Progress and future plans of the project "management of nitrogen in acid low activity clay soils in the humid tropics for food crop production"
    Kang, B.T. ; Kruijs, A. van der; Heide, J. van der - \ 1986
    Haren : IB (Rapport / Instituut voor Bodemvruchtbaarheid 14-86)
    akkerbouw - bacteriën - zware kleigronden - veldgewassen - voedselproductie - humide klimaatzones - uitspoelen - stikstof - stikstofkringloop - stikstofmeststoffen - onderzoek - bodem - bodemvruchtbaarheid - subtropen - tropen - toekomst - arable farming - bacteria - clay soils - field crops - food production - humid zones - leaching - nitrogen - nitrogen cycle - nitrogen fertilizers - research - soil - soil fertility - subtropics - tropics - future
    ANIMO : agricultural nitrogen model
    Berghuijs-van Dijk, J.T. ; Rijtema, P.E. ; Roest, C.W.J. - \ 1985
    Wageningen : ICW (Nota / Institute for Land and Water Management Research 1671) - 86
    bacteriën - uitspoelen - modellen - stikstof - stikstofkringloop - onderzoek - bodem - bacteria - leaching - models - nitrogen - nitrogen cycle - research - soil
    The research project ''Nitrogen behaviour in soil in relatitin to oxygen, water, and temperature" of which results are presented in this report, was initiated by the werking group "Water, bodem en Lucht" of the Landinrichtingsdienst of the Netherlands. Purpose of the project was to provide possibilities to make predictions about long-term nitrate contamination of groundwater as a result of chosen scenarios in land and water use, taking into account the influences of environmental factors. For this purpose the presented model ANIMO has been developed. During the rnadelling process it became clear that the completed model ANIMO would also be able to give ether results, like nitrogen lead on surface waters and development of organic matter properties of a soil profile, so that it can be considered as a complete (although not in every aspect detailed) model of nitrogen behaviour.
    Metingen en berekeningen van afbraak van organische stof in grond
    Groenwold, J. ; Vos, J. - \ 1984
    Wageningen : CABO (CABO-verslag no. 54) - 25
    bacteriën - oogstresten - incorporatie - stikstofkringloop - organische verbindingen - kwantitatieve analyse - bodem - bodemchemie - bacteria - crop residues - incorporation - nitrogen cycle - organic compounds - quantitative analysis - soil - soil chemistry
    In een rotatie met suikerbieten voor aardappelen werd geconstateerd dat er meer en langere blauwkleuring van de grond optrad, veroorzaakt door anaerobe afbraak van het ondergeploegde bieteblad en de bietekoppen, dan in de andere rotaties. Uit laboratoriumproeven werd geconcludeerd dat belemmeringen in de zuurstofaanvoer eerder oorzaak hiervoor zijn dan een bijzondere verteringskarakteristiek van de bietenresten. Uit verder onderzoek bleek nog dat de grootste omzettingssnelheden plaatsvonden vlak na het onderploegen en in mei en juni
    Het modelleren van de stikstofkringloop in de bodem : ten behoeve van het voorspellen van de effecten van alternatieven in de landinrichting op de nitraatuitspoeling
    Berghuijs-van Dijk, J.T. - \ 1984
    Wageningen : ICW (Nota / Instituut voor Cultuurtechniek en Waterhuishouding 1526) - 40
    bodemchemie - bacteriën - computersimulatie - stikstofkringloop - simulatie - simulatiemodellen - soil chemistry - bacteria - computer simulation - nitrogen cycle - simulation - simulation models
    Uitkomsten van het project Stikstofhuishouding in de bodem in relatie tot de zuurstof-, warmte- en warmtehuishouding, afkomstig van de Werkgroep Water, Bodem en Lucht van de Landinrichtingsdienst
    Onderzoek naar het nitraatgehalte van het ondiepe grondwater in de omgeving van Achterberg
    Tusveld, M.C.L. ; Welling, S.E. - \ 1984
    Wageningen : L.H. - 44
    grondwater - chemische eigenschappen - waterkwaliteit - verontreinigingsbeheersing - grondwaterverontreiniging - bescherming - bodem - uitspoelen - stalmest - nitraten - stikstofkringloop - bacteriën - nederland - utrecht - gelderland - gelderse vallei - groundwater - chemical properties - water quality - pollution control - groundwater pollution - protection - soil - leaching - farmyard manure - nitrates - nitrogen cycle - bacteria - netherlands - utrecht - gelderland - gelderse vallei
    Een bestudering van het verloop van het nitraatgehalte van het ondiepe grondwater en bepaling van de menselijke invloed op de samenstelling van het ondiepe grondwater door het chloridegehalte hiervan te vergelijken met het nitraatgehalte; dit in verband met de eutrofiering van het grond- en oppervlaktewater door bemestingsgiten (in een gedeelte van de Gelderse Vallei)
    Aspects of the oxygen-tolerance of nitrogen fixation in Azotobacter vinelandii
    Scherings, G.H. - \ 1983
    Landbouwhogeschool Wageningen. Promotor(en): C. Veeger, co-promotor(en): H.B.C.M. Haaker. - Wageningen : Scherings - 109
    azotobacter - pseudomonadaceae - microbiologie - stikstofkringloop - azotobacter - pseudomonadaceae - microbiology - nitrogen cycle
    Following the pioneering physiological studies of Haaker et al. on the generation of reducing equivalents for nitrogenase in Azotobactervinelandii, it seemed desirable to further characterize interactions between the likely ultimate electron donors (flavodoxin and/or ferredoxin) and nitrogenase. Isolation of these proteins was therefore necessary. Flavo- and ferredoxin from A.vinelandii have been prepared to purity; as far as nitro genase was concerned, however, it was deemed that the O 2 -tolerant nitrogenase complex as isolated originally by Bulen and LeComte should render information more physiologically relevant than could be the case using highly puri fied nitrogenase components (Av 1 + Av 2 ). In chapter II, results are described suggesting that the Bulen-LeComte nitrogenase complex, with fully reduced fla vodoxin as a source of reducing equivalents, has regulatory properties not exhibited by a more highly purified (Av 1 + Av 2 ) complex, due to the presence of a 'contaminating' third protein.

    This third protein appeared to be the same as that shown by Haaker etal. to be responsible for the oxygen-tolerance of the nitrogenase complex. The spectral properties and molecular weight are shown in chapter II to be identical to that of the [2Fe-2S] ferredoxin isolated earlier by Shethna etal. who, however, did not ascribe any physiological function to this pro tein. In chapters III and IV, the interactions between Av 1 , Av 2 and the third protein are further characterized, as well as the conditions necessary to induce the reconstitution of an oxygen-tolerant complex from the purified proteins. The relation between the oxygen-tolerant complex and the so-called 'switched-off state' of nitrogenase activity in vivo is discussed.

    Simulatie van stikstofverdeling in de grond in winter en voorjaar
    Zandt, P.A. ; Willigen, P. de - \ 1981
    Haren : I.B. (Rapport / Instituut voor Bodemvruchtbaarheid no. 4-81) - 33
    bacteriën - denitrificatie - stikstof - stikstofkringloop - bodem - lente - winter - bacteria - denitrification - nitrogen - nitrogen cycle - soil - spring - winter
    Resultaten van berekeningen ten aanzien van het verloop van het minerale-stikstofgehalte in de bodem worden vergeleken met meetresultaten
    Rock-phosphate mobilization induced by the alkaline uptake pattern of legumes utilizing symbiotically fixed nitrogen
    Aguilar Santelises, A. - \ 1981
    Landbouwhogeschool Wageningen. Promotor(en): A. van Diest. - Wageningen : Aguilar Santelises - 111
    bodem - stikstof - peulvruchten - fabaceae - kationenwisseling - absorptie - natrium - diffusie - ionen - bodemkunde - natuurfosfaat - stikstofkringloop - bacteriën - soil - nitrogen - grain legumes - fabaceae - cation exchange - absorption - sodium - diffusion - ions - soil science - rock phosphate - nitrogen cycle - bacteria
    The ability of plants to exert a certain degree of selection when absorbing nutrients often has as a consequence that on an equivalence basis unequal quantities of cationic and anionic nutrients are absorbed. To maintain electroneutrality inside and outside its tissues, the plant absorbs or extrudes ions not considered as nutritive ones. As a result of such regulatory actions of the plant, the pH in the root environment can be affected which in turn can exert an i nfluence on the solubility and availability of nutrients.

    In this dissertation, attention is paid to the implications of utilization of symbiotically fixed N 2 by legumes for the usefulness of rock phosphates as phosphatic fertilizers. The chain of thoughts is, as follows: 1. originally present soil phosphate and soil nitrate enable legumes to form nodules in which symbiotic N 2 fixation can take place which for its further growth will make the host plant independent of any form of combined N (NH4+and/or NO3-) ; 2. when the legume has exhausted the initial NO3-supply, but can continue to grow because of the availability of symbiotically fixed N 2 , it will absorb more cationic than anionic nutrients; 3. on account of this cationic uptake pattern, the growth medium in the vicinity of absorbing roots will acidify; 4. as a result of this acidification alkaline rock phosphates, when added as fertilizer, might be partially solubilized; 5. because of this solubilization induced by N 2 fixation, rock phosphates might be more useful P sources for legumes than for other crops such as cereals, and they might also be more useful for legumes utilizing symbiotically fixed N 2 than for the saw legumes under conditions of an ample supply of NO 3 -N.

    In a series of experiments, it was investigated whether this chain of thoughts could be verified and, if so, which limiting factors could manifest themselves and how these might be eliminated. These experiments were conducted in greenhouses with the use of two growth media, namely pure quartz sand and a sandy loam low in P which was located at a depth of a few meters in a sand quarry near Lunteren. The experimental crops used were soybean, alfalfa, peanut, and maize. The phosphate fertilizers employed were triple superphosphate and alkaline rock phosphates from Mali and Morocco.

    In experiment 1, use was made of sand as growth medium, soybean as test crop and superphosphate as P fertilizer. It could be shown that, as long as the crop could make use of NO 3 -N, soybean exerted a pH-raising effect on the sand. Shortly after the stage at which the NO 3 -N was exhausted and the plants transferred to symbiotically fixed N 2 as N source, a decline in pH could be observed. In the first weeks of growth, the pH-values of rhizosphere- and non-rhizosphere sand were found to differ. Probably as a result of intensification of the root system, later on these differences disappeared.

    In experiment 2, an evaluation was made of the ability of soybean, grown m sand, to make use of P supplied in the form of the two rock phosphates. With an ample supply of NO 3 -N, the plants appeared to be unable to utilize these P sources, but this was different for plants utilizing symbiotically fixed N 2 , on account of the fact that these latter plants succeeded in acidifying their root environment. With the use of superphosphate, the growth of plants utilizing fixed N 2 was very poor, which could be ascribed to P toxicity. To compensate for the absence of NO3-as major anionic nutrient, these plants appeared to have absorbed excessive quantities of phosphate. In the case of NO 3 -fed plants, P uptake was less extreme.

    Experiment 3 was comparable to experiment 2, except that the sandy loam was used as growth medium. It appeared that in this case the acidifying effect of the plants utilizing fixed N 2 was insufficient to solubilize the rock phosphates used. The short duration of the experiment, the P-fixing capacity and the pH-buffering capacity of the soil, and a shortage of available soil phosphate were factors likely to be responsible for the negative results obtained in this experiment.

    Since peanut is often grown m light-textured soils having low pH- buffering capacities, this crop was chosen as test crop in experiment 4 to examine its ability to utilize P applied in the 3 different fertilizer form to sand. Even when the superphosphate quantity applied was reduced to me-half of that applied to soybean in a previous experiment, P toxicity was still noticeable. For unknown reasons, symbiosis between host plant and Rhizobium strain was insufficiently effective to bring about an acidification of the sand. As a result, solubilization of rock phosphates did not take place. It was furthermore observed that peanut belongs to the group of plants exhibiting a neutral uptake pattern (equivalent quantities of cationic and anionic nutrients absorbed) when N is absorbed as NO3-.

    In experiment 5, alfalfa was grown m the sandy loam. With this perennial crop, the acidification induced by plants utilizing fixed N 2 appeared large enough to enable alfalfa to make use of P applied in rock phosphate form. In the case of NO3-nutrition, the soil pH became high enough to render the sparsely soluble Mali rock phosphate largely unavailable to alfalfa. It could be concluded that the influence exerted by perennial legumes m the soil pH can be large enough to overcome a buffering capacity the soil may have.

    The possibility exists that in extremely poor soils, lack of available P prevents the development of nodules so that symbiotic N 2 fixation cannot take place. In such cases, application of a small quantity of soluble P fertilizer may be sufficient to put into motion the chain of reactions eventually resulting in solubilization of rock phosphate that was also applied. In experiment 6, a small quantity of 32P-labeled KH 2 PO 4 was added to sand or sandy loam which was placed in pots m top of a larger quantity of sand or soil to which either me of the two rock phosphates was added. With the use of sand as growth medium, it was found that with the aid of the small quantity of KH 2 PO 4 applied, soybean could indeed make better use of the rock phosphates. With the soil, such a priming effect of the starter-KH 2 PO 4 was not observed. More so than in other experiments, low light intensity constituted an obstacle to a normal development of the N 2 -fixing mechanism, thus reducing the ability of the root system of soybean to acidify, its root environment.

    It is known that vesicular- arbuscular mycorrhiza (VAM) can make a contribution to the P nutrition of plants growing m P-depleted soil or m soil to which sparsely soluble rock phosphate was applied. In experiment 7, it was examined whether the joint actions of Rhizobium and VAM in mobilizing soil P and P added as rock phosphate would be more effective than the single actions of each of the micro-organisms . The experimental crop was again alfalfa grown m the sandy loam. It was found that for the control treatment (no fertilizerP added) and for the Mali rock phosphate treatment the quantities of P absorbed by the plants were indeed largest when both Rhizobium and VAM were active. In the superphosphate- and Morocco rock phosphate treatments, VAM did not make a contribution to the P nutrition of the plants, which can be seen as an indication that the availability of these fertilizers was high enough to meet the requirements of the alfalfa plants without any aid rendered by VAM.

    In experiment 8, it was shown that maize, as an example of a crop that in the case of NO3-nutrition raises the pH of its root environment, lacks the ability to utilize P applied in rock phosphate form. In this respect, the behavior of maize is similar to that of leguminous crops, like soybean and alfalfa, when these crops are amply supplied with NO 3-N and do not utilize symbiotically fixed N 2 .

    The conclusion to be drawn from the results obtained is that alkaline rock phosphates are relatively useful as P sources to c-raps which are capable of acidifying their root environment. Legumes possess this ability, provided that they utilize symbiotically fixed N 2 . In such cases, they withdraw from the soil more cationic than anionic nutrients, thereby exerting an acidifying effect m their root environment.

    Such an ability to solubilize rock phosphates is, therefore, dependent m the extent to which N 2 fixation can take place. Such a fixation can be hampered by low light intensities, but also by lack of a small quantity of readily available phosphate needed by the young plants to build up an N 2 -fixation mechanism. Once such a mechanism is operative, it can indirectly make a contribution to the mobilization of alkaline rock phosphates when these have been applied to the soil. From the results obtained it appeared that the initiation of a chain of reactions eventually leading to the solubilization of rock phosphate can be brought about by adding a small quantity of superphosphate or by establishing a symbiosis of legume and VA mycorrhiza.

    The results obtained provide opportunities for those countries which possess alkaline rock phosphates that do not lend themselves to being used as basic materials for the manufacturing of superphosphates. Application of these rock phosphates creates a possibility to grow legumes with only a slight investment in the form of rock phosphate needed to supply the plants with two highly important and expensive nutrients, namely nitrogen and phosphate.

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