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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It depends: : effects of soil organic matter in aboveground-belowground interactions in agro-ecosystems
Gils, Stijn Herman van - \ 2017
University. Promotor(en): Wim van der Putten; David Kleijn. - Wageningen : Wageningen University - ISBN 9789463436526 - 176
soil organic matter - agroecosystems - aphidoidea - fertilizers - wheat - rape - crop yield - ecosystem services - nutrient availability - pest control - organic farming - organisch bodemmateriaal - agro-ecosystemen - kunstmeststoffen - tarwe - koolzaad - gewasopbrengst - ecosysteemdiensten - voedingsstoffenbeschikbaarheid - plagenbestrijding - biologische landbouw

Over the last decades agricultural production increased drastically due to the use of external inputs. However, the use of external inputs has high environmental costs and may negatively influence ecosystem processes such as pollination and pest control that underpin agricultural production. Soil organic matter has been proposed as a potential alternative to external inputs as it relates to multiple yield promoting ecosystem processes. The aim of my thesis is to assess whether and how soil organic matter content alters the effect of some ecosystem processes and external inputs on crop yield. I examined whether soil organic matter alters biomass of wheat and oilseed rape under fertilizer supply. Other biotic and abiotic factors that operate at different spatial and temporal scales are also included in some of these experiments. I found that under controlled conditions soil organic matter may reduce the positive effect of mineral fertilizer supply on crop biomass. The reduction changed with the presence or absence of a pathogenic root fungus, but not with drought stress. Moreover, soil organic matter enhances performance of aphids under controlled greenhouse conditions, but the enhancement was less than fertilizer supply. None of these controlled experiments, however, showed that soil organic matter can be an alternative to mineral fertilizer supply. Under field conditions soil organic matter did not strongly affect plant nutrient availability or performances of aphid and its natural enemies. The relation between soil organic matter and plant biomass in a greenhouse experiment did not change with organic management or the duration of it, neither did it change with pollinator visitation rate, an ecosystem process that is managed on the landscape scale. These results suggest that soil organic matter may relate to ecosystem services that influence crop yield, whereas these relations might not be significant under field conditions. Collectively, all these results suggest that the relation between soil organic matter content and ecosystem processes that benefit crop yield is highly context dependent. I propose future research may focus on (1) the quality of soil organic matter rather than the content per se and (2) the relation between soil organic matter content and crop yield under realistic conditions in a longer term.

Examining growth, yield and bean quality of Ethiopian coffee trees : towards optimizing resources and tree management
Bote, Adugna - \ 2016
University. Promotor(en): Niels Anten, co-promotor(en): Jan Vos; F.L. Ocho. - Wageningen : Wageningen University - ISBN 9789462578319 - 138
coffea - coffea arabica - trees - growth - yields - quality - radiation - nitrogen - agroecosystems - bomen - groei - opbrengsten - kwaliteit - straling - stikstof - agro-ecosystemen

Coffee (Coffeaarabica L.)bean production and quality are determined by a diversity of interacting factors (e.g. shade, nitrogen, crop traits). Bean yield increases with increase in radiation, but adequate fertilizer suppliesare needed to sustain the productivity. This thesis analysed coffee tree growth, bean production and bean quality in relation to different degrees of exposure to radiation and nitrogen supply. Growth of leaves and branches and properties of leaves such as specific leaf area, nitrogen content per unit leaf area and light-saturated rate of photosynthesis were determined. Radiation interception and nitrogen uptake were also determined as were radiation use efficiency and apparent nitrogen recovery. Tree biomass and coffee bean yield responded positively to both radiation and nitrogen supply. Abundant bean yield to the detriment of vegetative growth, however, resultedin biennial bearing in coffee trees. Effects of fruit load on coffee treegrowth and productivity were studied for two consecutive years and the resultshowed that competition between fruit growth and vegetative growth predisposed the trees for biennial bearing. Reduced vegetative growth when fruit load is high reduces the number of flower bearing nodes and hence yields in the next season. Coffee quality is a sum of favourable characteristics that satisfies requirements of different actors in the coffee chain and is the factor determining the price on the coffee market. This study has also examined coffee quality attributes in relation to radiation and nitrogen, fruit load manipulation, and genotype by environment (different altitudes) interactions. The result indicated that factors and conditions that support non-limiting supply of resources for bean to grow and a sufficient long period of maturation promote coffee bean quality. Overall, the study gained further understanding of coffee tree growth, yield and bean quality responses to aforementioned factors and explored traits that underlie the patterns. Further works are required to use the traits and describe the behaviour of coffee trees in different agro-ecosystems.

Co-creation in the practice, science and movement of agroecology
Milgroom, J. ; Bruil, Janneke ; Leeuwis, C. - \ 2016
Farming Matters 32 (2016)1. - ISSN 2210-6499 - p. 6 - 9.
agroecosystems - sustainability - family farms - farmers' knowledge - knowledge transfer - agricultural production systems - food production - lifelong learning - agro-ecosystemen - duurzaamheid (sustainability) - familiebedrijven, landbouw - kennis van boeren - kennisoverdracht - agrarische productiesystemen - voedselproductie - levenslang leren
Knowledge building is central to agroecology rooted in family farming. But why?
What type of knowledge, and whose knowledge is mobilised? This issue of
Farming Matters explores what we really mean by co-creation of knowledge in
agroecology, why it is so essential for today’s challenges, and how it takes place
around the world.
Bedrijfseconomisch perspectief de maat genomen
Burg, S.W.K. van den; Rood, G.A. ; Lienen, Frederiek van; Veldhuis-van Essen, C. - \ 2016
Tijdschrift Milieu : Vereniging van milieuprofessionals 22 (2016)3. - p. 30 - 32.
agro-ecosystemen - zeewierenteelt - voedselproductie - biomassa productie - ecosysteemdiensten - financieren - bedrijfseconomie - agroecosystems - seaweed culture - food production - biomass production - ecosystem services - financing - business economics
Het concept natuurlijk kapitaal maakt de maatschappelijke waarde van de goederen en diensten waarin de natuur voorziet zichtbaar. Maar is dit concept ook bruikbaar bij de ontwikkeling van sluitende verdienmodellen? Bij een bedrijfseconomische toepassing staan drie aandachtspunten centraal: de kosten van het gebruik van natuurlijk kapitaal in vergelijking tot concurrerende aanpakken, de mogelijkheid om de waarde van ecosysteemdiensten daadwerkelijk te verzilveren, en de bereidheid van afnemers en consumenten om te betalen voor de verbetering van ecosysteemdiensten.
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
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.
Conservation of predaceous Coccinellidae species in greenhouse ecosystems
Papanikolaou, N.E. ; Milonas, P.G. ; Meijer, R.J.M. - \ 2016
BioGreenhouse (Fact sheet BioGreenhouse 7) - 2 p.
organic farming - horticulture - greenhouse horticulture - plant health - natural enemies - habitats - coccinellidae - agroecosystems - biological control - pesticides - biologische landbouw - tuinbouw - glastuinbouw - plantgezondheid - natuurlijke vijanden - agro-ecosystemen - biologische bestrijding - pesticiden
Conservation of natural enemies is an important component of pest management, which can improve their efficacy against target pests. Conserving predaceous Coccinelidae species in agricultural ecosystems is used to enhance their biocontrol contribution. Favourable conditions in these habitats can contribute to a more efficient population regulation of several pests. Conservation efforts focus on discouraging emigration from a crop system and enhance retention time of coccinelids in periods with low prey availability. Thus, the management of agroecosystems should focus on providing resources in such temporal and spatial scale that may prevent their emigration or attract them in habitats. In addition, in a greenhouse ecosystem, another conservation action is to reduce mortality and sublethal effects caused by insecticides.
Agrobiodiversiteit en ecosysteemdiensten
Geertsema, W. ; Werf, W. van der; Bianchi, F.J.J.A. ; Rossing, W.A.H. ; Schaminée, J.H.J. - \ 2015
Vakblad Natuur Bos Landschap (2015)mei. - ISSN 1572-7610 - p. 41 - 43.
akkerranden - vegetatietypen - landschapselementen - agrobiodiversiteit - agrarische bedrijfsvoering - agro-ecosystemen - biodiversiteit - ecosysteemdiensten - landbouw - zuidhollandse eilanden - field margins - vegetation types - landscape elements - agro-biodiversity - farm management - agroecosystems - biodiversity - ecosystem services - agriculture
Steeds vaker klinkt de roep om agrarische producten te produceren met minder negatieve gevolgen voor milieu en biodiversiteit en bijvoorbeeld in de gewasbescherming meer gebruik te maken van ecologische processen. De aanwezige biodiversiteit in een landschap bepaalt in hoeverre deze processen benut kunnen worden voor ecologisch intensieve landbouw. In de Hoeksche Waard is er al ervaring mee.
Natuurlijk kapitaal als bron voor verdere vergroening van het GLB
Melman, D. ; Doorn, A.M. van; Buij, R. ; Gerritsen, A.L. ; Heide, M. van der; Bos, E.J. ; Martens, S. ; Blanken, H. ; Holt, H. ten - \ 2015
Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2641) - 178
agro-ecosystemen - agrarisch natuurbeheer - gebiedsgericht beleid - ecosysteemdiensten - inkomen van landbouwers - gemeenschappelijk landbouwbeleid - salland - veenkolonien - agroecosystems - agri-environment schemes - integrated spatial planning policy - ecosystem services - farmers' income - cap
Onderzocht is in hoeverre het waarderen en verzilveren van ecosysteemdiensten, de zogenaamde TEEB-benadering, bruikbaar is voor het genereren van mogelijkheden voor verdere vergroening van het GLB vanaf 2020. Hier zijn twee gebieden bij betrokken: Salland en de Veenkoloniën. In gebiedsbijeenkomsten zijn belangrijke ecosysteemdiensten geïdentificeerd en besproken.
The legacy of phosphorus: agriculture and future food security
Sattari, S.Z. - \ 2014
University. Promotor(en): Martin van Ittersum; Lex Bouwman, co-promotor(en): Ken Giller. - Wageningen : Wageningen University - ISBN 9789462570948 - 210
fosfor - fosfaten - kringlopen - graslanden - veldgewassen - agro-ecosystemen - voedselzekerheid - phosphorus - phosphates - cycling - grasslands - field crops - agroecosystems - food security

Growing global demand for food leads to increased concern regarding phosphorus (P), a finite and dwindling resource. Debate focuses on current production and use of phosphate rock rather than on the amount of P required to feed the world in the future. While the time scale of P depletion is debatable, a critical question beyond the physical availability of P is whether P resource depletion can be managed by sustainable consumption of P.

We quantified P demand for cropland as well as grassland in 2050 at global scale. Methods employed included an extensive analysis of historical, long-term P application and agricultural production data and a modeling approach that considers major P flows in a soil-crop system. We applied a simple two-pool soil P (DPPS) model to reproduce historical crop and grass P uptake as a function of P inputs from fertilizer and manure and to estimate P requirements for crop and grass production in 2050. Accounting for legacy P in estimation of the required fertilizer in cropland leads to a reduced fertilizer requirement compared with other studies that did not account for residual soil P. In Europe, Asia, Latin America and Oceania, crop production can benefit from the residual P. In contrast, in Africa more than a five-fold increase in P application is needed to achieve the target P uptake in 2050.

I conclude that the future P requirements from fertilizer in cropland increase less than crop production increases, whereas in grassland the opposite is true. This is because much of the P in animal manure spread in cropland originates from grassland. The transfer of (manure) P from grassland to cropland is not compensated with the transfer of P in livestock feed from cropland to grassland – resulting in soil P depletion of grassland.

To achieve the target crop and grass production in the next four decades a global cumulative P input from mineral fertilizer and manure of ca. 1200 and 1215 Tg is needed in cropland and grassland, respectively. The amount of mineral fertilizer P needed in cropland and grassland systems in total is estimated to be 1380 Tg until 2050, corresponding to 10700 Tg phosphate rock. This amount of phosphate rock is about 16% of the total phosphate rock reserves currently thought to be available on the planet. Thus, we will not immediately run out of P, but mineral fertilizer prices may increase, which may pose a serious challenge to regions with low soil P stocks.

Finally, to provide an example of potential solutions to the global P scarcity, China as a key player in P consumption and production is studied and the feasibility of efficient use of P in China’s agriculture is discussed.

Building on resilience principles for sustainable agriculture : a draft framework
Cuijpers, W.J.M. ; Koopmans, C.J. ; Erisman, J.W. - \ 2014
Driebergen : Louis Bolk Instituut - 47 p.
duurzame landbouw - biologische landbouw - agro-ecosystemen - duurzaamheid (sustainability) - biodiversiteit - sustainable agriculture - organic farming - agroecosystems - sustainability - biodiversity
This paper introduces and explores the possibilities of a concept that may bridge apparent divergences within the sustainable agriculture approach. Sustainable agriculture concepts may depart from different paradigms, varying from securing global and local resource availability, to maintaining functional integrity of farming systems. Likewise, many different terms have been suggested to address the sustainability of farming systems. This paper departs from the concept of resilience, and from this base explores principles of sustainable agriculture.
Meer voedsel en minder gif? Het kan!
Rabbinge, R. - \ 2014
Tijdschrift Milieu : Vereniging van milieuprofessionals 2014 (2014)3. - p. 6 - 7.
landbouwsector - agro-ecosystemen - ecologisch evenwicht - biopesticiden - gewasbescherming - biologische bestrijding - agricultural sector - agroecosystems - ecological balance - microbial pesticides - plant protection - biological control
Grote delen van de wereld kampen met een structureel gebrek aan voedsel. Tegelijkertijd is nog steeds in veel landbouwsystemen sprake van intensief gebruik van gewasbeschermingsmiddelen. Op beide fronten is enorme winst te boeken door radicaal te kiezen voor een ecologische benadering. Onder de noemer Best Ecological Means is deze ontwikkeling de laatste jaren in een stroomversnelling geraakt.
The potential of carbon sequestration to mitigate against climate change in forests and agro ecosystems of Zimbabwe
Mujuru, L. - \ 2014
University. Promotor(en): Rik Leemans, co-promotor(en): Marcel Hoosbeek. - Wageningen : Wageningen University - ISBN 9789461739285 - 209
koolstofvastlegging - klimaatverandering - bossen - agro-ecosystemen - mitigatie - koolstofvastlegging in de bodem - koolstofcyclus - koolstof - zimbabwe - carbon sequestration - climatic change - forests - agroecosystems - mitigation - soil carbon sequestration - carbon cycle - carbon

Climate change adversely affects human livelihoods and the environment through alteration of temperatures, rainfall patterns, sea level rise and ecosystem productivity. Developing countries are more vulnerable to climate change because they directly depend on agriculture and natural ecosystem products for their livelihoods. Mitigation of climate change impacts includes practices that can store carbon (C) in soil and biomass thus, reducing concentrations of atmospheric carbon dioxide (CO2) and other greenhouse gasses. In addition, planted and natural forests that store large amounts of C, can become key resources for mitigating and reducing vulnerability to climate change, whilst infertile agricultural soils require large amounts of chemical and/or organic fertilisers to improve productivity. Increasing awareness about climate change mitigation has led to realisation of a need for sustainable land management practices and promoting soil C sequestration to reduce the greenhouse effects.

The C storage potential of agricultural soils is compounded by conventional tillage practices, covering large areas with only small portions of fields dedicated to conservation farming practices. Maintaining soil and crop productivity under these agricultural systems becomes a major challenge especially in rain-fed arid and semi-arid regions, characterised by long annual dry spells. Conservation tillage practices, such as no-till and reduced tillage, have been reported to increase soil organic carbon (SOC) stocks in agricultural systems as they reduce soil disturbance, whereas conventional tillage has been criticised for causing soil C losses, accelerating soil erosion and displacing of soil nutrients, despite benefits, such as reduced soil compaction, weed control and preparation of favourable seedbed, which have been reported under conventional tillage. The identification of appropriate agricultural management practices is critical for realisation of the benefits of Soil C sequestration and reducing emissions from agricultural activities.

This thesis was planned to improve our understanding on how tillage, fertilisation, tree planting or natural forest conservation can enhance C sequestration and thus mitigate climate change. The main goal was to quantify the influence of tillage, fertilisation and plantation forestry practices on C and N dynamics in bulk soil and density separated soil organic matter (SOM) fractions relative natural forest. Tillage treatments under reduced tillage (RP), no tillage (DS) and conventional tillage (CT) were compared with natural forests (NF) in sandy Haplic Arenosols and clayey Rhodic Ferralsols. Impacts of fertilisation were assessed from three fertility treatments; unfertilised control (control), nitrogen fertiliser (N Fert) and nitrogen fertiliser plus cattle manure (N Fert + manure) in conventionally tilled fields on Arenosols (sandy soil) and Luvisols (clayey soil) along two soil fertility gradients. Similarly, C and N storage in tree farming was studied using a Pinus patula chronosequence. Soil sampling followed randomised complete block design with four replications in agricultural systems and two replicates in each plantation age stands and natural forest. Sodium polytungstate (density 1.6 g cm-3) was used to isolate organic matter into free light fraction (fLF), occluded light fraction (oLF) and mineral associated heavy fraction (MaHF). Carbon an N were analysed by dry combustion and C and N stocks calculated using bulk density, depth and C and N concentration. The RothC model was used to match density separated fractions with conceptual model pools for agricultural and natural forest soils.

Findings from tillage studies showed significantly larger C and N stocks in natural forests than tillage systems despite the open access use of the natural forests. The C and N stocks were significantly lower in sandy than clayey soils. At 0–10 cm depth, SOC stocks increased under CT, RP and DS by 0.10, 0.24, 0.36 Mg ha−1yr−1 and 0.76, 0.54, 0.10 Mg ha−1yr−1 on sandy and clayey soils respectively over a four year period while N stocks decreased by 0.55, 0.40, 0.56 Mg ha−1yr−1 and 0.63, 0.65, 0.55 Mg ha−1yr−1 respectively. Under prevailing climatic and management conditions, improvement of residue retention could be a major factor that can distinguish the potential of different management practices for C sequestration.

Among the fertility treatments, there were significantly higher SOC and TON stocks under N Fert and N Fert + manure at 0-10 cm soil depth in Luvisols. Although this effect was not significant at 20-30 cm and 30-50 cm depth. On Arenosols, N Fert had highest C and N at all depths except at 0-10 cm. The storage of C and N on Luvisols, followed: control < N Fert < N Fert + manure whereas Arenosols had control < N Fert + manure < N Fert. Compared with control, N Fert and N Fert + manure enhanced fLF C on homefields and outfields by 19%, 24% and 9%, 22% on Luvisols and 17%, 26% and 26%, 26% respectively on Arenosols. Homefields on Luvisols, under N Fert and N Fert + manure had similar equilibrium levels, which were 2.5 times more than control.

Forests play a major role in regulating the rate of increase of global atmospheric CO2 storing C in soil and biomass although the C storage potential varies with forest type and plant species composition. In this research, storage of C and N were highest in moist forest and lowest in the Miombo woodland. In both natural and planted forests, above ground tree biomass was the major ecosystem C pool followed by forest floor’s humus (H) layer. The mineral soil had 45%, 31% and 24% of SOC stored at the 0–10, 10–30 and 30–60 cm soil depths respectively. Stand age affected C and N storage significantly having an initial decline after establishment recovering rapidly up to 10 years, after which it declined and increased again by 25 years. Average soil C among the Pinus compartments was 12 kg m-2, being highest at 10 years and lowest in the 1 year old stands. Organic N was also highest at 10 years and least at 25 years. The proportional mass of fLF and oLF in Miombo woodlands was similar while the other stands had higher fLF than oLF. The highest LF was in the moist forest. In the Pinus patula stands the fLF C contributed between 22−25%, the oLF C contributed 8−16% and MaHF C contributed between 60−70% to total SOC. Carbon in MaHF and oLF increased with depth while the fLF decreased with depth in all except the 1 and the 10 year old stands. Conversion of depleted Miombo woodlands to pine plantations can yield better C gains in the short and long run whilst moist forests provide both carbon and biodiversity. Where possible moist forests should be conserved and enrichment planting done in degraded areas to sustain them and if possible the forests can be considered as part of future projects on reduced emission from deforestation and degradation (REDD+). It is believed that REDD+ can promote both conservation and socio economic welfare, including poverty alleviation by bringing together the development of the forest and climate change link in African forests and woodlands. The focus on the monetary valuation and payment for environmental services can contribute to the attraction of political support for soil conservation. Developing countries therefore, need to formulate enabling economic and institutional land management policies that have positive impacts on poverty alleviation, food security and environmental sustainability.

Soil C models are used to predict impacts of land management on C storage. The RothC 2.63 model was used for estimating SOC stock under selected land management practices on the clayey and sandy soils of Zimbabwe. There is greater potential to store more C in clayey soils than sandy soils and in practices that receive more organic inputs. Results show that the RothC model pool of HUM + IOM is related to the measured MaHF from density fractionation and that the model can be used to estimate SOC stock changes on Zimbabwean agricultural and forest soils. The relationship between equilibrium levels estimated by the RothC model and those estimated using the Langmuir equation was good. A 1.5˚ C rise in temperature was found to cause the A and B systems on clayey soils to sequester more C. The results also show that, when holding all the other factors constant, the model is sufficiently sensitive to a rise in temperatures with sandy soils reaching an equilibrium much earlier than clayey soils. The modelling approach represents one of the most promising methods for the estimation of SOC stock changes and allowed us to evaluate the changes in SOC in the past period on the basis of measured data. However, since the data were obtained from short term experiments (4−9 years), further ground validation can be hampered by the lack of long-term experimental trials in the southern African region. The deficiency of adequate experimental sites also limits further work on model uncertainties. The understanding soil quality and dynamics however, helps to design sustainable agricultural systems, while achieving the urgently needed win-win situation in enhancing productivity and sequestering C.

Panarchy rules? : rethinking resilience of agroecosystems
Apeldoorn, D.F. van - \ 2014
University. Promotor(en): Ken Giller, co-promotor(en): Kasper Kok; Marthijn Sonneveld. - Wageningen : Wageningen University - ISBN 9789461739179 - 137
agro-ecosystemen - duurzaamheid (sustainability) - bedrijfssystemen - organisch bodemmateriaal - wiskundige modellen - systeemanalyse - nederland - zimbabwe - agroecosystems - sustainability - farming systems - soil organic matter - mathematical models - systems analysis - netherlands

This thesis explores the applicability of the resilience perspective on agro-ecosystems dynamics. It start out by using the five heuristics of the resilience perspective on intensive agricultural systems. Simulations with a dynamic farm model suggest that conventional farming short cuts the adaptive cycle leading to an ‘incremental adaptation’ trap. Panarchy is therefore claimed as a leading heuristic to understand long-term dynamics and current management characteristics. This interaction of long-term dynamics with current management leads to an asymmetry in the landscape. This asymmetry leads to windows of opportunities for farmers. However, disregarding the cross-scale nature of the asymmetry might also lead to a cascade of events that undermine the resilience of the landscape as whole. The cross-scale interactions of landscape dynamics and farm management suggest a co-evolution of production intensity and landscape pattern. Moreover trajectories of intensification might even be linked to certain tipping points of combinations of landscape characteristics and management. Therefore the landscape asymmetry might yield insight in agro-ecosystem functioning. The landscape asymmetry potentially provides a level of self-organisation above the farm. However, identifying the asymmetry appeared to be problematic. Next to scale issues, the current pattern does not necessary result from current management, leading to a de-coupling of pattern and process. A re-coupling of management and landscape asymmetry can exploit positive feedbacks. I suggest the use of identity to locate asymmetries and to use space-time substitutions to experiment with the typical slow variables that shape the asymmetry.

The theory developed in this thesis is grounded on empirical farm management data and dynamical model simulation of intensive dairy farming in the Netherlands and small-holder systems in Zimbabwe.

Sustainable land management in dynamic agro-ecosystems: an Integrated, multi-scale socio-ecological analysis in Western Kenya highlands
Mutoko, M.C. - \ 2013
University. Promotor(en): Rik Leemans, co-promotor(en): Lars Hein; C.A. Shisanya. - S.l. : s.n. - ISBN 9789461737854 - 157
grondbeheer - duurzaamheid (sustainability) - duurzaam bodemgebruik - agro-ecosystemen - hulpbronnenbeheer - hooglanden - natuurbeheer - kenya - land management - sustainability - sustainable land use - agroecosystems - resource management - highlands - nature management

This study was motivated by the puzzlingly localised implementation of available Sustainable Land Management (SLM) practices despite the urgent need to reduce both land degradation and general poverty levels in the western highlands of Kenya. This research aimed to not only unravel reasons for the restricted geographical diffusion of SLM practices but also make concrete contributions to foster the promotion of SLM practices. Four specific research objectives and questions were formulated, and an integrated, multi-scale socio-ecological systems framework designed to address these issues at various levels. At the farming system level, high livelihood diversity was found as households increasingly depend on off-farm income opportunities. Besides, results show low production efficiency (average 40%) across five distinct farm types with important implications on intensification in land use. The off-farm oriented and resource-poor farm types were the least likely to invest in SLM practices on their farms. For the forest ecosystem, the estimated local economic benefits of around US$ 450 ha-1 yr-1 were considerably less than half the forgone returns from agricultural activities if the forest were to be converted. Arguably, continued protection of the Kakamega rainforest is justified because of the unknown value of its rich biodiversity and stored carbon in its system, which does not currently generate local economic benefits. At the landscape level, this study found that Vihiga District has undergone rapid land-use changes in the past 25 years. In particular, there has been a major conversion of forest and bare land to agricultural land use. Results show that productivity of tea and to a lesser extent, vegetables increased but the yields of maize and beans—the most common crops—oscillated around 1 ton ha-1. As a result, per capita food crop production dropped by 28% during the past two decades. Empirical findings demonstrate that high and increasing population pressure on land does not necessarily lead to agricultural intensification. Finally, with stakeholder participation, I evaluate local potentials for initiating collaborative action towards wider promotion of SLM practices in the western highlands of Kenya. A positive correlation (rho = 0.83) was found between stakeholder co-operation and the success level of past SLM projects. Reasonable prospects such as some technology adoption activities and organisation of local actors were established, which are necessary for triggering the transformation process to sustainable state of productivity. Based on synthesis of the key findings presented in this thesis, I conclude that the difficulty of achieving wider geographical diffusion of SLM practices in the study area can be attributed to four main reasons. First, there is a practical challenge to properly target the technologies to the right farming households in order to achieve the greatest impacts. Second, the rampant decrease in productive resources (land, capital and labour) for farm production coupled with low efficiencies in common farm enterprises has created an additional aspect of poverty traps—a ‘maize-centred’ poverty trap—making it difficult for a majority of farmers to invest meaningfully in SLM practices. Third, increasing pressure on land from population growth has failed to stimulate better land management practices and efficient resource use in agriculture possibly because the community attempts to make for the shortfall from off-farm activities or by accessing the almost free forest resources where available in the district. Lastly, the low collaboration level among key stakeholders involved in promotion of various components of SLM practices indicates a thin spread of efforts on the ground and unexpectedly delays an accelerated technological transition process. Therefore, I recommend a paradigm shift to embrace a broader, integrated and multi-stakeholder approach to solving the problem of land degradation in the study area and other similar agro-ecosystems in SSA; an approach that equally promotes improved farm productivity and creates off-farm income opportunities.

Exploration of agro-ecological options for improving maize-based farming systems in Costa Chica, Guerrero, Mexico
Flores Sanchez, D. - \ 2013
University. Promotor(en): Martin Kropff, co-promotor(en): Walter Rossing; Egbert Lantinga. - S.l. : s.n. - ISBN 9789461736758 - 205
bedrijfssystemen - maïs - zea mays - agro-ecologie - agro-ecosystemen - agronomie - intensivering - tussenteelt - mexico - farming systems - maize - agroecology - agroecosystems - agronomy - intensification - intercropping

Keywords: farm diagnosis, farming systems, soil degradation, intercropping, maize, roselle, legumes, nutrient management, vermicompost, crop residues, decomposition, explorations.

In the Costa Chica, a region of Southwest Mexico, farming systems are organized in smallholder units. The dominant cropping systems are based on maize (Zea mays L.), either as monocrop or intercropped with roselle (Hibiscus sabdariffa L.). Continuous cropping, and unbalanced fertilizer management systems with an inadequate replenishment of organic matter stocks have caused depletion of soil fertility and low crop yields. This thesis aimed to evaluate alternative cropping systems in terms of their contribution to on-farm productivity and to regeneration of the soil resource base. A set of approaches including farm surveys, on-farm experiments and model-based calculations was applied to characterize farming systems, identify main livelihood constraints and evaluate alternative cropping and farming systems. Main constraints identified were low yields of the major crops maize and roselle, low levels of nitrogen, potassium and soil organic matter, low resource use efficiencies, high production costs, limited marketing opportunities and low prices of products. To address prevailing production constraints, farmer-managed experiments were established in two communities within the region. In on-farm experiments the legumes Canavalia (Canavalia brasiliensis Mart. Ex Benth) and Mucuna (Mucuna pruriens L.var. utilis (Wall ex Wight) Burk) were intercropped in (added to) maize monocrops and maize-roselle mixtures. Intercropping did not decrease maize and roselle yields, and resulted in major reductions of the weed biomass, as well as an increased N uptake by both the food crops and the cropping system as a whole. In nutrient management trials different sources of macro-nutrients were evaluated in maize monocrops and maize-roselle intercrops. The results showed that improvements at field scale are feasible in the short term. Partial replacement of mineral NPK by organic NPK in the form of vermicompost, leading to 10-20% lower total N and K inputs, did not result in lower maize yields or a reduced uptake of N and K. This suggests that the N and K from the vermicompost were utilized better by the maize crop than from the inorganic fertilizers due to lower leaching losses. An experiment on decomposition of and N release from aboveground biomass residues, crop root residues and vermicompost demonstrated that, although the pattern of decomposition varied depending on the type of organic material, most of the N was released within the cropping season. Particularly for vermicompost, only one third of its initial dry mass was decomposed, thus leaving significant amounts of residues for soil organic matter build-up. Model-based explorations were developed to assess the consequences of the experimental results at the field level for whole-farm performance. Results for eight case study farms demonstrated that changes in crop nutrition and animal husbandry can increase farm family income and improve organic matter balances. However, strategies to achieve these goals most effectively were distinct. To maximize family income required fertilizer-based cropping strategies, while rebuilding soil organic matter required investment in retaining, obtaining and applying sources of organic matter. Farms responded differently to the explored options, highlighting the need for crop nutrition strategies that are adjusted to the soil fertility status of individual fields to be most efficient. The explorations also showed that for six out of the eight farms the minimum family income standard could not be attained. The results imply that the current emphasis in policies to support smallholders by fertilizer subsidies requires adjustment to include promotion of technology development aimed at regeneration of the degraded resource base and to offer off-farm economic options.

Farming systems ecology : towards ecological intensification of world agriculture
Tittonell, P.A. - \ 2013
Wageningen : Wageningen Universiteit - ISBN 9789461736178 - 40
duurzame landbouw - intensieve landbouw - agro-ecosystemen - ecosystemen - voedselzekerheid - bedrijfssystemen - voedselproductie - sustainable agriculture - intensive farming - agroecosystems - ecosystems - food security - farming systems - food production
The model of intensification that is deeply rooted in the mind of scientists from the green revolution generation is obsolete. We need to think outside the box. Agriculture needs knowledge-intensive management systems to improve food security and incomes in the South, and to reduce the dependence on external (fossil fuel) inputs in the North. The design of landscapes that support an ecologically intensive agriculture creates opportunities for synergies between food production and ecosystem services. Most importantly, this can contribute to detoxify or food and the environment.
Influences of agricultural management practices on Arbuscular Mycorrhiza Fungal symbioses in Kenyan agro-ecosystems
Muriithi-Muchane, M.N. - \ 2013
University. Promotor(en): Thomas Kuijper, co-promotor(en): B. Vanlauwe; J. Jefwa. - S.l. : s.n. - ISBN 9789461735133 - 201
vesiculair-arbusculaire mycorrhizae - mycorrhizae - agro-ecosystemen - organische verbeteraars - stikstofmeststoffen - kunstmeststoffen - schimmels - plantenvoeding - bodemvruchtbaarheid - bodembiologie - gewasproductie - bodemstructuur - bodemkwaliteit - kenya - vesicular arbuscular mycorrhizas - mycorrhizas - agroecosystems - organic amendments - nitrogen fertilizers - fertilizers - fungi - plant nutrition - soil fertility - soil biology - crop production - soil structure - soil quality

Conservation agriculture (CA) and integrated soil fertility management (ISFM) practices are receiving increased attention as pathways to sustainable high-production agriculture in sub-Saharan Africa. However, little is known about the effects of these practices on arbuscular mycorrhizal fungi (AMF). The study aimed at understanding the long-term effects of (i) ISFM and CA on AMF communities and functioning, and on glomalin concentrations. The study also aimed at understanding the (ii) role of AMF in soil aggregation, plant nutrition and crop yield under field conditions and (iii) combined effect of AMF and earthworms on soil aggregation, plant nutrition and crop yield under greenhouse conditions. The study was conducted in two long-term field trials. The ISFM trial was in Kabete (central Kenya) and compared fertilization (nitrogen and phosphorus) and organic amendments (farmyard manure, crop residue) for 32 years, while the CA trial was in Nyabeda (western Kenya) and compared effect of tillage (conventional versus no-tillage), residue application, cropping system (monocropping versus rotation) and N-fertilization for 5 years. Long-term use of mineral fertilizer and organic amendments, as well as tillage and N fertilization altered AMF species composition, but the changes were relatively minor. Organic amendments alone or in combination with NP fertilization increased AMF incidence, whereas no-tillage in the presence of residue increased spore abundance and root colonization. N fertilization increased root colonization but had a negative effect on spore abundance and species richness. Crop rotation had no effect on AMF. Glomalin was also sensitive to management, but the response was site-specific. Glomalin responded more to CA in Nyabeda than ISFM in Kabete. N fertilization and residue increased glomalin, especially under conventional tillage. Path analysis indicated that AMF symbiosis and glomalin enhanced soil aggregation and crop nutrition and yield in both sites. The positive role of AMF on crop nutrition was stronger in Kabete than Nyabeda. However, yield and nutrient use efficiency were (very) low in Kabete. There was no interaction between AMF and earthworms on soil aggregation, but AMF enhanced soil aggregation. AMF interacted positively with the epigeic earthworm to enhance nutrient uptake and biomass production, but the endogeic earthworm negatively affected AMF symbiosis and function. The study highlights the potential of ISFM and CA practices in enhancing AMF diversity and activity, and indicates factors limiting AMF functioning under ISFM and CA systems. While AMF are important for agro-ecosystem functioning, remedying the non-responsive character of soils, especially Kabete, through judicious management of nitrogen and organic amendments remains a first priority.

Modeling the effects of saline groundwater and irrigation water on root zone salinity and sodicity dynamics in agro-ecosystems
Shah, S.H.H. - \ 2013
University. Promotor(en): Sjoerd van der Zee, co-promotor(en): R.W. Vervoort. - S.l. : s.n. - ISBN 9789461735256 - 201
grondwater - zout water - modelleren - irrigatiewater - wortels - zoutgehalte - agro-ecosystemen - bodemfysica - bodemzoutgehalte - groundwater - saline water - modeling - irrigation water - roots - salinity - agroecosystems - soil physics - soil salinity

Recent trends and future projections suggest that the need to produce more food and fibre for the world’ s expanding population will lead to an increase in the use of marginal-quality water and land resources (Bouwer, 2000; Gupta and Abrol, 2000; Wild, 2003). This is particularly relevant to less-developed, arid and semi-arid countries, in which problems of soil and water quality degradation are common (Qadir and Oster, 2004). The aim, therefore, should be to increase yield per unit of land rather than the area cultivated. More efforts are needed to improve productivity as more lands are becoming degraded. It is estimated that about 15% of the total land area of the world has been degraded by soil erosion and physical and chemical degradation, including soil salinization (Wild, 2003).

The main sources of soil salinity and sodicity development are groundwater and irrigation water. In discharge areas of the landscape, water exits from groundwater to the soil surface bringing the salts dissolved in it. The driving force for upward movement of water and salts is evaporation from the soil plus plant transpiration. Salt accumulation is high when the water table depth is less than a threshold. However, this threshold depth may vary depending on soil hydraulic properties and climatic conditions. Groundwater associated salinity and sodicity affects around 350 X 104km2in the world (Szabolcs, 1989).

In this thesis, the focus is to quantify and understand the salinity and sodicity dynamics, and the feedback on dynamics in groundwater dependent agro-ecosystems. First we have considered the impact of salt coming from groundwater on capillary fluxes and on the root zone water and salt dynamics. Groundwater can be a source of both water and salts in semi-arid areas, and therefore capillary pressure induced upward water flow may cause root zone salinization. To identify which conditions result in hazardous salt concentrations in the root zone, we combined the mass balance equations for salt and water, further assuming a Poisson-distributed daily rainfall and brackish groundwater quality. For the water fluxes (leaching, capillary upflow, and evapotranspiration), we account for osmotic effects of the dissolved salt mass using Van‘t Hoff’s law. Root zone salinity depends on salt transport via capillary flux and on evapotranspiration, which concentrates salt in the root zone. Both a wet climate and shallow groundwater lead to wetter root zone conditions, which in combination with periodic rainfall enhances salt removal by leaching. For wet climates, root zone salinity (concentrations) increases as groundwater is more shallow (larger groundwater influence). For dry climates, salinity increases as groundwater is deeper due to a drier root zone and less leaching. For intermediate climates, opposing effects can push the salt balance in either way. Root zone salinity increases almost linearly with groundwater salinity. With a simple analytical approximation, maximum concentrations can be related with the mean capillary flow rate, leaching rate, water saturation and groundwater salinity, for different soils, climates and groundwater depths.

A Soil sodicity (quantified by ESP) model based on the soil salinity model (as discussed above) has been developed. For sodicity calculations, we have used the Gapon equation favored in salinity research. The simulation results show that soil salinity and sodicity development in groundwater driven agro-ecosystems play a major role in soil structure degradation. To identify which conditions can make soil sodic, we have modeled the coupled water, salt, and cation balances. The root zone salinity Cand sodicity ESPgradually change to their long term average values. These long term average values are independent of the cation exchange capacity CEC. The rate of change depends inversely on the size of the root zone reservoir, i.e., on root zone thickness for C, and additionally on CEC, for ESP.Soil type can have a large effect on both the rate of approach of the long term steady state salinity and sodicity, and on the long term levels, as it affects the incoming and out-going water and chemical fluxes. Considering two possible sources of salts, i.e., groundwater and irrigation water (here represented by rainfall), the long term salt concentration Cof the root zone corresponds well with a flux weighted average of infiltrating and upflowing salt mass divided by the average water drainage. In full analogy, the long term ESPcan be approximated very well for different groundwater depths and climates. A more refined analytical approximation, based on the analytical solution of the water balance of Vervoort and Van der Zee(2008), leads to a quite good approximation of long term salinity and sodicity, for different soils, groundwater depths, and climates.

Modeling is an efficient tool to investigate water and solute movement in groundwater driven agro-ecosystems. However, in most available models (SWAP,MODFLOW/MT3D) continuing degradation of soil hydraulic properties as a result of rising Na+concentrations is ignored. Disregarding the soil hydraulic degradation due to sodicity level in some cases makes modeling water and solute movement within the soil profile questionable. We have translated the effects of soil salinity and sodicity into reduction in saturated hydraulic conductivity to quantify the feedback effects of reduction in saturated hydraulic conductivity on root zone fluxes, salinity, and sodicity under different groundwater depths and climates of Oenpelli and Tennant Creek Airport located in the North Territory of Australia. The reduction in saturated hydraulic conductivity due to salinity and sodicity (Ks(C,ESP))has been calculated by using the procedure developed by McNeal(1968). The significant feedback effects of Ks(C,ESP) on salt concentration and soil ESPdepend on many important parameters like groundwater depth, leaf area index, weather seasonality and non-seasonality, and soil type. Out of these important parameters, weather seasonality is the main driver that can develop significant feedback effects of Ks(C,ESP) onsalt concentration and soil ESP. Furthermore, Ks(C,ESP) although decreasing the capillary flux, leaching flux, and evapotranspiration, it increases the magnitude of runoff. Also when Ks(C,ESP)affects both capillary and leaching flux under seasonal rainfall, the feedback effects are significant compared to the partial feedback (Ks(C,ESP)affects only leaching flux, but not capillary flux).

In the second theme of this thesis, we have focused on optimizing irrigation water between two farms under water scarcity and salinity regimes. In arid and semi-arid regions, irrigation water is scarce and often saline. To reduce negative effects on crop yields, the irrigated amounts must include water for leaching and therefore exceed evapotranspiration. The leachate (drainage) water returns to water sources such as rivers or groundwater aquifers and increases their level of salinity and the leaching requirement for irrigation water of any sequential user. We develop a sequential (upstream-downstream) model of irrigation that predicts crop yields and water consumption and tracks the water flow and level of salinity along a river dependent on irrigation management decisions. The model incorporates an agro-physical model of plant response to environmental conditions including feedbacks. For a system with limited water resources, the model examines the impacts of water scarcity, salinity and inefficient application on yields for specific crop, soil, and climate conditions. As a general pattern we find that, as salinity level and technical inefficiency increase, the system benefits when upstream farms use less water than is available to them, to provide downstream farms with more and better quality water. We compute the marginal value of water, i.e. the price water that would command on a market, for different levels of water scarcity, salinity and levels of water loss.

In summary this thesis aims to understand theoretically how soil salinity and sodicity develop under different climates, groundwater depths, soil types, root zone thicknesses, and different groundwater salinities. The developed salinity sodicity model can be applied in potential salt affected areas to predict the long term salinity, sodicity trends. Furthermore, quantification of feedback effects of reduction in saturated hydraulic conductivity (Ks(C,ESP)) on root zone fluxes, salinity, and sodicity guide us towards better management of soil, vegetation, and irrigation/groundwater.

Soil Ecology and Ecosystem Services
Wall, D.H. ; Bardgett, R.D. ; Behan-Pelletier, V. ; Herrick, J.E. ; Jones, T.H. ; Ritz, K. ; Six, J. ; Strong, D.R. ; Putten, W.H. van der - \ 2012
Oxford : Oxford University Press - ISBN 9780199575923 - 406
bodemecologie - bodembiologie - ecosysteemdiensten - agro-ecosystemen - biologische bodemactiviteit - bodemflora - bodembiodiversiteit - plantengenetica - soil ecology - soil biology - ecosystem services - agroecosystems - biological activity in soil - soil flora - soil biodiversity - plant genetics
This book synthesizes contributions from leading soil scientists and ecologists, describing cutting-edge research that provides a basis for the maintenance of soil health and sustainability. It covers these advances from a unique perspective of examining the ecosystem services produced by soil biota across different scales - from biotic interactions at microscales to communities functioning at regional and global scales. The book leads the user towards an understanding of how the sustainability of soils, biodiversity, and ecosystem services can be maintained and how humans, other animals, and ecosystems are dependent on living soils and ecosystem services.
Assessing recovery potential of aquatic macroinvertebrate populations using ecological models
Galic, N.G. - \ 2012
University. Promotor(en): Paul van den Brink, co-promotor(en): Hans Baveco. - S.l. : s.n. - ISBN 9789461732286 - 247
macrofauna - waterinvertebraten - populatiedynamica - pesticiden - ecosysteemdiensten - ecologische risicoschatting - modellen - agro-ecosystemen - aquatic invertebrates - population dynamics - pesticides - ecosystem services - ecological risk assessment - models - agroecosystems
Doordat de groeiende wereldbevolking een steeds grotere druk op natuurlijke ecosystemen legt, wordt de vraag naar een goede methode voor het beoordelen van de mogelijkheid tot herstel van een systeem steeds groter. Dit is vooral relevant voor agrarische ecosystemen welke traditioneel als functie hebben om voedsel voor de menselijke populatie te produceren. Agrarische ecosystemen leveren echter ook andere ecosysteemdiensten zoals omzettingen van nutriënten, bestuiving, het op peil houden van een bepaalde bodemkwaliteit en structuur, maar ook esthetische en recreatieve diensten, waarvan de duurzaamheid moet worden gewaarborgd.
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