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.
Socio-Cultural and Economic Valuation of Ecosystem Services Provided by Mediterranean Mountain Agroecosystems
Bernues, A. ; Rodriguez-Ortega, T. ; Ripoll Bosch, R. ; Alfnes, F. - \ 2015
The aim of this work was to elucidate the socio-cultural and economic value of a number of ecosystem services delivered by mountain agroecosystems (mostly grazing systems) in Euro-Mediterranean regions. We combined deliberative (focus groups) and survey-based stated-preference methods (choice modelling) to, first, identify the perceptions of farmers and other citizens on the most important ecosystem services and, second, to value these in economic terms according to the willingness to pay of the local (residents of the study area) and general (region where the study area is located) populations. Cultural services (particularly the aesthetic and recreational values of the landscape), supporting services (biodiversity maintenance) and some regulating services (particularly fire risk prevention) were clearly recognized by both farmers and citizens, with different degrees of importance according to their particular interests and objectives. The prevention of forest fires (<50% of total willingness to pay) was valued by the general population as a key ecosystem service delivered by these agroecosystems, followed by the production of specific quality products linked to the territory (<20%), biodiversity (<20%) and cultural landscapes (<10%). The value given by local residents to the last two ecosystem services differed considerably (<10 and 25% for biodiversity and cultural landscape, respectively). The Total Economic Value of mountain agroecosystems was <120 J person21 year21, three times the current level of support of agro-environmental policies. By targeting and quantifying the environmental objectives of the European agri-environmental policy and compensating farmers for the public goods they deliver, the so-called ‘‘green’’ subsidies may become true Payments for Ecosystems Services.
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.
A Multi-Criteria Index for Ecological Evaluation of Tropical Agriculture in Southeastern Mexico
Huerta, E. ; Kampichler, C. ; Ochoa-Gaona, S. ; Jong, B. de; Hernandez-Daumas, S. ; Geissen, V. - \ 2014
PLoS One 9 (2014)11. - ISSN 1932-6203
land-use change - farming systems - sustainability indicators - cropping systems - soil properties - food security - fuzzy-logic - management - agroecosystems - biodiversity
The aim of this study was to generate an easy to use index to evaluate the ecological state of agricultural land from a sustainability perspective. We selected environmental indicators, such as the use of organic soil amendments (green manure) versus chemical fertilizers, plant biodiversity (including crop associations), variables which characterize soil conservation of conventional agricultural systems, pesticide use, method and frequency of tillage. We monitored the ecological state of 52 agricultural plots to test the performance of the index. The variables were hierarchically aggregated with simple mathematical algorithms, if-then rules, and rule-based fuzzy models, yielding the final multi-criteria index with values from 0 (worst) to 1 (best conditions). We validated the model through independent evaluation by experts, and we obtained a linear regression with an r(2) = 0.61 (p = 2.4e-06, d.f. = 49) between index output and the experts' evaluation.
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.
Earthworms increase plant production: a meta- analysis
Groenigen, J.W. van; Lubbers, I.M. ; Vos, H.M.J. ; Brown, G.G. ; Deyn, G.B. de; Groenigen, K.J. van - \ 2014
Scientific Reports 4 (2014). - ISSN 2045-2322
ecosystem services - soil carbon - n pools - management - nitrogen - growth - agroecosystems - agriculture - communities - tolerance
To meet the challenge of feeding a growing world population with minimal environmental impact, we need comprehensive and quantitative knowledge of ecological factors affecting crop production. Earthworms are among the most important soil dwelling invertebrates. Their activity affects both biotic and abiotic soil properties, in turn affecting plant growth. Yet, studies on the effect of earthworm presence on crop yields have not been quantitatively synthesized. Here we show, using meta-analysis, that on average earthworm presence in agroecosystems leads to a 25% increase in crop yield and a 23% increase in aboveground biomass. The magnitude of these effects depends on presence of crop residue, earthworm density and type and rate of fertilization. The positive effects of earthworms become larger when more residue is returned to the soil, but disappear when soil nitrogen availability is high. This suggests that earthworms stimulate plant growth predominantly through releasing nitrogen locked away in residue and soil organic matter. Our results therefore imply that earthworms are of crucial importance to decrease the yield gap of farmers who can't -or won't- use nitrogen fertilizer.
'Geen toekomst voor industriële landbouw' : zomercollege
Korthals, Michiel - \ 2014
food production - agricultural situation - ethics - animal welfare - agroecosystems - agroindustrial sector - livestock farming - animal production
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.

Peasant-driven agricultural growth and food sovereignty
Ploeg, J.D. van der - \ 2014
The Journal of Peasant Studies 41 (2014)6. - ISSN 0306-6150 - p. 999 - 1030.
rural-development - self-employment - latin-america - china - agroecosystems - construction - questions - crisis
The concept of food sovereignty presents us with an important theoretical and practical challenge. The political economy of agriculture can only take up this gauntlet through improving its understanding of the processes of agricultural growth. It is very difficult to address the issue of food sovereignty without such an understanding. Developing such an understanding involves (re)combining the political economy of agriculture with the Chayanovian approach. This paper gives several explanations (all individually valid but stronger in combination) as to why peasant agriculture results in sturdy and sustainable growth and also identifies the factors that undermine this capacity. The paper also argues that peasant agriculture is far from being a remnant of the past. While different peasantries around the world are shaped and reproduced by today's capital (and more specifically by current food empires), they equally help to shape and contribute to the further unfolding of the forms of capital related to food and agriculture. It is important to understand this two-way interaction between capital and peasant agriculture as this helps to ground the concept of food sovereignty. The article argues that the capacity to produce enough food (at different levels, distinguishing different needs, and so on) needs to be an integral part of the food sovereignty discourse. It concludes by suggesting that peasant agriculture has the best potential for meeting food sovereignty largely because it has the capacity to produce (more than) sufficient good food for the growing world population and that it can do so in a way that is sustainable.
Hoogleraar Pablo Tittonell over de transitie naar duurzame landbouw : duurzame voedselvoorziening vraagt om herontwerp van landbouw en wetenschap
Tittonell, Pablo - \ 2014
sustainable agriculture - agroecosystems - food production - organic farming - food security - farming systems - intensive farming
Habitat functionality for the ecosystem service of pest control: reproduction and feeding sites of pests and natural enemies
Bianchi, F.J.J.A. ; Schellhorn, N.A. ; Cunningham, S.A. - \ 2013
Agricultural and Forest Entomology 15 (2013)1. - ISSN 1461-9555 - p. 12 - 23.
agricultural landscapes - coccinellidae - agroecosystems - biodiversity - assemblages - coleoptera - density - aphids - sinks
1 Landscape management for enhanced natural pest control requires knowledge of the ecological function of the habitats present in the landscape mosaic. However, little is known about which habitat types in agricultural landscapes function as reproduction habitats for arthropod pests and predators during different times of the year. 2 We studied the arthropod assemblage on six crops and on the seven most abundant native plant species in two landscapes over 1 year in Australia. Densities of immature and adult stages of pests and their predators were assessed using beat sheet sampling. 3 The native plants supported a significantly different arthropod assemblage than crops. Native plants had higher predator densities than crops over the course of the year, whereas crops supported higher pest densities than the native plants in two out of four seasonal sampling periods. Crops had higher densities of immature stages of pests than native plants in three of four seasonal sampling periods, implying that crops are more strongly associated with pest reproduction than native plants. Densities of immature predators, excluding spiders, were not different between native plants and crops. Spiders were, however, generally abundant and densities were higher on native plants than on crops but, because some species disperse when immature, there is less certainty in identifying their reproduction habitat. 4 Because the predator to pest ratio on native plant species showed little variation, and spatial variation in arthropod assemblages was limited, the predator support function of native vegetation may be a general phenomenon. Incentives that maintain and restore native remnant vegetation can increase the predator to pest ratio at the landscape scale, which could enhance pest suppression in crops.
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