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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    When yield gaps are poverty traps: The paradigm of ecological intensification in African smallholder agriculture
    Tittonell, P.A. ; Giller, K.E. - \ 2013
    Field Crops Research 143 (2013). - ISSN 0378-4290 - p. 76 - 90.
    soil fertility management - nutrient use efficiencies - resource use efficiency - western kenya - conservation agriculture - exploring diversity - semiarid tropics - different scales - farming systems - field-scale
    Yield gaps are pervasive in African smallholder agriculture, and are large for almost all crops in all regions. There is consensus that poor soil fertility and nutrient availability are the major biophysical limitations to agricultural production in the continent. We identify two major yield gaps: (1) the gap between actual yields (YA) and the water-limited yield potential (Yw), which is the maximum yield achievable under rainfed conditions without irrigation if soil water capture and storage is optimal and nutrient constraints are released, and (2) The gap between YA, and a locally attainable yield (YL) which corresponds to the water and nutrient-limited yields that can be measured in the most productive fields of resource endowed farmers in a community. Estimates of these two yield gaps are given for major crops, together with a framework for how yield gaps can be estimated in a pragmatic way for different farming systems. The paradigm of ecological intensification which focuses on yield potential, soil quality and precision agriculture is explored for the African context. Our analysis suggests that smallholder farmers are unable to benefit from the current yield gains offered by plant genetic improvement. In particular, continued cropping without sufficient inputs of nutrients and organic matter leads to localised but extensive soil degradation and renders many soils in a non-responsive state. The lack of immediate response to increased inputs of fertiliser and labour in such soils constitutes a chronic poverty trap for many smallholder farmers in Africa. This necessitates a rethink for development policy aimed to improve productivity and address problems of food insecurity.
    Conservation Agriculture in mixed crop–livestock systems: Scoping crop residue trade-offs in Sub-Saharan Africa and South Asia
    Valbuena, D.F. ; Erenstein, O. ; Homann-Kee Tui, S. ; Abdoulaye, T. ; Claessens, L.F.G. ; Duncan, A.J. ; Gerard, B. ; Rufino, M. ; Teufel, N. ; Wijk, M.T. van - \ 2012
    Field Crops Research 132 (2012). - ISSN 0378-4290 - p. 175 - 184.
    smallholder farming systems - soil fertility management - pressure - food - productivity - strategies - community - dynamics - patterns - zimbabwe
    Conservation Agriculture (CA) is being advocated to enhance soil health and sustain long term crop productivity in the developing world. One of CA's key principles is the maintenance of soil cover often by retaining a proportion of crop residues on the field as mulch. Yet smallholder crop–livestock systems across Africa and Asia face trade-offs among various options for crop residue use. Knowledge of the potential trade-offs of leaving more residues as mulch is only partial and the objective of this research is to address some of these knowledge gaps by assessing the trade-offs in contrasting settings with mixed crop–livestock systems. The paper draws from village surveys in 12 sites in 9 different countries across Sub-Sahara Africa and South Asia. Sites were clustered into 3 groups along the combined population and livestock density gradients to assess current crop residue management practices and explore potential challenges to adopting mulching practices in different circumstances. Results show that although high-density sites face higher potential pressure on resources on an area basis, biomass production tends to be more substantial in these sites covering demands for livestock feed and allowing part of the residues to be used as mulch. In medium-density sites, although population and livestock densities are relatively lower, biomass is scarce and pressure on land and feed are high, increasing the pressure on crop residues and their opportunity cost as mulch. In low-density areas, population and livestock densities are relatively low and communal feed and fuel resources exist, resulting in lower potential pressure on residues on an area basis. Yet, biomass production is low and farmers largely rely on crop residues to feed livestock during the long dry season, implying substantial opportunity costs to their use as mulch. Despite its potential benefit for smallholder farmers across the density gradient, the introduction of CA-based mulching practices appears potentially easier in sites where biomass production is high enough to fulfil existing demands for feed and fuel. In sites with relatively high feed and fuel pressure, the eventual introduction of CA needs complementary research and development efforts to increase biomass production and/or develop alternative sources to alleviate the opportunity costs of leaving some crop residues as mulch.
    The political ecology of land management in the oil palm based cropping system on the Adja Plateau in Benin. NJAS - Wageningen
    Yemadje, H.R.M. ; Crane, T.A. ; Vissoh, V.P. ; Mongbo, R.L. ; Richards, P. ; Kossou, D.K. ; Kuyper, T.W. - \ 2012
    NJAS Wageningen Journal of Life Sciences 60-63 (2012). - ISSN 1573-5214 - p. 91 - 99.
    soil fertility management - tenure - ghana - farmers - gender - wenchi
    The Adja plateau (Benin) is densely populated by tenant and landowner farmers engaged in oil palm based cropping. Landowners use oil palm sap for the production of sodabi (a local spirit), and an oil palm fallow (if no crops are grown beneath the palms) to restore soil fertility. In this area, growing oil palm for its oil is uncommon. Tenants access the land under specific contracts but are not allowed to plant oil palm. They grow food crops beneath the oil palm and extend the cropping period by severely pruning the palms because their right to grow food crops terminates when the palms reach a height of 2 m. The competing claims between landowners and tenants and between oil palm and annual food crops result in conflicts over practices that either degrade or restore soil fertility. Using a political ecology perspective, we examined how two overlapping institutions shape access to and management of the land: the customary tenure system and the legal system that was introduced to regulate titling and contracting. These institutions have divergent implications for tenants and landowners, in terms of both social equity and land management practices. The implications of this institutional patchwork (bricolage) for joint learning to achieve sustainable agriculture are discussed.
    Liever zorgen vóór dan óver organische stof : beheer van organische stof op het melkveebedrijf
    Verloop, J. ; Oenema, J. - \ 2012
    V-focus 9 (2012)5. - ISSN 1574-1575 - p. 34 - 36.
    melkveehouderij - melkveebedrijven - bodemvruchtbaarheidsbeheer - organische stof - dierlijke meststoffen - dairy farming - dairy farms - soil fertility management - organic matter - animal manures
    Sinds 2006 gelden gebruiksnormen voor stikstof en fosfaat, die grenzen stellen aan de aanwending van organische mest op de bodem. Deze regels hebben indirect gevolgen voor de aanvoer van organische stof met dierlijke mest naar de bodem. Dit leidt soms tot zorg over de bodemvruchtbaarheid op lange termijn. Blijft het organische stofgehalte in de bodem wel op een goed niveau? Koeien & Kansen-deelnemers lopen voor op de bestaande regelgeving om problemen in een vroeg stadium te onderkennen. In dit artikel schetsen we de ontwikkelingen en gaan we in op het beheer, in het bijzonder voor bedrijven op droge zandgrond.
    30 vragen en antwoorden over bodemvruchtbaarheid
    Schils, R.L.M. - \ 2012
    Wageningen : Alterra, Wageningen-UR - 143
    bodemvruchtbaarheid - bodemvruchtbaarheidsbeheer - organische stof - bodembiologie - bemesting - voedingsstoffen - overheidsbeleid - mestbeleid - voedselproductie - biomassa productie - akkerbouw - melkveehouderij - biobased economy - biologische landbouw - grondbewerking - soil fertility - soil fertility management - organic matter - soil biology - fertilizer application - nutrients - government policy - manure policy - food production - biomass production - arable farming - dairy farming - biobased economy - organic farming - tillage
    Bodemvruchtbaarheid staat steeds nadrukkelijker op de agenda van politiek, overheid, bedrijfsleven en maatschappelijke organisaties. Deze publicatie is vooral geschreven voor medewerkers van deze organisaties, van rijksoverheid tot waterschap, en van productschap tot mestverwerker. Uiteindelijk draait het om de boeren die het land bewerken. Ook zij vinden in deze publicatie achtergronden over alle belangrijke aspecten van bodemvruchtbaarheid. De dertig vragen en antwoorden zijn grofweg in drie groepen ingedeeld. Eerst komen de klassiekers aan bod waarin de basiskennis wordt uitgelegd. De volgende groep vragen behandelt de actuele thema's zoals mestbeleid, energieproductie en klimaatverandering. Tot slot komen in de laatste vragen de kennisagenda en nieuwe ontwikkelingen aan bod.
    Poor people and poor fields? : integrating legumes for smallholder soil fertility management in Chisepo, central Malawi
    Kamanga, B. - \ 2011
    Wageningen University. Promotor(en): Ken Giller, co-promotor(en): Conny Almekinders; S.R. Waddington. - [s.l.] : S.n. - ISBN 9789461730046 - 168
    gewassen - bodemvruchtbaarheidsbeheer - maïs - peulgewassen - kunstmeststoffen - zelfvoorzieningslandbouw - kleine landbouwbedrijven - voedselzekerheid - landbouwhuishoudens - malawi - armoede - crops - soil fertility management - maize - legumes - fertilizers - subsistence farming - small farms - food security - agricultural households - malawi - poverty

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

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

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

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

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

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

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

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

    Competing use of organic resources, village-level interactions between farm types and climate variability in a communal area of NE Zimbabwe
    Rufino, M.C. ; Dury, J. ; Tittonell, P.A. ; Wijk, M.T. van; Herrero, M. ; Zingore, S. ; Mapfumo, P. ; Giller, K.E. - \ 2011
    Agricultural Systems 104 (2011)2. - ISSN 0308-521X - p. 175 - 190.
    soil fertility management - african smallholder farms - southern africa - systems - productivity - manure - strategies - efficiencies - nutrition - gradients
    In communal areas of NE Zimbabwe, feed resources are collectively managed, with herds grazing on grasslands during the rainy season and mainly on crop residues during the dry season, which creates interactions between farmers and competition for organic resources. Addition of crop residues or animal manure is needed to sustain agricultural production on inherently poor soils. Objectives of this study were to assess the effect of village-level interactions on carbon and nutrient flows, and to explore their impact on the long-term productivity of different farm types under climate variability. Crop and cattle management data collected in Murewa Communal area, NE Zimbabwe was used together with a dynamic farm-scale simulation model (NUANCES-FARMSIM) to simulate village-level interactions. Simulations showed that grasslands support most cattle feed intake (c. 75%), and that crop residues produced by non-cattle farmers sustain about 30% of the dry season feed intake. Removal of crop residues (0.3–0.4 t C ha-1 yr-1) from fields of non-cattle farmers resulted in a long-term decrease in crop yields. No-access to crop residues of non-cattle farmers increased soil C modestly and improved yields in the long-term, but not enough to meet household energy requirements. Harvest of grain and removal of most crop residues by grazing cattle caused a long-term decline in soil C stocks for all farm types. The smallest decrease (-0.5 t C ha-1) was observed for most fertile fields of cattle farmers, who manure their fields. Cattle farmers needed to access 4–10 ha of grassland to apply 3 t of manure ha-1 yr-1. Rainfall variability intensifies crop–livestock interactions increasing competition for biomass to feed livestock (short-term effect) or to rehabilitate soils (long-term effect). Prolonged dry seasons and low availability of crop residues may lead to cattle losses, with negative impact in turn on availability of draught power, affecting area under cultivation in consecutive seasons until farmers re-stock. Increasing mineral fertiliser use concurrently with keeping crop residues in fertile fields and allocating manure to poor fields appears to be a promising strategy to boost crop and cattle productivity at village level. The likelihood of this scenario being implemented depends on availability of fertilisers and decision of farmers to invest in rehabilitating soils to obtain benefits in the long-term. Adaptation options cannot be blind to what occurs beyond field and farm level, because otherwise recommendations from research and development do not fit the local conditions and farmers tend to ignore them.
    Drivers of land use change and household determinants of sustainability in smallholder farming systems of Eastern Uganda
    Ebanyat, P. ; Ridder, N. de; Jager, A. de; Delve, R.J. ; Bekunda, M. ; Giller, K.E. - \ 2010
    Population and Environment 31 (2010)6. - ISSN 0199-0039 - p. 474 - 506.
    soil fertility management - sub-saharan africa - cover change - nutrient balances - brazilian amazon - level evidence - southern mali - use patterns - dynamics - agriculture
    Smallholder farming systems in sub-Saharan Africa have undergone changes in land use, productivity and sustainability. Understanding of the drivers that have led to changes in land use in these systems and factors that influence the systems’ sustainability is useful to guide appropriate targeting of intervention strategies for improvement. We studied low input Teso farming systems in eastern Uganda from 1960 to 2001 in a place-based analysis combined with a comparative analysis of similar low input systems in southern Mali. This study showed that policy-institutional factors next to population growth have driven land use changes in the Teso systems, and that nutrient balances of farm households are useful indicators to identify their sustainability. During the period of analysis, the fraction of land under cultivation increased from 46 to 78%, and communal grazing lands nearly completely disappeared. Cropping diversified over time; cassava overtook cotton and millet in importance, and rice emerged as an alternative cash crop. Impacts of political instability, such as the collapse of cotton marketing and land management institutions, of communal labour arrangements and aggravation of cattle rustling were linked to the changes. Crop productivity in the farming systems is poor and nutrient balances differed between farm types. Balances of N, P and K were all positive for larger farms (LF) that had more cattle and derived a larger proportion of their income from off-farm activities, whereas on the medium farms (MF), small farms with cattle (SF1) and without cattle (SF2) balances were mostly negative. Sustainability of the farming system is driven by livestock, crop production, labour and access to off-farm income. Building private public partnerships around market-oriented crops can be an entry point for encouraging investment in use of external nutrient inputs to boost productivity in such African farming systems. However, intervention strategies should recognise the diversity and heterogeneity between farms to ensure efficient use of these external inputs.
    Striga infestation in northern Cameroon: Magnitude, dynamics and implications for managament
    Ayongwa, G.C. ; Stomph, T.J. ; Hoevers, R. ; Ngoumou, T.N. ; Kuyper, T.W. - \ 2010
    NJAS Wageningen Journal of Life Sciences 57 (2010)2. - ISSN 1573-5214 - p. 159 - 165.
    soil fertility management - sub-saharan africa - hermonthica control - savanna zone - nigeria - land - sahel - productivity - cultivation - challenges
    Surveys of Striga (S. hermonthica (Del.) Benth.) infestation in northern Cameroon over the period 1987–2005 assessed Striga dynamics and evaluated its control strategies. In that period the percentage of Striga-infested fields increased in North and Far-North Provinces. Striga incidence increased more in maize fields than in the already heavily infested sorghum fields, where it remained almost constant. During the study period increased land pressure led to a reduction in the use of fallow and a higher frequency of cereal (mono-) cropping. Yields from farmers’ fields did not correlate with Striga incidence, confirming farmers’ prioritization of soil fertility, weeds, and labour for weeding as production constraints, rather than Striga. We discuss how conceptualization of Striga as a weed in the research arena may have led to a misunderstanding of farmers’ constraints. The decline of the cotton industry reduced farmers’ access to fertilizers, while access to organic manure remained limited, increasing the soil fertility constraint. We conclude that two decades of emphasis on Striga were unsuccessful. Enhanced crop yield through soil fertility management should be the entry point to tackle low yields and further worsening of the Striga situation
    Het belang van groencompost
    Haan, J.J. de - \ 2010
    Nieuwe oogst / Magazine gewas 6 (2010)7. - ISSN 1871-093X - p. 18 - 19.
    proeven op proefstations - prestatie-onderzoek - tests - groenbemesters - bodemvruchtbaarheid - gewassen - mest - dekgewassen - bodemvruchtbaarheidsbeheer - station tests - performance testing - tests - green manures - soil fertility - crops - manures - cover crops - soil fertility management
    Groencompost wordt een aantal belangrijke positieve effecten toegedicht, maar onderzoek laat zien dat het gaat om investeren voor de lange termijn. Praktijkonderzoek Plant en Omgeving heeft samen met de Branche Vereniging Reststoffen (BVOR) en vijf agrarische ondernemers in diverse sectoren gekeken naar de effecten van de toediening van groencompost.
    Hulpmeststoffen : eigenschappen en innovaties
    Anonymous, ; Cuijpers, W.J.M. - \ 2010
    manures - innovations - soil fertility - fertilizer application - soil fertility management - overijssel
    Hulpmeststoffen: eigenschappen en innovaties
    Anonymous, ; Cuijpers, W.J.M. - \ 2010
    manures - innovations - soil fertility - compound fertilizers - use value - fertilizer application - soil fertility management - noord-limburg
    Do mixed-species legume fallows provide long-term maize yield benefit compared with monoculture legume fallows?
    Ndufa, J.K. ; Gathumbi, S.M. ; Kamiri, H.W. ; Giller, K.E. ; Cadisch, G. - \ 2009
    Agronomy Journal 101 (2009)6. - ISSN 0002-1962 - p. 1352 - 1362.
    soil fertility management - western kenya - tree prunings - nitrogen release - planted fallows - organic-matter - quality - rotation - mineralization - agroforestry
    The deliberate planting of fast-growing N2-fixing legume monoculture species in rotation with cereal crops can be an important source of N for soil fertility replenishment. We hypothesized that mixed-species fallows have a higher potential of giving long-term residual benefits in terms of biomass, nutrients, and quality of residuals leading to long-term nutrient supply to postfallow maize (Zea mays L.) crops. To test these hypotheses, two experiments were established in farmers' fields on very fine Kandiudalfic Eutrudox soils with monoculture and mixed-species fallows. Treatments included: sesbania [Sesbania sesban (L.) Merr.], crotalaria (Crotalaria grahamiana Wight and Arn.), pigeonpea [Cajanus cajan (L.) Millsp.], siratro [Macroptilium atropurpureum (DC.) Urb.], and calliandra (Calliandra calothyrsus Meissn.) as monoculture-species fallow and mixture fallows of sesbania + crotalaria, sesbania + pigeonpea, sesbania + siratro, or sesbania + calliandra compared with continuous maize cropping with or without N fertilizer, and natural weed fallow. Total aboveground biomass ranged from 4.1 to 20.5 Mg ha-1 for monoculture and 7.8 to 23.3 Mg ha-1 for mixed-species fallows. Recyclable fallow biomass N ranged from 70 to 313 kg ha-1 and there was a positive interaction in some mixtures leading to increased N accumulation. Postfallow maize yields for fallows over five cropping seasons were 161-272% or 61-103% higher when compared with continuous maize without or with N fertilizer, respectively. Long-term postfallow effects on maize yield were linearly related to the amount of recycled fallow N yield. Thus, choice of fallow species to mix should be primarily driven by a better risk management strategy and an increased basket of multiple products and services
    Linking participatory and GIS-based land use planning methods; A case study from Burkina Faso
    Hessel, R. ; Berg, J. van den; Kabore, O. ; Kekem, A.J. van; Verzandvoort, S.J.E. - \ 2009
    Land Use Policy 26 (2009)4. - ISSN 0264-8377 - p. 1162 - 1172.
    soil fertility management - sub-saharan africa - desertification debate - degradation - views - sahel
    Sustainable land use planning is crucial for realizing the aim of food security and for combating land degradation in the Sahel. A participatory land use planning workshop was organised in a village in the eastern region of Burkina Faso to investigate land use problems, their causes, effects and possible solutions. Participatory research tools and GIS were combined to get insight into possible conflicts or synergies between different land use options as mapped by different ethnic groups. Pictograms were used to locate alternative land use options on the map, after which they were digitised for analysis with GIS. The workshop confirms the importance of integrating scientific and local knowledge to develop concrete options for sustainable land use that fit to local realities and aspirations. Local people are knowledgeable about the driving forces behind land degradation, they take actions to combat the effects of degradation, and they have concrete ideas about alternative land use options. The use of GIS proved its added value in the participatory process of integrated land use planning. The maps that were produced also facilitate discussions between community members, researchers and government representatives at the regional level, both regarding current land use problems and regarding alternative options as perceived by the local population.
    Beyond resource constraints - Exploring the biophysical feasibility of options for the intensification of smallholder crop-livestock systems in Vihiga district, Kenya
    Tittonell, P.A. ; Wijk, M.T. van; Herrero, M. ; Rufino, M.C. ; Ridder, N. de; Giller, K.E. - \ 2009
    Agricultural Systems 101 (2009)1-2. - ISSN 0308-521X - p. 1 - 19.
    soil fertility management - western kenya - farm-scale - simulation-models - dynamics - efficiencies - strategies - gradients - impact - manure
    During participatory prototyping activities in Vihiga, western Kenya, farmers designed what they considered to be the ideal farm [Waithaka, M.M., Thornton, P.K., Herrero, M., Shepherd, K.D., 2006. Bio-economic evaluation of farmers¿ perceptions of viable farms in western Kenya. Agric. Syst. 90, 243-271]: one in which high productivity is achieved through optimising crop-livestock interactions. We selected four case study crop-livestock farms of different resource endowment (Type 1-4-excluding the poorest farmers, Type 5, who do not own livestock) and quantified all relevant physical flows through and within them. With this information we parameterised a dynamic, farm-scale simulation model to investigate (i) current differences in resource use efficiencies and degree of crop-livestock interactions across farm types; and (ii) the impact of different interventions in farm Types 3 and 4 on producing the desired shifts in productivity towards the ideal farm. Assuming no resource constraints, changes in the current farm systems were introduced stepwise, as both intensification of external input use (fertilisers and fodder) and qualitative changes in the configuration of the farms (i.e. changing land use towards fodder production, improving manure handling and/or changing cattle breeds). In 10-year simulations of the baseline, current scenario using historical weather data the wealthiest farms Type 2 achieved food self-sufficiency (FSS) in 20% of the seasons due to rainfall variability, whereas the poorer Type 4 only achieved FSS in 0 to 30% of the seasons; soil organic C decreased during the simulations at annual rates of ¿0.54, ¿0.73, ¿0.85 and -0.84 t C ha¿1 on farms of Type 1-4, respectively; large differences in productivity and recycling efficiency between farm types indicated that there is ample room to improve the physical performance of the poorer farms (e.g. light and water use efficiency was 2-3 times larger on wealthier farms). Simulating different intensification scenarios indicated that household FSS can be achieved in all farm types through input intensification, e.g. using P fertilisers at rates as small as 15 kg farm¿1 season¿1 (i.e. from 7 to 28 kg ha¿1). Increasing the area under Napier grass from c. 20 to 40% and reducing the area of maize, beans and sweet potato in farms of Type 3 and 4 increased their primary productivity by c. 1 t ha¿1 season¿1, their milk production by 156 and 45 L season¿1, respectively, but decreased the production of edible energy (by 2000 and 250 MJ ha¿1 season¿1) and protein (by 20 and 3 kg ha¿1 season¿1). By bringing in a more productive cow the primary productivity increased even further in Farm Type 3 (up to 5 t ha¿1 season¿1), as did milk production (up to c. 1000 L season¿1), edible energy (up to c. 10,000 MJ ha¿1 season¿1) and protein (up to c. 100 kg ha¿1 season¿1). The impact of livestock management on the recycling of nutrients and on the efficiency of nutrient use at farm scale can be large, provided that enough nutrients are present in or enter the system to be redistributed. An increase in N cycling efficiency through improved manure handling from 25 to 50% would increase the amount of N cycled in the case study farms of Type 1 and 2 by only ca. 10 kg season¿1, and only 1-2 kg season¿1 in Type 3 and 4. The various alternatives simulated when disregarding resource constraints contributed to narrow the productivity and efficiency gaps between poorer and wealthier farms. However, the feasibility of implementing such interventions on a large number of farms is questionable. Implications for system (re-)design and intensification strategies are discussed
    Identifying key entry-points for strategic management of smallholder farming systems in sub-Saharan Africa using the dynamic farm-scale simulation model NUANCES-FARMSIM
    Wijk, M.T. van; Tittonell, P.A. ; Rufino, M.C. ; Herrero, M. ; Pacini, C. ; Ridder, N. de; Giller, K.E. - \ 2009
    Agricultural Systems 102 (2009)1-3. - ISSN 0308-521X - p. 89 - 101.
    soil fertility management - term crop response - western kenya - exploring diversity - resource-allocation - use efficiencies - field-scale - productivity - nitrogen - integration
    African smallholder farming systems are complex, dynamic systems with many interacting biophysical subcomponents. In these systems the major inputs and outputs are managed by human agency ¿ the farmers. To analyse potential developmental pathways of smallholder farming systems in sub-Saharan Africa (SSA), we recognised the need for a tool that can capture the effects and consequences of decision-making on the use of resources. Here we describe and apply such a new modelling tool, developed within the NUANCES framework (Nutrient Use in ANimal and Cropping systems: Efficiencies and Scales), called NUANCES-FARMSIM (FARM SIMulator), an integrated crop ¿ livestock model developed to analyse African smallholder farm systems. NUANCES-FARMSIM was used to analyse a representative case study farm in the highlands of Western Kenya, a site for which each of the components of FARMSIM has been thoroughly tested. We present the results of a sensitivity analysis which showed the model to be sufficiently robust to identify key management options that explain most of the variability in farm productivity, and the long-term consequences of these options for the case study farm. The analyses showed clearly that the most important decisions are those related to the interactions between the different components of the farm and therefore justify the need of integrating crop and livestock components within one modelling tool. The allocation of limited resources across the farm, and the way organic matter is recycled or redistributed within the farm determines the long-term production capacity of the system. The results of the sensitivity analyses further showed that for the case study farm in Western Kenya a strong focus on improving the reliability of the subsystem level or process descriptions will only result in minor improvement in simulating productivity at farm level
    Biodiversity, carbon stocks and sequestration potential in aboveground biomass in smallholder farming systems of western Kenya
    Henry, M. ; Tittonell, P.A. ; Manlay, R.J. ; Bernoux, M. ; Albrecht, A. ; Vanlauwe, B. - \ 2009
    Agriculture, Ecosystems and Environment 129 (2009)1-3. - ISSN 0167-8809 - p. 238 - 252.
    soil fertility management - agroforestry systems - allocation - productivity - environment - forests
    While Carbon (C) sequestration on farmlands may contribute to mitigate CO2 concentrations in the atmosphere, greater agro-biodiversity may ensure longer term stability of C storage in fluctuating environments. This study was conducted in the highlands of western Kenya, a region with high potential for agroforestry, with the objectives of assessing current biodiversity and aboveground C stocks in perennial vegetation growing on farmland, and estimating C sequestration potential in aboveground C pools. Allometric models were developed to estimate aboveground biomass of trees and hedgerows, and an inventory of perennial vegetation was conducted in 35 farms in Vihiga and Siaya districts. Values of the Shannon index (H), used to evaluate biodiversity, ranged from 0.01 in woodlots through 0.4¿0.6 in food crop plots, to 1.3¿1.6 in homegardens. Eucalyptus saligna was the most frequent tree species found as individual trees (20%), in windrows (47%), and in woodlots (99%) in Vihiga and the most frequent in woodlots (96%) in Siaya. Trees represented the most important C pool in aboveground biomass of perennial plants growing on-farm, contributing to 81 and 55% of total aboveground farm C in Vihiga and Siaya, respectively, followed by hedgerows (13 and 39%, respectively) and permanent crop stands (5 and 6%, respectively). Most of the tree C was located in woodlots in Vihiga (61%) and in individual trees growing in or around food crop plots in Siaya (57%). The homegardens represented the second C pool in importance, with 25 and 33% of C stocks in Vihiga and Siaya, respectively. Considering the mean total aboveground C stocks observed, and taking the average farm sizes of Vihiga (0.6 ha) and Siaya (1.4 ha), an average farm would store 6.5 ± 0.1 Mg C farm¿1 in Vihiga and 12.4 ± 0.1 Mg C farm¿1 in Siaya. At both sites, the C sequestration potential in perennial aboveground biomass was estimated at ca. 16 Mg C ha¿1. With the current market price for carbon, the implementation of Clean Development Mechanism Afforestation/Reforestation (CDM A/R) projects seems unfeasible, due to the large number of small farms (between 140 and 300) necessary to achieve a critical land area able to compensate the concomitant minimum transaction costs. Higher financial compensation for C sequestration projects that encourage biodiversity would allow clearer win¿win scenarios for smallholder farmers. Thus, a better valuation of ecosystem services should encourage C sequestration together with on-farm biodiversity when promoting CDM A/R projects.
    Talking soil science with farmers
    Tittonell, P.A. ; Misiko, M. ; Ekise, I.E. - \ 2008
    LEISA : ILEIA newsletter for low-external-input and sustainable agriculture 24 (2008)2. - ISSN 1569-8424 - p. 9 - 11.
    bodemvruchtbaarheid - kenya - oost-afrika - bodemvruchtbaarheidsbeheer - kennis van boeren - soil fertility - kenya - east africa - soil fertility management - farmers' knowledge
    When agricultural researchers visit farms in order to gather information for their research programmes, farmers rarely get proper feedback. Research information on scientific concepts such as soil fertility and nutrient balances is often considered too abstract for them. Researchers in Kenya returned to farmers to discuss their results in the context of Farmer Field Schools. Through the workshops that ensued, they managed to find a common language to bridge the communication gap.
    Ex ante assessment of dual-purpose sweet potato in the crop-livestock system of western Kenya: a minimum-data approach
    Claessens, L. ; Stoorvogel, J.J. ; Antle, J.M. - \ 2008
    Agricultural Systems 99 (2008)1. - ISSN 0308-521X - p. 13 - 22.
    soil fertility management - agricultural production systems - semi-humid tropics - dairy-cows - pennisetum-purpureum - nutrient balances - economic-analysis - farming systems - maize stover - feed
    Mixed crop¿livestock systems have a crucial role to play in meeting the agricultural production challenges of smallholder farmers in sub-Saharan Africa. Sweet potato is seen as a potential remedial crop for these farmers because of its high productivity and low input requirements, while its usefulness for both food and feed (dual-purpose) make it attractive in areas where land availability is declining. In this paper, we develop and apply a `minimum-data¿ methodology to assess ex ante the economic viability of adopting dual-purpose sweet potato in Vihiga district, western Kenya. The methodology uses and integrates available socio-economic and bio-physical data on farmers¿ land use allocation, production, and input and output use. Spatially heterogeneous characteristics of the current system regarding resources and productivity are analyzed to assess the profitability of substituting dual-purpose sweet potato for other crops currently grown for food and feed. Results indicate that a substantial number of farmers in the study area could benefit economically from adopting dual-purpose sweet potato. Depending on assumptions made, the adoption rate, expressed as the percentage of the total land under adopting farms, is between 55% and 80%. The analysis shows that the adoption rate is likely to vary positively with the average total yield of dual-purpose sweet potato, the harvest index (the ratio between tuber and fodder yields), the price of milk, and the nutritional value of available fodder. This study demonstrates the usefulness of the minimum-data methodology and provides evidence to support the hypothesis that dissemination of the dual-purpose sweet potato could help improve the livelihoods of smallholder farmers operating in mixed crop¿livestock systems in east Africa.
    Increasing land pressure in East Africa: The changing role of cassava and consequences for sustainability of farming systems
    Fermont, A.M. van; Asten, P.J.A. van; Giller, K.E. - \ 2008
    Agriculture, Ecosystems and Environment 128 (2008)4. - ISSN 0167-8809 - p. 239 - 250.
    soil fertility management - western kenya - gradients - farmers - maize - crops
    Increasing land pressure during the past three to four decades has transformed farming systems in the mid-altitude zone of East Africa. Traditional millet-, cotton-, sugarcane- and/or banana-based farming systems with an important fallow and/or grazing component have evolved into continuously cultivated cassava or cassava/maize-based systems. Within three to four decades, cassava cultivation increased from 1¿11 to 16¿55% of cropped fields in our six study sites. Declining soil fertility, and not labour or food shortage, was apparently the primary trigger for this transformation. The land use changes have increased nutrient offtakes and reduced nutrient recycling rates. Cassava and maize now account for 50¿90% of nutrient removal. Whereas single-season fallows were the most important source of nutrient recycling on cropped fields in the past, currently cassava litterfall and maize stover contribute roughly 70% of nutrient recycling, with 50¿70% of N, P and K recycled in cassava litterfall. This may explain why many farmers reason that cassava `rests¿ the soil. With increasing land use pressure farmers progressively use cassava as an `imitation fallow¿ throughout their farm. Farmers increasingly target cassava to poor fertility fields characterized by low pH and available P. High cassava intensities are nonetheless maintained on more fertile fields, probably to guarantee regeneration of soil fertility on all fields. Once cassava is targeted to poor fertility soils, farmers have run out of low-input management options and need to intensify management to maintain system productivity. As cassava is now used by more farmers and on a larger acreage than fallowing in the studied farming systems, cassava cropping could perhaps serve as an excellent entry point to strengthen system sustainability.
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