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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N2Africa Annual Report 2019
Dontsop-Nguezet, Paul M. ; Ampadu-Boakye, Theresa ; Ronner, E. ; Baars, Edward ; Kanampiu, Fred ; Giller, K.E. ; Vanlauwe, B. ; Adjei-nsiah, Samuel ; Wolde-Meskel, E. ; Ebanyat, Peter ; Baijukya, Frederick ; Dianda, M. ; Sanginga, Jean-Marie ; Woomer, P.L. ; Chikowo, Regis ; Phiphira, Lloyd ; Kantengwa, Speciose ; Leonardo, W. ; Kamai, Nkeki ; Thuijsman, E.C. ; Schilt-van Ettekoven, C. - \ 2019
Wageningen : N2Africa (N2Africa project report 120) - 78 p.
Annual report, Key milestones, objectives, progress, biological nitrogen fixation, grain legumes, Nigeria, Borno State, Ghana, Tanzania, Ethiopia, Uganda, DR Congo, Rwanda, Kenya, Malawi, Zimbabwe, Mozambique
Vulnerability and adaptation options to climate change for rural livelihoods – A country-wide analysis for Uganda
Wichern, Jannike ; Descheemaeker, Katrien ; Giller, Ken E. ; Ebanyat, Peter ; Taulya, Godfrey ; Wijk, Mark T. van - \ 2019
Agricultural Systems 176 (2019). - ISSN 0308-521X
Crop suitability - East Africa - Household food security - Impact assessment - Multi-level

Rural households in sub-Saharan Africa earn a substantial part of their living from rain-fed smallholder agriculture, which is highly sensitive to climate change. There is a growing number of multi-level assessments on impacts and adaptation options for African smallholder systems under climate change, yet few studies translate impacts at the individual crop level to vulnerability at the household level, at which other livelihood activities need to be considered. Further, these assessments often use representative household types rather than considering the diversity of households for the identification of larger-scale patterns at sub-national and national levels. We developed a framework that combines crop suitability maps with a household food availability analysis to quantify household vulnerability to climate-related impacts on crop production and effects of adaptation options. The framework was tested for Uganda, identifying four hotspots of household vulnerability across the country. Hotspots were visually identified as areas with a relatively high concentration of vulnerable households, experiencing a decline in household crop suitability. About 30% of the households in the hotspots in (central) southwest were vulnerable to a combination of 3 °C temperature increase and 10% rainfall decline through declining suitability for several key crops (including highland banana, cassava, maize and sorghum). In contrast only 10% of the households in West Nile and central northern Uganda were negatively affected, and these were mainly affected by declining suitability of common beans. Households that depended on common beans and lived at lower elevations in West Nile and central north were vulnerable to a 2 to 3 °C temperature increase, while households located at higher elevations (above 1100–2000 m.a.s.l. depending on the crop) benefited from such an increase. Options for adaptation to increasing temperatures were most beneficial in northern Uganda, while drought-related adaptation options were more beneficial in the southwest. This framework provides a basis for decision makers who need information on where the vulnerable households are, what crops drive the vulnerability at household level and which intervention efforts are most beneficial in which regions.

N2Africa Podcaster no. 56 : Putting nitrogen fixation to work for smallholder farmers in Africa: April, May and June 2019
Schilt-van Ettekoven, C. ; Giller, K.E. ; Ronner, E. ; Abdulkadir, Birhan ; Wolde-Meskel, Endalkachew ; Adjei-Nsiah, S. ; Kamai, Nkeki ; Baijukya, F.P. ; Ebanyat, Peter ; Ninsiima, P. ; Tamiru, Amanuel - \ 2019
Wageningen : N2Africa project (N2Africa Podcaster 56) - 12 p.
Co-design of improved climbing bean production practices for smallholder farmers in the highlands of Uganda
Ronner, E. ; Descheemaeker, K. ; Almekinders, C. ; Ebanyat, P. ; Giller, K.E. - \ 2019
Agricultural Systems 175 (2019). - ISSN 0308-521X - p. 1 - 12.
Legumes - Multi-criteria - Participatory - Phaseolus vulgaris

We evaluated the usefulness of a co-design process to generate a relevant basket of options for climbing bean cultivation in the context of a large-scale project. The aim was to identify a range of options sufficiently diverse to be of interest for farmers of widely-different resource endowment. The co-design process consisted of three cycles of demonstration, evaluation and re-design in the eastern and southwestern highlands of Uganda in 2014–2015. Evaluations aimed to distinguish preferences of farmers between the two areas, and among farmers of different gender and socio-economic backgrounds. Farmers, researchers, extension officers and NGO staff re-designed treatments for demonstrations in the next season. Climbing bean yields and evaluation scores varied between seasons and sites. Evaluation scores were not always in line with yields, revealing that farmers used multiple evaluation criteria next to yield, such as marketability of varieties, availability of inputs and ease of staking methods. The co-design process enriched the basket of options, improved the relevance of options demonstrated and enhanced the understanding of preferences of a diversity of users. Developing options for resource-poor farmers was difficult, however, because they face multiple constraints. The basket of options developed in this study can be applied across the East-African highlands, with an ‘option-by-context’ matrix as a starting point for out-scaling. The study also showed, however, that consistent recommendations about the suitability of technologies for different types of farmers were hard to identify. This highlights the importance of a basket of options with flexible combinations of practices rather than developing narrowly specified technology packages for static farm types.

N2Africa Annual Report 2018
Ampadu-Boakye, Theresa ; Ronner, E. ; Kanampiu, Fred ; Giller, K.E. ; Baars, Edward ; Vanlauwe, B. ; Adjei-nsiah, Samuel ; Wolde-Meskel, E. ; Ebanyat, Peter ; Baijukya, Frederick ; Sanginga, Jean-Marie ; Woomer, P.L. ; Chikowo, Regis ; Phiphira, Lloyd ; Kantengwa, Speciose ; Leonardo, W. ; Kamai, Nkeki ; Thuijsman, E.C. ; Schilt-van Ettekoven, C. - \ 2019
Wageningen : N2Africa (N2Africa project report 111) - 77 p.
Annual report, Key milestones, objectives, progress, biological nitrogen fixation, grain legumes, Nigeria, Borno State, Ghana, Tanzania, Ethiopia, Uganda, DR Congo, Rwanda, Kenya, Malawi, Zimbabwe, Mozambique
Stakeholder Consultations Report
Ebanyat, Peter ; Abetu, Tamiru A. ; Ayesiga, C. - \ 2019
Wageningen : N2Africa (N2Africa project report 108) - 24 p.

Climbing bean x highland banana intercropping in the Ugandan highlands
Ronner, E. ; Thuijsman, E.C. ; Ebanyat, Peter ; Giller, K.E. - \ 2019
- 24 p.

From best fit technologies to best fit scaling: incorporating and evaluating factors affecting the adoption of grain legumes in Sub-Saharan Africa
Farrow, Andrew ; Ronner, Esther ; Brand, Greta J. Van Den; Boahen, Stephen K. ; Leonardo, Wilson ; Wolde-Meskel, Endalkachew ; Adjei-Nsiah, Samuel ; Chikowo, Regis ; Baijukya, Fredrick ; Ebanyat, Peter ; Sangodele, Emmanuel A. ; Sanginga, Jean-Marie ; Kantengwa, Speciose ; Phiphira, Lloyd ; Woomer, Paul ; Ampadu-Boakye, Theresa ; Baars, Edward ; Kanampiu, Fred ; Vanlauwe, Bernard ; Giller, Kenneth E. - \ 2019
Experimental Agriculture 55 (2019)S1. - ISSN 0014-4797 - p. 226 - 251.
The success of scaling out depends on a clear understanding of the factors that affect adoption of grain legumes and account for the dynamism of those factors across heterogeneous contexts of sub-Saharan Africa. We reviewed literature on adoption of grain legumes and other technologies in sub-Saharan Africa and other developing countries. Our review enabled us to define broad factors affecting different components of the scaling out programme of N2Africa and the scales at which those factors were important. We identified three strategies for managing those factors in the N2Africa scaling out programme: (i) testing different technologies and practices; (ii) evaluating the performance of different technologies in different contexts; and (iii) monitoring factors that are difficult to predict. We incorporated the review lessons in a design to appropriately target and evaluate technologies in multiple contexts across scales from that of the farm to whole countries. Our implementation of this design has only been partially successful because of competing reasons for selecting activity sites. Nevertheless, we observe that grain legume species have been successfully targeted for multiple biophysical environments across sub-Saharan Africa, and to social and economic contexts within countries. Rhizobium inoculant and legume specific fertiliser blends have also been targeted to specific contexts, although not in all countries. Relatively fewer input and output marketing models have been tested due to public–private partnerships, which are a key mechanism for dissemination in the N2Africa project.
How do climbing beans fit in farming systems of the eastern highlands of Uganda? Understanding opportunities and constraints at farm level
Ronner, E. ; Descheemaeker, K. ; Marinus, W. ; Almekinders, C.J.M. ; Ebanyat, P. ; Giller, K.E. - \ 2018
Agricultural Systems 165 (2018). - ISSN 0308-521X - p. 97 - 110.
Legumes - Multi-criteria - Participatory - Phaseolus vulgaris - Smallholder

Climbing beans offer potential for sustainable intensification in the East-African highlands, but their introduction requires a major change in the cropping system compared with the commonly grown bush bean. We explored farm-level opportunities, constraints and trade-offs for climbing bean cultivation in the eastern highlands of Uganda. We established current food self-sufficiency, income, investment costs and labour, and assessed the ex-ante, farm-level impact of four climbing bean options on these indicators. Input for this assessment were a detailed characterization of 16 farms of four types, and on-farm, experimental data of adaptation trials of climbing bean. Climbing beans generally improved food self-sufficiency and income, but often required increased financial investment and always demanded more labour than current farm configurations. Opportunities for integration of climbing beans on small farms were limited. Although some of the poorest farmers accrued the largest absolute benefits from climbing beans, their ability to make the necessary investments is questionable. The analysis was translated into a simple-to-use modelling tool to enable participatory analysis of the outcomes with farmers of the four farm types to understand their perspectives and decision-making. The discussions revealed a recent increase in market prices for climbing bean resulting in growing interest in their cultivation in the eastern highlands. A lack of seed and stakes was limiting climbing bean cultivation, and a sufficient amount of climbing bean seed needs to be ensured through strengthening of farmer cooperatives and improved storage.

Soyabean response to rhizobium inoculation across sub-Saharan Africa : Patterns of variation and the role of promiscuity
Heerwaarden, Joost van; Baijukya, Frederick ; Kyei-Boahen, Stephen ; Adjei-nsiah, Samuel ; Ebanyat, Peter ; Kamai, Nkeki ; Wolde-Meskel, Endalkachew ; Kanampiu, Fred ; Vanlauwe, Bernard ; Giller, Ken - \ 2018
Agriculture, Ecosystems and Environment 261 (2018). - ISSN 0167-8809 - p. 211 - 218.
Bradyrhizobium - Promiscuous varieties - Response variability - Smallholder farmers - Soyabean - Sub saharan Africa - Sustainable intensification
Improving bacterial nitrogen fixation in grain legumes is central to sustainable intensification of agriculture in sub-Saharan Africa. In the case of soyabean, two main approaches have been pursued: first, promiscuous varieties were developed to form effective symbiosis with locally abundant nitrogen fixing bacteria. Second, inoculation with elite bacterial strains is being promoted. Analyses of the success of these approaches in tropical smallholder systems are scarce. It is unclear how current promiscuous and non-promiscuous soyabean varieties perform in inoculated and uninoculated fields, and the extent of variation in inoculation response across regions and environmental conditions remains to be determined.We present an analysis of on-farm yields and inoculation responses across ten countries in Sub Saharan Africa, including both promiscuous and non-promiscuous varieties. By combining data from a core set of replicated on-farm trials with that from a large number of farmer-managed try-outs, we study the potential for inoculation to increase yields in both variety types and evaluate the magnitude and variability of response.Average yields were estimated to be 1343 and 1227. kg/ha with and without inoculation respectively. Inoculation response varied widely between trials and locations, with no clear spatial patterns at larger scales and without evidence that this variation could be explained by yield constraints or environmental conditions. On average, specific varieties had similar uninoculated yields, while responding more strongly to inoculation. Side-by side comparisons revealed that stronger responses were observed at sites where promiscuous varieties had superior uninoculated yields, suggesting the availability of compatible, effective bacteria as a yield limiting factor and as a determinant of the magnitude of inoculation response.
Farmers' use and adaptation of improved climbing bean production practices in the highlands of Uganda
Ronner, E. ; Descheemaeker, K. ; Almekinders, C.J.M. ; Ebanyat, P. ; Giller, K.E. - \ 2018
Agriculture, Ecosystems and Environment 261 (2018). - ISSN 0167-8809 - p. 186 - 200.
Adoption - Co-design - East Africa - Legumes - Nitrogen fixation - Phaseolus vulgaris - Smallholder

Climbing beans offer potential for sustainable intensification of agriculture, but their cultivation constitutes a relatively complex technology consisting of multiple components or practices. We studied uptake of improved climbing bean production practices (improved variety, input use and management practices) through co-designed demonstrations and farmer-managed adaptation trials with 374 smallholder farmers in eastern and southwestern Uganda. A sub-set of these farmers was monitored one to three seasons after introduction. About 70% of the farmers re-planted climbing beans one season after the adaptation trial, with significant differences between eastern (50%) and southwestern Uganda (80-90%). Only 1% of the farmers used all of the improved practices and 99% adapted the technology. On average, farmers used half of the practices in different combinations, and all farmers used at least one of the practices. Yield variability of the trials was large and on average, trial plots did not yield more than farmers' own climbing bean plots. Yet, achieved yields did not influence whether farmers continued to cultivate climbing bean in the subsequent season. Uptake of climbing beans varied with household characteristics: poorer farmers cultivated climbing beans more often but used fewer of the best-bet practices; male farmers generally used more practices than female farmers. Planting by poorer farmers resulted in adaptations such as growing climbing beans without fertilizer and with fewer and shorter stakes. Other relationships were often inconsistent and farmers changed practices from season to season. The diversity of farmer responses complicates the development of recommendation domains and warrants the development of a basket of options from which farmers can choose. Our study shows how adoption of technologies consisting of multiple components is a complicated process that is hard to capture through the measurement of an adoption rate at a single point in time.

Review of policies relating to legume intensification in N2Africa countries
Stadler, Minke ; Giller, K.E. ; Kanampiu, Fred ; Sangodele, Emmanuel A. ; Ebanyat, Peter ; Wolde-Meskel, Endalkachew ; Baijukya, Frederick ; Adjei-Nsiah, S. ; Sanginga, Jean-Marie ; Kantengwa, Speciose ; Woomer, P.L. ; Chikowo, Regis ; Phiphira, Lloyd ; Leonardo, W. ; Kamai, Nkeki ; Schilt-van Ettekoven, C. - \ 2017
N2Africa project (N2Africa project report 107) - 38 p.
The ‘N2Africa Review of policies relating to legume intensification in N2Africa counties’ showed that governments in N2Africa countries acknowledge the importance of legume intensification and its significant potential to contribute to improving food security and health, especially for poor families.
At global level, the seventeen Sustainable Development Goals (SDGs) of the 2030 Agenda for Sustainable Development developed by the United Nations (UN) aim to end all forms of poverty, fight inequalities and tackle climate change, while ensuring that no one is left behind. The SDGs recognize that ending poverty must go hand-in-hand with strategies that build economic growth and addresses a range of social needs including education, health and job opportunities, amongst others. Governments are expected to take ownership and establish national frameworks for the achievement of the seventeen goals. Particularly, SDG2 ‘End hunger achieve food security and improved nutrition and promote sustainable agriculture’ seeks sustainable solutions to end hunger in all its forms and to achieve food security. It entails improving the productivity and incomes of small-scale farmers by promoting equal access to land, technology and markets, sustainable food production systems and resilient agricultural practices.
The Comprehensive Africa Agriculture Development Programme (CAADP) is the pan-African policy framework for agricultural transformation, wealth creation, food security and nutrition, economic growth and prosperity for all. The CAADP Results Framework 2015 – 2025 is prepared by the Food and Agriculture Organisation (FAO) of the UN in cooperation with the New Partnership for Africa’s Development (NEPAD) Steering Committee. It recognizes the importance of increasing yield of food grains, tubers and legumes to catalyse transformation of Africa’s agricultural systems and presents critical actions required to achieve agricultural development agenda targets. Furthermore, the Association for Strengthening Agricultural Research in Eastern and Central Africa (ASARECA) serves as a platform for promoting regional research and in the sharing of benefits and spillovers that derive from such research. The association focuses on four thematic areas that are well aligned to the major ongoing regional and continental initiatives. These include (i) Integrated capacity strengthening, (ii) Development and scaling up of technologies and innovations, (iii) Policy advocacy, market analysis and institutional arrangement, (iv) Knowledge and information management. High yielding climbing bean varieties and training on different staking options are included in ASARECA projects that scale up best practices to address farmers’ needs.
National governments in the N2Africa countries all developed national policies aimed at increasing agricultural productivity, improving food security, diversifying food production to improve nutrition, and increasing agricultural incomes of the rural people. All national policies refer to legumes, mostly indirectly (e.g. intercropping practices, as measure for soil fertility, amongst others). Table 1 presents the N2Africa target legumes mentioned in national policies per N2Africa country.

All national policies aim at increasing the production and productivity of various legumes by various strategies, such as (i) adopting modern production techniques, (ii) strengthening coordination, institutional capacity and skills across the key actors, (iii) providing timely and appropriate market entry support for effective market development and (iv) scaling up production and trade, amongst others. Rhizobia are only referred to in a few national policies (e.g. Ethiopia, Kenya, Malawi and Rwanda). The Tanzanian government is the only government that developed an explicit policy tool to promote the pulses sector (e.g. common bean, cowpea, pigeonpea, green gram and chickpea, mung bean and Bambara nut).
The study results will be completed and used to provide recommendations to governments about best-fit legume technologies, how to increase production and productivity of various legumes and how to stimulate farmers’ use.
Mining for gold: large scale data management and analysis of on-farm legume trials : N2Africa - Putting nitrogen fixation to work for smallholder farmers in Africa
Heerwaarden, J. van; Lubbers, M.T.M.H. ; Adjei-Nsiah, S. ; Bayukija, F. ; Ebanyat, P. ; Kamai, Nkeki ; Sangodele, E. ; Wolde-Meskel, E. ; Abdulkadir, Birhan ; Amppiah, Arnold ; Epel, A. ; Mzandah, A. ; Muhammad, S. ; Ukem, B. ; Onyinge, J. ; Othieno, A. ; Sekham, J. ; Ampadu-Boakye, Theresa ; Franke, L. - \ 2016
N2Africa Action Areas in Ethiopia, Ghana, Nigeria, Tanzania and Uganda in the N2Africa Project
Farrow, Andrew ; Wolde-Meskel, Endalkachew ; Adjei-Nsiah, S. ; Sangodele, E. ; Kamara, A. ; Kamai, Nkeki ; Baijukya, F. ; Ebanyat, Peter - \ 2015
N2Africa project - 23 p.
Co-design of improved climbing bean technologies for smallholder farmers in Uganda
Ronner, E. ; Descheemaeker, K.K.E. ; Almekinders, C.J.M. ; Ebanyat, P. ; Giller, K.E. - \ 2015
In: Proceedings of the 5th International Symposium for farming Systems Design, Montpellier, 7-10 September 2015. - - p. 263 - 264.
N2Africa Phase II 6 months report
Adjei-Nsiah, S. ; Sangodele, E. ; Wolde-Meskel, E. ; Baijukya, F.P. ; Ebanyat, P. ; Sanginga, J. ; Woomer, P.L. ; Katengwa, S. ; Chikowo, R. ; Leonardo, W.J. ; Boahen, S. ; Phiphira, L. ; Brand, G.J. van den; Giller, K.E. - \ 2014
N2Africa - 34 p.
Effects of cattle and manure management on the nutrient economy of mixed farms in East Africa: A scenario study
Snijders, P.J.M. ; Meer, H.G. van der; Onduru, D.D. ; Ebanyat, P. ; Ergano, K. ; Zake, J.Y.K. ; Wouters, A.P. ; Gachimbi, L.N. ; Keulen, H. van - \ 2013
African Journal of Agricultural Research 8 (2013)41. - ISSN 1991-637X - p. 5129 - 5148.
This paper explores effects of animal and manure management in a dairy unit on the nutrient economy of crop-livestock farms in East Africa. For this purpose, 8 cattle management scenarios have been developed based on farming systems in Mbeere, Kenya (extensive), Wakiso, Uganda (semi-intensive) and Kibichoi, Kenya (intensive). Three baseline scenarios represent present-day cattle management; five improved scenarios use the same dairy breeds but have improved nutrition, using younger grass, more legumes and moderate amounts of concentrates. These improvements strongly increase milk production per cow, but also N, P and K excretion in manure. The 8 cattle management scenarios are combined with 2 levels of manure management technology: a baseline technology, reflecting actual manure management and related losses of plant nutrients, and an improved technology with lower losses. Nutrient losses for each technology level have been derived from a thorough analysis of published information. This showed that current systems of collection and storage of the excreta of confined dairy cows are associated with large nutrient losses, in particular of N. These losses cause serious deficits on the N, P and K balances of the crop-livestock farms. Therefore, significant external N, P and K inputs and better manure management are required to sustain the production levels assumed and to avoid further soil fertility depletion in the region. The paper identifies several possibilities for this and concludes that there is a strong need for integral on-farm studies aiming at development of sustainable dairy production systems.
Impacts of heterogeneity in soil fertility on legume-finger millet productivity, farmers ' targeting and economic benefits
Ebanyat, P. ; Ridder, N. de; Jager, A. de; Delve, R.J. ; Bekunda, M. ; Giller, K.E. - \ 2010
Nutrient Cycling in Agroecosystems 87 (2010)2. - ISSN 1385-1314 - p. 209 - 231.
smallholder farms - western kenya - use efficiency - maize - management - gradients - savanna - biomass - crop - technologies
Targeting of integrated management practices for smallholder agriculture in sub-Saharan Africa is necessary due to the great heterogeneity in soil fertility. Experiments were conducted to evaluate the impacts of landscape position and field type on the biomass yield, N accumulation and N2-fixation by six legumes (cowpea, green gram, groundnut, mucuna, pigeonpea and soyabean) established with and without P during the short rain season of 2005. Residual effects of the legumes on the productivity of finger millet were assessed for two subsequent seasons in 2006 in two villages in Pallisa district, eastern Uganda. Legume biomass and N accumulation differed significantly (P <0.001) between villages, landscape position, field type and P application rate. Mucuna accumulated the most biomass (4.8–10.9 Mg ha-1) and groundnut the least (1.0–3.4 Mg ha-1) on both good and poor fields in the upper and middle landscape positions. N accumulation and amounts of N2-fixed by the legumes followed a similar trend as biomass, and was increased significantly by application of P. Grain yields of finger millet were significantly (P <0.001) higher in the first season after incorporation of legume biomass than in the second season after incorporation. Finger millet also produced significantly more grain in good fields (0.62–2.15 Mg ha-1) compared with poor fields (0.29–1.49 Mg ha-1) across the two villages. Participatory evaluation of options showed that farmers preferred growing groundnut and were not interested in growing pigeonpea and mucuna. They preferentially targeted grain legumes to good fields except for mucuna and pigeonpea which they said they would grow only in poor fields. Benefit-cost ratios indicated that legume-millet rotations without P application were only profitable on good fields in both villages. We suggest that green gram, cowpea and soyabean without P can be targeted to good fields on both upper and middle landscape positions in both villages. All legumes grown with P fertiliser on poor fields provided larger benefits than continuous cropping of millet.
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.
A road to food? : efficacy of nutrient management options targeted to heterogeneous soilscapes in the Teso farming system, Uganda
Ebanyat, P. - \ 2009
Wageningen University. Promotor(en): Ken Giller, co-promotor(en): Nico de Ridder. - [S.l. : S.n. - ISBN 9789085854227 - 218
bodemvruchtbaarheid - landgebruik - bedrijfssystemen - rotaties - plantenvoeding - gebruiksefficiëntie - systeemanalyse - uganda - nutrientenbeheer - soil fertility - land use - farming systems - rotations - plant nutrition - use efficiency - systems analysis - uganda - nutrient management
Key words: Land use change; Heterogeneity in soil fertility; Targeting; Integrated soil fertility management; Nutrient use efficiencies; Rehabilitation of degraded fields; Fertiliser requirements, Finger millet; QUEFTS model; Smallholder systems; sub-Saharan Africa.

Poor soil fertility in smallholder farming systems in sub-Saharan Africa is recognised as a major factor responsible for low per capita food production and escalating food insecurity. Increasing food production in most smallholder farming systems requires intensification with nutrient inputs. Targeting nutrient management interventions to heterogeneity can greatly enhance the use efficiency of the scarce nutrient inputs and can help in identification of ‘best fits’ (most suitable options for niches within the systems). This thesis aimed at contributing to understanding how to target nutrient management options to heterogeneity for improved crop production in the Teso farming system in eastern Uganda.
Land use change analysis between 1960 and 2001 showed that 48-78% more land was brought into cultivation and disappearance of communal grazing lands. Productivity of the farming system is also low. Population growth, political-instability-mediated collapse of institutions that supported production and marketing of cotton, and cattle rustling account for the changes in land use and productivity of the system. Balances of N, P and K were positive on larger farms (LF) and negative on the medium farms (MF), small farms with cattle (SF1) and without cattle (SF2), but were negative at the crop scale on all the farm types. Livestock, crop yield, labour availability and access to off farm income are the sustainability indicators in the system.
There were no topographic-gradients in soil pH, SOC, total N, Exch. Mg, Exch. Ca, Exch. K, CEC, sand and clay in the two villages with different geo-morphological features characterised except for extractable P which was 3 - 5 times higher in the in the top soils of the profiles in the valley bottoms than those in the upper landscape position of the toposequences. Soil organic carbon (SOC) concentrations significantly differed (P<0.05) in surface soil properties between landscape positions and even significantly much larger (P<0.001) between field types. Fields classified as of good, medium and poor soil fertility by farmers had average SOC concentrations of respectively 9.3-15 g kg–1, 6.6-11 g kg–1, 5.5-7.0 g kg–1. In contrast with other studies in smallholder farming systems in sub-Saharan Africa, spatial analysis did not reveal a particular generalized pattern in variability in soil fertility across farms. Within-farms, larger contents of SOC were associated with larger amounts of silt + clay and on locations of former kraals. The field scale, which is easily recognised by farmers, is an important entry point for targeting soil fertility management technologies.
Heterogeneity in soil fertility affected performance of legumes established with and without P and their residual effect on subsequent finger millet crops. Legume biomass and N accumulation differed significantly (P<0.001) between villages, landscape position, field type and P application rate. Mucuna accumulated the most biomass (4.8-10.9 Mg ha–1) and groundnut the least (1.0-3.4 Mg ha–1) on both good and poor fields in the upper and middle landscape positions. N accumulation and amounts of N2-fixed by the legumes followed a similar trend as biomass, and was increased significantly by application of P. Grain yields of finger millet were significantly (P<0.001) higher in the first season after incorporation of legume biomass than in the second season after incorporation. Finger millet also produced significantly more grain yield in good fields (0.62-2.15 Mg ha–1) compared with poor fields (0.29-1.49 Mg ha–1). Farmers preferred growing groundnut and were not interested in growing pigeonpea and mucuna. They preferentially targeted grain legumes to good fields except for mucuna and pigeonpea to poor fields. Benefit-cost ratios indicated that legume-millet rotations without P application were only profitable on good fields. Green grams, cowpea and soyabean without P can be targeted to good fields on both upper and middle landscape positions in both villages but mucuna without P to poor fields on the middle landscape position in Chelekura village and cowpea without P to poor fields on the upper landscape position in Onamudian village.
Application of N, P fertilisers alone (0, 30, 60, 90 kg ha–1), N+P at equal rates of single application, and manure (3 t ha–1) supplemented with N (0, 30, 60 and 90 kg ha–1) to degraded fields closed the within farm yield gap in finger millet by only 24%-43 %. The inability of the options to close the yield differences was because of poor nutrient use efficiencies (<25%) and other nutrient limitations (S and K) and physical limitations due to surface crusting. With large heterogeneity in soil fertility within smallholder farming systems, blanket recommendations are of limited value.
Using the Quantitative Evaluation of Fertility of Tropical Soils (QUEFTS) model calibrated for finger millet, balanced fertiliser requirements for a target millet yield of 2000 kg ha–1 was estimated at 83 kg N ha–1 and 52 kg P ha–1 and 56 kg K ha–1 for the sandy loam soils of Chelekura village and 64 kg N ha–1 and 31 kg P ha–1 and 40 kg K ha–1 for the sandy clay loam soils in Onamudian village. Targeting nutrient management options can result in larger benefits from nutrient management interventions and specific attention can be afforded to specific constraints to avoid wastage of resources. Combining organic resources and mineral fertilisers is needed for higher crop yields and nutrient use efficiencies. However, the SOC thresholds for higher mineral fertiliser use efficiencies need to be determined for different soil types (silt + clay) and crops as well as making farm/ system scale reconfigurations of cropping systems that will enhance efficiency in resource use. Supportive policy frameworks should be put in place to enhance investment in soil fertility management and thus increase food production.

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