Giller K.E.,Wageningen University |
Tittonell P.,CIRAD - Agricultural Research for Development |
Rufino M.C.,Wageningen University |
van Wijk M.T.,Wageningen University |
And 23 more authors.
Agricultural Systems | Year: 2011
African farming systems are highly heterogeneous: between agroecological and socioeconomic environments, in the wide variability in farmers' resource endowments and in farm management. This means that single solutions (or 'silver bullets') for improving farm productivity do not exist. Yet to date few approaches to understand constraints and explore options for change have tackled the bewildering complexity of African farming systems. In this paper we describe the Nutrient Use in Animal and Cropping systems - Efficiencies and Scales (NUANCES) framework. NUANCES offers a structured approach to unravel and understand the complexity of African farming to identify what we term 'best-fit' technologies - technologies targeted to specific types of farmers and to specific niches within their farms. The NUANCES framework is not 'just another computer model'! We combine the tools of systems analysis and experimentation, detailed field observations and surveys, incorporate expert knowledge (local knowledge and results of research), generate databases, and apply simulation models to analyse performance of farms, and the impacts of introducing new technologies. We have analysed and described complexity of farming systems, their external drivers and some of the mechanisms that result in (in)efficient use of scarce resources. Studying sites across sub-Saharan Africa has provided insights in the trajectories of change in farming systems in response to population growth, economic conditions and climate variability (cycles of drier and wetter years) and climate change. In regions where human population is dense and land scarce, farm typologies have proven useful to target technologies between farmers of different production objectives and resource endowment (notably in terms of land, labour and capacity for investment). In such regions we could categorise types of fields on the basis of their responsiveness to soil improving technologies along soil fertility gradients, relying on local indicators to differentiate those that may be managed through 'maintenance fertilization' from fields that are highly-responsive to fertilizers and fields that require rehabilitation before yields can improved. Where human population pressure on the land is less intense, farm and field types are harder to discern, without clear patterns. Nutrient cycling through livestock is in principle not efficient for increasing food production due to increased nutrient losses, but is attractive for farmers due to the multiple functions of livestock. We identified trade-offs between income generation, soil conservation and community agreements through optimising concurrent objectives at farm and village levels. These examples show that future analyses must focus at farm and farming system level and not at the level of individual fields to achieve appropriate targeting of technologies - both between locations and between farms at any given location. The approach for integrated assessment described here can be used ex ante to explore the potential of best-fit technologies and the ways they can be best combined at farm level. The dynamic and integrated nature of the framework allows the impact of changes in external drivers such as climate change or development policy to be analysed. Fundamental questions for integrated analysis relate to the site-specific knowledge and the simplification of processes required to integrate and move from one level to the next. © 2010 Elsevier Ltd.
Mlalazi B.,Queensland University of Technology |
Welsch R.,Albert Ludwigs University of Freiburg |
Namanya P.,Queensland University of Technology |
Namanya P.,National Agricultural Research Laboratories Kawanda |
And 6 more authors.
Planta | Year: 2012
Carotenoids occur in all photosynthetic organisms where they protect photosystems from auto-oxidation, participate in photosynthetic energy transfer and are secondary metabolites. Of the more than 600 known plant carotenoids, few can be converted into vitamin A by humans and so these pro-vitamin A carotenoids (pVAC) are important in human nutrition. Phytoene synthase (PSY) is a key enzyme in the biosynthetic pathway of pVACs and plays a central role in regulating pVAC accumulation in the edible portion of crop plants. Banana is a major commercial crop and serves as a staple crop for more than 30 million people. There is natural variation in fruit pVAC content across different banana cultivars, but this is not well understood. Therefore, we isolated PSY genes from banana cultivars with relatively high (cv. Asupina) and low (cv. Cavendish) pVAC content. We provide evidence that PSY in banana is encoded by two paralogs (PSY1 and PSY2), each with a similar gene structure to homologous genes in other monocots. Further, we demonstrate that PSY2 is more highly expressed in fruit pulp compared to leaf. Functional analysis of PSY1 and PSY2 in rice callus and E. coli demonstrates that both genes encode functional enzymes, and that Asupina PSYs have approximately twice the enzymatic activity of the corresponding Cavendish PSYs. These results suggest that differences in PSY enzyme activity contribute significantly to the differences in Asupina and Cavendish fruit pVAC content. Importantly, Asupina PSY genes could potentially be used to generate new cisgenic or intragenic banana cultivars with enhanced pVAC content. © 2012 Springer-Verlag.
Francesconi G.N.,National Agricultural Research Laboratories Kawanda |
Agricultural Economics (United Kingdom) | Year: 2015
We use new data on 500 Farmer-Based Organizations (FBOs) in Ghana and regression analysis to reveal determinants of collective investments and the case of the Millennium Development Authority's (MiDA) agricultural program in Ghana to demonstrate that development programs offering hard incentives may be counterproductive in promoting collective action. We show that when a program sets criteria for participation and offers in-cash and in-kind support to selected FBOs, it may promote rent-seeking and crowd out equity capital formation. This is so because FBOs may have formed for the sole purpose of benefitting from incentives offered by the program and thus lack an economic justification, which is an important condition for progression through the cooperative life cycle. Further, by setting stringent participation criteria, the program may end up selecting younger organizations while it is the more consolidated organizations that are able to connect to business development services (BDS) and engage in more offensive collective action. © 2015 International Association of Agricultural Economists.
Musinguzi P.,Makerere University |
Tenywa J.S.,Makerere University |
Ebanyat P.,Makerere University |
Basamba T.A.,Makerere University |
And 3 more authors.
Geoderma Regional | Year: 2015
Ferralsols are chemically poor soils, with management challenges associated with soil fertility heterogeneity and nitrogen limitations. Proper assessment of soil organic matter fractions can be instrumental in understanding the causes of limited nitrogen supply, and thus addressing soil fertility heterogeneity. A study was conducted in cultivated and uncultivated Ferralsols, in order to assay soil organic carbon (SOC), its particle-size fractions and their influence on soil fertility heterogeneity across small farms in central Uganda. Soil samples were taken from the 0-15 and 15-30 cm depths from 30 cultivated fields classified as of low fertility, medium fertility and high fertility, and from two nearby sites in a native shrubland as references. Soil samples were physically fractionated into sand (2000-63 μm), silt (63-2 μm) and clay (< 2 μm). Total SOC and N were analyzed in bulk samples and each size fraction, and the Carbon Management Index (CMI), a widely used indicator of soil quality, was calculated for each field. The CMI in cultivated soils was far below the 100% in reference soils, reaching 34.7, 40.3 and 87% in low, medium and high fertility fields, respectively. SOC and N concentrations decreased in particle-size separates in the order clay > silt > sand. The SOC pool and N in the clay-sized fraction were correlated to soil fertility indicators. More N was stored in the silt + clay size fractions, a generally more stable pool, than in the more labile sand-sized pool. The SOC pool in sand size fractions was far below in low and medium fertility soils than in a reference uncultivated soil. Thus, the sand-sized pool emerged as the most likely cause of limited N supply in cultivated low-input Ferralsols in Uganda. © 2015 Elsevier B.V. All rights reserved.
Mukamuhirwa F.,Makerere University |
Tusiime G.,Makerere University |
Mukankusi M.C.,National Agricultural Research Laboratories Kawanda
Euphytica | Year: 2015
Micronutrient malnutrition especially iron (Fe) and zinc (Zn) has disastrous consequences for the more vulnerable members of the human society, especially poor women and pre-school children in developing countries. The common bean (Phaseolus vulgaris L.), an important grain legume directly consumed by humans provides cheap and important quantities of protein and calories and is an excellent source of some minerals (Fe and Zn) and vitamins which qualify it as perfect food. Unfortunately, many of the adapted bean market class varieties are low in these nutrients. Therefore there is need for biofortification of these varieties with Fe and Zn through plant breeding and genetic engineering in order to contribute to improved health of bean consumers. The objective of this study was to determine the mode of inheritance of high Fe and Zn concentration in selected bean varieties. Six parents high and low in Fe and Zn were crossed following a full diallel crossing design. Populations were advanced from F1 to F2. F3 seed were analyzed for Fe and Zn concentration using X-ray fluorescence. The study showed that both additive and non-additive gene effects are important in determining the expression of high Zn and Fe concentration even though additive gene effects contributed more. Narrow sense heritability of Fe and Zn was high estimated at 71 % for Fe and 83 % for Zn. Significant maternal and reciprocal effects suggest also that cytoplasmic inheritance is involved in Zn and Fe concentration. Strong positive correlation between Fe and Zn concentrations (r = 0.75) was observed suggesting that these micronutrients are not independently inherited. The positive relationship between Fe and Zn plus the negative relationship observed between Zn and seed size (r = 56) suggest that Zn and Fe accumulation is controlled multigenically or oligogenically with some genes affecting the concentration of both minerals. The variability in seed mineral concentration among crosses was larger for Fe (47–77 ppm) than for Zn (28–38 ppm). © 2015, Springer Science+Business Media Dordrecht.
Jansen J.A.,University of Nebraska - Lincoln |
Wortmann C.S.,University of Nebraska - Lincoln |
Stockton M.A.,University of Nebraska - Lincoln |
Kaizzi C.K.,National Agricultural Research Laboratories Kawanda
Agronomy Journal | Year: 2013
Financial constraints commonly limit fertilizer use by smallholder farmers as they strive to maximize net returns on their investments. Fifteen crop-nutrient response functions, including six crops, were derived from the results of 80 trials conducted in Uganda. The net return to nutrient application for typical fertilizer use costs and grain prices in Uganda was greatest for a small amount of N applied to dry bean (Phaseolus vulgaris L.), followed by N applied to rice (Oryza spp.), P applied to groundnut (Arachis hypogaea L.) and soybean [Glycine max (L.) Merr.], and then N applied to maize (Zea mays L.) and grain sorghum [Sorghum bicolor (L.) Moench]. Net returns were less for the remaining nine response functions. The Uganda Fertilizer Optimization Tool was developed for Uganda to maximize net returns to fertilizer use for finance-limited crop management. It considers the area of each crop to be planted, fertilizer costs, expected grain value, and the money available for investment. The tool optimizes across response functions to provide the crop-nutrient-rate combinations expected to maximize net returns. In an example with 1 ha each of the above six crops and US$170 available for fertilizer use, the optimized net return was US$1918 compared with US$676 and US$804 for US$170 of fertilizer applied to maize and rice, respectively, at rates to maximize net returns per hectare. This approach to fertilizer use of maximizing net returns on investment can gradually enable much increased fertilizer use because of the relatively high returns on investment compared with traditional fertilizer use recommendations. © 2013 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved.