Micronutrient deficiencies (MNDs) remain widespread among people in sub-Saharan Africa1–5, where access to sufficient food from plant and animal sources that is rich in micronutrients (vitamins and minerals) is limited due to socioeconomic and geographical reasons4–6. Here we report the micronutrient composition (calcium, iron, selenium and zinc) of staple cereal grains for most of the cereal production areas in Ethiopia and Malawi. We show that there is geospatial variation in the composition of micronutrients that is nutritionally important at subnational scales. Soil and environmental covariates of grain micronutrient concentrations included soil pH, soil organic matter, temperature, rainfall and topography, which were specific to micronutrient and crop type. For rural households consuming locally sourced food—including many smallholder farming communities—the location of residence can be the largest influencing factor in determining the dietary intake of micronutrients from cereals. Positive relationships between the concentration of selenium in grain and biomarkers of selenium dietary status occur in both countries. Surveillance of MNDs on the basis of biomarkers of status and dietary intakes from national- and regional-scale food-composition data1–7 could be improved using subnational data on the composition of grain micronutrients. Beyond dietary diversification, interventions to alleviate MNDs, such as food fortification8,9 and biofortification to increase the micronutrient concentrations in crops10,11, should account for geographical effects that can be larger in magnitude than intervention outcomes.

Research results published regarding the impact of soil and water conservation practices in the highland areas of Ethiopia have been inconsistent and scattered. In this paper, a detailed review and synthesis is reported that was conducted to identify the impacts of soil and water conservation practices on crop yield, surface run-off, soil loss, nutrient loss, and the economic viability, as well as to discuss the implications for an integrated approach and ecosystem services. The review and synthesis showed that most physical soil and water conservation practices such as soil bunds and stone bunds were very effective in reducing run-off, soil erosion and nutrient depletion. Despite these positive impacts on these services, the impact of physical soil and water conservation practices on crop yield was negative mainly due to the reduction of effective cultivable area by soil/stone bunds. In contrast, most agronomic soil and water conservation practices increase crop yield and reduce run-off and soil losses. This implies that integrating physical soil and water conservation practices with agronomic soil and water conservation practices are essential to increase both provisioning and regulating ecosystem services. Additionally, effective use of unutilized land (the area occupied by bunds) by planting multipurpose grasses and trees on the bunds may offset the yield lost due to a reduction in planting area. If high value grasses and trees can be grown on this land, farmers can harvest fodder for animals or fuel wood, both in scarce supply in Ethiopia. Growing of these grasses and trees can also help the stability of the bunds and reduce maintenance cost. Economic feasibility analysis also showed that, soil and water conservation practices became economically more viable if physical and agronomic soil and water conservation practices are integrated.

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A B S T R A C TSmall-scale irrigation is playing an important role in adapting to climate change, achieving food security, and improving household incomes. The Ethiopian Government considers irrigated agriculture as a primary engine of economic growth and plans to increase the current level of irrigation infrastructure three-fold by the end of 2015. However, there has been concern regarding the performance and management of existing small-scale irrigation. Based on the assessment of 52 small-scale irrigation schemes, and three case study sites, we describe the challenges and interventions required to improve irrigation water management in Ethiopia. Though most schemes are operational, many do not operate at full capacity, due to design failures, excessive siltation, poor agronomic and water management practices, and weak local institutions. In addition to low returns, there is competition for irrigation water between upstream and downstream users, vegetable growers and cereal growers, and between farmers with large irrigable plots and those with small plots. Despite these challenges, our field assessment revealed that small scale irrigation increases crop yields, improves crop diversification, and reduces the risk of crop failure. We emphasize in this paper the need for incentives to improve productivity and minimize conflicts, while enhancing innovation capacity, developing scheme-specific intensification strategies, and promoting collective action. We also describe how benefits from water investments could be substantially increased by overcoming design constraints, * j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / w r r strengthening water user associations, and protecting catchments.

The greatest challenge for tropical agriculture is land degradation and reduction in soil fertility for sustainable crop and livestock production. Associated problems include soil erosion, nutrient mining, competition for biomass for multiple uses, limited application of inorganic fertilizers, and limited capacity of farmers to recognize the decline in soil quality and its consequences on productivity. Integrated soil fertility management (ISFM) is an approach to improve crop yields, while preserving sustainable and long-term soil fertility through the combined judicious use of fertilizers, recycled organic resources, responsive crop varieties, and improved agronomic practices, which minimize nutrient losses and improve the nutrient-use efficiency of crops. Soil fertility and nutrient management studies in Ethiopia under on-station and on-farm conditions showed that the combined application of inorganic and organic fertilizers significantly increased crop yields compared to either alone in tropical agro-ecosystems. Yield benefits were more apparent when fertilizer application was accompanied by crop rotation, green manuring, or crop residue management. The combination of manure and NP fertilizer could increase wheat and faba bean grain yields by 50%-100%, whereas crop rotation with grain legumes could increase cereal grain yields by up to 200%. Although organic residues are key inputs for soil fertility management, about 85% of these residues is used for livestock feed and energy; thus, there is a need for increasing crop biomass. The main incentive for farmers to adopt ISFM practices is economic benefits. The success of ISFM also depends on research and development institutions to provide technical support, technology adoption, information dissemination, and creation of market incentives for farmers in tropical agro-ecosystems.

SUMMARYProjections suggest that annual per capita water availability in the Indo-Ganga Basin (IGB) will reduce to a level typical for water-stressed areas. Producing more crop and livestock products, per unit of agricultural water invested, is advocated as a key strategy for future food production and environmental security in the basin. The objective of this study was to understand the spatio-temporal dynamics of water requirements for livestock feed production, attendant livestock water productivity (LWP) and implications for the future sustainable use of water resources. We focused on three districts in the IGB representing intensive (higher external inputs, e.g. fertilizer, water) and semi-intensive (limited external input) crop-livestock systems. LWP is estimated based on principles of water accounting and is defined as the ratio of livestock beneficial outputs and services to the water depleted and degraded in producing these. In calculating LWP and crop water productivity (CWP), livestock, land use, land productivity and climatic data were required. We used secondary data sources from the study districts, field observations and discussions with key informants to generate those data sets. Our result showed that the volume of water depleted for livestock feed production varied among the study systems and was highly affected by the type of feed and the attendant agronomic factors (e.g. cropping pattern, yield). LWP value was higher for intensive systems and affected by agricultural water partitioning approaches (harvest index, metaolizable energy). LWP tended to decrease between 1992 and 2003. This can be accounted for by the shift to a feeding regime that depletes more water despite its positive impacts on animal productivity. This is a challenging trend with the advent of and advocacy for producing more agricultural products using the same or lower volume of water input and evokes a need for balanced feeding, by considering the nutritive value, costs and water productivity of feed, and better livestock management to improve LWP.

When crops are exposed to drought there is commonly an increase in solute-pool of the plant tissue. A series of experiments were conducted in 1994 and 1995 in the University of Hohenheim, Germany, to evaluate whether drought-induced solute accumulation per se will improve drought resistance, to determine the species of active osmotica involved, and to identify alternative mechanisms in grain legumes, namely Common bean (Phaseolus vulgaris) faba bean (Vicia faba), pea (Pisum sativum), and chickpea (Cicer arietinum). Drought, equivalent to soil water potential of-0.64 MPa, decreased the leaf water potential to-1.67,-1.83,-0.34 and-1.32 MPa and resulted in dry matter yield reduction of 36.4%, 23.9%, 17.6% and 14.5% in faba bean, pea, common bean, and chickpea, respectively. Higher yield of chickpea and common bean under drought was augumented by turgor maintenance. The highest degree of turgor (1.0 MPa) was in common bean, though it had the lowest solute accumulation. Thus, a decrease in osmotic potential was not the only strategy of turgor maintenance in legumes. Increase in solute pool in all was due to concentration effect as a result of water loss and growth inhibition, except in chickpea. The major osmotica in chickpea were of organic origin, namely sugars and sugar alcohols contributing more than 50%, and amino compounds 20% of the osmotic pool. Calcium was the only inorganic osmoticum contributing 19% of the pool. Concentration of solutes in the cell-sap did not necessarily indicate the level of contribution to the osmotic pool, as the most abundant ions (e.g., potassium) did not contribute to osmotic adjustment under drought. It was concluded that it is vital to differentiate solutes accumulated as a concentration effect from active osmotica using cell water volume of control plants before considering solute concentration as a selection criterion for breeding drought resistant varieties/crops.