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To tackle the problem of soil erosion and moisture stress, the government of Ethiopia introduced a yearly mass campaign where communities get together and implement various soil and water conservation (SWC) and water harvesting (WH) practices. Although the interventions are believed to have reduced soil erosion/sediment yield and enhanced surface and ground water, quantitative information on the impacts of various options at different scales is scarce. The objective of this study was to assess the impacts different land uses, SWC and WH interventions on water and suspended sediment yield (SSY) at plot and watershed scales in the central highlands of Ethiopia. Standard erosion plot experiments and hydrological stations were used to monitor the daily water and SSY during 2014 to 2017. The results show differences between treatments both at plot and watershed scales. Runoff and soil loss were reduced by an average 27 and 37%, respectively due to SWC practices at the plot level. Overall, SWC practices implemented at the watershed level reduced sediment yield by about 74% (in the year 2014), although the magnitude of sediment reduction due to the SWC interventions reduced over time. At both scales it was observed that as the number of years since SWC measures have been in place increased, their effectiveness declined due to the lack of maintenance. This study also revealed that extrapolating of plot data to watershed scale causes over or under estimation of net erosion.

Improving fertilizer use efficiency has remained a challenge, particularly for small-scale farming in undulating ‘abnormal’ landscapes of East Africa. Milne's 1930s concept on ‘Catena’ was considered as a breakthrough in understanding soil variability and its implication on productivity in East African highlands. However, there is limited information on how the ‘Catena’ features could be used for fine tuning fertilizer recommendations. We initiated multiple on-farm replicated experiments in three wheat-growing districts (Endamohoni, Lemo and Worreilu) in the Ethiopian highlands in 2014, 2015 and 2016 to assess landscape positions affecting crop-nutrient responses, identify yield limiting nutrients across the ‘Catena’ (N, P, K, S and Zn) and quantify effects of landscape positions on resources use efficiency. We clustered farmlands across the ‘Catena’ (Hillslopes, Midslopes and Footslopes) based on land scape positions in the respective locations. Wheat yield was more strongly and significantly affected by landscape positions (P < 0.001) than by nutrient sources or rates. The crop response to fertilizers was 50 to 300% higher in foot slopes than in hillslopes, depending on locations and inputs levels. With increasing slope, there was a decrease in a crop fertilizer response due to a significant decrease in soil organic carbon, clay content and soil water content, with r2 of 0.95, 0.86 and 0.96, respectively. The difference in the crop response between landscape positions was significantly higher (P < 0.05) with higher rates of nutrient applications (>N92 P46) while differences between landscape positions diminish at lower rates. Yield benefits due to application of K was significant only in the dry years (P < 0.05), while there was hardly any yield benefit from the application of zinc and sulfur. The crop nitrogen recovery fraction and crop water productivity decreased with an increasing slope regardless of nutrient combinations. The results indicated that the landscape position could be considered as a proxy indicator for targeted fertilizer application, particularly in farms with undulating topographic features. Hillslopes are better served by the application of organic fertilizers along with conservation measures as applying higher rates of mineral fertilizer in hillslopes would rather increase the risk of downstream nutrient movement.

Empowering women farmers to participate in agricultural research is a key strategy for sustainable agricultural development. Women empowerment has the potential to improve their roles in agricultur...

The Rural Household Multiple Indicator Survey (RHoMIS) is a standardized farm household survey approach which collects information on 758 variables covering household demographics, farm area, crops grown and their production, livestock holdings and their production, agricultural product use and variables underlying standard socio-economic and food security indicators such as the Probability of Poverty Index, the Household Food Insecurity Access Scale, and household dietary diversity. These variables are used to quantify more than 40 different indicators on farm and household characteristics, welfare, productivity, and economic performance. Between 2015 and the beginning of 2018, the survey instrument was applied in 21 countries in Central America, sub-Saharan Africa and Asia. The data presented here include the raw survey response data, the indicator calculation code, and the resulting indicator values. These data can be used to quantify on- and off-farm pathways to food security, diverse diets, and changes in poverty for rural smallholder farm households., Measurement(s)Demographics • cultivated environment • Household Environment • economic performanceTechnology Type(s)SurveyFactor Type(s)country • yearSample Characteristic - OrganismHomo sapiensSample Characteristic - EnvironmentfarmSample Characteristic - LocationCentral America • Sub-Saharan Africa • Asia Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.11637786

Non-technical summary Until the past half-century, all agriculture and land management was framed by local institutions strong in social capital. But neoliberal forms of development came to undermine existing structures, thus reducing sustainability and equity. The past 20 years, though, have seen the deliberate establishment of more than 8 million new social groups across the world. This restructuring and growth of rural social capital within specific territories is leading to increased productivity of agricultural and land management systems, with particular benefits for those previously excluded. Further growth would occur with more national and regional policy support. Technical summary For agriculture and land management to improve natural capital over whole landscapes, social cooperation has long been required. The political economy of the later twentieth and early twenty-first centuries prioritized unfettered individual action over the collective, and many rural institutions were harmed or destroyed. Since then, a wide range of social movements, networks and federations have emerged to support transitions towards sustainability and equity. Here, we focus on social capital manifested as intentionally formed collaborative groups within specific geographic territories. These groups focus on: (1) integrated pest management; (2) forests; (3) land; (4) water; (5) pastures; (6) support services; (7) innovation platforms; and (8) small-scale systems. We show across 122 initiatives in 55 countries that the number of groups has grown from 0.50 million (in 2000) to 8.54 million (in 2020). The area of land transformed by the 170–255 million group members is 300 Mha, mostly in less-developed countries (98% groups; 94% area). Farmers and land managers working with scientists and extensionists in these groups have improved both environmental outcomes and agricultural productivity. In some cases, changes to national or regional policy supported this growth in groups. Together with other movements, these social groups could now support further transitions towards policies and behaviours for global sustainability. Social media summary Millions of geographically based new social groups are leading to more sustainable agriculture and forestry worldwide.

Introduction Ethiopia has made efforts to tackle the challenges of low crop and livestock productivity and degradation of land resources through various rural development strategies. However, increasing demands for food, animal feed, fuel, and income-generating activities are putting pressure on the land. In this paper, we describe the production pressure and competition between crop and livestock production, quantify rates of land-use/cover (LULC) changes, and examine driving forces and consequences of land conversion. Methods The study was conducted in Gudo Beret watershed, North Shewa Zone of Amhara region, Ethiopia. It used a combination of methods including remote sensing, household interviews, field observations, focus group discussions, and key informant interviews. Supervised and unsupervised image classification methods were employed to map LULC classes for 31 years (1984–2016). Results The results of satellite remote sensing revealed that 51% of the land in the study area was subject to accelerated land conversions. The household survey results indicated that feed resources and grain production pressures were 1.43 and 1.34 t ha−1 respectively. The observed annual changes in plantation and settlement areas were 2.6% and 2.9%. This was mainly at the expense of bushland and grazing land systems. Cropland increased (0.4% year−1) while grazing land reduced (3.5% year−1) under contrasting dynamics and competitive changes. An increase in human and livestock populations and farm expansion were major drivers of land conversion that adversely affected household livelihoods and the natural ecosystem. The consequences of these pressures resulted in a lack of animal feed, low crop-livestock productivity, and a reduction in natural vegetation coverage. Conclusions We suggest that sustainable land resource management, more integrated crop-livestock production, and the use of productivity-enhancing technologies could play a role in managing competition for land resources.

The central Ethiopian highlands where most human and livestock populations concentrated have experienced a drastic change in land use and land cover (LULC) of the landscapes. This study was aimed to define the rate and pattern of LULC changes in Dendi-Jeldu hilly-mountainous areas in the central Ethiopia. Aerial photographs of years 1957 and 1995, and Landsat images taken at 1995 and 2014 were used to analyze the historical land use and land cover (LULC) changes. The study covered an area of about 438 km2. The analysis extracted from these remote sensing data revealed that, in 1957, the dominant LULCs were pastureland, cultivated land (cropland) and forestland covering 49, 25 and 20% of the total area, respectively. Remarkable LULC change dominated by cultivated land expansion (now covering 68% of the total area), however, claimed vast areas under pastureland (main), forestland and woodland. Deforestation in particular, would have been greater if Chilimo forest (remnant afro-montane forest) was not under state control. Plantation forestry exclusively dominated by eucalyptus species also showed substantial expansion into pastureland in the period between 1957 and 1995, and cultivated land between 1995 and 2014. In the period 1957 to 2014 cultivated land, plantation land and settlement were increased by 170%, 13,674% and 172% respectively, while pastureland, forestland and woodland declined by 67%, 73% and 100%, respectively. Change from natural habitat (pastureland, forestland and woodland) to other land uses (cultivated, plantation and settlement lands) is likely to have a large impact on biodiversity, land degradation and beyond.

In 2012, Africa RISING conducted participatory community analysis (PCA) as the first phase of a participatory development approach in the Ethiopian highlands. The PCA identified trends, constraints...

CONTEXT Sustainable intensification is one approach to increasing food production without undermining sustainability goals. In recent years new tools and indicators have been developed for broad-based assessment of sustainable intensification. However, most of these tools have been applied at field level and assessing individual technologies, while integrated assessments of multiple novel practices at farm-to-village level are lacking. OBJECTIVE In this study we develop and apply a data collection, analysis, and interpretation approach that results in a replicable and rapid method for a multi-variate assessment of sustainable intensification. METHODS Drawing on a survey of 779 participant farmers, and using the Sustainable Intensification Assessment Framework, we quantified 27 indicators grouped into five domains: agricultural production, economics, environment, human welfare, and social. We applied an expert-led threshold setting exercise to re-scale indicators, permitting aggregated and dis-aggregated visualisation onto a common axis. We developed a graphic evaluation approach to communicate the multiple domain and indicator scores and applied this approach to quantify trade-offs and synergies related to agricultural productivity in four contrasting sites in Ethiopia. RESULTS AND CONCLUSIONS In each site there was a notable and significant gradient of production intensity, although average crop and livestock productivity remained well below attainable levels. Higher levels of productivity were correlated with higher scores in the economic, social and agricultural domains, and in some sites they were also positively correlated with the human welfare and environmental domains. In no case was increased production intensity correlated with lower scores in any of the sustainability domains, indicating that in these relatively low-intensity systems increases in productivity will go hand-in-hand with improvements in most other sustainability domains. Synergies can overrule trade-offs in these smallholder systems in Ethiopia, if managed well. SIGNIFICANCE This is one of very few studies of multiple sustainable intensification technologies implemented concurrently at the household to community level. Most studies focus on individual technologies or practices within specific niches of the farming system. The method could be developed further for efficient application to various large-scale development or intensification projects, and could potentially make use of existing smallholder information databases.

Soil fertility depletion is a major constraint of smallholder farming in sub-Saharan Africa. We tested the aftereffects of green manures, namely vetch (Vicia sativa L.), lupin (Lupinus polyphyllus L.), and lablab (Lablab purpureus L.) incorporated into the soil compared to three fertilizer levels (0/0, 23/0, and 78/20 kg N/P ha−1) and evaluated their effect on soil fertility status and wheat yield in acidic Nitisols of southern Ethiopia, for three consecutive years (2017–2019). The treatments were laid out in a randomized complete block design with three replications. In 2017 and 2018, green manures were sown in March and April, respectively, using short rains and incorporated into the soil during late flowering stage, either (i) the whole shoot and root biomass were plowed under, (ii) shoot biomass was transferred to non-treated plots or (iii) only the below ground root biomass was used. Wheat was sown during long rains during the same growing season a month after the incorporation of green manures. In 2019, wheat was grown on the residual plots with the application of an additional 64/20 kg N/P ha−1. Results revealed that in 2017 and 2018 the application of vetch and lupin green manure resulted in grain yield advantages of 49 and 32 % and 34 and 19 %, respectively, over 0/0 and 23/0 kg N/P ha−1, though it produced less grain yield compared to higher fertilizer rates. In 2019, the addition of vetch and lupin whole biomass treatments gave significantly higher wheat yield over fertilizer treatments, with yield advantages of 18–26 %. Similarly, root biomass only also produced a significantly higher yield than fertilized plots. The yield benefits from green manures were due to improved soil water content, improved P-availability, significantly increased exchangeable K, Ca, and Mg, and increased pH by about 0.5 units. The residual effect of green manures could compensate for up to 33 % of the recommended rate of 78 N kg ha−1. We conclude that niche-based integration of green manures could improve yield, enhance soil carbon sequestration and sustain crop-livestock systems, whereby the above ground biomass could serve as quality livestock feed without compromising soil fertility benefits.

An enormous effort is underway in Ethiopia to address soil erosion and restore overall land productivity. Modelling and participatory approaches can be used to delineate erosion hotspots, plan site- and context-specific interventions and assess their impacts. In this study, we employed a modelling interface developed based on the Revised Universal Soil Loss Equation adjusted by the sediment delivery ratio to map the spatial distribution of net soil loss and identify priority areas of intervention. Using the modelling interface, we also simulated the potential impacts of different soil and water conservation measures in reducing net soil loss. Model predictions showed that net soil loss in the study area ranges between 0.4 and 88 t ha− 1 yr− 1 with an average of 12 t ha− 1 yr− 1. The dominant soil erosion hotspots were associated with steep slopes, gullies, communal grazing and cultivated areas. The average soil loss observed in this study is higher than the tolerable soil loss rate estimated for the highland of Ethiopia. The scenario analysis results showed that targeting hotspot areas where soil loss exceeds 10 t ha− 1 yr− 1 could reduce net soil loss to the tolerable limit (

Sustainable intensification (SI) is at the forefront of food security discussions as a means to meet the growing demand for agricultural production while conserving land and other resources. A broader definition of SI is emerging that takes into account the human condition, nutrition and social equity. Next steps require identification of indicators and associated metrics, to track progress, assess tradeoffs and identify synergies. Through a systematic, qualitative review of the literature we identified SI indicators, with a primary focus on African smallholder farming systems. We assessed indicators and metrics for which there is consensus, and those that remain contested. We conclude that, while numerous metrics for evaluating SI systems exist, many often-cited indicators lack strong sets of associated metrics.

The performance, expansion and contribution of tree lucerne has not reached to its full potential due to a number of factors. An action on-farm research was conducted with men and women farm households to (a) compare survival and growth of tree lucerne across contrasting sites and growing niches, and (b) identify the key determinants of tree lucerne survival and growth on farms in the crop-livestock systems. The research was conducted in eight research kebeles (the smallest administrative unit in the country) of the four Africa RISING (Africa Research in Sustainable Intensification for the Next Generation) project sites. Eight farmer research groups (FRGs) were formed in consultation with the group members. Each FRG consisted of 25–30 men and women farmers representing a range of social groups. Each farmer participating in the research received on average 50 seedlings. A total of 253 farmers participated in the research. After planting, data on survival, growth, root collar diameter and management were collected at 9 months using simple field monitoring tools. A total of ten sample plants were selected from the field of each farmer who planted tree lucerne, and these were labelled for continuous growth measurements. The on-farm research measurement was supplemented by cross-sectional survey data collected from a sample of FRG member households in the eight research kebeles. A combination of descriptive statistics, multivariate statistical techniques and econometric models were used for data analysis. The results of the study show that percentage survival on-farm were significantly higher for tree lucerne planted in backyards than those planted in outfields and for middle-resource class households. Household size, access to reliable water supply, and management factors—including fencing and watering planted-seedlings, mulching during dry periods, clean spot weeding and applying organic fertilizers—significantly enhanced survival and growth of tree lucerne in the planting sites.

Scaling is a ubiquitous concept in agricultural research in the global south as donors require their research grantees to prove that their results can be scaled to impact upon the livelihoods of a large number of beneficiaries. Recent studies on scaling have brought critical perspectives to the rather technocratic tendencies in the agricultural innovations scaling literature. Drawing on theoretical debates on spatial strategies and practical experience of agricultural innovation scaling in Ethiopia, this paper adds to the current debate on what constitutes scaling and how to overcome critical scaling constraints. The data for the paper came from a qualitative assessment using focus group discussions, key informant interviews, and document analysis on scaling work done in Ethiopia by a USAID-funded research for development project. The paper concludes with four broad lessons for the current understating of agricultural innovation scaling. First, scaling of agricultural innovations requires a balanced focus on technical requirements and associated social dynamics surrounding scaling targets, actors involved and their social relations. Second, appreciating the social dynamics of scaling emphasizes the fact that scaling is more complex than a linear rolling out of innovations towards diffusion. Third, scaling may not be strictly planned; instead, it might be an extension of the innovation generation process that relies heavily on both new and long-term relationships with key partners, trust, and continuous reflection and learning. Fourth, the overall implication of the above three conclusions is that scaling strategies need to be flexible, stepwise, and reflective. Despite the promises of flourishing scaling frameworks, scaling strategies it would appear from the Africa RISING experience that, if real impact is to be achieved, approaches will be required to be flexible enough to manage the social, processual and emergent nature of the practice of scaling.

The sustainable intensification of agricultural systems offers synergistic opportunities for the co-production of agricultural and natural capital outcomes. Efficiency and substitution are steps towards sustainable intensification, but system redesign is essential to deliver optimum outcomes as ecological and economic conditions change. We show global progress towards sustainable intensification by farms and hectares, using seven sustainable intensification sub-types: integrated pest management, conservation agriculture, integrated crop and biodiversity, pasture and forage, trees, irrigation management and small or patch systems. From 47 sustainable intensification initiatives at scale (each >104 farms or hectares), we estimate 163 million farms (29% of all worldwide) have crossed a redesign threshold, practising forms of sustainable intensification on 453 Mha of agricultural land (9% of worldwide total). Key challenges include investment to integrate more forms of sustainable intensification in farming systems, creating agricultural knowledge economies and establishing policy measures to scale sustainable intensification further. We conclude that sustainable intensification may be approaching a tipping point where it could be transformative.

The objective of this study was to determine the effect of supplementing increasing levels of dried tagasaste (Chamaecytisus palmensis) leaf on the nutrition and performance of sheep fed a basal diet of barley straw. The study had four treatments, which involved supplementation of dried tagasaste leaf at 100, 200, 300, and 400 g/day. Twenty-four yearling Menz sheep (weight 17 ± 0.83 kg) were assigned to one of the four treatments in a randomized complete block design. The experiment comprised a feeding trial lasting for 90 days, a digestibility trial, and carcass evaluation using all animals. Samples of the feed consumed, refused, and feces were analyzed for nutrients. Intake and digestibility of dry matter (DM) and nutrients increased linearly (P

Bio-economic farm models are tools to evaluate ex-post or to assess ex-ante the impact of policy and technology change on agriculture, economics and environment. Recently, various BEFMs have been developed, often for one purpose or location, but hardly any of these models are re-used later for other purposes or locations. The Farm System Simulator (FSSIM) provides a generic framework enabling the application of BEFMs under various situations and for different purposes (generating supply response functions and detailed regional or farm type assessments). FSSIM is set up as a component-based framework with components representing farmer objectives, risk, calibration, policies, current activities, alternative activities and different types of activities (e.g., annual and perennial cropping and livestock). The generic nature of FSSIM is evaluated using five criteria by examining its applications. FSSIM has been applied for different climate zones and soil types (criterion 1) and to a range of different farm types (criterion 2) with different specializations, intensities and sizes. In most applications FSSIM has been used to assess the effects of policy changes and in two applications to assess the impact of technological innovations (criterion 3). In the various applications, different data sources, level of detail (e.g., criterion 4) and model configurations have been used. FSSIM has been linked to an economic and several biophysical models (criterion 5). The model is available for applications to other conditions and research issues, and it is open to be further tested and to be extended with new components, indicators or linkages to other models., Les modèles bioéconomiques de ferme sont des outils pour évaluer ex-post ou anticiper ex-ante l'impact des changements des politiques et des technologies sur l'agriculture, l'économie et l'environnement. Récemment, différents BEFMs ont été développés, souvent dans un seul but ou localisation, mais aucun de ces modèles n'a été réutilisé plus tard à d'autres fins ou lieux. Le Farm System Simulator (FSSIM) fournit un cadre générique permettant l'application de BEFMs dans différentes situations et à diverses fins (estimation des fonctions d’offre, évaluations détaillées régionale ou par type de ferme…). FSSIM est conçu comme un cadre de modélisation intégré avec des composants qui représentent les objectifs des agriculteurs, le risque, le calibrage, les politiques publiques, les activités courantes, les activités alternatives, les différentes activités de production (par exemple, les cultures annuelles et pluriannuelles et l’élevage). Le caractère générique du modèle FSSIM est évalué selon cinq critères en examinant ses applications. FSSIM a été appliqué à diverses zones pédoclimatiques (critère 1) et à plusieurs types d'exploitations (critère 2) avec différentes spécialisations, intensités et tailles. Dans la plupart des applications FSSIM a été utilisé pour évaluer les effets des changements des politiques et dans deux applications pour évaluer l'impact des innovations technologiques (critère 3). Dans les différentes applications, plusieurs sources de données, niveau de détail (par exemple, le critère 4) et configurations du modèle ont été utilisés. FSSIM a été couplé à un modèle économique et à plusieurs modèles biophysiques (critère 5). Le modèle est disponible pour des applications à d'autres conditions et enjeux de la recherche, et il est ouvert à de nouveaux essais et à être étendue avec de nouveaux composants, indicateurs ou liens vers d'autres modèles.

As population density increases, crops and livestock become increasingly integrated as farming systems intensify. In order to increase output per unit of land farmers are forced to alter feeding practices as availability of feed resources change. In order to make appropriate recommendations to farmers it is important to understand these changes. The present paper describes a study in two areas in the Central highlands of Kenya representing areas of low and high population density and consequently low (LI) and high (HI) levels of intensification. Quantity and source (on or off-farm) of feed DM offered by type and milk production were monitored regularly for one year. Seasonal effects were considered by comparing parameters measured in months above and below average rainfall recorded in each area. Numbers of animals owned were higher in LI compared to HI, and milk production per animal similar. However production expressed per unit of land, an indicator of intensification was significantly higher (p

As systems intensify, crops and livestock become increasingly integrated. Forage from crops becomes a larger component of overall forage supply in small-scale systems. This paper integrates information from field trials, studying the effect of varying maize planting density, with modelling approaches to compare this with supplementation of maize stover, genetic improvement of stover digestibility and replacement of the maize crop with planted forage in east and southern Africa. Aggregate analyses for small-scale intensive (SSI) systems producing milk were carried out using a suite of models including CERES, CROPGRO, DRASTIC and ANORAC, scaling-up to regional level using GIS information. Increasing planting density increased the yield of thinnings, but decreased grain and stover yields. Model predictions of milk production from the thinnings and stover produced from one hectare of maize indicated that economic benefits to increased planting density could be achieved when the grain:milk price ratio was low, despite the negative effect on grain yield. Supplementation showed the greatest economic returns with small positive impacts on soil fertility and maize production. Replacing maize with planted forage inevitably increased milk at the expense of maize production. Again, for this intervention, grain:milk price ratios ranging from 0.19 to 2.88 across sub-Saharan Africa are likely to influence the decision of the farmer whether or not to trade milk for grain. Genetic enhancement of the digestibility of maize stover was found to have little impact on milk production because diets based on stover were deficient in nitrogen, preventing animals from benefiting from the increased energy supply resulting from digestibility increases. Other factors such as market access and stability, as well as individual objectives such as cash flow, food security and risk minimisation, were not explored in the present study but will influence household decisions. More complex analyses, accounting for these factors, may be required to predict adoption behaviour, however, the results of the study can be used to evaluate the potential returns to investment in research in the different areas using an economic surplus model.

The recent increased emphasis on impact assessment is due in part to the rapidly changing nature of funding for agricultural research and the shifts that have occurred in what is expected of the agricultural research community. The reasons for doing impact assessment are relatively clear: ex post studies can determine the impact of past investment in research on target beneficiaries and are a way to learn some of the lessons of the past. Ex ante studies can provide information to assist in the allocation of scarce research resources to activities that best match donors’ development objectives. In practice, impact assessment is often contentious and almost always difficult, particularly when livestock are involved. In this paper, we outline methods that can be used in ex ante impact assessment, and illustrate some of these in relation to three recent studies on improved food-feed crops in different places: improving the quality of millet and sorghum stover in India, using dual-purpose cowpea in West Africa, and alternatives for utilizing maize stover in the mixed systems of East and Southern Africa. Such impact assessments are neither cheap nor quick, and the methods that are most appropriate in any situation will depend not only on the resources and expertise available but most importantly on the exact nature of the questions being asked and the end-users of the results. Much remains to be done to maximize the utility of such assessments, particularly in the areas of quantitative model development, rapid qualitative method development, more effective integration of biophysical and socio-cultural indicators and approaches, and provision of baseline data against which to measure progress. Research resource allocation may well retain its somewhat haphazard nature in the future, but given the challenges facing agriculture in developing countries, a mechanism for attempting to ensure that research and extension really do contribute to widely held development goals has to be based on more than trial and error.

The role of livestock in nitrogen cycling in mixed crop‐livestock farming systems of sub-Saharan Africa was explored. Cattle were fed a range of diets to investigate the effects on partitioning of nitrogen between urine and faeces and on the chemical composition of the manures produced. The trade-offs in efficiency between using the feed resources as a direct soil amendment for crop production compared with feeding to livestock and use of the manure as a fertiliser are discussed. Increased dry matter (DM) and nitrogen intake of a poor quality basal diet (barley straw) was achieved by supplementation with 15 and 30% of DM offered as Calliandra calothyrsus, Macrotyloma axillareor poultry manure. Urinary-N excretion for the basal diet (0.5 mg kg 1 liveweight (W) per day) was similar to C. calothyrsus at 15 and 30% supplementation (1.3 and 0.8 mg kg 1 W per day, respectively) and M. axillare at 15 and 30% supplementation (0.4 and 0.6 mg kg 1 W per day, respectively). In contrast, feeding poultry manure, a supplement containing highly degradable N, resulted in larger excretions of excess rumen ammonia as N in the urine, 17.5 and 23.2 mg kg 1 W per day for 15 and 30% supplementation, respectively. Diets containing the largest rate of C. calothyrsus supplementation had the lowest digestibility of N in the acid detergent fibre (ADF) and neutral detergent fibre (NDF) fractions. This was reflected in faeces from cattle fed diets supplemented with C. calothyrsus, which had substantially greater amounts of N bound to fibre (ADF and NDF) fractions than faeces from the other diets. When incubated in leaching tubes prunings of C. calothyrsus showed net N mineralisation from week 2, whereas barley straw, M. axillare and poultry manure immobilised N for >28, 24 and >28 weeks, respectively. Faeces derived from supplementation with C. calothyrsusand M. axillare resulted in shorter nitrogen immobilisation in leaching tubes (16 weeks) than supplementation with poultry manure (24 weeks) when compared with faeces derived from animals fed straw only (28 weeks). Similarly, reduced N uptake from 10-week-old maize plants was observed in pots to which faeces had been added compared with the control treatment. A second crop of maize had increased N uptake. Feeding poor quality crop residues like barley straw to animals produces manures with a decreased capacity to immobilise mineral N in the soil. This was shown

Mixed crop-livestock systems provide livelihoods for a billion people and produce half the world’s cereal and around a third of its beef and milk. Market orientation and strong and growing demand for food provide powerful incentives for sustainable intensification of both crop and livestock enterprises in smallholders’ mixed systems in Africa. Better exploitation of the mutually reinforcing nature of crop and livestock systems can contribute to a positive, inclusive growth trajectory that is both ecologically and economically sustainable. In mixed systems, livestock intensification is often neglected relative to crops, yet livestock can make a positive contribution to raising productivity of the entire farming system. Similarly, intensification of crop production can pay dividends for livestock and enhance natural resource management, especially through increased biomass availability. Intensification and improved efficiency of livestock production mean less greenhouse gases per unit of milk and more milk per unit of water. This paper argues that the opportunities and challenges justify greater investment in research for development to identify exactly where and how ‘win-win’ outcomes can be achieved and what incentives, policies, technologies and other features of the enabling environment are needed to enable sustainable, integrated and productive mixed crop-livestock systems.

In sub-Saharan Africa the importance of nutrient cycling in mixed farming systems is poorly understood, and there is a paucity of information in the literature. The vital role played by livestock in regulating fluxes through nutrient cycles is often ignored in experimentation and crop modelling although, in farming practice, the animal is an integral part of the system. The aim of this review is to highlight animal-related factors which can influence the dynamics of nitrogen (N) cycling in mixed farming systems on the sub-continent. Marked changes in seasonal feed availability and nutritive value occur which affect both the quantity and quality of excreta. The partition of N excretion between urine and faeces can also fluctuate widely with changes in diet composition, and may be influenced by the degradability of the dietary protein in the rumen. The presence of tannins in feeds has been shown to be negatively correlated with protein degradability and digestibility. Different species and classes of livestock produce excreta with varying nutrient concentrations. By controlling animal movements, adjusting carrying capacity in a grazing situation, or storing and distributing excreta from animals kept in confinement, a farmer can influence the proportions of nutrients returned to the soil. Losses of nutrients in storage and on application can be appreciable. The management of the soil and the returned nutrients will determine the losses incurred after application and the quantity potentially available to the crop. The farmer will also decide on the crops to be grown and their management. Crops differ in their nutrient requirements and the efficiency of utilisation. The partition of nutrients between grain and the vegetative parts of the plant affect the nutritive value of the components. When residues are grazed in situ, consumption will depend on animal numbers and the length of time spent grazing. Animals select preferred plant parts, and appreciable losses due to trampling and soiling may occur. The many factors influencing nutrient cycling provide opportunities for decision-making by the farmer. This process can be helped by mathematical modelling where the effects of different management options can be simulated. In taking account of animal-related factors, more realistic simulation models can be developed for the study of crop production in mixed farming systems in sub-Saharan Africa.

Sanda et al. (1999) studied the effects on crossbred steer liveweight gain of alternating the same quantities of napier grass and barley straw at five day intervals over a 40 day period. These animals lost significantly more weight (pin vivodigestibility or intake. The present study was designed to test the hypothesis that there are gradual changes in the rumen environment as animals adapt to the intake of a given forage and that, during this adaptive phase nitrogen is not used efficiently, which could explain the poor performance.