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A significant increase in the global demand of animal products is expected in the near future, because of evolving food consumption patterns in emerging countries. To fulfil the needs, a “Livestock Revolution” should occur and it will have to target in priority smallholder farms in developing countries, as they are the main actors in supply chains of milk and meat. To achieve such an increase in milk yield and live weight gain within numerous farms, new tools of intervention have to be tested. In fact, in many developing countries, State services are currently withdrawing from their traditional support to farmers, and therefore innovative methods should be set-up. They will also require a more responsible implication of the stakeholders in supply chains, particularly with well organized farmers’ associations. In areas characterized by water stress and climate change, this should be a top priority issue in the agenda of agricultural development institutions. As livestock production involves many processes from water to forage biomass elaboration and dietary rations conceptions, it is generally acknowledged that it necessitates important volumes of water. In this article, an example of an intervention research is presented from the Tadla irrigation scheme (centre of Morocco) as an illustration of intensive cattle production in a context of irrigation in a semi arid region (less than 300 mm of annual rainfall). Results related to follow-ups of water productivity through cattle farming and trials to increase the average milk yield per cow are presented. A reflection on the possibilities to use "virtual water" and on the generalisation of such methods to a whole population of dairy farmers in a supply basin (i.e. an irrigation scheme) is finally developed with its consequences on the economic sustainability of smallholder units. Thus, a capacity building process is urgently required to upgrade farmers’ performances. This will induce the adoption of sound on-farm practices, from irrigation systems to soil fertility management and forage biomass production. It will also rely on the continuous design of balanced dietary rations for lactating cows and their impacts on cattle load (number of cattle per ha of forage). Finally, more attention should be paid to the existing farmers’ co-operatives, which would constitute crucial operators in disseminating innovation processes to face the challenges of water shortage in cattle production systems.

This paper examines a number of agronomic field experiments in different regions of sub-Saharan Africa to assess the associated variability in the efficiencies with which applied and available nutrients are taken up by crops under a wide range of management and environmental conditions. We consider N and P capture efficiencies (NCE and PCE, kg uptake kg-1 nutrient availability), and N and P recovery efficiencies (NRE and PRE, kg uptake kg-1 nutrient added). The analyzed cropping systems employed different soil fertility management practices that included (1) N and P mineral fertilizers (as sole or their combinations) (2) cattle manure composted then applied or applied directly to fields through animal corralling, and legume based systems separated into (3) improved fallows/cover cropscereal sequences, and (4) grain legume-cereal rotations. Crop responses to added nutrients varied widely, which is a logical consequence of the wide diversity in the balance of production resources across regions from arid through wet tropics, coupled with an equally large array of management practices and inter-season variability. The NCE ranged from 0.05 to 0.98 kg kg-1 for the different systems (NP fertilizers, 0.16-0.98; fallow/cover crops, 0.05-0.75; animal manure, 0.10-0.74 kg kg-1), while PCE ranged from 0.09 to 0.71 kg kg-1, depending on soil conditions. The respective NREs averaged 0.38, 0.23 and 0.25 kg kg-1. Cases were found where NREs were[1 for mineral fertilizers or negative when poor quality manure immobilized soil N, while response to P was in many cases poor due to P fixation by soils. Other than good agronomy, it was apparent that flexible systems of fertilization that vary N input according to the current seasonal rainfall pattern offer opportunities for high resource capture and recovery efficiencies in semi-arid areas. We suggest the use of cropping systems modeling approaches to hasten the understanding of Africa's complex cropping systems. (Resume d'auteur)

Metadata only record The prevalence of soil degradation and production constraints for smallholder farmers in Central Kenya offers an opportunity for the application of conservation agriculture practices. However, much variability exists between smallholders, rendering the benefits of CA quite site specific. The purpose of this study was to determine the effects of minimum tillage and mulches on maize yields of twenty-one farms with varying soil fertility, size, and, cropping seasons. Two tillage and two crop residue trials were compared across three soil fertility classes from 2007 to 2009. It was determined that minimum tillage practices are inappropriate for good and poor soil fertility and most beneficial for farms of medium soil fertility. In order to raise agricultural productivity in Sub-Saharan Africa, additional studies that account for heterogeneity among smallholders is critical.

Traditional farming systems in Sub-Saharan Africa depend primarily on mining soil nutrients. The African green revolution aims to intensify agriculture through the dissemination of integrated soil fertility management (ISFM). This paper develops a robust and operational definition of ISFM based on detailed knowledge of African farming systems and their inherent variability and of the optimal use of nutrients. The authors define ISFM as a set of soil fertility management practices that necessarily include the use of fertilizer, organic inputs and improved germplasm, combined with the knowledge on how to adapt these practices to local conditions, aimed at maximizing agronomic use efficiency of the applied nutrients and improving crop productivity. All inputs need to be managed in accordance with sound agronomic principles. The integration of ISFM practices into farming systems is illustrated with the dual-purpose grain legume–maize rotations in the savannas and fertilizer micro-dosing in the Sahel. Finally, the dissemination of ISFM practices is discussed.

Variability of soil fertility within, and across farms, poses a major challenge for increasing crop productivity in smallholder systems of sub- Saharan Africa. This study assessed the effect of farmers' resource endowment and nutrient manage- ment strategies on variability in soil fertility and plant nutrient uptake between different fields in Gokwe South (ave. rainfall *650 mm year -1 ; 16.3 per- sons km -2 ) and Murewa (ave. rainfall *850 mm year -1 ; 44.1 persons km -2 ) districts, Zimbabwe. In Murewa, resource-endowed farmers applied manure ((3.5 t ha -1 year -1 ) on fields closest to their home- steads (homefields) and none to fields further away (outfields). In Gokwe the manure was not targeted to any particular field, and farmers quickly abandoned outfields and opened up new fields further way from the homestead once fertility had declined, but homefields were continually cultivated. Soil available P was higher in homefields (8-13 mg kg -1 ) of resource-endowed farmers than on outfields and all fields on resource constrained farms (2-6 mg kg -1 ) in Murewa. Soil fertility decreased with increasing distance from the homestead in Murewa while the reverse trend occurred in Gokwe South, indicating the impact of different soil fertility management strategies on spatial soil fertility gradients. In both districts, maize showed deficiency of N and P, implying that these were the most limiting nutrients. It was concluded that besides farmers' access to resources, the direction of soil fertility gradients also depends on agro-ecological conditions which influence resource management strategies.

SAD CT1 ridaura@supagro.inra.fr Nutrient Cycling in Agroecosystems: formerly Fertilizer Research ; FI 2008 1.282; International audience; Smallholder farming systems in sub-Saharan Africa are often nutrient-limited, and therefore imports must be increased to compensate exports and losses. To explore whether the properties of nutrient cycling networks relate to the systems'capability to sustain rural families, we investigated N flows within contrasting crop-livestock systems in Ethiopia, Kenya and Zimbabwe applying concepts from ecological network analysis. Farm households were conceptualised as networks, the compartments were the household and their farming activities which were connected by the N flows. Indicators assessing network size, activity and cycling, and the organisation and diversity of the N flows were compared with system productivity and food self-sufficiency. Results showed that organisation and diversity of N flows to, from and within the farm households differed more between farms of different resource endowments than across sites. The amount of N cycled per household was small and comparable across sites: less than 25 kg N year-1, and for the poor households less than 5 kg N year-1. Poor households with soil N stocks that were 50-60% smaller than wealthier households depended more on external inputs (e.g. a dependence of 65% vs. 45% in Zimbabwe). Productivity was positively related to network size, its organisation and N cycling, but utilisation efficiencies were different across sites in relation to soil N stock and the importance of livestock for N flows. Greater size of the N flow network and its organisation led to increased productivity and food self-sufficiency, reducing dependence, which may increase the adaptability and reliability of smallholder crop-livestock systems.

The productivity and residual benefits of four grain legumes to sorghum (Sorghum bicolor) grown in rotation were measured under semi-arid conditions over three cropping seasons. Two varieties of each of the grain legumes; cowpea (Vigna unguiculata); groundnut (Arachis hypogaea); pigeon pea (Cajanus cajan); Bambara groundnut (Vigna subterranea), and sorghum were grown during the first season. The same experiment was implemented three times in different, but adjacent fields that had similar soil types. At the end of the season the original plots were split in two and residues were either removed or incorporated into the subplots. The following season sorghum was planted in all subplots. In 2002/03 (314 mm rainfall) cowpeas produced the largest dry grain yield (0.98 and 1.36 t ha¿1) among the legumes. During the wettest year (2003/04, 650 mm rainfall) groundnut had the highest yields (0.76 to 1.02 t ha¿1). In 2004/05 (301 mm rainfall) most legume yields were less than 0.5 t ha¿1, except for pigeon pea. Estimates of % N from N2-fixation from the legumes were 15¿50% (2002/03), 16¿61% (2003/04) and 29¿83% (2004/05). Soil water changes during the legume growth cycle were proportional to varietal differences in total legume biomass. Sorghum grain yield after legumes reached up to 1.62 t ha¿1 in 2003/04 compared with 0.42 t ha¿1 when following sorghum. In 2004/05, sorghum yields after legumes were also higher (up to 1.26 t ha¿1) than sorghum after sorghum. Incorporation of crop residues had no significant effect on sorghum yield. Beneficial effect of legumes on yields of the subsequent sorghum crop were more readily explained by improvements in soil nitrogen supply than by the small observed changes in soil water relations. Our results demonstrate clear potential benefits for increasing grain legume cultivation in semi-arid environments through the use of improved germplasm, which also gave substantial increases in subsequent sorghum productivity (up 200% in a wet season and 30¿100% in a dry season), compared with an unfertilized sorghum crop following sorghum.

In the tropics, pest infestation is often a major constraint to agricultural production. Moreover, research earmarked for pest control and pest knowledge is minimal compared to that of research conducted with application to industrialized countries. When pests are not easily controlled this may lead to substantial decreases in yield and high yield variability. This research provides insight into sources of yield variability that in turn generates information for farmers, local extension agents, and the international development community. This research will also contribute to the improvement of outcomes on smallholder cocoa farms in the tropics. SysCoor-5 (Policy and Governance)

Corresponding author at: Tropical Soil Biology and Fertility Institute of the International Centre for Tropical Agriculture (TSBF-CIAT), P.O. Box 30677, Nairobi, Kenya.; fax: +254 20 524763; International audience; The spatial variability in crop yields commonly observed in smallholder farms of sub-Saharan Africa is often caused by gradients of declining soil fertility with increasing distance from the homestead. This heterogeneity means that recommendations based on regional soil surveys are of limited value. The variability in soil qualities within farms must be considered when designing management strategies, and their feasibility analysed by integrating results at the farm livelihood scale. For this purpose, we have developed the model FARMSIM, a dynamic bio-economic model for analysis and exploration of trade-offs in resource and labour allocation in heterogeneous smallholder farms. Focusing on farm-scale strategies, the approach to simulation of soil and crop processes in EARMSIM (the sub-model FIELD) is designed to be simple, but to keep the necessary degree of complexity to capture heterogeneity in resource use efficiencies. To test our approach, the sub-model FIELD was calibrated against chronosequences of woodland clearance in three agroccological zones of Zimbabwe (with soil textures of 3, 10, 35% clay), and used to simulate: (i) the creation of soil fertility gradients, and (ii) different strategies of N, P and manure applications to maize and soyabean rotations in homefields and outfields of smallholder farms on clayey and sandy soils. The results of the simulation of managernent strategies were tested against on-farm experimental data from Murewa, Zimbabwe. The model produced satisfactory predictions (r(2) : 0.6-0.9) of long-term changes in soil organic C, of crop responses to N and P and of nutrient use efficiencies across a wide range of yields and different field types. This demonstrated the broad applicability of the model despite the sparse data required for initialisation. However, the model results were less accurate in predicting crop responses to N and P applications in the outfields on sandy soils. Experimental evidence indicated yield limitation by Ca and Zn deficiencies in highly depleted outfields on sandy soils, which were not included mechanistically in the current version of FIELD. Repeated applications of 16 t ha(-1) year(-1) of manure allowed larger responses to applied N and P after 3 years of experimentation; such a corrective effect of manure was simulated to be due to improved N and P recovery efficiencies in the model. In combination with the experimental data, the simulation results suggested that soil fertility gradients affect nutrient use efficiencies, operating mostly on the efficiencies of nutrient capture rather than conversion. A typology of fields according to the type of management interventions needed is introduced, based on a generic application of FIELD with this parameterisation

Poverty in Kenya has been on the increase over the last decade. It is estimated that 56% of the total population live in absolute poverty. Most of the poor reside in rural areas where agriculture is the main livelihood activity. Majority of Kenya's farmers are smallholders. They account for 75% of the total agricultural output and about 70% of marketed agricultural produce. The fate of smallholder agriculture in this country is therefore central to poverty reduction. A collapse in output and incomes from smallholder agriculture is likely to have damaging welfare effects and retard pro-poor economic growth. Smallholders often operate in a risky environment, which affects the level and variability of household resource endowments and income. The importance of risk analysis in smallholder production systems arises from the fact that strategies to help farmers raise their productivity and income require an understanding of how risk affects their production decisions. Using cross-sectional input-output data from 240 randomly selected households from Vihiga and Kilifi districts covering the 2003/4 agricultural year, and time series data on yields, this study investigates how risk affects farmers' production choices in the crop-livestock systems. Further, it explores the possibility of improving production and income on these smallholder farms. Linear programming and MOTAD are used in analysis. Results indicate there is potential to improve production and income on these smallholder farms through a change in the enterprise mix. The farm plans are sensitive to risk, with trade-offs occurring between higher risk and returns.

In the Philippines, farmers have often cited the lack of access to capital as the main impediment to increasing agricultural production. Production and marketing ex penditures of smallholder farmers are predominantly financed by traders and household savings. Product, input and credit markets are strongly interlinked and involve both formal and informal sectors. This research aims to understand the existing financial systems available to smallholder livestock farmers in Western Leyte, Philippines. It investigates the constraints and problems faced by livestock farmers in relation to access to capital, identifies opportunities to overcome credit constraints and formulates recommendations for improving access of smallholder farmers to credit.

This paper analyses the farm economic viability of genetically modified (GM) corn in the Philippines. Data was collected from 114 farmers in Isabela province including non-GM, Bacillus thuringiensis (Bt), herbicide tolerant (HT) and BtHT corn farmers. Results of univariate analysis showed that non-GM corn was not statistically different from Bt, BtHT and HT corn in terms of production output, net income, production-cost ratio and return on investment. Multivariate econometric analysis for the agronomic input variables showed a higher return on investment for Bt corn as the only significant difference between seed types. Next, pest occurrence and severity variables were included in the regression to address endogeneity. The Blinder-Oaxaca decomposition method was used to further investigate differences between growers of BtHT corn and non-GM corn into an endowment and a coefficient effect. The decomposition analysis showed that BtHT corn has a negative impact on return on investment as revealed by the negative signs of the overall mean gap and the characteristics and coefficient components. In contrast, the overall mean gap for net income indicated that adopting BtHT corn could potentially increase non-GM growers’ income mainly from better control of corn borer pest even though mean levels of borer occurrence are lower for non-GM growers.

Information on fertilizer response in cassava in Africa is scarce. We conducted a series of on-farm and on-station trials in two consecutive years to quantify yield responses of cassava to mineral fertilizer in Kenya and Uganda and to evaluate factors governing the responses. Average unfertilized yields ranged from 4.2 to 25.7 t ha-1 between sites and years. Mineral fertilizer use increased yields significantly, but response to fertilizer was highly variable (- 0.2 to 15.3 t ha-1). Average yield response per kg applied nutrient was 37, 168 and 45 and 106, 482 and 128 kg fresh yield per kg of applied N, P and K, respectively in 2004 and 2005. Fertilizer response was governed by soil fertility, rainfall and weed management, but was not influenced by variety, pest and disease pressure and harvest age. Relative N and K yields were positively correlated to SOC and exchangeable K, while response to fertilizer decreased on more fertile soils. Still, fertilizer response varied widely on low fertility soils (e.g. on soils with

In a sample of 384 farms, 79 per cent applied some fertilizer in the survey year 1976/77, rate of adoption varied from 95 per cent in case of Boro HYV to 41 per cent in case of Jute. Only 37 per cent of recommended doze was applied in Boro HYV compared to 66 per cent for Boro LYV, 76 per cent for Jute, 37 per cent for T. Aman and 30 per cent for Aus. Proper mix was applied to around 60 per cent of Boro LYV and HYV areas and around 20 per cent in case of Aus, Jute and Tobacco. Fertilizing experience, size of farm, tenurial status, availability of institutional credit and purchase of fertilizer from government licensed dealers has significant influence on the rate and mix of fertilizer application.