Can low-input agriculture in semi-arid Burkina Faso feed its soil, livestock and people?

International audience

英语. Agriculture in semi-arid Burkina Faso is dominated by mixed crop-livestock smallholder farms with limited investment capacity in production factors, such as improved seeds, fertilizer and equipment. Hence, to make a living, farmers try to make the best use of available resources based on principles of agro-ecology, including crop diversity and nutrient and biomass recycling. We investigated farm-level management of resources (soil, crops and livestock) through time to assess whether the current management options were able to sustain crop and livestock production and fulfil household food requirements. We ran a one-year detailed farm monitoring campaign in collaboration with 22 volunteer farmers representing the diversity of the farming system in our study area. We quantified inputs and outputs in the cropping system (177 fields) for one rainy season. In addition, the weekly dynamics of crop residues left on field were quantified. Moreover, inflow and outflow of resources at farm level were quantified weekly. The cropping system was characterized by a negative nitrogen balance of about 12 kg N/ha/year, with market-oriented farms and large livestock owners having the most negative balance. Legumes grown (sole and intercropping) contributed to alleviate the nitrogen depletion by adding 15 kg N/ha/year to the nitrogen inputs through atmospheric fixation. However, cereal-legume inter cropping did not significantly reduce the nitrogen deficit in comparison to sole cereal cropping mainly because of the small proportion of legumes (8%) in intercropped fields. Livestock grazed crop residues left on the soil (739 kg dry matter/ha on average) at a rate of 26 76 kg/ha/week, thus strongly reducing the potential for mulching in the region. Livestock protein requirements were rarely met from farm-produced feed with average feed gaps ranging between 40% and 89% of the daily requirements for small and large herd keepers respectively. Large livestock (cattle) owners relied on transhumance during the rainy season, grazing and frequent purchase of crop residues and concentrates to feed their livestock. We estimated that grazed biomass provided on average at least 73% and 58% of metabolizable energy and protein feed requirement of livestock respectively. Concerning food availability, the amount of grain produced was generally enough to fulfil household energy requirements (89-175% of required energy, in kcal), even if households with higher people to land ratio were not selfsufficient. We concluded that the current farm management, even if it provides enough food for the majority of investigated farms, results in soil fertility mining and poor crop livestock production and integration. Our detailed farm data indicate that an appropriate diversity of crops and a better integration of legume crops in the cropping system, associated to improved manure and forage management is needed to sustain crop and livestock production.