Characterisation of farming systems in southern Rwanda

II.2.3. Mixed systems

Smallholder mixed farming systems in SSA (Sub-Sahara Africa) are highly complex due to intricate interactions between the soil, crops and livestock. Productivity of crops and livestock is among many factors limited by poor availability of nutrient resources. Crop-livestock interactions are mediated by the use of crop residues to feed livestock, and the reciprocal use of manure to fertilize crops. Manure is integral source of nutrients for crops in many smallholder farming systems where small amounts of external fertilizer inputs are used, farmers concentrate fertilizer and labour resources on plots closed to the homesteads. This differential management of plots creates gradients of decreasing soil fertility with distance away from homesteads (Zingore et al., 2006). Competition of agriculture and livestock activities for land is very common in SSA including Rwanda. In the 1940's human and animal populations increased dramatically, and land previously reserved for grazing was converted into cropping lands. This led to continuous cultivation and increased vulnerability to soil erosion; reduced pastures resulted in fewer animals and less manure; and farmers were forced to try buying manure. Livestock provided an important and stabilizing component of the farming system by maintaining soil nutrients. Due to competition for land, the number of animals per household was progressively diminishing and this led to a degradation of soil fertility since there were no alternative sources of manure for smallholder farmers across rural areas in the country. www.fao.org/AG/aga/lspa/LXETML/tech/ch3b.htm (April, 2007)