Inequality, agro-pastoral exchanges, and soil fertility gradients in southern Mali

Nutrient balances aggregated at the continental, national, or regional levels for African farming systems are usually reported as strongly negative. At the landscape or farm scale, the most commonly reported variability is the gradient of decreasing soil fertility from intensively managed “home” fields to more extensively managed “bush” fields. Case study evidence from an agro-pastoral community of southern Mali’s cotton zone showed that “home” and “bush” fields differed significantly in nutrient balances and soil fertility status but that inter-household differences related to household practice and social factors were even more important. Plot and household-level soil nutrient balances were calculated in 1996–1997 from participatory exercises such as resource flow mapping, participant observation, and soil sampling. The overall community-level nutrient balances averaged −9.2 kg N ha−1, +0.8 kg P ha−1, and −3.4 kg K ha−1, with significant inter-household variation. Soil analysis confirmed significant variation in soil nutrient status at both the landscape and plot levels. Comparing the scale and patterns of input use inequality using Gini coefficients showed the range of coefficients attributable to household behaviours matched or surpassed those attributable to distance factors alone. Input use intensity declined with increasing distance from nutrient sources but field level nutrient balances were better explained by household practice than by distance. Systemic differences in household asset ownership, use, and resource allocation behaviour suggested that much of the diversity seen in the nutrient balances and soil analyses was due to persistent inter-household inequality and the consequent exchanges of agro-pastoral resources. Inter-household negotiations for inputs (such as exchanges of manure and carts) and household-level decisions about input allocation created, exploited, and reinforced a mosaic of soil fertility “hotspots” surrounded by less fertile and less intensively managed patches.