Empirically modelling the interaction between intensification and climatic risk in semiarid regions

Abstract

In many developing countries, yield increases obtained through intensification of agriculture seems necessary to face the high population growth rate. In the case of rainfed agriculture of semiarid regions the effect on yield of some intensive farming practices is highly variable, however, due to interactions with rainfall distribution and amount. This paper presents a model (SARRA) to perform regional comparisons of the risk associated with intensive practices in semiarid environments. The model, built for this specific and restricted objective, is suitable for crops and regions where few data are available. The intensification level of a given crop situation is assumed to be the potential yield that would be obtained without any water constraint. The model was calibrated and validated for millet in Senegal and then run for three locations in that country, using long-term sequences of climatic data from wet and dry periods. Three potential yield levels and two runoff loss levels were tested for each location and period. At one site, the study revealed that using management to increase potential yield is highly risky. In a location only 200 km south of the former, the risk associated with intensive practices is much less, provided that all rainfall infiltrates. Considering 25% rainfall loss by runoff, which was reported to be common in this region, however, the risk associated with high yield potential increases. This case study highlighted the extent to which the risk faced by farmers in semiarid regions can vary spatially and with management practices. The approach proposed in this paper appears suitable for use in designing agricultural development strategies in semiarid regions.