The effect of temporal variation on inputs and outputs of future-oriented land use systems in West Africa

The (semi-) arid area of West Africa is characterized by erratic rainfall that causes highly variable performances of cropping systems. This creates difficulties in strategic decision-making based on future-oriented production systems. In this paper, the degree of variation in inputs and outputs of future-oriented millet (Pennisetum glaucum L.) systems is quantified using a dynamic crop growth simulation model and a static technical coefficient generator. To determine inputs and outputs of future-oriented millet systems under (semi-) arid conditions, the target-oriented approach was operationalized for low-yielding conditions. Economic yield, N-loss and labor requirement were used as benchmarks for outputs and inputs of future-oriented land use systems. Weather data for 31 year characterize two sites in the (semi-) arid zone of Mali, while for each site two soil types with distinct properties were considered. In all four physical environments, inputs and outputs of millet systems have coefficients of variation (CV) exceeding 50%. Consequences of the variable performances of these systems are discussed for both policy-makers and designers of future-oriented systems. Engineering tools exist which help policy-makers to quantify consequences of variability at different scale levels so that variability can be reduced or better managed. Examples are given of future-oriented cropping systems aimed at less variable yield. At one site, fine tuning of the sowing date to seasonal water availability reduced CVs yield to 20-30% while long-term average yields increased with 40 to more than 130%. Water conservation measures increased yields by 40-230% and reduced their CVs by 28-50% in all four physical environments. Effects of various cultivation methods on the variability in inputs and outputs of future-oriented cropping systems can be rapidly explored using these tools. In addition, systematic analysis using such tools allows explicit analysis of gains and costs of various alternatives simultaneously.