Application of crop simulation modeling and GIS to agroclimatic assessment in Burkina Faso

Rainfed crop production is the main source of food and income in Burkina Faso. Environmental conditions are characterized by low and erratic rainfall, compounded by high temperatures and radiation loads. These factors make inadequate water availability the major cause for low crop yields and frequent crop failures. This paper outlines the procedure used to investigate the water-limited growth environment of an improved millet cultivar in Burkina Faso. A daily time-step cropping system simulation model (CropSyst) was used to simulate the soil water budget components and millet production potential, both spatially and temporally, by coupling the model with databases of soil type, long-term weather, and crop management using a geographic information system (GIS). From the cropping model outputs, two agroclimatic indices (Aridity Index and Crop Water Stress Index) that show the water-limited growth environment of the millet crop throughout the country were quantified and mapped with the help of the GIS. This allowed the identification of agroclimatic zones, as determined by the crop water needs. Millet productivity decreased from the south to the north of the country in relation with rainfall isolines and soil types. Locations with less than 500 mm of annual rainfall are marginal for millet, particularly on planosols and arenosols. In regions with rainfall above 700 mm, moisture availability is not a major limiting factor for the 90-day millet production, especially on regosols, cambisols, acrisols and nitosols. Overall, the approach followed in this study appeared promising for quantifying the growth environment of millet as affected by soil type and weather. It could also help to provide guidelines for crop water management and analysis of the suitability of improved crop cultivars.