干旱区生态环境知识资源中心

Irrigation schemes for rice in the Sahel, an arid region traversed by several large rivers, were generally designed for rice double cropping. The level and temporal and spatial variability of potential yields in various seasons (wet, cold-dry and hot-dry) is thought to be high because of high solar radiation, but has not been quantified. We conducted a simulation-based study on the spatial, seasonal and year-to-year variability of potential yields. On the basis of growth analyses in lice garden experiments, we developed the rice yield model ORYZA_S which emphasizes the response of rice to extreme temperatures. It combines, in modified form, the phenological model RIDEV and the yield model ORYZA1. Simulation results indicated that potential rice yields in the Sahel are largely driven by temperature, with the solar radiation being abundant most of the time. Among the major physiological determinants of yield were the extremely variable crop duration which largely depends on floodwater temperature, the susceptibility of leaf area expansion to chilling, and spikelet sterility caused by heat or chilling. Temperature also affected kernel weight at maturity and dry matter partitioning to leaves. Potential grain yields vary between 4 ton ha(-1) in the hot-dry season in continental parts of the Sahel, and 10 tons in the hot-dry season in the Senegal river delta and in the wet season at the southern fringe of the Sahel. Yields dropped close to zero due to sterility in all environments if plants were sown later in the wet season (September-October). On the basis of the spatial and temporal variability of potential yields, and in consideration of results of previous characterization studies, we conclude by proposing environment specific applied research foci for irrigated rice in the Sahel.