Plant phosphorus and rice yield in an Ultisol of the humid forest zone in West Africa

Little attention has been devoted to calibrating plant tissue tests for phosphorus (P) in the field for upland rice in West Africa, although information is needed for improving crop production through efficient P nutrition. A field experiment was conducted under rainfed conditions in the 1994 season to establish the relationships between plant P content and grain yield of upland rice grown on an Ultisol, having a range in extractable P, in the humid forest zone of Ivory Coast. The critical limit of P content in the whole rice plant tops at the tillering stage, at 90% relative grain yield, was found to be 2 g kg‐1 P for the four upland rice cultivars tested. Total P uptake in the biomass was significantly correlated with rice grain (r=0.81, n=20) and straw (r=0.79) yields of the cultivars