Response of interspecific and sativa upland rices to Mali phosphate rock and soluble phosphate fertilizer.

In West Africa, two-thirds of upland rice is grown on acidic phosphorus (P)-deficient soils. Phosphorus is one of the most limiting-nutrients affecting crop productivity. A three-year field experiment was conducted on a Ferralsol in Cote d'Ivoire to study the response of four interspecific rice cultivars and a sativa (control cultivar) to Tilemsi phosphate rock (PR) and soluble triple superphosphate (TSP) fertilizer. PR was applied at 0, 150, 300, and 450 kg ha-1 P once in the first year and residual effects were measured in the following years. TSP (0, 50, 100 and 150 kg ha-1 P) was applied yearly. More significant yield increasing (38%) was observed in the second year. Annual application of 50 kg P ha-1 as TSP or a one-time application of 150 kg P ha-1 as PR was the optimum rate for the production of all cultivars. Higher rates of P from TSP (100 and 150 kg P ha-1) gave 2-3 times greater residual P in soil than the optimum rate, inducing no further response of rice. Two interspecific cultivars were identified as the most acid- and low P-tolerant cultivars for improving rice production in West Africa humid forest zone. [ABSTRACT FROM AUTHOR]