Lowland Rice Nutrient Responses for the Guinea and Sudan Savannas of Nigeria

Yield response of irrigated lowland rice (Oryza sativa L.) to nutrient application was determined to improve the information base for fertilizer use in the Sudan and Southern Guinea Savannas of Nigeria. Economically optimal rates (EOR) and agronomic efficiency (AE) were determined. Five N levels and four levels each P, K, and Zn were evaluated with two varieties at two locations. Nitrogen effects varied by variety and location but mean paddy yield with 0 kg ha–1 N was 3.4 Mg ha–1 and was increased by 1.3 Mg ha–1 with 40 kg ha–1 N. The mean EOR of N with fertilizer use cost to paddy price ratios (CP) of 2 to 6 were 56 to 38 kg ha–1 N, respectively. Yield increases with P, K and Zn application were infrequent. Paddy yield was increased in one of four cases with up to 1.5 kg ha–1 Zn. There were no paddy yield increases but some decreases with application of Mg-S-B in addition to N-P-K-Zn. The overall AE of N at EOR with a CP of 4 was 25.3 kg kg–1. The profit potential of N application was greater for Faro 44 compared with Faro 52 at both locations. Financially constrained farmers who opt to apply N at 50 compared with 100% EOR when CP was 4 can expect 16% less yield increase but 67% higher AE and value to cost ratio. Application of fertilizer N, maybe with P at Kadawa, can be highly profitable for irrigated lowland rice in these agroecological zones