Effect of nitrogen and phosphorus fertilization on maize/rice intercropping system at Samaru, northern Nigeria

Abstract

The generally low fertility status of the savanna soils requires the application of fertilizers to supply adequate amounts of nutrients needed by cereal crops to raise yields. The effect of nitrogen (N) and phosphorus (P) on grain yield, soil nitrogen and uptake of N and P by maize (Zea mays L.) and rice (Oryza sativa L.) in a mixed cropping system was studied in a field experiment at the Samaru Farm of the Institute for Agricultural Research in 1990 and 1992. Factorial combinations of four levels of N (0, 60, 120 and 180 kg N ha^-1) and three levels of P (0, 13.2 and 26.4 kg P ha^-1) were laid in a randomized complete block design with four replications. The number of tillers per rice plant increased significantly with increasing levels of N up to 180 kg N ha^-1 while cobs/m2 of maize increased only up to 60 kg N ha^-1, but the response of leaf area index (LAI) to increasing levels of N was not consistent. The significant increase in these variables as affected by P was only from 0 to 13.2 kg ha^-1. However, the application of 13.2 kg P ha^-1 at each level of N significantly (P < 0.05) increased maize and rice yields, with the highest grain yields of both crops recorded when 120 kg N ha^-1 and 13.2 kg P ha^-1 were applied. Crude protein increased in maize and rice leaves with increasing levels of N up to 120 kg N ha^-1, but the effects of P on the variable was not consistent. Percent P in crop leaves was unaffected by the application of increasing levels of N and P, and no interaction effect was observed between the levels of N and P. Soil analysis after harvest showed that increasing levels of N and P increased the residual N and P in the soil. For sufficient supply of N and P to raise maize and rice yields, and to have reasonable residual amounts of these elements in the savanna soils at Samaru, the application of 120 kg N ha^-1 and 13.2 kg P ha^-1 seem adequate.

Ghana Journal of Agricultural Science Vol. 37 2004: 3-13