Fertilizer Responses in Swamp Rice (Oryza sativa L.) in Northern Nigeria

Summary

A series of N × P field experiments with irrigated rice, conducted over the period 1958–1962 on the same plots on alluvial soils considered representative for most of the bottom ‘fadama’ land in Niger and Ilorin Provinces, Northern Nigeria, showed small increases with medium dressings of P₂O₅ and large responses with high dressings of N. The N responses showed considerable variation between soil types and years. The variation between soil types was attributed to different cation exchange capacities, which resulted in NH₄′ leaching from the root zone at different rates. The variation in N responses between years was probably due to different physiological timings of the top dressings. Results of chemical analyses of straw and grain samples of the 1961 crop were used to estimate the percentage of N and P₂O₅ recovered by the crop with the various treatments over the untreated plots in the previous years of the experiments on two soil types. The recovery percentages for the different levels of N on the clay ‘basin’ soils were moderate, about 18 per cent, whereas those for the sandy ‘levee’ soils were lower, averaging only 9 per cent. Recovery of P₂O₅ varied from good at medium N levels (14 per cent) to moderate at high N levels (9 per cent) on the basin soils. Recovery of P₂O₅ on the levee soils was poor. The utilisation of the recovered N (75 lb paddy/lb N) and P₂O₅ (42 lb paddy/lb P₂O₅) was very good for N and fair for P₂O₅.