Efficiency of nitrogen fertilizer use under rainfed maize and irrigated wheat at Kadawa, northern Nigeria

Abstract

Field trials were conducted at Kadawa, northern Nigeria, during 1975–77 to study the efficiency of nitrogen fertilizer use under maize (Zea mays L.)—wheat (Triticum aestivum L.) rotation; the study also examined the impact of continuous N use on some soil properties. Grain and straw dry matter yields, grain N content, crop N uptake and whole plant N concentration of wheat at different growth stages increased significantly with increasing levels of N application. Per cent increases in mean grain yield of N treated plots over control were 77, 131 and 141 for maize and 195, 308 and 326 for wheat at 60, 120 and 180 kg N per ha levels, respectively. The calculated N rates for maximum yield were 177.5 and 164.0 kg N per ha for maize and wheat, respectively. Short-term beneficial effect of dung on maize yield was ascribed to its additional N supply. Urea and calcium ammonium nitrate (CAN) were equally good for both maize and wheat; full and split N application gave no significant difference in yield. The values for mean fertilizer N recovery over all the crops were 64, 58 and 44% respectively, at 60, 120 and 180 kg N per ha levels.

Nitrogen application at the highest rate (180 kg per ha) reduced the soil pH significantly in the top 40 cm of the soil profile. The magnitude of soil acidification at levels of N below 120 kg per ha was not appreciable in this study. High N application also depleted the soil of its cations at differential rates. Other factors such as N source, time of N application and addition of dung along with N fertilizer did not have much influence on the rate of short-term soil acidification due to N fertilizer use.