ISSN: 0041-3216

ISSN: 0041-3216 (Online), 0041-3216 (Print)
Volume 54 Number 1
Research Papers
Effect of sulphur-coated urea on nutrient uptake by maize (Zea mays L.)
R.C. Dalal
The effects of soluble sources of N, ammonium sulphate (AS), urea ammonium phosphate (UAP) and urea, and controlled release N sources, sulphur-coated urea (SCU-8·9, SCU-1·1 and SCU-0·9) of differing N release rates, applied at 0, 50, 100 and 200 kg/ha on an acidic soil, were compared in terms of P, K, Ca and Mg uptake. P uptake usually increased with increasing N rate and SCU-1·1 and SCU-0·9 gave larger uptakes of N and P than the soluble sources. When the N rate of AS was increased from 100 to 200kg/ha, P uptake was not increased, possibly because of the adverse effect of increasing exchangeable Al. The same change in N rate of AS and UAP tended to depress K, Ca and Mg uptakes. On increasing the rate from 100 to 200 kg/ha, SCU-1·1 and SCU-0·9 increased K, Ca and Mg uptake. The factors responsible for the differences in nutrient uptake due to N sources were probably the difference in nitrification rates and consequent changes in soil pH and exchangeable Al, soil NH4-N/NO4-N ratio, and the maintenance of soil NO3-N levels during crop growth.