Relative efficiency of zinc sulfate and zinc oxide-coated urea in rice-wheat cropping system

Rice-wheat cropping system covers about 24 million hectares in China, India, Pakistan, Nepal, and Bangladesh, and zinc deficiency is widespread in rice-wheat belts of all these five countries. The current practice of applying zinc sulfate heptahydrate (ZnSO4 center dot 7H(2)O) to soil is problematic because of the poor quality of the nutrients available in the market to the farmers. Zinc (Zn)-coated urea is therefore being manufactured to guarantee a good-quality Zn source. This article reports the results from a field study conducted to study the relative efficiency of zinc sulfate and zinc oxide (ZnO)-coated ureas in rice-wheat cropping system. The highest grain yield of rice-wheat cropping system was obtained with 2.0% coating of urea. Zinc sulfate was also a better coating material than ZnO. Partial factor productivity, agronomic efficiency, apparent recovery, and physiological efficiency of applied Zn decreased as the level of Zn coating was increased.