Polyolefin-coated urea improves nitrogen use efficiency and net profitability of rice-rice cropping systems

Abstract

An effective N management could match N availability with crop demand to maximize nitrogen use efficiency (NUE) and to optimize N application rate. using polyolefin-coated urea (Pocu) to replace regular or non-coated urea (Ncu) might be an option to achieve such objectives. A 2-year field study with five fertilization treatments was conducted in a rice-rice cropping system, in Qiyang, Hunan, southern China. The treatments include a control, both NCU and POCU at 150 and 300 kg N ha-1 yr-1. The results showed that average annual NUE and grain yield over 2-years were significantly greater under POCU (50% and 11.4 t ha-1 yr-1, respectively) than under NCU (36% and 10.6 t ha-1 yr-1, respectively). Based on their price of both rice grains and fertilizers in 2014 with a quadratic model, an optimal N rate was calculated as 178-203 kg N ha-1 yr-1 under POCU but 364-374 kg N ha-1 yr-1 under NCU. A decrease of 46-50% N inputs could be thus achieved under POCU than under NCU. The use of slow release urea fertilizer such as POCU could maintain high grain yield and grower's income, increase NUE and decrease N losses in such rice-rice cropping systems in southern China. Application of POCU was hence agronomically practical and cost-effective over NCU in rice plantation.