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Abstract
Controlled-release urea (CRU) and its placement method in rice production were investigated during 2007 and 2008 seasons. Controlled-release urea was applied at 62.5, 125, and 187.5 kg nitrogen (N) ha−1, and the urea was 187.5 kg N ha−1. All the CRU treatments were applied to the nursery beds once, and they were brought into the paddy field during transplanting, while the urea treatment was split into three applications from the plowing to the harvest. The results showed that rice seedlings with CRUs germinated and grow well and there was no salt damage at the nursery stage. The CRU treatment with 125 kg N ha−1 had 33% less N than urea treatment (187.50 kg N ha−1), but it produced significantly higher grain and straw yields, higher total N uptake and total apparent N uptake efficiency. In addition, all the CRU treatments effectively decreased floodwater ammonium (NH4 +)-N and nitrate (NO3 −)-N concentrations, pH, and N runoff.
ACKNOWLEDGMENTS
This work was funded by the Science Tackle Key Problem of Shandong Province (Grant No. 2009GG10006002), National 11th Five-Year Science and Technology Supporting Plan (Grant No. 2006BAD10B07), Science of Kingenta (Grant No. 33299), and Natural Science Foundation of Shandong Provence (Grant No. Y2008.D29), and National Natural Science Foundation of China (Grant No. 30871593). The authors thank Dr. Yuncong Li, Dr. Xu Zhao and Guangxi Xing for their valuable suggestions and linguistic revision on the manuscript, and Mr. Baolei Jiang for his assistance in field sampling and management.