Effects of controlled release fertilizer on rice yield and nitrogen use efficiency

Overfertilization-low N fertilizer use efficiency are prominent problem in rice production in China. How to improve nitrogen use efficiency (NUE) and eliminate its impact on environment has been being a commonly concerned subject all over the world. Field experiments were carried out to test the effects of controlled release fertilizer (CRF, including American Scotts company product and pilot scale one manufactured in fertilizer science research lab, SCAU, being (AgroBB)), uncoated compound(Com) and chemical fertilizer (NPK) on rice yield and nitrogen use efficiency under the same amount of N, P_2O_5 and K_2O. Chemical fertilizer is splitting dressed (40% of N is basal dressed and the rest is top-dressed divided into two times); however, for the other treatments, fertilizers are single basal dressed. Results showed that rice grain yields of CRF treatments increased significantly by 8.57% to 12.45% for the early rice and 9.64% to 11.49% for the late rice respectively compared to the compounds treatment. The difference of the grain yield between the pilot product of AgroBB treatment and Scotts treatment is not significant. Compared to compound treatment, grain yield of NPK treatment increased by 2.47% and 7.20% for the early and late rice respectively. Agronomy nitrogen use efficiency (ANUE, being difference of grain yield between nitrogen and non-nitrogen treated plot divided by N applied) on each treatment of the early rice was higher than that of the late rice. ANUE of Scotts, (AgroBB) and NPK treatments were 26.93% to 29.82%, 18.52% to 25.06% and 5.35% to 18.69% significantly higher than that of compound respectively. However, there was no significant difference of ANUE between Scotts and (AgroBB,) AgroBB and NPK treatment respectively. Nitrogen fertilizer recovery efficiency (NRE, being difference of N uptake between nitrogen and non-nitrogen treated plot divided by N applied) of Scotts, AgroBB and NPK treatment increased by 25.72% to 28.82%, 3.75% to 23.70% and 8.46% to 27.73% compared to compound treatment respectively. ( Results) also indicated that although there was no significant difference between NRE of CRF and NPK splitting application treatment, the ANUE and PNUE of CRFs was remarkably greater than that of NPK treatment.