Effects of Stabilized Nitrogen Fertilizer on Grain Yield and Nitrogen Use Efficiency of Summer Maize

A summer maize field experiment was carried out in 2013 to investigate the effects of stabilized nitrogen fertilizer rates on yield, nitrogen accumulation, nitrogen efficiency of summer maize, and economic efficiency. Compared with no stabilized nitrogen fertilizer, the yield of stabilized nitrogen fertilizer treatments as 90, 150, 210 N kg·hm-2 and 270 N kg·hm-2 increased 36.7%, 62.1%, 76.6%and 81.9%respectively. Total N absorbed by above ground parts increased 39.0%, 60.3%, 79.0%and 113.4%, and economic benefits increased 36.1%, 61.2%, 72.7%and 77.1%respectively. Compared with farmer conventional nitrogen fertilizer practices, the yield of stabilized nitrogen fertil-izer treatments as 210 N kg·hm-2 and 270 N kg·hm-2 increased 7.3%and 10.5%respectively. Total N absorbed by above ground parts in-creased 3.2%and 23.0%, and economic benefits increased 9.7%and 11.4%respectively. The results demonstrated that stabilized nitrogen fertilizer application significantly promoted growths yield and N accumulation. 210 N kg·hm-2 and 270 N kg·hm-2 increased total nitrogen absorption higher than farmer conventional nitrogen fertilizer practices. Nitrogen apparent recovery efficiency(NARE)and nitrogen agronom-ic efficiency(NAE)of application with stabilized nitrogen fertilizer were significant higher than those of farmer conventional nitrogen fertiliz-er practices. Nitrogen partial factor productivity(NPFP)of applied stabilized nitrogen fertilizer was higher than that of conventional nitrogen fertilizer practices. Nitrogen physiological efficiency(NPE)was higher than that of conventional nitrogen fertilizer practices with exception of 270 N kg·hm-2. Based on summer corn yield and N use efficiency, the optimum stabilized nitrogen fertilizer application rate was 210 N kg·hm-2