Application of Controlled Release Urea Increased Maize N Uptake, Environmental Benefits and Economic Returns Via Optimizing the Temporal and Spatial Distribution of Soil Mineral N

Controlled-release urea (CRU) was regarded as a kind of promising fertilizer, which can meet the nitrogen (N) demand of crops over the entire growing period by gradually releasing N nutrient, and could decrease N losses. Evaluating the comprehensive application effects of CRU on the maize yield and further revealing its application mechanism were the focus of this study. Field experiments were conducted for three growing seasons in two places in Northeast of China to investigate the effects of CRU on the yield, N uptake of maize, mineral N dynamics during the maize growing period. The N balance of soil-crop system, NH3 volatilization, and economic analysis were also evaluated to illustrate the environmental and economic efficiency of CRU application. The field experiment consisted of 4 treatments, including (1) no N fertilizer input (CK), (2) application of conventional urea at 210 kg N ha-1 (U), (3) application of polyurethane-coated urea at the same N application rate with U (PCU); and (4) application of polyurethane-coated urea with 20% N reduction application at 168 kg N ha-1 (0.8PCU). Our results indicated that the yield and NUE of maize in PCU treatment were increased by 4.3% and 17.6% (P<0.05) compared with those in U. Even under 0.8PCU treatment with 20% reduction CRU application rate, the maize yield was still sustained and NUE was increased by 20.6%. Applying CRU performed well in soil-crop N balance in agro-ecosystem, apparent N recovery rate was increased by 18.1% and apparent N losses rate was decreased by 36.2% compared to those in U. Furthermore, applying CRU could maintain higher mineral N contents in 0-60 cm especially in 0-20 cm soil layer compared to U at different growing stages, and the NO3--N concentrations reached 9.8 mg kg-1 in PCU, but only 1.1 mg kg-1 in U in 0-20 cm soil layer at the maturity stage of maize. At the same time, applying CRU could decrease cumulative NH3 volatilization loss by 26.2%, achieve 8.8% higher net profit that these in U. In conclusion, applying CRU could promote N uptake by maize, achieve environmental and economic benefit through optimizing the temporal and spatial distribution of soil mineral N. And proper use of CRU (0.8PCU) can promote the coordination effect between N nutrient supply and yield response. We suggested that CRU should be encouraged to further promote and popularize in maize production