N2O emissions and yield in maize field fertilized with polymer-coated urea under subsoiling or rotary tillage

Fertilizer application and tillage practices play an important role in agricultural production, whereas excess N input could create considerable N2O emissions. However, it is unclear whether urea types under subsoiling or rotary tillage have effects on yield and N2O emissions in maize field. We investigated the effects on N2O emissions and maize (Zea mays L.) yield of tillage (rotary tillage [R] alone and rotary tillage following subsoiling [S]) and two types of urea (polymer-coated urea [P] and conventional urea [C]) applications, respectively, at the sowing [0] and V6 [6] stages in a clay loam soil. N2O emissions varied from 1 to 11 kg N2O-N ha(-1). Compared with S soil, the R soils produced greater N2O emissions. Compared with conventional urea, polymer-coated urea increased maize production and fertilizer-induced N2O emission, but had no significant effect on yield scaled N2O emission. The increase of N2O emission was mainly related to water-filled pore space affected by tillage and soil nitrate and ammonium N concentrations affected by urea types. Polymer-coated urea topdressing at the V6 stage in S soils was better for producing a higher yield with lower N2O emission. The results indicate that R soils had more significant N2O emission than S soils during a wet climate; and polymer-coated urea can increase grain yield with a slight higher N2O emissions, whereas changing the application stage can decrease the cumulative N2O emissions without reducing the yield.