Synchronizing nitrogen supply and uptake by rainfed maize using mixed urea and slow-release nitrogen fertilizer

Mixed urea and slow-release nitrogen fertilizer (MUS) is a promising nitrogen (N) fertilizer alternative to the conventional split urea (U) fertilization or independent fertilization with slow-release N fertilizer (SRN), which can increase crop yields and minimize fertilizer and environmental costs. This study was aimed to explore the release characteristics of MUS under different precipitation conditions and determine whether MUS facilitates the supply-demand synchrony of N for rainfed maize. The impact of U, SRN and MUS (U: SRN = 3:7) under two N application rate (180 and 240 kg N ha(-1)) on N absorption, NO3--N residue and net return of fertilizers were assessed during three consecutive years (starting in 2016). Results showed that N release from MUS was better synchronized with the N demand of rainfed maize relative to U and SRN, because N under MUS was released evenly during the maize growing seasons. Nitrogen uptake and the N remobilization efficiency in vegetative organs after silking under MUS were largely increased by 19-28% and 14-37% compared with the other treatments, respectively. In addition, the soil NO3--N residue under MUS decreased by 5-17% relative to other treatments. Physiological efficiency of N, grain yield and net return of MUS under 180 kg ha(-1) were significantly increased by 6-34%, 14-111% and 16-118% compared with the other treatments, respectively. In conclusion, the application of MUS under N rate of 180 kg ha(-1) enhanced N uptake and grain yield, and reduced fertilizer costs and soil N losses for rainfed maize in Northwest China.