Effects of maize residue return rate on nitrogen transformations and gaseous losses in an arable soil

Residue return in combination with synthetic nitrogen (N) fertilizer is increasingly being considered to be beneficial to soil fertility and crop yield. In most studies, however, attention has mainly been paid to the way that significant changes in the soil N mineralization process affect the soil N cycle, while the effect of different residue return amounts on ammonia (NH3) volatilization and nitrous oxide (N2O) emissions, potentially the most important components of N losses and environmental effects has, to a certain extent, been neglected, notably in north-eastern China. Therefore, a trial was set up in an Alfisol/arable soil during 2015-2016 to monitor annual NH3 volatilization and N2O emission dynamics from a fertilized maize field with residue return at different rates. Treatments included N fertilizer alone and N fertilizer in combination with either half or the full yield of the maize residue (5.8 x 10(3) or 11.6 x 10(3) kg ha(-1), respectively) returned to the soil surface after harvest. Over a growing season of maize, the NH3 volatilization loss rate from the full residue return treatment was 4.6%, which was significantly lower than that in the N fertilizer application only and half residue return plots (6.1%). Meanwhile, residue return rates showed a significant effect on annual N2O emissions from the maize system. Half residue return increased N2O emission (921.1 g N.ha(-1)), while full residue return marginally decreased N2O emissions (862.6 g N.ha(-1)) during the maize growing season, compared to the fertilizer-only treatment (881.2 g N.ha(-1)) (P < 0.05). In spite of the fact that N2O emissions in the non-growing season increased with the quantity of maize residue applied, the return of the full yield of maize residue to the soil could reduce both annual NH3 and annual N2O losses and increase soil total N and C storage after long-term use. It is suggested that residue application rate is a key factor when assessing residue benefits but the influence is in a nonlinear pattern. The combined application of full maize residue and synthetic N fertilizer is a promising N management strategy for mitigating gaseous N emissions.