Film-mulched drip irrigation achieves high maize yield and low N losses in semi-arid areas of northeastern China

Traditional flood irrigation (FI) and excessive nitrogen (N) fertilizer application are the main causes of unrealized yield potential and low water and N use efficiency (NUE) of maize in semi-arid regions of northeast China. The yield gap, NUE, and N losses were adopted to quantify the yield potential and optimal N fertilizer rate of maize under film-mulched drip irrigation (MDI), and different N fertilizer levels (0, 70, 140, 210, 280, and 350 kg N ha(-1), denoted as N0, N70, N140, N210, N280, and N350, respectively) were applied under MDI and FI conditions from 2018 to 2020. The maize yield first increased and then decreased with increasing N fertilizer in both MDI and FI, but the highest yield was 23.5% higher in MDI (210 kg N ha(-1)) compared to that in FI (280 kg N ha(-1)). Compared with FI, MDI significantly increased the proportion of N accumulation and its contribution to grain N at the post-silking stage, and improved water productivity and NUE at the same N rate. Under the conditions of obtaining the highest yield treatment (N210 under MDI and N280 under FI), MDI increased N recovery efficiency (REN), agronomic efficiency (AEN), partial factor productivity (PFPN), water productivity, and irrigation water productivity by 29.2% points, 16.2 kg kg(-1), 22.3 kg kg(-1), 1.3 kg m(-3), and 4.4 kg m(-3), respectively. In addition, MDI significantly reduced NO3-N leaching in the 60-200 cm soil layer and apparent N loss, while NO3-N content in the 0-60 cm layer increased over FI. The range of N fertilizer required to obtain high maize yield under MDI and FI were 199-220 and 236-260 kg ha(-1), respectively, by simulating the relationship between the N fertilize rate and maize yield, apparent N loss, and REN. Overall, MDI resulted in a 24.3% higher maize yield, 27.4% points higher REN, 15.7% lower N fertilizer application, and 45.3% lower N loss compared to FI. Therefore, the N fertilizer application strategy of MDI in this study could achieve higher maize yield, water productivity, and NUE, and reduce the risk of soil NO3-N leaching in continuous maize cropping systems. The results of this study can provide a scientific basis for N fertilizer management under MDI in the semi-arid region of northeastern China.