Effects of nitrogen fertilizer management on nitrogen absorption, utilization and soil inorganic nitrogen content under film mulch drip irrigation of maize

For reasonable application of nitrogen fertilizer under film mulch and drip irrigation in the semi-arid region of Jilin Province, a field experiment was conducted to investigate the effects of different nitrogen doses on spring maize yield, nitrogen utilization efficiency, nitrogen accumulation characteristics, soil inorganic nitrogen content and nitrogen balance during the growth period. The drip-irrigated film mulch experiment was conducted in 2016-2017 for N1 (100% basal fertilizer), N2 (50% basal fertilizer + 50% jointing fertilizer), N3 (30% basal fertilizer + 50% jointing fertilizer + 10% belling fertilizer + 10% flowering fertilizer) and N4 (20% basal fertilizer + 30% jointing fertilizer + 20% belling fertilizer + 20% flowering fertilizer + 10% filling fertilizer) nitrogen inputs. The results showed that grain yield under N2, N3 and N4 treatments were all significantly higher than that under N1 treatment. The highest maize yield was obtained under N4 treatment, increasing by 22.44% (2016) and 35.31% (2017) over that under N1 treatment. Absorption utilization efficiency, agronomic efficiency and partial factor productivity of nitrogen under N2, N3 and N4 treatments were all significantly higher than those under N1 treatment, respectively increasing in the ranges of 52.02%-83.21%, 63.69%-120.78%, 11.85%-22.46% (in 2016) and 92.44%-129.38%, 127.23%-203.09%, 22.10%-34.01% (in 2017). The highest increase was under N4 treatment. Nitrogen accumulation increased significantly with increasing nitrogen fertilizer application from jointing stage to mature stage, with the highest value under N4 treatment after flowering stage. Compared with N1 treatment, soil inorganic nitrogen content improved at the 0-20 cm soil layer under N2, N3 and N4 treatments after flowering stage, but dropped at the 40-100 cm soil layer at maturity stage. Nitrogen loss significantly reduced under N2, N3 and N4 treatments compared with that under N1 treatment, and it was lowest under N4 treatment in terms of nitrogen balance of the soil-crop system. In conclusion, optimum management strategy was obtained for 20% nitrogen base fertilizer, 30% dose at jointing stage, 20% at belling stage, 20% at flowering stage and 10% at filling stage. This gave a total nitrogen fertilizer application of 210 kg·hm^-2 under the experimental field conditions.