Optimizing irrigation and N fertigation regimes achieved high yield and water productivity and low N leaching in a maize field in the North China Plain

Over-input of nitrogen (N) fertilizer coupled with flood irrigation resulted in low N and water productivity and serious NO3--N leaching in maize fields in the North China Plain (NCP). Drip-fertigation can enhance water-N use efficiency by precisely regulating water and N fertilizer application. In this study, a three-year drip-fertigation experiment on maize was carried out during the 2018–2020 growing seasons with three irrigation levels, i.e. 50 (W1, 100 %), 40 (W2, 80 %), and 30 mm (W3, 60 %), and five N levels, i.e. 0 (N0), 90 (N1), 180 (N2), 270 (N3), and 360 (N4) kg ha−1 were designed to investigate the responses of soil water consumption, NO3--N distribution, grain yield (GY), N uptake (UN), and water-N productivity to different irrigation and N application regimes. The results demonstrated that 80 % deficit irrigation (W2) obtained comparable GY to sufficient irrigation (W1), but significantly increased water productivity (WP) by 7.2 % compared with W1. Soil NO3--N contents in the 0–100 cm soil layers increased as the N application rate increased, but decreased with the increase of irrigation level. When the N application rate exceeded 180 kg N ha−1, soil NO3--N contents in the 60–100 cm soil layers were greatly increased. With the increasing N application rate, GY increased first and then tended to be stabilized when the N application rate reached 180 kg ha−1, UN showed an increased trend, while N agronomic efficiency (AEN) showed a decreased trend, the N recovery efficiency (REN) increased firstly and then decreased. When water consumption ranged from 374 to 388 mm and N application rate from 186 to 257 kg ha−1, respectively, GY and WP obtained 95 maximum values and AEN got 70 % maximum value, simultaneously. In conclusion, the regime of N application rate at about 180 kg ha−1 coupled with 40 mm irrigation level (per event) is recommended for drip-fertigated maize fields in the NCP.