Modelling the effects of cropping systems and irrigation methods on water consumption, N fates and crop yields in the North China Plain

Conventional cropping system and irrigation method not only cause groundwater decline but also result in groundwater nitrate contamination by N leaching in the North China Plain (NCP). A two-year field experiment was conducted in Yuanyang County, Henan province of China. The experiment consisted of three irrigation methods (flood irrigation (FI), drip irrigation (DI), and rainfed (RF)) with three cropping systems, including winter wheat (WW) -* summer maize (SM), 2H1Y, WW -* SM -* spring maize (SPM), 3H2Y and continuous SPM (1H1Y). The WHCNS (soil water-heat-carbon-nitrogen-simulator) model was used to assess the effects of combining cropping systems and irrigation methods on crop yields, water consumption, N fates, water and N use efficiencies (WUE and NUE). Results showed that compared to FI, the DI irrigated 2H1Y, 3H2Y and 1H1Y cropping systems lowered annual average soil evaporation rates by 8 % to 36 %, drainage by 61 % to 74 %, runoff by 37 % to 49 %, N leaching by 58 % to 62 % and NH3 volatilization by 33 % to 55 %. Overall, the order of crop yields for different irrigation methods under the same cropping system was DI > FI > RF and the order of crop yields for different cropping systems under the same irrigation method was 2H1Y > 3H2Y > 1H1Y. However, the WUEs and NUEs of different cropping systems varied with different irrigation methods. All cropping systems showed maximum WUEs and NUEs under the DI method compared to FI and RF conditions. The DI irrigated 1H1Y cropping system had maximum annual average WUE and NUE, followed by the 2H1Y cropping system. Since the DI irrigated 3H2Y and 1H1Y cropping systems caused substantial production loss by 26 % to 45 % compared to 2H1Y, we concluded that the DI method combined with the 2H1Y cropping system would be the best management practice in this region.