Modelling water consumption, N fates and maize yield under different water-saving management practices in China and Pakistan

Abstract

Excessive water and fertilizer input in conventional farming practices not only lead to low production but also damaged the ecosystem by causing groundwater decline and groundwater nitrate contamination. The two-year field experiments were conducted at Zhengzhou of China and TandoJam of Pakistan sites, respectively. The WHCNS (soil-water-heat-carbon-nitrogen-simulator) model was used to simulate soil water dynamic, nitrogen (N) fate and maize yield under different irrigation practices, including farmer-based full flood irrigation (FI), drip irrigation (DI) and rainfed (RF) at the Zhengzhou site. Treatments of the TandoJam site were full flood irrigation (F100), moderate deficit irrigation (F75) and high deficit irrigation (F50) to meet the 100%, 75% and 50% crop evapotranspiration, respectively. Results showed that the model precisely simulated water consumption, fates of N, crop growth, and yield at both sites. In Zhengzhou site, we found the lowest grain yield in the RF system, whereas the DI increased average grain yield by 9.8%, decreased 62.5% water consumption compared to FI for the two years. Moreover, the DI had a negligible amount of drainage, runoff, and N leaching, which subsequently improved water use efficiency (WUE) up-to 24.5% and 9.1% fertilizer N use efficiency (FNUE). In TandoJam site, compared to F100, the F75 produced almost equal grain yield with 25.1% water-saving, reduced 42.5% drainage and 11.8% runoff, 57% N leaching, enhanced 4.1% WUE and 14.9% FNUE. Furthermore, results suggested that too deficit irrigation, for example, F50, could cause serious yield loss or complete crop failure, because the weather condition of the TandoJam site is very hot.