Irrigation management for spring maize grown on saline soil based on SWAP model

Abstract

Soil salinization and water quality deterioration severely limit the development of irrigation agriculture in arid areas. Transient numerical models such as the agro-hydrological Soil-Water-Atmosphere-Plant (SWAP) model have played an important role in agricultural irrigation management. In order to find the optimal irrigation practices for spring maize grown on saline soil in Shiyang River Basin, the SWAP model was calibrated and validated to simulate water-salt transport and relative yield based on field experiments in 2008 and 2009. The average annual precipitation in this area is about 164mm. Experimental observations of soil water content, soil salinity and maize growth were made in lysimeters filled with disturbed loam soil having saturation extract water salinity (ECe) around 5.76dSm−1. Six irrigation treatments altogether including three levels of irrigation water amount: 100%, 67% and 50% ETc (evapotranspiration, 510mm) and two levels of irrigation water salinity: 0.65 and 3.2dSm−1 were arranged, each treatment with 3 replications for each treatment. The acceptable root mean square error (RMSE), mean relative error (MRE), the Nash and Sutcliffe model efficiency (NSE), the coefficient of determination (R2) between simulation and observation of soil water content, salt concentration and relative yield demonstrated that the calibrated SWAP model was applicable to irrigation management evaluation for maize grown on saline soil. Based on the analysis of simulated water and salt balance, relative yield and relative water use efficiency, the optimal irrigation schedule of maize grown on the saline soil for 50% hydrologic year was irrigation amount of 460mm with four times, for both fresh water 0.65dSm−1 (80Fr) and slight saline water 3.2dSm−1 (80Sal3). Compared to fresh irrigation treatment, higher soil water content and salt concentration, and lower relative yield and relative water use efficiency were obtained by saline irrigation treatment. However, for the maize grown on saline soil, the effect of irrigation amount at high level on relative yield and water use efficiency was unobvious with the difference less than 4%. Relative yield with 0.74 and 0.63 can be obtained by 80Fr and 80Sal3 every year after soil water-salt reached balance.