Searching for optimal practices for water saving, salinity control and yield increase in an arid and salinity irrigated area of China using the SWAP-based method.

Abstract: The Hetao Irrigation District (HID) is located in the arid region along the upper reach of the Yellow River and is an important grain production area in northwest China. Water diverted from the Yellow River is an indispensable water supply of the crop production in this region. Unfortunately, traditional irrigation, drainage and fertilization practices have resulted in severe soil salinization and inefficient of water use, which poses a great challenge to food security and water resources. Therefore, it is important to search a new practice that can achieve water saving, salinity control, and yield increase simultaneously. To this end, this study applied a framework that combined the SWAP model and a multi-criteria decision-making method.

First, we used a total of 21 station-years of experimental data from 12 spring wheat and spring maize sites for parameter calibration by the PEST package. The sensitive parameters of spring wheat and spring maize were obtained, and the evaluation showed that the SWAP model is capable of simulating seasonal variations of leaf area index, evapotranspiration, soil moisture and soil salt content. Specially, we showed that the parameters SALTMAX (threshold salt concentration in soil water) and TSUMEA (temperature sum from emergence to anthesis) were obviously different from the default values of wheat and maize in the SWAP.

Second, we designed simulation scenarios based on the combinations of irrigation, drainage and fertilization practices, constrained by the local customs and water supply from the Yellow River. The simulated crop yield, water use efficiency (i.e., the crop production per irrigation water amount), and soil salt content change were obtained by the SWAP model.

Finally, based on the SWAP-simulated results, optimal practices were obtained with the help of the VIKOR method, a multi-criteria decision-making method which has the advantage of objectively determining the weights of water use efficiency, crop yield, and soil salt content change. Compared with the traditional practices by farmers, the optimal practice can not only increase crop yield by 20 per cent and improve water use efficiency by more than 10 per cent, but also ensure the soil salt content does not increase.

 

Keywords: Irrigation; Drainage; Fertilization; SWAP model; VIKOR method