Multi-objective optimization of winter irrigation for cotton fields in salinized freeze-thaw areas

Abstract

The adaptive management of saline-alkali land and water resources can effectively alleviate land degradation and water depletion, and appropriate irrigation can improve crop yield and production efficiency. Based on the soil changes and comprehensive crop benefits under different initial soil environments, the optimization of the irrigation amount of cotton in saline-alkali areas is of great significance for the improvement of agricultural production of these areas in developing countries and even worldwide. The responses of farmland with various degree of salinization to different winter irrigation amounts in seasonal freeze-thaw arid areas should therefore be further explored. In this study, the soil moisture-temperature-salinity changes and the crop growth responses of three cotton fields with different salinization levels (5.15, 8.17, and 11.15 g·kg-1) under four winter irrigation amounts (0, 3000, 3600, and 4200 m3·ha-1) were intensively investigated via a two-year field experiment in Xinjiang Province, China. The results demonstrate that winter irrigation significantly improved the soil moisture-temperature-salinity environment during the freeze-thaw period, and the influence was affected by the field salinization level. The initial salinity of salinized field promoted soil thawing and water storage, and inhibited soil freezing and salt leaching. The intraspecific relationship of salinized cotton fields changed from competition to promotion under winter irrigation, and soil salinity weakened the optimization of the intraspecific relationship. The multiple correlations between the benefit indexes of cotton were significantly strengthened under winter irrigation, and the negative effect of the soil salinization level on the cotton benefit indexes was stronger than that of the winter irrigation amount. Based on a multiple regression analysis, the optimal winter irrigation amounts for cotton fields with mild, moderate, and severe salinization were found to be 3416.83–4256.14, 4256.14–6502.96, and 6502.96–9614.24 m3·ha-1, respectively. This research provides a theoretical basis for determining the appropriate winter irrigation amount for cotton fields with various degrees of salinization in seasonal freeze-thaw arid regions.