Temporal and Spatial Dynamics of Soil Salinity after Different Durations of Plastic Film-based Mulching in a Drip-irrigated Cotton (Gossypium hirsutum L.) Field in Southern Xinjiang,China

Objective] Plastic film-based mulching is widely used to improve water harvesting and crop productivity in semiarid areas. It is also extensively used for cotton (Gossypium hirsutum L.) production in inland northwestern China, especially in temperature-and rainfall-limited areas. However, it is unclear whether the technology can sustainably maintain the soil water level and salt balance. The primary objectives of this study were as follows: (i) to determine whether different durations of plastic film-based mulching influenced temporal and spatial variations in soil salinity in drip-irrigated cotton fields; and (ii) to determine the optimum duration for plastic film-based mulching. Method] We imposed six treatments, plastic film-based mulching continuously for 40, 55, 70, 85, and 100 d, as well as a control (CK) for the whole growth period, in drip-irrigated cotton fields in the oasis of southern Xinjiang. Result] The mean soil water content in the 0–80-cm layers increased as the plastic film-based mulching duration increased. Compared with CK, the soil water content decreased from 14.5% to 7.5% from 40 d to 85 d, and the soil water content of the 100-d film mulching treatment was 4.4% greater than that of the CK. The average soil salt content increased as the plastic film-based mulching duration decreased, and there was a greater influence on the 0–40-cm soil layer than on the 60–80-cm soil layer. The longer the film mulching duration, the greater the salt suppression effect. However, after a plastic film-based mulching duration of more than 100 d, the moisture preservation and salt suppression began to decline. Conclusion] The 85-d to 100-d period in which salt suppression was associated with plastic film-based mulching approximately covers the whole cotton growth period. These results provide a theoretical basis for the control of soil salinization and for maintaining high yields in the cotton fields of Xinjiang.