Abstract
Winter irrigation is one of the water and salt management practices widely adopted in arid irrigated areas in the Tarim Basin located in the Xinjiang Uygur Autonomous Region in the People’s Republic of China. A winter irrigation study was carried out from November 2013 to March 2014 in Korla City. A cotton field was divided into 18 plots with a size of 3 m × 3 m and five winter irrigation treatments (1200 m3/ha, 1800 m3/ha, 2400 m3/ha, 3000 m3/ha, and 3600 m3/ha) and one non-irrigation as a control were designed. The results showed that the higher winter irrigation volumes allowed the significant short-term difference after the irrigation in the fields with the higher soil moisture content. Therefore, the soil moisture in the next sowing season could be maintained at the level which was slightly lower than field capacity and four times that in the non-irrigation treatment. The desalination effect of winter irrigation increased with the increase of water irrigation volume, but its efficiency decreased with the increase of water irrigation volume. The desalination effect was characterized by short-term desalination, long-term salt accumulation, and the time-dependent gradually decreasing trend. During the winter irrigation period, air temperature was the most important external influencing factor of the soil temperature. During the period of the decrease in winter temperatures from December to January, soil temperature in the 5-cm depth showed no significant difference in all the treatments and the control. However, during the period of rising temperatures from January to March, soil temperature in the control increased significantly, faster than that in all treatments. Under the same irrigation volume, the temperature difference between the upper soil layer and the lower soil layer increased during the temperature drop period and decreased during the temperature rise period. In this paper, we proposed the proper winter irrigation volume of 1800–3000 m3/ha and suggested that the irrigation timing should be delayed to early December or performed in several stages in the fields with the drainage system. Under the current strict water management and fixed water supply quota situation, the methods are of great practical significance.
Highlights
Cotton is one of the most important economic crops in Xinjiang Uygur Autonomous Region, China
Flood irrigation is considered as the pre-requisite for a high yield, and it is generally believed that winter irrigation has more beneficial impacts
According to the results obtained at deeper groundwater depth, winter irrigation showed a significant effect on groundwater storage
Summary
Cotton is one of the most important economic crops in Xinjiang Uygur Autonomous Region, China. The cotton planting mode commonly used is winter or spring irrigation plus drip irrigation under plastic mulch Under this cropping pattern, drip irrigation ensures the crop water requirement which can leach the salinity of the root zone. Due to the lesser water quantity in drip irrigation, salinity mainly accumulates at the edge of the wet zone, reducing the rate of emergence in the coming year To solve this problem, flood irrigation is applied to leach salt from October to November every year. Flood irrigation is considered as the pre-requisite for a high yield, and it is generally believed that winter irrigation has more beneficial impacts It leaches the salts from the plant root zone, and stores winter water for spring. Regular winter irrigation volume is generally between 3000 and 4500 m3 /ha and accounts for 75% of cotton water consumption [2]
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