Effect of frozen saline water irrigation in winter on soil salt and water dynamics,germination and yield of cotton in coastal soils

A three-year field experiment was conducted to investigate soil water and salt dynamics, cotton emergence, seedling salt content and cotton seed yield in coastal soils (Xiaoshan, Haixing County of Hebei Province) under frozen saline water irrigation in winter. The irrigation water salinity and volume were 8.15~14.27 g·L^-1, and 180 mm, respectively. After saline ice melt-water infiltration in spring, the soil was mulched with plastic film to prevent further soil salinization via evaporation. The results showed that soil salt and water contents at sowing in 2009, 2010 and 2011 were respectively 0.32%, 0.29% and 0.17% and 26.2%, 25.0% and 24.2% under saline ice water irrigation. This implied that longer saline ice water irrigation had better soil desalination effect, providing suitable soil water and salt conditions for cotton growth. While cotton germination rate was above 85% under saline ice water irrigation treatment, few cotton seeds emerged under the control treatment (no irrigation and no mulching) due to high soil salinity. Seedling sodium content decreased by 57.6%~64.5% under saline ice water irrigation but potassium and calcium contents remained higher than the control. This prevented mono-ion problems in cotton plants, which further enhanced normal metabolism in cotton plant tissues. Salt content of the topsoil decreased further with the arrival of rainfall, which further ensured normal cotton growth. Overall, cotton seed yield reached 2 643.8~3 607.7 kg·hm^-2 with that of the succeeding year higher than preceding year. The above findings showed that frozen saline water irrigation in winter improved cotton growth in coastal soils in north China.