Leaching amount and timing modified the ionic composition of saline-alkaline soil and increased seed cotton yield under mulched drip irrigation

•Salt leaching could reclaims saline-alkaline soils for agricultural development.•Increasing leaching amount could decrease the soil ions and increase the yield.•Soil sodium had the greatest negative effect on seed cotton yield.•Optimal leaching pattern was obtained for 225 mm leaching at seedling and budding stages.