Two sites with different soil fertility in cotton region in Yangtze river basin were chosen to study the effects of potassium application rate and time on the soil K forms and soil fertility in cotton. The results showed that with the increasing of basal K application rate, the contents of water-soluble K, non-specifically adsorbed K, specifically adsorbed K and slowly available K increased significantly in two sites, but the con- tent of mineral K did not change significantly; the contents of available N and available P decreased, but the contents of organic matter, total N and total P did not change significantly; the application of K improved the soil urease, phosphatase and invertase activities, but high K （300 kg K2O/hm^2） decreased enzyme activities and the application of K had no effect on hydrogen peroxidase activity. The plant K accumulation, the total biomass and the lint yield increased significantly with the increasing of K application rate. When the K appli- cation rate was 150 kg K2O/hm^2 , there were no significant differences of soil nutrient, enzyme activities and the lint yield between the split application of K （50% basal applied and 50% top-dressed at the beginning of flowering ） and the basal application, but when the K application rate was 300 kg K2O/hm^2 , the indices of the split application of K were superior to ones of the basal application. For the two sites, the treatment of 150 kg K2O/hm^2 basal-applied and 150 kg K2O/hm^2 top-dressed showed the highest cotton yield and soil fertility.
Journal of Soil and Water Conservation
K application rate
K application time