中文摘要：

选取长江流域棉区2个土壤肥力不同的试验地点，研究施钾量与施钾时期对棉田土壤钾素形态与土壤肥力的影响。结果表明：随一次性基施钾量的增加，2个试验点土壤水溶性钾、非特殊吸附钾、特殊吸附钾和缓效钾含量均显著增加，矿物钾含量变化不显著；土壤速效氮和速效磷含量降低，土壤有机质、全氮与全磷含量没有明显变化。增施钾肥促进土壤脲酶、转化酶和磷酸酶活性提高，但高钾处理（300kgK2O／hm^2）显著抑制其活性，施钾对过氧化氢酶活性没有影响。施钾显著提高植株钾素累积量、生物量及皮棉产量。在150kgK2O／hm^2施钾量下，分期施钾处理（50％基施＋50％初花期追施）的土壤养分、酶活性以及皮棉产量均与一次性基施处理没有显著差异；而在300kgK2O／hm^2施钾量下，分期施钾处理各项指标均显著高于一次性基施。2个试验点均以基施150kgK2O／hm^2＋追施150kgK2O／hm^2处理土壤肥力与棉花产量最高。

英文摘要：

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.