Effects Of Potassium Application Rate And Matter On Soil Fertility And Potassium USE Efficiency In Cotton

Production valued of nitrogen and despised potassium, which leaded to the lack of potassium of arable land gradually increasing. Cotton belongs to crops of liking potassium. The cotton premature aging problem caused by potassium deficiency is increasingly serious. In addition, the shortage of potassium resources in China, therefore needs to strengthen the cotton potassium nutrition research, looking for a suitable potassium rate and matter, to achieve the optimal management of potassium fertility and improve the potassium use efficiency. Insect-resistant hybrid cotton(siza 3) was chosen, and field experiments were carried out in Dafeng(120°13’E,32°56’N) in 2011 and in Nanjing (118°50’E,32°02’N) in 2012, with three potassium rate (0、150、300 kg K2O/ha) and two potassium matter(the basal application and the split application). The study focused on:Effects of potassium application rate and matter on soil nutrients, soil enzyme activities, soil microbial biomass, cotton yield and potassium use efficiency. The main results were as follows:1 Effects of potassium application rate and matter on soil nutrientsWith the increasing of basal K application rate, the contents of water-soluble K, non-specifically adsorbed K, specifically adsorbed K and slowly available potassium increased significantly in two sites, but the content of mineral K did not change significantly. But when the original soil potassium content was higher, too much potassium caused fertilizer waste (Dafeng site K300). With the increasing of basal K application rate, the water-soluble K and non-specifically adsorbed K of available potassium proportion increased, in addition, available potassium and slowly available potassium of total potassium proportion also increased. This suggested that a moderate potassium rate made for soil potassium transformation to absorption easily state of soil potassium, increasing the ability of soil potassium supply. With the increasing of basal K application rate, the contents of available N and available P decreased, but the contents of organic matter, total N and total P did not change significantly. When the K application rate was 150 kg K2O/ha, there were no significant differences of soil nutrients 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/ha, the contents of soil nutrients of the split application of K were superior to ones of the basal application.2 Effects of potassium application rate and matter on soil enzyme activities and microbial biomassWith the increasing of basal K application rate, soil urease activity, phosphatase activity, invertase activity, soil Cmic content, soil Nmic content, soil Bc/Oc ratio and soil Bc/Bn ratio increased significantly in two sites, but high K (300 kg K2O/ha) decreased enzyme activities and soil microbial biomass, and the application of K had no effect on hydrogen peroxidase activity. When the K application rate was 150 kg K2O/ha, there were no significant differences of enzyme activities and soil microbial biomass 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/ha, enzyme activities and soil microbial biomass of the split application of K were superior to ones of the basal application.3 Effects of potassium application rate and matter on cotton yield and potassium use efficiencyThe plant K accumulation, the total biomass and the lint yield increased significantly with the increasing of K application rate. In addition, K accumulation and Biomass accumulation distribution to reproductive organ also increased with the increasing of K application rate. This suggested that the application of K made for the formation and accumulation of photosynthetic product of cotton and photosynthetic product transferring to reproductive organ. When the K application rate was 150 kg K2O/ha, there was no significant differences of the lint yield between the split application of K and the basal application, but when the K application rate was 300 kg K2O/ha, the lint yield of the split application of K was superior to ones of the basal application.