| In order to explore the mechanism of phosphorus fixation and release in cotton field under different phosphorus application levels for many years,the phosphorus adsorption-desorption properties and influencing factors of 5 phosphorus application levels（P0,P75,P150,P300,P450）and different layers（0-5 cm,5-10 cm,10-20 cm,20-40 cm）of grey desert soil in typical cotton fields in Xinjiang from 2016 to 2019 were investigated.The correlation between the adsorption-desorption of soil phosphorus and the phosphorus efficiency of cotton was analyzed,which furnished a scientific rationale with the reasonable application of phosphorus fertilizer in cotton field soil and the improvement of cotton yield.The major results are as follows:（1）The adsorption-desorption properties of soil phosphorus in cotton field were significantly different under different phosphorus application levels for four consecutive years.The soil with higher phosphorus application had the lower adsorption and higher desorption.In 2016（initial year of the experiment）,the adsorption-desorption properties of soil phosphorus in cotton field were slightly different from those in other years.Under the treatment of no phosphorus and low phosphorus（P0,P75）,the soil adsorption capacity was relatively small,and the desorption capacity and desorption rate were relatively large.In the vertical space of cotton field soil,the deeper the soil layer,the stronger the adsorption capacity and the weaker the desorption capacity.Compared with the first year,for P0 and P75 treatments,the adsorption of phosphorus was increasingly,and the desorption decreased with years.For other treatments（P150,P300,P450）,the soil phosphorus absorption decreased year by year,and the desorption increased under the four-year field assessment.And P450 treatment easily caused the risk of phosphorus loss.（2）The effects of soil physicochemical characters on phosphorus adsorption properties of cotton field under different phosphorus application treatments for four consecutive years were analyzed.A significant positive correlation was observed between the content of clay and silt,cation exchange capacity in cotton field and the maximum adsorption capacity of soil phosphorus,in which the cation exchange capacity only had significant impact on 0-5 cm soil layer.The soil sand,available phosphorus and total phosphorus,calcium carbonate,total salt and soil pH were negatively correlated with the maximum adsorption capacity.The soil total phosphorus and calcium carbonate only had significant correlation with maximum absorption in 0-20 cm soil layer,soil salinity only had significant impact on 5-40 cm soil layer,and soil pH value only had significant impact on 0-5cm soil layer.However,there was no significant correlation between soil organic matter and adsorption characteristics of phosphorus in each soil layer.（3）Cotton yield,phosphorus use efficiency and balance response to adsorption-desorption properties of soil phosphorus were considered,the phosphorus fertilizer efficiency was higher when the phosphorus application amount was 75-150 kg P2O5/hm2.The application of 75-150 kg P2O5/hm2 fertilizer in cotton field not only significantly increased cotton yield（14.25%-31.87%higher than that without phosphate fertilizer）,but also ensured higher utilization efficiency of phosphate fertilizer.In addition,it could influence the absorption（Xm was 600-900 mg/kg）and release（desorption rate was 10%-14%）of soil to phosphorus at this phosphorus application amount.The dynamic equilibrium point of adsorption-desorption level could maintain relatively high cotton yield and phosphorus efficiency. |
