Phosphorus Forms And Release Characteristics Of Plastic Shed Soils With Different Planting Years

With the increase of protected cultivation years,the soil nutrient imbalance appeared,which affected the absorption and utilization of nutrients by crops.Especially because of the low utilization rate of phosphate fertilizer,it is easy to accumulate phosphorus in soil under the condition of large amount of phosphate fertilizer applied in protected cultivation.Therefore,in order to understand the status of phosphorus in plastic shed soils of different planting years in different regions of Liaoning Province,based on the analysis of p H,organic matter,total nitrogen,alkali hydrolyzable nitrogen,total phosphorus,available phosphorus,total potassium,available potassium and other indicators of plastic shed soils in Haicheng,Tieling and Tai'an of Liaoning Province,systematic research was carried out on the plastic shed soils with different planting years in Haicheng and Tieling areas The distribution of different forms of phosphorus and phosphatase and the release characteristics of phosphorus in plastic shed soil with different planting years were studied.The correlation between carbon,nitrogen,p H and other factors and the distribution of soil phosphorus and the ecometric characteristics of C/N,C/P and N/P were discussed.The results provide certain data support and theoretical guidance for rational fertilization and sustainable utilization of plastic shed soil.The main results are as follows:?1?The average contents of available N,P and K were 226±109.77mg/kg,189.44±94.71mg/kg and 179.13±74.14mg/kg,respectively.99%of the plastic shed soil alkali hydrolyzable nitrogen content reached the medium level,100%of the facility soil available phosphorus content reached the rich level,75%of the facility soil available potassium content was in the middle upper level.?2?The average contents of total carbon,total nitrogen and total phosphorus of plastic shed soil in Liaoning Province were 26.56±7.97g/kg,2.67±0.79g/kg and3.32±0.69g/kg,respectively.The total phosphorus content of 96%of the sampling sites reached the rich level.?3?The average values of C/N,C/P and N/P of plastic shed soil in Liaoning Province were 9.96±1.03,8.92±5.04 and 0.90±0.51,respectively,which were lower than the average level of farmland soil in China.With the increase of planting years,the C/N ratio in Plastic shed soil remained relatively stable,and the change trend of C/P and N/P was greatly affected by the accumulation of phosphorus in plastic shed soil.?4?With the increase of planting years,the total phosphorus,available phosphorus and inorganic phosphorus in plastic shed soil first increased and then decreased.In Haicheng area,the total phosphorus reached the peak at the 27th year,and the total inorganic phosphorus and available phosphorus reached the peak at the 22nd year.The total phosphorus and inorganic phosphorus reached the peak in the 23rd year.?5?Except Ca₂-P and Ca₈-P peaked in the 27th year of planting in Haicheng area,other forms of inorganic phosphorus reached the peak at the 22nd year of planting;the content of Al-P and O-P increased with the planting years in Tieling area,and other forms of inorganic phosphorus showed a trend of first increase and then decrease,and reached the peak at the 23rd year of planting.The main inorganic phosphorus in soil is Ca₈-p,Fe-P and Al-P.Ca₂-P,Ca₈-P and Fe-P were positively correlated with available P,and Ca₈-P,Al-P and available P were significantly positively correlated with total P.?6?With the increase of planting years,the activities of neutral phosphatase,acid phosphatase and alkaline phosphatase were the lowest in the 22nd year of planting in Haicheng area,and the three phosphatases in Tieling area showed the trend of increasing first and then stabilizing.Acid phosphatase was negatively correlated with iron phosphorus and aluminum phosphorus,negatively correlated with dicalcium phosphorus,and positively correlated with total phosphorus;alkaline phosphatase was negatively correlated with iron and phosphorus.?7?In the first 10 hours,the release rate of phosphorus was faster,and the release amount reached 65-75%of the whole release process.Elovich equation can better describe the phosphorus release process.Phosphorus release rate and maximum phosphorus release rate were significantly positively correlated with Ca₂-P,Fe-P and available phosphorus,and significantly positively correlated with Al-P and total phosphorus.