Effects Of Phosphorus Application On Inorganic Phosphorus Forms And Phosphorus Uptake By Cotton In Irrigated Gray Desert Soil

Rational application of phosphorus fertilizer is an effective guarantee to reduce the accumulation of phosphorus in soil,improve the availability of phosphorus and promote crop growth.Through soil culture and pot experiment,comprehensively considering phosphorus fertilizer,soil and crop,this study discussed the effects of phosphorus application on inorganic phosphorus forms and phosphorus uptake by cotton in irrigated gray desert soil,so as to provide reference for the efficient utilization of phosphorus fertilizer.The soil culture experiment took irrigated gray desert soil as the research object,and set six treatments:no phosphate fertilizer（CK）,the basal application of triple super phosphate（TSP）,the basal application of mono-ammonium phosphate（MAP-B）,the basal application of ammonium polyphosphate（APP-B）,the one time drip application of mono-ammonium phosphate（MAP-D）and the one time drip application of ammonium polyphosphate（APP-D）,to study the effects of phosphorus fertilizer varieties and application methods on the forms of Olsen-P and inorganic phosphorus.The pot experiment took Xinnong 3 cotton as the selected crop,and set four treatments:no phosphate fertilizer（CK）,the basal application of triple super phosphate（TSP）,the basal application of mono-ammonium phosphate（MAP-B）and the basal application of ammonium polyphosphate（APP-B）,to study the effects of different phosphorus fertilizer varieties on soil inorganic phosphorus forms and availability and cotton phosphorus absorption.The main conclusions of this study are as follows:（1）In the soil culture experiment,without phosphorus application treatment in gray desert soil inorganic phosphorus was given priority to with Ca₁₀-P and O-P,respectively 47.94%and 23.76%of the total inorganic phosphorus.The basal application treatments of three phosphate fertilizers（TSP,MAP-B and APP-B）all raise 0-20 cm Olsen-P,inorganic phosphorus,PAC and the proportion of Ca₂-P,Ca₈-P,Al-P,Fe-P in grey desert soil,improved the phosphorus supply capacity of 0-20 cm soil layer,but its content and the ratio among the three（TSP,MAP-B and APP-B）were not significant.（2）In the soil culture experiment,compared with the basal application treatments of MAP and APP,the one-time drip application of them only significantly increased Olsen-P,inorganic phosphorus,PAC and the proportion of Ca₂-P and Ca₈-P at 0-5 cm soil layer of gray desert soil,significantly reduced the proportion of Ca₁₀-P,and improved the phosphorus supply capacity of 0-5 cm soil layer.（3）In pot experiment,ammonium polyphosphate can improve the availability of soil phosphorus at flowering and boll stage,improve the phosphorus nutrition of cotton at flowering and boll stage.APP-B treatment at flowering and boll stage of Olsen-P and Ca₂-P content were significantly higher than the MAP-B and TSP processing.APP-B treatment at flowering and boll stage of root,stem and leaf,reproductive organs accumulated phosphorus and phosphorus uptake were significantly higher than that of the TSP and MAP-B treatments.（4）Ca₂-P,Ca₈-P,Al-P,Fe-P,O-P content and Olsen-P content,PAC,accumulation of phosphorus uptake were very significant positive correlation（P<0.01）,and the correlation coefficient of Ca₂-P was the largest.It showed that Ca₂-P is the main source of Olsen-P and is easy to be absorbed and utilized by crops.The contribution of various forms of inorganic phosphorus to Olsen-P was Ca₂-P（0.37）>Al-P（0.32）>Ca₈-P（0.28）>O-P（0.12）,and the contribution of Fe-P and Ca₁₀-P to Olsen-P were negative.To sum up,the basal application treatments of three phosphate fertilizers all improved the phosphorus supply capacity of 0-20 cm soil layer,and the one-time drip application treatments of MAP and APP only significantly improved the phosphorus supply capacity of 0-5 cm soil layer;the basal application of ammonium polyphosphate can improve the soil phosphorus availability and improve cotton phosphorus nutrition at flowering and bolling stage.Triple super phosphate,monoammonium phosphate and ammonium polyphosphate all improved soil phosphorus supply capacity,and the effect of basal application was better than that of one-time drip application;at the same time,ammonium polyphosphate is more suitable for cotton growth than triple super phosphate and monoammonium phosphate.