Research On The Phosphorus Forms Of Typical Soils In Northern China Based On The Hedley Method

The large-scale application of phosphate fertilizers in northern my country in the past20 years has led to a large accumulation of soil phosphorus and greatly increased soil available phosphorus content.However,due to the low utilization rate of phosphate fertilizer by crops,the prerequisite for achieving the goal of"reducing application and increasing efficiency"lies in understanding the northern soil Phosphorus pool morphology characteristics and the relationship between soil available phosphorus content and phosphorus morphology is proved.In this paper,the morphological transformations of inorganic phosphorus and organic phosphorus in the cultivated soils of different soil types under representative northern crop systems and their change patterns were systematically studied using Tiessen’s modified Hedley grading system.The relationships between soil inorganic phosphorus and organic phosphorus components and available phosphorus were analyzed using simple correlation analysis,path analysis and stepwise regression.Principal component analysis was used to explore the relationship between each soil phosphorus forms and organic matter,p H and calcium carbonate,in order to obtain the change characteristics and effectiveness of different soil inorganic phosphorus and organic phosphorus forms.The results of this work are as follows:1.The main forms and abundance of phosphorus in typical soils under the northern crop system were investigated.（1）The total phosphorus content of black soil,albic soil,chernozem soil,dark brown soil,cinnamon soil,fluvo-aquic soil,louvre soil,and chestnut soil reached 350.22-1162.41 mg kg^-1and 374.73-1233.44 mg kg^-1,respectively,374.20-1021.63 mg kg^-1,437.06-1978.51 mg kg^-1,467.48-919.61 mg kg^-1,603.72-1383.66mg kg^-1,649.50-1628.65 mg kg^-1,639.91-1262.14 mg kg^-1;（2）The phosphorus in the eight soils was dominated by inorganic phosphorus.The total inorganic phosphorus of black soil,albic soil,chernozem soil and dark brown soil under the spring maize monocropping system was 204.28-703.39 mg kg^-1,205.71-721.39 mg kg^-1,219.35-597.68 mg kg^-1,294.42-896.80 mg kg^-1,respectively,the inorganic phosphorus content of cinnamon soil,fluvo-aquic soil and loess soil under the winter wheat-summer corn rotation system was335.62-694.47 mg kg^-1,540.33-1149.79 mg kg^-1,515.63-1317.54 mg kg^-1,respectively,the content of chestnut soil under the potato monoculture system was 596.91-949.68 mg kg^-1;The total organic phosphorus content of black soil,albic soil,chernozem,dark soil,brown soil,cinnamon soil,fluvo-aquic soil,loess soil and chestnut soil reached 145.94-459.02 mg kg^-1,169.02-512.05 mg kg^-1,154.85-423.95 mg kg^-1,142.64-1081.71 mg kg^-1,131.86-225.14 mg kg^-1,63.39-233.87 mg kg^-1,133.87-111.11 mg kg^-1,43.00-312.46 mg kg^-1,respectively;the organic phosphorus content under spring maize monoculture system occupied a large proportion relative to the organic phosphorus content in other farming systems.（3）Among the eight typical soil inorganic phosphorus forms,all of them were dominant by D.HCl-P（dilute hydrochloric acid extractable phosphorus）,especially the loess soil had the highest content,and the proportion of D.HCl-P to inorganic phosphorus in black soil,albic soil,chernozem soil and dark brown soil was about 60%on average,while the rest of the soils with low organic matter content had more than 80%of D.HCl-P;the Residual-P content under the spring maize monocropping system is higher High,while the average content of Residual-P in the rest of the soil occupied only a few tens on average.2.Clarify The intrinsic relationship between the phosphorus forms and Olsen-P in soils was clarified.Correlation analysis between the phosphorus forms in eight soils and Olsen-P showed that active phosphorus（Resin-P,Na HCO₃-Pi,Na HCO₃-Po）,moderately active inorganic phosphorus（Na OH-Pi）all showed significant positive correlations with Olsen-P,while stable phosphorus（D.HCl-P,C.HCl-Pi,C.HCl-Po,Residual-P）were poorly correlated with Olsen-P.It shows that in different soil types,the composition of various forms of phosphorus is relatively stable,and the other forms of phosphorus have a certain influence on each other in the continuous extraction process,except for D.HCl-P,C.HCl-Pi,C.HCl-Po and Residual-P,the other forms of phosphorus all have activities of varying sizes,and can be transformed into each other under certain conditions.From the correlation analysis,it was inferred that Na HCO₃-Pi of black soil,albic soil,cinnamon soil,fluvo-aquic soil,and chestnut soil had the best correlation with available phosphorus,while the available phosphorus of chernozem,dark brown soil and loess soil had the strong correlation with Resin-P.3.Different sources of available phosphorus in typical soils were distinguished.Path analysis and stepwise regression analysis between each phosphorus form and Olsen-P in eight soils showed that:the effective phosphorus source of available phosphorus under the spring maize monocropping system were Resin-P and Na OH-Pi,except for Na HCO₃-Pi in albic soil;available phosphorus sources of available phosphorus in fluvo-aquic soil and cinnamon soil under winter wheat-summer maize rotation system were both Na HCO₃-Pi;Resin-P had the highest effectiveness in loess soil;and the effective phosphorus sources of chestnut soil were Resin-P and Na HCO₃-Pi.4.The relationship between each forms of phosphorus and soil physicaochemical properties（organic matter,p H,and calcium carbonate）under different crop systems was clarified.Principal component analysis showed that the p H in cinnamon soil,loess soil,and chestnut soil were negatively correlated with phosphorus forms under the same crop system.The p H of black soil and white slurrysoil,dark brown soil and fluvo-aquic soil were positively correlated with insoluble phosphorus,and negatively correlated with active phosphorus.All phosphorus forms of chernozem were positively correlated with p H.The content of calcium carbonate of albic soil,dark brown soil,fluvo-aquic soil,and loess soil were positively correlated with active phosphorus and negatively correlated with stable phosphorus,while the calcium carbonate content of black soil and chernozem were negatively correlated with active phosphorus and positively correlated with stable phosphorus.The content of calcium carbonate in cinnamon soil and chestnut soil is negatively correlated with all phosphorus forms;the organic matter of black soil,albic soil,chernozem,cinnamon soil,and loess were positively correlated with active phosphorus,and negatively correlated with stable phosphorus,All of the phosphorus forms of dark brown soil,fluvo-aquic soil,chestnut soil were positively correlated with organic matter.In summary,the following conclusions were obtained from this study:（1）Compared with the total phosphorus content in the second soils survey,the total phosphorus in the soil under each crop system have been significantly increased,and the soils phosphorus was dominated by stable phosphorus;（2）The correlation between active phosphorus and Olsen-P was strong in different soils;（3）The available phosphorus sources of different soils were active inorganic phosphorus（Resin-P,Na HCO₃-Pi）or potentially active inorganic phosphorus（Na OH-Pi）;（4）Different physical and chemical properties have different effects on each phosphorus form in different soils.Therefore,low-phosphorus soil can be converted from difficult-to-use phosphorus into active phosphorus by adjusting soil p H and organic matter,thereby maintaining a high effective phosphorus pool,which can enhance the potential phosphorus supply capacity of the soil,and meet the demand of high crop yield.