Characteristic And Influence Of Biologically-based Phosphorus Fractions In The Soil

As phosphorus deficiency is a prevalent constraint of agriculture in China,the application of mineral phosphorus?P?fertilizers to farmland is of essential measure to maintain crop yields.A suitable fractionation method of phosphorus is a key to effectively assess soil P componential features.Since the introduction of Zhang and Jackson phosphorus fractionation method in 1956,the method of soil phosphorus fractionation has experienced a process from difficult to easy,and complex to simple.However,at present,there is no uniform standard in the widely used phosphorus fractionation method in the world.Each method has different degrees of defects and deficiencies.Therefore,there are a large number of phosphate fertilizer applications in view of the current situation of the increasing environmental problem.It is of great significance to study the status and availability of phosphorus in soil,and to reveal the improvement of environmental protection and agricultural productivity.In the study,392 soil samples were collected from the provinces of China,which were divided into dry land,paddy soil,forest soil,and grassland soil.Here a new biologically-based P?BBP?method was used to evaluate the P fractions.The main conclusions were as follows:?1?The soil P was divided into four components:?1?soluble or interception of rhizosphere?CaCl₂-P?,?2?inorganic combined,organic acid complexation?Citrate-P?,?3?enzyme mineralization of organic P?Enzyme-P?,?4?potential activation of inorganic P?HCl-P?.In the process of experiment,the Enzyme-P extraction method of Deluca was overestimated by the phosphorus fractionation method.Then use the pure water instead of the original method of 50 mmol·L^-1 sodium acetate solution.Finally,the alkaline phosphatase was added to the original base,which made the organic phosphorus fractions more comprehensive and representative.?2?In the farmland ecosystem,the relationships between biologically-based P fractions and standard Olsen-P were investigated,and driving factors of P fractions were identified.Then the results showed that P content were in order of HCl-P>Citrate-P>Enzyme-P>CaCl₂-P.All P components of upland soil displayed a higher level than that of paddy soil.Moreover,the P components were highly positive correlated with the Olsen-P,suggesting that each P component was contributed to soil P availability.However,it was found that Olsen-P was most highly correlated with CaCl₂-P and Enzyme-P?R²=0.336;R²=0.358?in upland soil,while Olsen-P was most highly with Citrate-P and HCl-P?R²=0.428;R²=0.427?in paddy soil.This result indicated that available P of upland soil was mainly from organic P mineralization and soluble P,and available P in paddy soil was mainly from inorganic P activation.?3?In natural ecological system,the relationships between biologically-based P fractions and standard Olsen-P were investigated,and driving factors of P fractions were identified.Then the results showed that P content were in order of HCl-P>Citrate-P>Enzyme-P>CaCl₂-P.All P components of greensward displayed a higher level than that of forest soil.Moreover,the P components were highly positive correlated with the Olsen-P,suggesting that each P component was contributed to soil P availability.However,it was found that Olsen-P was most highly correlated with Citrate-P and HCl-P?R²=0.312;R²=0.367?in forest soil,while Olsen-P was most highly with Enzyme-P?R²=0.540?in greensward.This result indicated that available P of forest soil was mainly from organic P mineralization and inorganic P,and available P in greensward was mainly from soluble P activation.?4?Redundancy analysis?RDA?showed that the P components were mainly affected by soil pH,which suggested that it could enhance the P availability via regulating soil pH in the agricultural activities.