石灰性土壤无机磷分级体系的研究

本文提出了一个适用于石灰性土壤无机磷分级的新体系。它的特点是将石灰性土壤中的磷酸钙盐分成三种类型：⑴磷酸二钙型；⑵磷酸八钙型；⑶磷灰石型。并用混合浸提剂浸提磷酸铁盐。磷酸铝盐和闭蓄态磷酸盐的浸提方法与张守敬的土壤磷的分级体系同。新体系的三级磷酸钙盐之和相当于张的分级体系的NH#-4Cl和H#-2SO#-4溶性磷，非闭蓄态磷酸铁盐与闭蓄态磷酸盐之和，在这两个体系中也基本相当。但在张的体系中，磷酸钙盐绝大部分都进入H#-2SO#-4浸提液一级，而非闭蓄态的磷酸铁盐大多被混入闭蓄态磷酸盐之中。

A SUGGESTED FRACTIONATION SCHEME OF INORGANIC PHOSPHORUS IN CALCAREOUS SOILS

A new soil inorganic-P fractionation scheme is presented in this paper, in which calcium phosphate is classified into three groups; dicalcium phosphate-type, octocalcium phosphate-type and apatite-typs, and Fe-P is extracted with NaOH-Na_2CO_3. The recovery rates of synthetic phosphates in calcareous soils are at the range of 85-99%.Compared with Chang and Jackson's scheme, it shows no remarkable difference in the amount between the total of three groups of calcium phosphates in this scheme and the total of NH_4Cl-soluble and H_2SO_4 -soluble phosphate in Chang and Jackson's scheme; and so does the total of unoccluded Fe-P and occluded-phosphate between two schemes. But in Chang and Jackson's scheme all the calcium phosphates are in one group of H_2SO_4 extractant, and the extracted amount of unoccluded Fe-P is only a trace. But in this scheme, the three groups of calcium phosphates and much unoccluded Fe-P can be extracted. There may be of significance on further study of the relationship between the transformation of phosphorus form in calcareous soil and plant phosphorus nutrition.