Effect of soil properties on the forms of inorganic phosphorus in alkaline-calcareous soils of different agroclimatic zones

The effect of soil properties on distribution of inorganic P fractions in 28 basic‐calcareous soils and on their contribution to available P was determined by using partial correlation coefficient and regression analysis. None of the soil properties significantly contributed to saloid‐P (i.e., extractable in 1N NH4 Cl), while Al‐P has significant correlation with pH. Fe‐P content of soils decreased significantly with pH and CaCO3, but increased with organic carbon, cation exchange capacity (CEC), clay, and active Fe contents. The pH, pH + CEC, pH + CEC + Fe contributed 41.5, 57.0, and 60.8% variation in Fe‐P, respectively. Among the soil properties considered, only CaCO3 contributed significantly to Ca‐P. Available P decreased with an increase of pH, and increased with an increase of organic carbon, CEC, and clay. The contribution of pH, pH + CEC, pH + CEC + CaCO3 + organic carbon to available P was 26.2, 32.6, 33.8, and 36.2%, respectively. Available P was significantly and positively correlated with saloid‐P, Al‐P, but not with Ca‐P. The contribution of inorganic P fractions to available P was 88.0%, while saloid‐P and saloid‐P + Fe‐P contributed 45.0 and 82.0%, respectively.