Fate of Fertilizer P in Soils: Inorganic Pathway

Abstract

Soils never fertilized with P have usually a low P concentration (<0.02 mg l−1) in soil solution, which is below the crop needs. In acid soils, added P is adsorbed on the surfaces of iron and aluminum (hydr)oxides or, in calcareous soils, predominantly precipitated as calcium phosphates. Abundant organic and inorganic P fertilization in the industrial world has elevated the P status of agricultural soils and the large P surplus remains at least partly available to plants. In acidic soils Degree of P Saturation (DPS) can be used to indicate to which extent the potential sites for P sorption are already occupied. Repeated P applications increase the DPS and decreases P retention, and in calcareous soils, relatively easily soluble calcium phosphates are accumulated. Abundant residual fertilizer P results in a higher P concentration in soil solution. P supplying power in such soils is sufficient to meet the crop needs for several years, even decades, with P additions equaling to or smaller than the crop P uptake and apparently 100 % utilization of fresh fertilizer P can be achieved.