Phosphorus speciation in the fertosphere of highly concentrated fertilizer bands

The factors affecting chemical transformations of phosphorus (P) in highly concentrated fertilizer bands have received little attention, with no previous studies having utilized in situ approaches to examine these changes in P speciation within the fertosphere. In the present study, an incubation experiment was conducted to examine the impact of soil properties, the form of P and the co-application of K on changes in P speciation in highly concentrated fertilizer bands. In non-calcareous soils, the precipitation of P as Al-P minerals was found to be critical, with decreases in pH increasing solubilization of soil Al, increasing the precipitation of Al-P minerals, and hence markedly decreasing potential P availability. As a result, factors altering pH, including soil properties and the form of the P fertilizer, are important in determining P availability through regulation of Al-P precipitation. In a calcareous soil, P availability was greatly reduced due to precipitation of Ca-P minerals. The co-application of K resulted in comparatively subtle changes in P speciation, being most pronounced in soils with a high cation exchange capacity, likely by altering Ca- and Mg-P precipitation. The finding that soil properties and the form of P supplied were more important than the co-application of K in controlling P solubility indicates that optimizing P form is important when designing fertilizer placement strategies.