Influence of Natural Drainage on the Distribution and Forms of Phosphorus in Some Iowa Prairie Soils

Abstract

AbstractTotal, inorganic, organic, and available P were determined for 12 loess‐derived prairie soil profiles. The amount of total phosphorus (TP) is high near the surface, has minimum values from 1 to 3 ft, has maximum values from 3 to 6 ft, and has nearly uniform values below 6 to 7 ft. The higher amounts near the surface are due to organic phosphorus (OP). The amount of OP in the poorly drained soils is about one‐half that in the better drained members of the topo‐sequence.Differences in organic carbon (OC)/OP ratios between the poorly and better drained soils are appreciable, with the poorly drained soils having the higher ratios.Difference in extractable or available phosphorus (AP) within and between profiles may be interpreted when pH, extractable Fe and Al, rooting depth of plants, TP and OC/OP ratios are considered. Phosphorus differences between soils of southeast and southwest Iowa are appreciable. The role of P in soil genesis studies is discussed.