Measurement of available soil phosphorus under conventional and no‐till management

The objective of the investigation was to compare the predominant forms of P in fields of an acid Matapeake soil under no‐till and conventional‐till management. The fields, which differed in extent of contact between soil and fertilizer P, also differ in forms of P. Fertilizer P remained in the uppermost layer of no‐till fields and was, therefore, not in as close proximity to the plant (corn) roots as P was in conventional‐till fields. Nevertheless, fertilizer P in the no‐till fields underwent only limited conversion to forms less available to plants and thus, in part, may have accounted for similar plant uptake rates of P in no‐till and conventional‐till fields. One method used to analyze P in the Matapeake soil was the double‐acid‐extraction method. This method is used by several state soil‐testing laboratories of the eastern and southeastern United States, where acid soils like Matapeake are common. The double‐acid‐extraction method underestimated the soil P available for plant uptake.