Soil Phosphorus Distribution as Affected by Manure Compost Phosphorus Concentration and Incorporation

Phosphorus (P) from manure can become an environmental pollutant if applied to soil at rates in excess of plant uptake. This research examined the effects of composted beef cattle manures from two feeding regimens on soil P storage and forms. Composted manures were applied in the spring before planting (preplant) with incorporation, in spring after planting (postplant) without incorporation, or in winter without incorporation. Soils were sampled following 1 and 2 years of treatment at depths to 15.0 cm. All P fractions from both composted manures increased over pre-amended levels. High-P composted manure increased total P (TP) and inorganic P (IP) more than low-P composted manure. Total P and IP were greater in soils receiving low-P composted manure postplant than in those receiving manure preplant. Accumulation of TP and IP in uppermost depths was greater in the second year of composted manure application than in the first year. Appropriately managing composted manure requires integrating P concentration, time of application, and incorporation.