TECHNICAL ARTICLES PHOSPHORUS AVAILABILITY TO BARLEY FROM MANURES AND FERTILIZERS ON A CALCAREOUS SOIL

High concentrations of animal production in the United States have increased the concern about the environmental fate of phosphorus (P) in manures. We conducted a growth chamber study to develop phosphorus source coefficients (PSCs) for manures and fertilizers typically land ap-plied and incorporated into calcareous soils of the western United States as well as to determine the potential plant P availability of these sources. Six manure types (swine solids from low phytate and regular barley diets, swine liquid, dairy liquid, beef solid, and dairy compost) and four fertil-izer (mono calcium phosphate, mono ammonium phosphate, polymer-coated mono ammonium phosphate, and ammonium polyphosphate) P amendments were applied to two Portneuf soils at a rate of 60 mg P kg-1, incubated for 2 weeks, then planted with barley grown for 7 weeks. Soil samples were analyzed before barley planting and then at 4 and 7 weeks after planting, whereas plant samples were analyzed at 4 and 7 weeks. Increases in soil water soluble (WS-P) and bicarbonate P (Olsen P) from P additions generally followed the pattern [fertilizer P]> {liquid manures]> [solid or composted manures]. Plant shoot biomass and plant P accumulation were similar except swine manures were greater than inorganic P sources and beef manure was less than both. Determining relative P solubility of manure and fertilizer sources will be beneficial when estimating P losses from land application of manures and may be used to assign weighting coefficients to manure sources in risk assess-ments such as a P site index, with limited impact on P availability to crops. (Soil Science 2005;170:401-412