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

Abstract

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 applied 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 fertilizer (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 assessments such as a P site index, with limited impact on P availability to crops.