The loading, solubility, mobility, and plant availability of P is a
growing environmental concern to regulators and planners of nutrient
management plans, confined animal feeding operations, and wastewater
land application permit sites. Insufficient information is available
on how P reacts from different organic sources when applied to calcareous
soils. A field study was conducted to determine the interactions
among P application rate, source, extractability, and soil organic carbon
(OC) concentration. A Portneuf silt loam (Coarse-silty, mixed,
superactive, mesic Durinodic Xeric Haplocalcids) topsoil and freshly
exposed subsoil were fertilized with monocalcium phosphate (MCP),
cheese whey, and dairy manure. Organic matter added with the whey
did not influence soil OC concentrations whereas organic matter
added with the manure doubled the subsoil OC and increased the
topsoil OC concentrations. Bicarbonate and saturation paste extractable
ortho- and organic-P concentrations were linearly related to soil
OC concentrations but were not related to the amount of ortho- or
organic-P added. All forms of P increased more per unit of added P
in the order manure > whey > MCP and were correlated with the soil
OC concentrations. These results suggest organic waste applications
should be managed from :oil P test data rather than on P application
rates
