Enzymatic hydrolysis of organic phosphorus in soils and dairy feces

The objectives of this research were to determine the effect of increasing metal complexing agents on the concentration of organic phosphorus hydrolyzed by phosphatase and phytase in soils and dairy feces. Additional objectives were to develop an analytical approach for the direct detection of phytic acid in dairy feces and to evaluate the effectiveness of enzyme hydrolysis as a method to determine specific organic phosphorus compounds in dairy feces.; Increasing concentrations of EDTA or citrate were added to soil and dairy feces samples followed by incubation with phytase, phosphatase, or no enzyme for a control. Orthophosphate was determined to quantify the extent of organic phosphorus hydrolysis. Phytic acid was also detected in acid extracts of dairy feces by 31P nuclear magnetic resonance (31P NMR) and quantified by a new method using capillary electrophoresis.; The amount of organic phosphorus hydrolyzed by phytase and total soluble metals increased with increasing citrate and EDTA concentrations in soils. Organic phosphorus hydrolyzed by phosphatase and total soluble organic phosphorus also increased but to a much smaller degree. Organic phosphorus hydrolyzed by phytase increased with increasing EDTA concentration in dairy feces. Organic phosphorus hydrolyzed by phosphatase was independent of EDTA concentration in dairy feces.; These results support the hypothesis that removing metal bridges from organic phosphorus compounds with metal complexing agents increases the efficacy of phytase and phosphatase in soils and phytase in dairy feces. The relative amount of potentially available organic phosphorus in soils depends on soil type, soil amendments, and land use. Calcium appears to control the availability of organic phosphorus in the soils tested. The amount of potentially available organic phosphorus and phytic acid in dairy feces increased as the amount of supplemental orthophosphate added to the feed ration increased. Enzyme hydrolysis is useful as an indicator of potential organic phosphorus bioavailability but is limited in its ability to determine specific organic phosphorus compounds.