Effect of Poultry Manure Amendment on Soil Phosphatase Activity

Animal manure has traditionally been used as a fertilizer source. Manure phosphorus (P) exists in many forms, not all of which are immediately available. Microbial and plant-derived phosphatases can mineralize some organic P forms. Increased understanding of effects of manure application on soil phosphatase activity and subsequent P lability is needed to effectively use manure fertilizers. To determine short-term effects of manure amendment on soil phosphatase activity, we aerobically incubated two Maine soils with layer hen manure at 0, 7, or 14 mg manure per g soil (denoted Control, PML, and PMH, respectively) at 25^oC for 108 days and examined activities of phosphomonoesterase (acid, pH 6.5; alkaline, pH 11.0), and phosphodiesterase. Poultry manure amendment impacted both phosphomonoesterase and phosphodiesterase activity. During the early phase of the incubation (Days 0-24) the pattern of phosphodiesterase activity with PMH differed from Control and PML, with decreased activity at Day 14 and a 3x increase at Day 24. Acid phosphomonoesterase activity increased with amendment in the early incubation stages (days 3-14) in both soils, with highest activity levels observed at the lower (PML) amendment rate. Amended Newport soil (coarse-loamy, mixed, frigid Typic Haplorthod) had higher alkaline phosphomonoesterase activity from Day 0-24 but increases were not observed until Day 14 in Caribou soil (fine-loamy, isotic, frigid Typic Haplorthod). These results suggest that manure amendment may affect enzyme activities differently depending upon soil characteristics, including pH and texture and that high manure application rates could inhibit phosphomonoesterase activity, particularly in acidic soils.