Influence of Phytase and High Available Phosphorous Corn Diets on Solubility and Plant Uptake of P, Cu, and Zn in Poultry Manure and Manure-Amended Soils
Poultry manure is a useful nutrient source but recently it has raised environmental concern due to possible P movement from P saturated soils to waterbodies. This study was conducted to determine the effects of using phytase and high available phosphorous corn diets on the solubility and plant uptake of P, Cu, and Zn in poultry manure and soils amended with manure. Five diet treatments were used in the study: 1) normal phytic acid corn and 0.135% inorganic P (NPA), 2) normal phytic acid corn, 600 units phytase, and 0.135% inorganic P (NPA+Phytase), 3) normal phytic acid corn and 0.345% inorganic P (NPA+P), 4) high available phosphorous corn and 0.135% inorganic P (HAP), 5) high available phosphorous corn, 600 units phytase, and 0.135% inorganic P (HAP+Phytase). The NPA+P diet and NPA+Phytase diets are most similar to the conventional and alternative phytase supplemented diets currently used commercially. Three Virginia soils (Groseclose, Cecil, Mahan) were amended with manure from the diet treatments at rates of 25 and 50 g/kg and P and Cu were extracted with 0.01 M CaCl2 and Mehlich III extractant after incubation periods of 6 and 12 months. Corn was grown in a greenhouse experiment using these same Virginia soils and sand amended with 8.96 Mg/ha poultry manure from each of the five diet treatments. Poultry manure was nonsequentially extracted for determination of P, Cu, and Zn fractions. Comparing the alternative NPA+Phytase, HAP, and HAP+Phytase treatments to the conventional NPA+P treatment on an N- (nitrogen) basis all reduced both CaCl2 and Mehlich III-soluble P concentrations (P<0.05). Comparing these same treatments on a P-basis increased P extracted with CaCl2 24, 26, and 37%, respectively, and P extracted with Mehlich III P 5, 4, and 9%, respectively (P<0.05). The alternative NPA+Phytase and HAP+Phytase treatments increased water-soluble Cu compared to the conventional NPA+P on both a N- and P-basis, while no differences were observed in Mehlich III solubility between these treatments (P<0.05). The alternative NPA+Phytase treatment did not differ in Pand Cu in corn tissue or plant uptake when compared to the NPA or NPA+P (N- or P-basis) treatments. No difference in Zn in corn tissue was observed between these treatments on a N-basis, while NPA+Phytase was higher on a P-basis. Plant uptake of Zn was higher in the NPA+Phytase treatment compared to the NPA+P treatment on both a N- and P-basis. Addition of phytase reduced P solubility from all reagents except for CaCl2 (P<0.05). Replacing the conventional NPA+P treatment for the alternative NPA+Phytase treatment resulted in higher Cu concentrations for all reagents except for K-pyrophosphate and nitric acid. This same replacement increased Zn extracted by water, CaCl2, and CaNO3, while it reduced Zn extracted by HCl, acetic acid, PbNO3, K-pyrophosphate, and NH4-oxalate in the light. The use of phytase decreased P solubility from manure amended soils when treatments are compared on an equal N-basis, and increased P solubility when compared on an equal P-basis. No effect on plant uptake of P or Cu occurredfrom the NPA+Phytase treatment.