Effect of drying on phosphorus distribution in poultry manure

Laboratory drying may alter manure phosphorus (P) distribution. The effects of freeze, air (22 degrees C), and oven (65 degrees C) drying on sequentially fractioned poultry manure P were examined. Higher drying temperatures resulted in lower percentage of dry matter. Increased H2O- and decreased sodium bicarbonate (NaHCO3)-extractable P with drying provided evidence that drying increases poultry manure P solubility. Labile fractions were predominantly inorganic P (P-i), whereas sodium hydroxide (NaOH) and hydrochloric acid (HCl) fractions had significant amounts of organic P (P-o). Drying altered H2O- and NaHCO3-extractable P-i but had no consistent effect on P-o in these fractions. This work suggests that variations due to drying should be taken into consideration when evaluating manures for P availability or when comparing data in which different drying methods have been utilized.