Phosphorus Fraction Determination On a Long-Term No-till Rotation.

Continuous no-tillage wheat, corn, and soybean systems are commonplace in the Mid-Atlantic. Conservation tillage impacts soil properties due to a lack of soil mixing. This study compared long-term, no-tilled soils that have received no P fertilizer (control), inorganic P fertilizer (triple super phosphate, TSP), non-amended poultry litter (PL), and poultry litter amended with alum (PLA). A long-term no-till rotation (corn – wheat – soybean – fallow) was initiated in 2003 in Painter, VA on a Bojac sandy loam. Poultry litter treatments (PL and PLA) were applied at 6.7 Mg ha^-1 to wheat and 11.2 Mg ha^-1 prior to corn planting. The TSP treatment received fertilizer applied as triple super phosphate based on soil testing. Soil samples were taken from 0 to 5 cm from years 2000, 2004, 2008, 2010, and 2011. Additional soil depths (5-15 cm and 15-30 cm) were analyzed for 2004 and 2011. Soils were analyzed via sequential fractionation extractions for loose P, Al bound P, Fe bound P, reductant soluble P (RSP), and Ca bound P. Total inorganic P was also estimated by summation of the fractions. Significant differences in shallow soil samples (0-5 cm) were found in concentrations of loose P after one year of fertilizer application, and continued to have significant differences over time. In 2008, 2010, and 2011, PL and PLA treatments were significantly higher in loose P and Al bound P than the control and TSP treatments. No differences were observed for Fe bound P. PLA was significantly greater in RSP and Ca bound P in 2010. In 2011, total inorganic P was significantly higher in the PL and PLA treatments than the control and TSP treatments. Few differences were seen in soil P fractions in samples below 5 cm. In conclusion, alum additions can reduce loose P at 0-5 cm.