Phosphorus Determination In Long-Term No-Tillage Rotation Study.

Continuous no-tillage wheat, corn, and soybean systems are commonplace in the Mid-Atlantic region. Conservation tillage affects soil properties throughout the horizon due to a lack of soil mixing. The focus of this study is to compare long-term, no-tilled soils that have received no P fertilizer (control), inorganic P fertilizer (soil test P, STP), non-amended poultry litter (PL), and poultry litter amended with alum (PLA). A long-term no-till rotation (corn – wheat – soybean – fallow – corn) 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 (approximately 120 kg N ha^-1) to wheat and 11.2 Mg ha^-1 (approximately 200 kg N ha^-1) prior to corn planting. The STP 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, and 2010. Soils were analyzed for pH and Mehlich 1 extractable P (M1-P). In 2000, there were no significant differences in pH (average = 6.19; p = 0.3887). By 2010, there were no significant differences between treatment pH (average = 5.09; p = 0.2000); however, the PL and PLA treatments had generally higher pH (5.11 and 5.30, respectively) than STP and no-P control treatments (4.91 and 5.05, respectively). In 2000, there were no significant differences in M1-P (average = 95 mg P kg^-1; p = 0.8738). However, by 2010, PLA had higher M1-P than PL (273 and 187 mg P kg^-1; p = <0.0001). Both the no-P control and STP treatments were lower (83 and 102 mg P kg^-1) than both PL treatments. In conclusion, in a long-term no-till system, amending PL with alum will increase Mehlich-1 extractable P compared to non-amended PL, but does not seem to significantly impact overall soil pH.