Nutrient Management Planning and Soil Phosphorus Status in Maryland Soils.

Nutrient management planning has been mandatory in Maryland since promulgation of the Water Quality Improvement Act in 1998, but little is known about how this mandate affected soil phosphorus (P) status. This study analyzed archived soils from a P-loading and phytoremediation study conducted at three sites, where manure was added from 1995-1997 at five different application rates. Beginning in 1998, plots were managed the same and no further P was added. Archived soils from 2001, 2004, 2006, and 2012 were analyzed for ammonium oxalate and Mehlich-3 extractable P, iron (Fe), and aluminum (Al). Degree of phosphorus saturation (the molar ratio of P to Fe + Al) will be calculated using both Mehlich-3 (DPS_M3) and ammonium oxalate (DPS_ox), with calculation of the α-value using a P isotherm and Langmuir equation. Additionally, pH and organic matter content, using the loss on ignition (LOI) method, will be determined. Results of this study will increase understanding of soil P dynamics and how soil P changes over time in high P sites, which is important when designing effective strategies to mitigate P loss. Potential implications of findings from this study in regards to P management strategy will be discussed.