|Fiorellino, Nicole - Chesapeake College|
|Coale, Frank - University Of Maryland|
|Kratochvil, Robert - University Of Maryland|
|Mulkey, Alisha - Maryland Department Of Agriculture|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2018
Publication Date: 5/3/2018
Citation: Vadas, P.A., Fiorellino, N.M., Coale, F.J., Kratochvil, R., Mulkey, A.S. 2018. Estimating legacy soil phosphorus impacts on phosphorus loss in the Chesapeake Bay Watershed. Journal of Environmental Quality. 47:480-486.
Interpretive Summary: Agricultural phosphorus (P) loss from fields and water quality degradation continues to be an issue in the Chesapeake Bay watershed. Since many of the soils in the watershed have high P levels, information is needed on how long it will take to reduce soil P and how much related P loss will decrease. We used the Annual P Loss Estimator (APLE) model to estimate soil P drawdown and P loss for cropland in Maryland. Based on APLE results, reducing soil P throughout the state to agronomic levels could reduce P loss to the Chesapeake Bay by 42%. However, it may take 30-40 years to reach this 42% target. Combining soil P drawdown with aggressive soil conservation could reduce P loss by 63%. Overall, there appears to be a potential to substantially reduce P loss in Maryland to the Chesapeake Bay, but it will require a continued effort to reduce both soil P and P transport from all cropland.
Technical Abstract: Agricultural nutrient management is an issue due to phosphorus (P) loss from fields and water quality degradation. This is especially true in watersheds where a history of P application in excess of crop needs has resulted in elevated soil P (legacy P). As practices and policy are implemented in such watersheds to reduce P loss, information is needed on time required to draw down soil P and how much P loss can be reduced by drawdown. We used the Annual P Loss Estimator (APLE) model to simulate soil P drawdown in Maryland, and to estimate P loss at a statewide scale associated with different combinations of soil P and P transport. Simulated APLE soil P drawdown compared well measured rates from three field sites, showing APLE can reliably simulate P dynamics for Maryland soils. State-wide APLE simulations of average annual P loss from cropland (0.93 kg ha-1) also compared well to estimates from the Chesapeake Bay Model (0.87 kg ha-1). APLE results suggest it is realistic to expect that a concerted effort to reduce high P soils throughout the state can reduce P loss to the Chesapeake Bay by 42%. However, P loss reduction would be achieved gradually over several decades since soil P drawdown is very slow. Combining soil P drawdown with aggressive conservation efforts to reduce P transport in erosion could achieve a 63% reduction in state-level P loss. This 63% reduction could be considered a maximum amount possible that is still compatible with modern agriculture.