Keywords

Legacy Soil Phosphorus, Chesapeake Bay, APLE model

Start Date

25-6-2018 10:40 AM

End Date

25-6-2018 12:00 PM

Abstract

Agricultural phosphorus (P) management is an issue due to P)losses 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). Simple modeling approaches rather than complex watershed models are needed to rapidly generate Information on realistic expectations for time required to drawdown soil P and how much P loss can be reduced. We used the Annual P Loss Estimator (APLE) model to simulate rates of soil P drawdown in Maryland, and to estimate P loss at a statewide scale associated with different combinations of soil P and P transport. APLE results for rates of soil P drawdown compared well measured rates from three field sites, showing APLE can reliably simulate soil P dynamics for Maryland soils. State-wide APLE simulations of P loss also compared well to estimates from the Chesapeake Bay Model. 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 37%. However, this 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 though runoff and erosion could achieve a 51% reduction in state-level P loss. This 51% reduction could be considered a maximum amount possible that is still compatible with modern agriculture.

Stream and Session

F5: New and Improved Methods in Agricultural Systems Modelling

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Jun 25th, 10:40 AM Jun 25th, 12:00 PM

A rapid approach for estimating the impact of legacy soil phosphorus in the Chesapeake Bay watershed

Agricultural phosphorus (P) management is an issue due to P)losses 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). Simple modeling approaches rather than complex watershed models are needed to rapidly generate Information on realistic expectations for time required to drawdown soil P and how much P loss can be reduced. We used the Annual P Loss Estimator (APLE) model to simulate rates of soil P drawdown in Maryland, and to estimate P loss at a statewide scale associated with different combinations of soil P and P transport. APLE results for rates of soil P drawdown compared well measured rates from three field sites, showing APLE can reliably simulate soil P dynamics for Maryland soils. State-wide APLE simulations of P loss also compared well to estimates from the Chesapeake Bay Model. 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 37%. However, this 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 though runoff and erosion could achieve a 51% reduction in state-level P loss. This 51% reduction could be considered a maximum amount possible that is still compatible with modern agriculture.