|Fiorellino, Nicole - University Of Maryland|
|Mcgrath, Joshua - University Of Kentucky|
|Coale, Frank - University Of Maryland|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2017
Publication Date: 5/8/2017
Citation: Fiorellino, N.M., McGrath, J.M., Vadas, P.A., Bolster, C.H., Coale, F.J. 2017. Use of annual phosphorus loss estimator (APLE) model to evaluate a phosphorus index. Journal of Environmental Quality. doi:10.2134/jeq2016.05.0203 46(6):1380-1387.
Interpretive Summary: Phosphorus loss in runoff from farms can pollute local waters; this is a noted problem in the Chesapeake Bay watershed. Tools have been developed to help policy makers and farmers estimate what areas on farms are responsible for the most loss and consequently should be managed differently. Maryland’s Phosphorus Site Index (MD-PSI) has been used to guide agricultural phosphorus management in Maryland since 2002. The Index was recently revised and renamed the University of Maryland Phosphorus Management Tool (UM-PMT). To evaluate how well the new tool estimates the risk of phosphorus loss from fields, researchers used the Annual Phosphorus Loss Estimator (APLE) model, developed by the USDA Agricultural Research Service, and diverse datasets for Maryland management and field conditions. There was poor correlation between phosphorus loss estimates of the UM-PMT and of APLE, so they modified the UM-PMT. The resulting tool (renamed the UM PMT-2) had strong correlation with APLE outputs, showing it can reliably estimate the risk of phosphorus loss for a variety of field and management conditions. This is an important step in the evolution of national phosphorus indexes to make them more reliable in their phosphorus loss risk prediction.
Technical Abstract: Maryland’s Phosphorus Site Index (MD-PSI) has been used to guide management decisions to minimize the potential for phosphorus (P) loss from agricultural fields in Maryland since 2002. The index was recently revised and renamed the University of Maryland Phosphorus Management Tool (UM-PMT), and the most significant change was a shift from a multiplicative to a component formulation. The Annual Phosphorus Loss Estimator (APLE) model is a field-scale P loss quantification tool that was used to evaluate the UM-PMT and assign weighting coefficients to the P loss components. A simulated dataset of approximately 10,000 points across Maryland was created to perform the evaluation while a measured dataset (n=382) of fields statewide was used to assess the suggested modifications. Poor correlation was observed between P loss components of the UM-PMT and outputs of APLE using the simulated dataset. Modifications were made to the UM-PMT, including replacement of categorical variables with continuous variables. Weighting coefficients were calculated for each component of the UM-PMT and the resulting equation was renamed the Phosphorus Management Tool 2 (PMT-2). High correlation coefficients were calculated between P loss components of PMT-2 and APLE outputs for both the simulated and measured dataset. This evaluation is an important step forward in the evolution of national P Indexes to make them more reliable in their P loss risk prediction.