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Annual Phosphorus Loss Estimator (APLE) home page
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The Annual P Loss Estimator (APLE) is an annual time step and simulates sediment bound and dissolved P loss in surface runoff and annual changes in soil test P. This empirically based model was designed for use by those without significant modeling experience and relies on a handful of commonly measured input variables. APLE considers different kinds of animal manure (beef, dairy, poultry, swine), applied either by machine or by grazing beef or dairy cattle, and highly soluble commercial fertilizers. APLE was initially developed and coded as an Microsoft Excel spreadsheet to provide a modeling option for users with limited modeling experience and lack of access to expensive software packages.

The APLE model was developed by Peter A. Vadas (peter.vadas@usda.gov) in 2009 and updated by Carl H. Bolster (carl.bolster@usda.gov) in 2022. 

Major updates

     Version 3.0;May 2022:

  1. Soil bulk density is now a user-defined input.
  2. Option for using the SCS Curve Number method for calculating annual runoff.
  3. Errors can be assigned to each model input. These errors are used to estimated model prediction uncertainties using Monte Carlo simulations.

     APLE2026; January 2026

This version of APLE includes a Graphical User Interface (GUI) application (APLE2026) to provide a cleaner and more intuitive user interface, improved graphics, and enhanced data analysis. This novel software package of APLE provides a more seamless way to run the model and view model output thereby enhancing the functionality of APLE. It currently does not include ability to assign errors to model inputs but is expected to be updated in late 2026 to include this option.

In the future, any updates to APLE will only be reflected in this version (APLE2026) so users are encouraged to download and use this version.

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Downloads Available

APLE2026 is a desktop application of APLE released in January 2026

  • APLE2026 software
  • APLE2026 User's Manual
  • APLE2026 input file

APLE 3.0 is the latest version in Microsoft Excel (released in 2022)

APLE-Lots is a version of APLE developed specifically for simulating dissolved and particulate P loss from outdoor feedlots. 

 

The Wisconsin Soil Nutrient Application Planner (SnapPlus) uses many of the equations in APLE and can be accessed here

 

References:

 

Bolster, C.H., B.M. Wessel, P.A. Vadas, and N.M. Fiorellino. 2022. Sensitivity and uncertainty analysis for predicted soil test phosphorus using the Annual Phosphorus Loss Estimator model. Journal of Environmental Quality. doi: 10.1002/JEQ2.20328.

Bolster, C.H., P.A. Vadas, and D. Boykin. 2016. Model parameter uncertainty analysis for an annual field-scale P loss model. Journal of Hydrology 539: 27–37. doi: 10.1016/j.jhydrol.2016.05.009.

Bolster, C.H., and P.A. Vadas. 2013. Sensitivity and uncertainty analysis for the Annual Phosphorus Loss Estimator Model. Journal of Environmental Quality 42(4): 1109–1118. doi: 10.2134/jeq2012.0418.

Vadas, P.A., L.W. Good, P.A. Moore, and N. Widman. 2009. Estimating Phosphorus Loss in Runoff from Manure and Fertilizer for a Phosphorus Loss Quantification Tool. Journal of Environmental Quality 38(4): 1645–1653. doi: 10.2134/jeq2008.0337.

Vadas, P.A., N.M. Fiorellino, F.J. Coale, R. Kratochvil, A.S. Mulkey, et al. 2018. Estimating Legacy Soil Phosphorus Impacts on Phosphorus Loss in the Chesapeake Bay Watershed. Journal of Environmental Quality 47(3): 480–486. doi: 10.2134/jeq2017.12.0481.

Vadas, P.A., B.C. Joern, and P.A. Moore. 2012. Simulating Soil Phosphorus Dynamics for a Phosphorus Loss Quantification Tool. Journal of Environmental Quality 41(6): 1750–1757. doi: 10.2134/jeq2012.0003.