The Nutrient Tracking Tool (NTT) was designed and developed by the Texas Institute for Applied Environmental Research (TIAER), Tarleton State University with funding from USDA Office of Environmental Markets, USDA-NRCS Conservation Innovation Grants program, and various state agencies.

NTT is a web-based, site-specific application that estimates nutrient and sediment losses at the field scale or at the small watershed scale.

Agricultural producers and land managers can define a number of management scenarios and generate a report showing the expected nutrient loss differences between any selected scenarios for a given field or small watershed.

NTT compares agricultural management systems to calculate a change in expected flow, nitrogen, phosphorus, sediment losses, and crop yield. Estimates are made using the APEX model (Williams et al. 2000). Results represent average losses from the field based on 35 years of simulated weather.

NTT requires regional soils, climate and site-specific crop management information. NTT currently provides selections for every U.S. county, but it has only been validated for a limited number of states and counties. As validation becomes possible in other parts of the country, parameter files may be updated for additional counties in future versions.

There are two versions of new NTT program available:

For more information regarding NTT, please refer to Saleh et al. (2011 and 2014).

About APEX

NTT uses a biophysical simulation model, the Agricultural Policy Environmental eXtender model (APEX), version 0806, to process user supplied information (APEX; Williams et al., 2000). Below are characteristics of the APEX model.


Last updated: 16 Feb 2018

The information contained in NTT (Nutrient Tracking Tool) has been tested for use in the Ohio counties surrounding Lake Erie, in the Mississippi Delta, Missouri, Yakima County in the State of Washington, the northern portion of Oregon, Maryland, Delaware, Pennsylvania, Virginia, Puerto Rico, and Sonoma County in California. Because your area of interest may contain unique features, the program may not provide the appropriate results in your area when model default parameters are used. All input data and results should be carefully reviewed as errors or omissions in the input data may lead to misleading outcomes. We are currently in the process of completing the testing and validating NTT across the US (this page will be updated accordingly as new information becomes available).

If you have questions regarding the application of NTT or are interested in having it calibrated and validated for your area, please contact Dr. Ali Saleh at (254)592-1975 ( or Ms. Mindy Selman at (202) 401-0531 (

Finally, although NTT has been tested by its developers, NO warranty, expressed or implied, is made as to the validity of the results and functioning of the program and related program material, nor shall the fact of distribution constitute any such warranty; and NO responsibility is assumed by the developers in connection therewith. The user assumes all risks and responsibilities for the use and application of NTT and interpretation of the results generated from the tool. The authors and their affiliated institution, TIAER, Tarleton State University, and any other U.S. Government agencies will NOT be liable to NTT users for any damage, including lost profits, lost savings, lost time, actions by regulatory agencies, or any other direct or indirect incidental or consequential damages occurring from the use of or inability to use NTT, its databases, its results, or its documentation for any purpose.


Peter J. A. Kleinman , A. N. Sharpley , K. Gartley , W. M. Jarrell , S. Kuo , R. G. Menon , R. Myers , K. R. Reddy & E. O. Skogley. 2007. Interlaboratory comparison of soil phosphorus extracted by various soil test methods. Journal of Communications in Soil Science and Plant Analysis Volume 32, 2001 - Issue 15-16 Pages 2325-2345.

Saleh, A, O. Gallego, and E. Osei. 2015. Evaluating Nutrient Tracking Tool and simulated conservation practices. Journal of Soil and Water Conservation. July/August 2015—Vol. 70, No. 4.

Saleh, O. Gallego, E. Osei, H. Lal, C. Gross, S. McKinney and H. Cover. 2011. Nutrient Tracking Tool—a user-friendly tool for calculating nutrient reductions for water quality trading. Soil and Water Conservation Society. November/December 2011 vol. 66 no. 6 400-410.

Williams J.R., Arnold J.G., Srinivasan R. 2000. The APEX Model. BRC Report No. 00-06, Oct. 2000.

Winchell, M., D. Meals, S. Folle, J. Moore, D. Braun, C. DeLeo and K. Budreski. 2011. Identification of critical source areas of phosphorus within the Vermont sector of the Missisquoi Bay basin. Grand Isle, VT: Lake Champlain Basin Program.

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