ARS | Publication request: Modeling the Effects of Conservation Tillage on Water Quality at the Field Scale

Submitted to: Soil and Water Conservation Society Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 2009
Publication Date: July 11, 2009
Citation: Heathman, G.C., Pappas, E.A., Smith, D.R. 2009. Modeling the Effects of Conservation Tillage on Water Quality at the Field Scale [abstract]. Soil and Water Conservation Society Annual Conference, July 11-15, 2009. Dearborn, Michigan. 2009 CDROM.

Technical Abstract: The development and application of predictive tools to quantitatively assess the effects of tillage and related management activities should be carefully tested against high quality field data. This study reports on: 1) the calibration and validation of the Root Zone Water Quality Model (RZWQM) to assess the effects of no-till and conventional tillage practices on surface water quality in two 2.5 ha tile-drained agricultural fields in the Upper Cedar Creek Watershed (UCCW) over a 4-year period (2005-2008); and 2) the evaluation of model performance in simulating subsurface drain flows and associated chemical losses, primarily, nitrogen, phosphorous, and atrazine. Both fields are instrumented with state-of-the-art water quality samplers, weather stations and soil moisture sensors, and located in one of 14 benchmark watersheds in the national USDA-ARS Conservation Effects Assessment Project (CEAP). Model performance for daily runoff response was assessed using the Nash-Sutcliffe Efficiency coefficient (ENS), coefficient of determination (R2), Root Mean Square Error (RMSE), ratio of RMSE to the standard deviation of measured data (RSR), and percent bias (PBIAS). The results show that the RZWQM was able to simulate water and chemical transport to runoff and subsurface flow with sufficient quality, and should serve as a satisfactory tool in the CEAP initiative to quantify the impact of conservation tillage practice on water quantity and quality at the field scale. This, in turn, should aid our understanding of conservation assessment at the watershed scale.