372-5 Using the Apex Model to Support Refinement and Regionalization of Southern P Assessment Tools.
See more from this Division: ASA Section: Environmental QualitySee more from this Session: Progress on the Regional P Index Conservation Innovation Grants
Field testing of the Agricultural Policy/Environmental eXtender (APEX) model has been performed using data for runoff, sediment and P losses from small watersheds (6.8-26 ha) and plots (0.02-0.8 ha) in 8 generalized physiographic regions in 5 southern states. Initial uncalibrated predictions of APEX evidenced that model’s default settings underestimated observed values of runoff, sediment and P losses. Preliminary calibrated parameters have been observed to fall into ranges proposed in other APEX simulation studies. Estimated model efficiency coefficients ((R2>0.7) and Nash-Sutcliffe (NSE> 0.42)) values are representative for very accurate model predictions. However, P and sediment loads predicted during irrigation events could importantly affect model efficiency (R2>0.47 and NSE>0.35). In addition to accurate water quantity and quality prediction, APEX has been able to predict the effects of the different agricultural practices on physical and chemical soil properties (e.g. pH, soil P).
See more from this Session: Progress on the Regional P Index Conservation Innovation Grants