Evaluating manure release parameters for nonpoint contaminant transport model KINEROS2/STWIR

Release of manure components is an important element of modeling applications in environmental water quality. The scarcity of experimental data and the multiplicity of the approaches for modeling release kinetics of the manure components introduce uncertainty and reduce reliability of overland flow and contaminant transport models. The goal of this study was to estimate release parameters for different manure components and provide input for KINEROS2/STWIR model developed for pathogen risk assessment associated with livestock operations. The objectives of this work were to evaluate reliability and robustness of the manure release parameters estimated based on individual and grouped release kinetics of soluble, particulate and combination of particulate and soluble materials from surface applied manure. The parameters of Bradford-Schijven model were evaluated from the experimental data on release of chloride, water-extractable phosphate-P, total bioactive P, organic carbon, enterococci and E. coli from surface applied manure measured in the runoff-box and runoff-plot experiments. The results showed that release of different manure components from surface applied manure can be reliably predicted with just a single set of parameters characterizing the kinetics of manure mass release. We demonstrated that the manure release parameters could be estimated more reliably when the model fit was performed using data for different manure components pooled together, while the model fit to a single release curve produced correlated parameters. The model parameters appeared to be robust and transferable from the calibration to validation datasets without any or with only minor losses of the model accuracy.