A degree-day concept for estimating degradation time under field conditions.

Development of degradation rate information for crop protection products in soil is typically a time consuming and costly process. Therefore, development of methodology that would allow extrapolation of limited degradation information to wider field conditions in a predictive fashion would be desirable. This study presents an approach that uses a modified heat unit model to estimate organic compound degradation time using limited datasets. The model requires daily soil or air temperature and volumetric water content. Predictions based on the model for three different compounds in five different field studies were within 80% of measured values based on soil analysis. Results from this research indicate that the model was able to predict compound half-life values across all sites with r2 = 0.99.