Fig. 5. Measured and predicted pendimethalin concentration versus time in the top 25 mm of surface soil for the no-mulch (top figure) and no-till (bottom figure) treatments. Two applications were made during 1999: spring application on Day 0 (26 March) and layby (preemergence) on Day 73 (7 June). Simulations are based on best fit using the first-order decay model (Eq. [1]).