Fig. 4. Chemical concentration in percolate during the first 5.5 d after rainfall initiation (1000 h EST, 1 May 2000). The vertical lines represent the range of concentrations from the four lysimeters. The symbols represent the average alachlor and metribuzin concentration at approximately 0.06 and 0.09 d after rainfall initiation. The maximum concentrations occurred at approximately 0.10 d after rainfall initiation. Herbicide concentration determined from discrete samples except Days 2.2 and 5.5 were composite samples.