REDUCTION OF 2,4-D LOAD IN SURFACE RUNOFF DOWN A GRASSED WATERWAY

The effectiveness of a grassed waterway in decreasing 2,4-D content in surface runoff was investigated. Corn plots were treated with 2,4-D (0. 56 kg/ha) and runoff produced by applying simulated rain was directed through a 24. 4-m-long grassed waterway. The 2,4-d concentrations were measured under wet and dry antecedent waterway and plot conditions. Reduction in 2,4-D load in waterways results from water loss by infiltration, sediment loss, and by attachment-absorption on vegetative and organic matter. Of the simulated rainfall applied 1 day after application of 2,4-D, 50% of the water ran off the plots under dry antecedent soil conditions, and 78% ran off under wet conditions. Infiltration reduced runoff flowing down the waterway an additional 25% under dry conditions and 2% under wet conditions. Suspended sediment reduction in the waterway was 98 and 94% of the total amount moving from the plot for the dry and wet waterway conditions, respectively.