Effectiveness of Vegetated Buffer Strips in Reducing Pesticide Transport in Simulated Runoff

Several processes take place within vegetated buffer strips that affect their performance. To better understandthese processes, a runoff study was conducted to evaluate vegetated buffer strips performance in reducing atrazine,metolachlor, and chlorpyrifos transport as affected by the drainage area to buffer strip area ratio. The simulated runoff watermixed with pesticidetreated soil was distributed onto six vegetated buffer strips, each 1.52 m wide . 20.12 m long, locateddownslope of the inflow distribution tank in a well established vegetated grassed waterway. These strips provided for threereplications of two inflow rates designated as drainage area/buffer strip area ratio treatments of 15:1 and 30:1. Infiltrationfor the 15:1 treatment averaged 38.8% of the inflow volume, whereas it averaged 30.4% for the 30:1 treatment. Sedimentretention efficiencies averaged 90.1% and 86.8% for the 15:1 and 30:1 treatments, respectively. Concentrations of atrazineand metolachlor associated with sediment outflows from the strips were larger than their respective inflow concentrations,while the results were opposite for chlorpyrifos. Concentrations in runoff water for both atrazine and metolachlor in outflowfrom the strips were smaller than the inflow concentrations; again, the results were opposite for chlorpyrifos. The 15:1treatment retained an average of 52.5% of the total input of atrazine, 54.4% of metolachlor, and 83.1% of chlorpyrifos.Corresponding numbers for the 30:1 treatment were 46.8% for atrazine, 48.1% for metolachlor, and 76.9% for chlorpyrifos.Analysis of variance using the randomized block design showed that differences of percent retention of pesticide betweentreatments were not significant for any of the three pesticides at the 10% significance level. A lack of significant differenceindicates either a need for more than three replications and/or larger area ratio treatments to be studied. The results of thisstudy indicate that a 30:1 area ratio buffer strip could perform equally as well as a 15:1 area ratio buffer strip. Thus, lessland would be required under buffer strips to get the desired results.