IVatershed Scale Impacts of Buffers and Upland Conservation Practices on Agrochemical Delivery to Streams

watershed scale irnpact. Our objective was to estimate the watershed scale impact of grass buEers by comparing sediment and agichemical losses from two adjacent 14 1 165 hectare watersheds, one with conservation buffers and one without. Rainfall derived m o f f events frorn 2002-2003 were monitored for water runoff, TSS, phosphorous and atrazine loss. A conservation-watershed included 0.8 Ism of grass buffers and 0.8 kix of riparian forest buffer, ridge-tilled corn, corn-beans-alfalfa rotation, terraces and grassed waterways. A controlwatershed had no buffers, disk-tilled, continuous corn and grassed waterways. The same application rate and method for atrazine to corn was used in each watershed. Total rainfall during the April-June monitoring period was similar in 2002 and 2003; however, the conservation-watershed produced only 27 m of runoff, compared to 47 m Erom the control. Over two years, TSS and phosphorous losses per hectare were reduced by 97% and 95%, respectively, in the conservation-watershed. Atrazine loss per hectare was 57% less in the conservation watershed. A separation technique showed that for 2002 other conservation practices reduced TSS by 84% and buffers reduced TSS by an additional 13% compared to the control. Similarly, other conservation practices reduced atrazine losses by 29% and buffers accounted for an additional 3 1%. On a watershed scale buffers can add benefit to a conservation system.