The Use of Grassed Buffer Strips to Remove Pesticides, Nitrate and Soluble Phosphorus Compounds from Runoff Water

Experiments on grassed buffer strips have been conducted since 1993 by ITCF (Institut Technique des Céréales et des Fourrages) at three research farms (La Jaillière, Bignan and Plélo). Literature data and conclusions drawn from previous work with isoproturon and diflufenican were confirmed in a range of soil and cropping conditions: grassed buffer strips are effective in restricting pollutant transfer in runoff; those with widths of 6, 12 and 18 m reduced runoff volume by 43 to 99·9%, suspended solids by 87 to 100%, lindane losses by 72 to 100% and loss of atrazine and its metabolites by 44 to 100%. More than 99% of isoproturon and 97% of diflufenican residues in runoff were removed by buffer strips. Nitrate and soluble phosphorus in runoff were reduced by 47 to 100% and by 22 to 89%, respectively. At La Jaillière, a rainfall simulator was used in 1995 to verify that buffer strips are still effective in conditions of intense runoff. Investigation of the influence of sowing direction during the 1994–95 cropping period at Bignan showed that sowing perpendicular to the slope seemed to be beneficial in reducing pesticide content in runoff.