Dow AgroSciences is committed to a stewardship programme to protect the long-term future of propyzamide, one of the best options for tackling blackgrass in arable rotations. Farmers are advised to establish grass buffers between crops and water courses, to establish crops using non-inversion techniques and to pay attention to soil and weather conditions at the time of application.

"The wet autumn and winter of 2012/13 meant a wide range of crop protection products were detected in surface waters," said Andy Bailey, a senior biologist at Dow. "In recent years, we have learnt much about minimising the risk of our herbicide reaching water. We will be working with farmers and their advisers to ensure the risks to surface water is minimised. Without growers cooperation there is every likelihood that the products Kerb Flo 500 and newly launched AstroKerb will face restrictions on use."

Dow AgroSciences has funded independent research at the Game and Wildlife Conservation Trust’s Loddington estate and at the University of Newcastle’s Cockle Park Farm.

At Loddington on sloping land (5-12% gradient), two establishment techniques – ploughing and non-inversion to 15-20cm were compared. Both run-off and drain flow were monitored.

"The use of a 6m buffer strip, significantly reduced run-off," said Mr Bailey. "The width of the strip needs to be varied according to the slope. The steeper the slope, the wider the buffer strip."

At Cockle Park, three different establishment techniques were trialled on a slope of 2%: Plough + power harrow to 20cm; a single pass, tined cultivation at 22cm depth; and light disc/press to 10cm.

"Most drain flow and surface run-off came from the ploughed land," said Mr Bailey. "Least flow of propyzamide to drains occurred from min-tillage, but there was little difference in either non-inversion technique when it came to surface run-off."

Further work will be commissioned, but it is clear that establishment technique affects potential for oilseed rape herbicide to reach surface water and non-inversion techniques significantly reduce risk.

However, good stewardship also requires attention to soil and weather conditions at the time of application. Kerb Flo 500 and AstroKerb should not be applied when soils are frozen or waterlogged (ie when drains are running); nor when heavy rain is likely within 48 hours of application.