Metazachlor and Quinmerac Water Stewardship

Updated May 2020

Protection of Water: Best Practice Advice

Why Metazachlor matters

Oilseed rape is an important break crop in the arable rotation. It is especially important on heavy land where spring crop establishment can be difficult.

Metazachlor and quinmerac are a foundation for winter oilseed rape weed control programmes and so are key active ingredients for the crop, but in common with some other major herbicides, they have been detected in watercourses at levels that risk non-compliance with the Water Framework Directive (WFD), the legislation drawn up to protect all surface and ground waters.

The water companies report that if they cannot show progress in reducing pesticide concentrations in raw water abstracted for drinking water supply, there will be further restrictions on chemistry. To date, DEFRA has looked at voluntary measures to deliver WFD compliance with regulation being the approach of last resort, understanding growers’ needs and the agronomic challenges they face.

Joint initiative from BASF and Adama

BASF and Adama joined forces on a European basis in 2016 to develop stewardship guidelines specifically for metazachlor and quinmerac. Following the guidance will mitigate the threat to water and build on the general best practice advice within the Voluntary Initiative (VI) . Both companies are also active in the 'OSR Herbicides? Think Water' stewardship campaign, now including MTZ matters.

Oilseed rape is an important break crop in the arable rotation. It is especially important on heavy land where spring crop establishment can be difficult.

Propyzamide, carbetamide and clopyralid; other OSR herbicides found in surface waters

With all key OSR herbicides having been found in surface water and under threat, stewardship applies to all. Through the use of best management practice (BMP) and by maintaining the number of herbicide options, OSR weed control will be managed into the future.

How can Metazachlor and Quinmerac reach water?

The major route by which metazachlor and quinmerac are entering water is via field sources such as surface run-off or via field drainage. Spillages are also an issue, which need to be avoided. Field sources represent a far greater challenge, with minimisation reliant upon sound agronomics.


In line with all metazachlor and quinmerac label approvals from 2015, individual and total applications should be limited to a maximum of 750g metazachlor and 250g quinmerac per hectare.


wHen2gO BASF have developed the wHen2gO smart tool for water stewardship. Following the guidance of wHen2gO will help to reduce the risk to water. Alternatively the following closed period for applications apply:

  • Drained fields, including temporary – aim for 1st October, cut off 15th October
  • Applications after 1st October can be made as long as soil and seedbed conditions are good and drains are not flowing
  • Drained fields in Surface Water Drinking Water Safeguard Zones cut off 1st October (visit the Environment Agency's 'Check Zones' for zone details).

Is your land at risk?

The majority of heavy, drained soils are likely to be at risk of metazachlor and quinmerac reaching surface water. To date, many central areas of England have been officially identified by the Environment Agency as Surface Water Drinking Water Safeguard Zones for metazachlor and/or quinmerac.

To find out if your land, or if the land you advise upon, falls is in an ‘at risk’ catchment, enter your postcode at the Environment Agency’s ‘Check Zones’ website. The interactive map will reveal if the area is within a Safeguard Zone and if metazachlor and/or quinmerac are mentioned, then the most stringent stewardship application timing advice is relevant to you.

Technical Services Hotline

Voluntary Initiative

Click here to go to the Voluntary Initiative website


wHen2go Smart Tool

wHen2g0 is a smart tool which helps to improve application timings of metazachlor and quinmerac, to minimise the risk to water.

Discover more

Metazachlor and Quinmerac

How to view Surface Water Drinking Water Safeguard Zones (SWDWSgZ) using
on the Environment Agency’s “Check Zones” website