Getting the best out of Kerb

Soil and weather conditions can affect the performance of residual herbicides. To maximise the efficacy of Kerb* Flo:

• soil temperature (at 30cm depth) should be 10°C and falling
• soil moisture deficit should be 50mm and decreasing

Optimal conditions for applications of Kerb* Flo are now. Soil temperatures have declined over the last two weeks in many areas. Widespread rainfall has reduced soil moisture deficits considerably with field capacity reached in some parts of the UK which may delay application.

The opportunity to treat with Kerb Flo should be taken. Where crop canopies are very well developed, better results will be achieved from applications of Kerb Flo made once frost has opened the canopy, allowing treatments to reach the soil surface.

Take all possible precautions to prevent contamination of surface waters with any applications of Kerb Flo.

Weather Data for week ending 17th November 2009

If you would like advice for counties of England or Wales not shown here, please contact UKHotline@dow.com or your local Dow AgroSciences representative.

Analysis of data for 2002-2009
In preparation for the Kerb/oilseed rape season, an analysis of weather records was undertaken comparing values for soil temperature and soil moisture deficit for the beginning of September 2009, over different years, to see if they could tell us anything. The data analysed is from 2002 to 2009 inclusive. The results are presented in the graphs below.

Main conclusions for 2009

For most areas, soil temperatures are slightly lower this year than last (which is good), but not outside values for recent years. The exception is the South Eastern region, where soil temperature is around half a degree warmer. This is driven mainly by the values for Kent and East Sussex, which are around one degree warmer.

Values for soil moisture deficit are appreciably higher (worse) this year, by as much as 60 mm in some regions.

What does this mean for applications of Kerb this autumn?

For optimal performance from propyzamide, applications should be made when soil temperatures have got down to 10°C, and will continue to fall, and soil moisture deficit is no more than 50 mm (and falling). These values are normally reached around the first week of November, with little variation year-on-year.

This year soil temperatures are, generally, favourable for this time of year. Even if we have an "Indian summer" they are unlikely to start climbing at this time of year. The limiting factor, potentially, is soil moisture deficit - many seedbeds are still very dry. However, we still have adequate time for these to be "corrected" before applications of propyzamide begin.

As in previous years, up-to-date, in-season values for soil temperature and soil moisture deficits will be supplied by Dow AgroSciences as the season progresses. This data should allow advisors and growers to identify when conditions are suitable for Kerb applications to begin.