Soil monitoring tool available to guide propyzamide planning

The tool can highlight trends and help propyzamide users assess whether soil temperatures are low enough
The tool can highlight trends and help propyzamide users assess whether soil temperatures are low enough

A soil monitoring tool, based on weekly site-specific soil temperature and moisture data, has been published by AHDB Cereals & Oilseeds to guide propyzamide planning.

Soil temperature and soil moisture levels are both important factors which influence the efficacy of this herbicide in winter oilseed rape (WOSR).

Based on data from AHDB’s weather station network, the tool can highlight trends and help propyzamide users assess whether soil temperatures are low enough and soil moisture levels adequate enough for optimum application.

Effective weed control

Propyzamide, for many growers, is a key active ingredient within black-grass spray programmes. No resistance to the herbicide has been recorded and high levels of black-grass control can be achieved within WOSR.

Extensive trials conducted over many autumns, however, show that applications must be made when soil moisture is sufficient and soil temperatures have dropped to, and are forecast to stay under, 10°C at depth to get the most out of the active ingredient.

Dr Paul Gosling, who manages weed research at AHDB, said: “When applied to warm soils, propyzamide breaks down relatively quickly and concentrations in the root zone can reduce to the point where it can no longer kill black-grass.

“We’ve developed this tool to help growers monitor soil conditions and calculate the optimum time to apply propyzamide-based herbicides. Some sites have started to dip under the 10°C threshold.”

Soil temperature and moisture

Soil temperature and soil moisture data from 30 weather stations, located at AHDB Recommended Lists trial sites across England, Scotland and Wales, can be accessed within the tool.

For each site, average weekly soil temperatures, taken at a depth of 15cm, are displayed.

Dr Gosling continued: “We use measurements at 15cm because it provides a stronger measure of temperature trends than those taken nearer the soil surface.”

Adequate soil moisture is also important to allow propyzamide to move in the top few centimetres of the soil.

Weekly soil moisture information, recorded at a depth of 10cm, is also shown for each site.

Dr Gosling concluded: “The trends displayed can help focus in-field monitoring efforts to decide whether fields are warming up or cooling down, and wetting up or drying out.”