Roundup Best Practice: Application Technique

Equipment should be properly maintained and calibrated according to good agricultural practice. All equipment capable of producing the volume and spray quality outlined below should be suitable for the application of Roundup.

Dose rate

The correct dose rate should be used for the degree of infestation. Where other factors such as growing conditions, weed growth stage etc are less than optimum, reduced rates are more likely to lead to disappointing results.

Water volume

High water volumes >250L/ha, give drops with low concentration of glyphosate, leading to poorer results. We do not recommend more than 200l/ha except in thick oilseed rape crops where 250 litres will help coverage and penetration. In most other areas, 80–100 litres of water gives equally good if not superior results, as both glyphosate and surfactant concentrations are higher improving uptake. Where low volumes are used the margin for error is less and the equipment must be properly calibrated and maintained.

Spray quality – conventional

To protect high diversity found in field margins, conservation headlands and beetle banks it is essential to minimise glyphosate drift from target areas. There are now many types of low drift equipment introduced under the LERAPS scheme, which greatly reduce drift. Roundup products are designed to optimise plant deposition at the same time minimise drift.

Label recommendations are for conventional 80° or 110° flat fan nozzles, but the use of air inclusion nozzles, pre-orifice low drift nozzles and Airtec equipment is possible where target weeds are suitable.

• The aim is to produce droplets in the Medium-Coarse category as defined by the British Crop Protection Council, (BCPC), (droplet diameter 200-400 microns). Avoid droplets < 100 microns. Drops larger than 400 microns are more likely to roll off the leaf

• With a large drop, the longer liquid phase helps direct uptake through stomata. This is an important method of entry for a water-soluble chemical like glyphosate. Fine droplets on a hot day means concentrated drops, leading to more scorch and less uptake

• A pressure range 1.5–2.5 bar should be suitable. Avoid high pressures; > 2.5 bars. Check with nozzle manufacturers’ literature and operate nozzles at their designated pressure, never try to increase output by increasing pressures higher than the nozzle rating

• Tractor forward speed should be related to nozzle output characteristics. The typical range is 4–10 kph. Slower speeds should be selected for pre-harvest applications and where ground conditions would cause excessive boom bounce and yawing at higher speeds

Caution: Where targets are small, e.g. spike –1 leaf grasses in stale seedbeds, the optimum droplet size for deposition is nearer 200 microns. Where target plants are large then the 400 microns, coarse drop gives the opportunity for a wider weather window determined by wind speed. Where black-grass at the spike stage is the target, the large droplets (300-500 microns) produced by low drift nozzles will not give satisfactory control and conventional flat fan nozzles should be used.