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Correct residual herbicide application critical
Date added: 24/11/08 |
With herbicides in rape accounting for over half of total crop protection inputs, it is important that they are used at the right time and under the right conditions regarding both weed control and minimising risk of water pollution, says ProCam’s Technical Director Dr. David Ellerton.
“At last the soil temperature and moisture conditions are suitable for the application of residual herbicides such as propyzamide and carbetamide in winter oilseed rape and winter beans, Dr Ellerton says.
“The application window for optimum consistency is normally November and December. In oilseed rape, growers can apply these herbicides with their Phoma fungicide to save on costs. In beans, propyzamide is applied pre-emergence of the crop.”
The correct use of herbicides is a crucial part of maintaining oilseed rape profitability, he says.
“Data from our 4cast database indicates that the average cost of production per tonne (including seed, fertiliser and sprays) for winter oilseed rape is £84/tonne and for the top 25% of farmers is £61/tonne.
“Of these costs of production, approximately half can be attributed to crop protection products and over half of these spray costs were made up by herbicides. By optimising herbicide application through using the correct product, dose and timing, the top 25% growers spent £16.21 per tonne on herbicides compared to £21.92 for the average and £30.15 for the bottom 25%.”
It is vital that herbicides are used to best effect and that means using a high enough dose rate and applying them under optimal conditions, he adds.
“Residual herbicides work best when the soil is cold, less than 8ºC. At this temperature the weeds have slowed down and are unlikely to outgrow the treatment. Cold soils also reduce microbial breakdown of the products, thereby increasing their persistency so that weed flushes are controlled.”
“Soil moisture also helps to redistribute the herbicide into the rooting zone of weeds and can aid uptake by susceptible weeds. The weather is crucial for best results. If conditions are not appropriate, then don’t apply it and wait until they are,” Dr Ellerton says.
Activity on grass-weeds can be helped by adding in a contact-acting graminicide, but application timing will be the same as for the single product applied alone. Broad-leaved weed spectrum can be broadened by mixing with either prosulfocarb (Defy) or pendimethalin (Stomp).
“Because the residual herbicides, propyzamide and carbetamide, are not used in cereals, they are able to act in a cleaning capacity when it comes to grass-weeds in rape and beans. They are vital actives to retain in the battle against black-grass and other grass-weeds and all care must be taken to retain them in the herbicide armoury.”
For this reason David Ellerton warns growers to focus on avoiding any risk of water pollution.
“Make sure that you leave a big enough buffer zone. Avoid any risk of run-off. If it is too wet, then just don’t spray.”
If growers fail to avoid water pollution, they run the risk of losing these valuable herbicides and this will mean that oilseed rape and beans will not be viable in areas of high weed pressure, with a knock-on effect for grass-weed control in cereals, concludes Dr. Ellerton.
Ends.
PRM204
24th November 2008
For further information please contact Dr. David Ellerton, ProCam Ltd., Royston, Herts. Telephone: 01763 261592
Issued by Philip Hainey, Proterra Ltd., Stamford, Lincs. Telephone: 01780 756299
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