Growers are reminded there is still time to sterilise land this spring as part of their weed control strategies for the coming season – an option which some growers think they missed back in the autumn.
Nick Ottewell, general manager for Vitacress in Kent grows over 240 hectares of babyleaf salads equating to around 45 tonnes per week per season. "Due to our drilling pressures and cropping requirements we carry out both spring and autumn soil sterilising treatments using Basamid (dazomet)," he says.
"Wild rocket is our second most popular leaf but at the moment there are no usable pre emergence herbicides available for it, so unless we get good effective weed control and sterilise the ground before the crop goes in we can have real problems," explains Nick.
"It’s very effective. In the first year following treatment we don’t need any herbicides on the crops at all – especially vital for wild rocket.
"We’re applying Basamid at 500kg/ha to a depth of 45cm and its working well for us," says Nick. "And a big plus is that we don’t have to use polythene sheeting to seal the surface."
Although we’re using Basamid primarily for the weed control, there’s no doubt it benefits the control of soil diseases too – reducing carry over and build up of infection between crops, adds Nick.
Peter Shakespeare, Certis’ sales manager explains that the MITC (methylisothiocyanate) gas released on contact with a moist soil offers growers control for a wide spectrum of soil pests, nematodes, fungal diseases as well as weeds and weed seeds.
Nick emphasises the importance of getting the soil conditions right before treatment. "Adequate moisture is critical to get the best results with Basamid. The amount of soil moisture will obviously depend on your soil type, but for us we’re on silty, brick soils which means after 7-8 mm of rain we can get a good ’smear seal’ on the surface," he says. This ensures that the gas is retained in the treated profile to maximise efficacy.
Growers should be aiming to apply Basamid at the optimum moisture level - 60-70% of water holding capacity. This will help ensure that sufficient MITC gas is rapidly released from the Basamid granules.
"Soil temperature is also critical," explains Nick. "In spring you need a temperature of 9-10oC to get the concentration of gas within the soil right. The warmth and moisture in the soil will encourage weeds to germinate and fungi to break dormancy, increasing susceptibility to the sterilant, he adds.
Nick says he has the confidence that there is no risk of a residues whatsoever. "The soil sterilant works quickly and breaks down fast once treatment is complete."
Growers considering Basamid should experiment with soil depths and dose rates to find the right compromise and effectiveness for them, urges Nick.
