Excessively wet soils this year are more likely to be dried by the presence of covers than kept wetter. However, sun and wind must be allowed to reach the soil surface for adequate drying predrilling.
“Whilst many cover crops may have already been desiccated either by glyphosate or grazing, in some situations of late establishment limited growth has been allowed to continue and spray off opportunities have been limited, “ says Dick Neale of Hutchinsons.
“SFI rules for overwinter covers also means that termination is not realistically possible until mid-January and spraying opportunities and field access has been very limited this year.”
His advice is that some thinner covers may in fact be better left until nearer drilling for desiccation, although this depends very much on species within covers, soil type and following crop and its likely drilling date.
“It’s worth remembering blackgrass re growth on bare soil can also be considered under the same rule set as covers with regards to desiccation.”
Desiccation options
Grazing with sheep is increasingly being used, and there are several considerations to take into account.
“It is important the grazier understands that many covers are being grown for soil conditioning and not exclusively sheep grazing. Therefore, the stock will graze the top growth very rapidly and will need moving on before soil surface damage occurs.
“For this reason, roughly twice the cover grazing area is required compared to a traditional stubble turnip crop where the sheep are left on to clear all the tubers (the tubers are what puts condition on the sheep whereas the top growth provides a maintenance feed).”
“Again, this must be clearly understood and accounted for as more work is expected of the grazier (moving fences, water and stock) for less weight gain in the sheep. Grazing fees must reflect this, it is a compromise between soil conditioning, cover crop processing and feed value to the grazier. Only sheep from 6 months old should graze multispecies covers, do not graze ewes with lambs at foot, as milk taint can occur.”
Spraying
It is important adequate rates must be used (1000g minimum) with an adjuvant like Spryte Aqua CF, he says.
“Low temperatures and shading will impact performance and legume species like crimson clover, berseem clover and vetch will often survive treatment. This is rarely a problem if herbicide in the following crop is effective or the following crop is tall like beans or maize or more smothering like peas.
“Kyleo is usually used in mixture with additional glyphosate around 3 l/ha and should be used where surviving brassica or phacelia will impact the following crop. This approach requires expensive post emergence herbicide treatment, if any exists.
Mr Neale notes Kyleo is also helpful where a larger cover bulk needs reducing more quickly to improve the drills’ ability to cope with aftermath adding the importance of treatment to sowing safe periods.
“Shark (carfentrazone-ethyl) can also be a very useful addition to glyphosate for a range of species that are more tolerant of glyphosate and is vital where nettles form part of the cover on lighter soils but also useful on brassica species – remember it has a 1-month gap to planting a crop.”
Cultivation
Cultivation to kill and better facilitate drilling always remains an option in controlling cover crops, says Mr Neale.
“However If a drill will not cope with the situation, then it is better to cultivate as required, rather than risk failure of a crop – you only get one chance at establishing a spring crop!
“Only do what’s required. Remember the benefit of the cover is largely underground so for example if ploughing, plough as shallowly as possible or work the top just enough to facilitate accurate sowing.
Remember, the covers are rooted, and drills will often cope well as the residue does not ‘drag’. It is often worth an early run up and down with an empty drill to see if it copes, before cultivations are used, he says.
