With regular rain showers causing drilling delays for many growers in northern England and Scotland, sowing cover crops has not necessarily been a top priority. But with the weather more settled, Will Shepherd, of Shepherd Seeds, says there is still time to establish a competitive cover crop.
To do so, he says it is important to select a mixture containing species which are capable of establishing well in soils which may only be 14-15degC.
He says: “A cereal-based cover crop is always going to provide the best option when being sown late as they tend to grow away quickly.
“Blackoats and winter vetch would be a good option for this time of year– winter vetch will establish much better in cooler conditions than spring vetch would and will continue to fix nitrogen at temperatures as low as 7degC.
“Forage rye and vetch is another good one – forage rye will grow very quickly giving fast ground cover – although diversity is key to cover cropping at this time of year, mixtures do not need to be anything fancy, they just needs to cover the otherwise exposed soil,” he says.
Where soils are warmer, 18-19degC, according to Mr Shepherd, growers looking to remove compaction could consider including tillage radish in the cover crop mix.
“With a tap root which can exceed 30cm, tillage radish is an option for those wanting to remove compaction – but growers need to be confident it is going to establish, so it should only be sown in more forgiving conditions.”
While there is still scope to establish a beneficial cover crop, Mr Shepherd suggests a cut-off date for sowing of mid-October, although this may vary depending on location and soil conditions. “When you get beyond mid-October the soil temperatures really start to drop and so does establishment,” he says.
Where crops are sown around this timing, he advises increasing the seed rate by about 15 to 20 per cent to ensure sufficient plant populations are achieved.
In order to get the best out of late-drilled cover crops, he recommends treating the cover crop with the same attention to detail as a cashcrop – drilling seed rather than broadcasting it, rolling the field to gain good seed-to-soil contact and applying slug pellets where necessary.
“At this time of year, the only way to establish a cover crop is to drill it as you would a cereal – soil surfaces in parts of England are very dry and so the seed really does need to be put into moisture.”
A small nitrogen application, either placed with the seed or applied soon after germination, can help increase the amount of green cover produced going into winter, according to Mr Shepherd. “This obviously adds extra cost but the potential benefits, including reduced soil erosion, improved drainage and the removal of compaction, hugely outweigh the costs.”
While some growers are looking to destroy summer-sown cover crops as early as February, given the growth of late-drilled cover crops will likely be limited compared to those sown in summer or early autumn, Mr Shepherd suggests allowing them to grow for as long as possible the following spring to maximise crop growth.
“Essentially, a lot of the benefit gained from a cover crop is a result of it growing actively in the ground. Realistically, if you spray off an October-drilled cover crop in February, it would not have had much of an opportunity to put roots down and to trap nitrogen.
“Therefore, cover crops which have been drilled late should be allowed as long as possible in the ground before being sprayed off with glyphosate or rolled.
Source: Will Shepherd, Shepherd Seeds