Keeping soil protected from the elements is one of the fundamentals for preventing soil erosion, but the impact that different cover crop types have below the ground has been investigated by Cranfield University.
Looking at different root traits including length, mass, surface area density and root hair length, it was found that a combination of oats, mustard and phacelia were most efficient at reducing soil loss by water erosion.
Presenting the findings, Dr Linda Deeks of Cranfield University said: “It was a mix of thin stems and thick stems and changes in flexibility of those stems that seem to give the best results.
“Previously we’ve been pushing large tap roots to bust through compaction. Actually, what we’ve found consistently is large tap roots can do that, but it is also the finer roots in some plants like oats that also prove important.”
However, some of the benefits of cover crops bring are unlikely to be seen immediately, she added.
Trials looking at the role of cover crops in lettuce and cereal rotations found that in the first year there was no difference in earthworm numbers when a cover crop was grown.
By year two, where cover crops had been grown in sequence there was a three-fold increase in earthworm populations.
Dr Deeks added: “There is a longevity effect here. Cover crops can work as bioengineers to improve soil structure, but they require time. It’s not a quick fix like the plough.”
Cover crops could also play a valuable role in boosting crop nutrition. Speaking at the Soils Hub, grower David White said buckwheat had helped him to reduce the need for artificial fertilisers on farm.
He said: “We put some starter fertiliser on oilseed rape but otherwise we don’t buy P and K. I’ve had my farm mapped twice now with nutrition maps and soil texture maps - when I studied what is in the soil, there’s a lot of nutrition that is locked up and isn’t available.
“On our high pH soils, phosphate is in the soil but is less readily available. By growing buckwheat for instance, which mines phosphate, it releases it and is returned for the cash crops to grow on.
“I’m having sporadic soils samples now and sending samples from individual soils off on an annual basis to make sure I’m not shooting myself in the foot and I’m not running our indices down. The results I’m getting back show that our indices our maintained without spending money on imported inputs.”