Webinar: Herbal leys for long-term soil health gains
The use of herbal leys is growing among farmers.
This has been partly driven by SFI payments, but also through a wider appreciation of the benefits they bring.
These include:
Nitrogen fixing to reduce fertiliser use
Accessing nutrients and minerals to benefit crop, animal and human health
Resilience to drought to provide reliable grazing
Reducing the worm burden in livestock
Increased soil biology, organic matter, carbon storage and productivity
In the latest in our Winter Webinar series, we were joined by Paul Totterdell, Director of Cotswold Seeds, and Ian Wilkinson, Cotswold Seeds owner, to discuss the benefits of herbal leys for soil health. Ian is also founder of FarmED, near Chipping Norton.
Beef, sheep and arable farmer Stuart Johnson, who is a member of our mentoring team, also described how he has put herbal leys to use on his farm.
You can watch the full webinar here:
"Diversity really is key when we look at herbal ley mixtures,” says Paul.
“If we're really going to tap into all the benefits that we have on offer from all the wonderful species available to us we need to make sure that we include as many as possible.”
Ian says Cotswold Seeds ensure their herbal ley mixes always contain three functional groups of plants: grasses, legumes and herbs.
"None of them are more important than the other,” he says.
“Some of the plants are hardier in upland areas. Some of them are better in the wet. Some of them are better in the dry, in the warm, in the cold. So that's why we need this diversity.”
The power of herbs and legumes
“Legumes are probably best known for their ability to fix nitrogen in the soil,” says Ian.
“They don't necessarily solve the nitrogen challenge completely, but they certainly help us to offset a lot of the cost of buying nitrogen fertiliser. There has been a lot more interest in these herbal leys recently on the conventional side because of this.
“Legumes are also very deep-rooting. They're great for pollinators but they're also very protein rich. So if you're looking at introducing livestock into your arable rotations this is really important, high quality forage.”
“The good thing about many of these plants is that they continue to grow and stay green when everything else is parched. ”
Herbs also have deep roots which help to break up and aerate the soil, as well as to mine minerals to make them available for cash crops.
“This also makes them very drought tolerant,” says Ian.
“The good thing about many of these plants is that they continue to grow and stay green when everything else is parched.
“Anything we can do to get moisture in the soil and hold it there will be great for farming. It's also great for the public good in terms of flood management.”
High nutrient value forage
“When we talk about animal health we're talking about getting the right vitamins and minerals into us, but it's also about the protection of the animals,” says Paul.
“Some of the plants that we use in these herbal lays help battle against the worm burden that we are often fighting in our animals.
“Up to £85 million a year is spent on artificial wormers. That's damaging to the pocket, but it's also very damaging to the soil, because when wormers get into the soil they can cause quite significant damage to a lot of the biology.
Grazing on herbal leys reduces the worm burden in cattle
“Plants like sainfoin and birdsfoot trefoil, for example, have something called condensed tannins. The tannins in these plants prevent the worm from reproducing.They also reduce bloat in cattle and they reduce greenhouse gas emissions.”
Using herbal leys as a natural way to control worms also reduces the risk of them developing resistance to treatments.
In addition, Paul says it keeps the number of worms in the animals within a manageable level without killing them off entirely.
“It's not this boom and bust situation that we can create by using artificial wormers,” he says.
“We all have worms in us. We would not be here if we did not have worms as part of our physiology. We need a little bit to keep us going.”
Advice on how to plant herbal leys
Paul says it is best to plant herbal leys at a shallow depth, in a well prepared seedbed and then roll them in firmly.
"Because they're small seeds, you have to be careful about putting them in too deeply or putting them into cold soil,” he says.
“They really ought to be in warm soil where they have a good chance of establishment.
“They also need to be as evenly spread as possible. They're small seeds, so in each seed there's a limited amount of energy for that plant to get up and going. They don't want too much competition.”
It is best to plant herbal leys in at a shallow depth, in a well prepared seed bed
Particular care needs to be taken when overseeding areas where other plants, such as grasses, are already established.
"When you have existing plants already there with a leaf on them, they are going to be serious competition for plants that you've overseeded,” says Paul.
“We're slotting these small, vulnerable seeds into a completely established ley.
“You need to consider things like really harrowing hard before overseeding. Also be careful not to include grasses with an overseed or, if you do, very little, because they're very easy to establish and they will smother other species.”
Terminating herbal leys
“We know that we've got wonderful soil structure under these herbal leys, but the big question is what are we going to do when we terminate them?” says Ian.
“Are we going to take all this lovely, structured, cake-like soil, plough it up and put another crop in and ruin it?”
One option is to spray off the plants with glyphosate.
However, Ian says farmers need to seriously consider the long-term effects of this on soil health and other biology.
“We need to think very carefully about what our options are beyond that, not least because regulations may well come and make this option less appealing for a number of reasons,” he says.
One technique Ian has been experimenting with is using a Vibroflex.
"We've had fairly good results this winter from a light rip three or four times and probably burning no more diesel than using a plough and power harrow," he says.
"I think it's left the soil structure in a lot better condition.
"It looks better. You can see mycorrhizal activity there in the soil. You can smell the soil, the structure is better. Everything about this technique seems better to me than the plough.”
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