It plays a major role in controlling environmental interactions, regulating water flow and quality and storing carbon to maintain the balance of gases in the air.
It provides varied habitats and sustains biodiversity but soil also preserves cultural and archaeological heritage, gives us raw materials and provides a platform for the built environment.
Soil quality is defined as its ability to carry out these functions, but it is under threat around the world. Soil degradation is a problem in agriculture which not only undermines food production but also has major effects on accelerating climate change.
David Michie, deputy director of Soil Association Scotland, says: “Soil is globally important and in the UK there has been degradation and lost soils.
“Some parts of Scotland with really good quality soils that can produce fruit, vegetables and arable crops have been damaged, and we have such a small strip of good soil that we really need to look after it.”
In the uplands Michie points to the problem of peatland drainage. He says: “It was a deliberate policy decades ago to drain the peat to produce grasslands and for tree planting, but we now know that peat is a really important way of storing carbon, mitigating greenhouse gas emissions, for biodiversity and clean water.
“We need to protect our soils as a resource and asset not just for farmers, but for the whole of Scotland. Soils are an important part of our natural capital and many businesses are looking at investing in natural capital in the future.”
Innovative techniques are used in soil care but in the end it comes down to field trials. And the Soil Association works with groups of farmers to test theories.
For instance they are currently testing mob grazing, which involves allowing fields of grass to grow long and then putting in a high number of livestock for just a few days.
The idea is that long grass has long roots, which benefits the soil, and will produce seed heads which benefit wildlife. If farmers find that it is better for the livestock as well, then it has advantages all round.
Michie says: “Mostly you need to support and enable farmers to find out what works in each situation, and as we become more informed you have to change behaviour and decisions.”
Improvements have to come about at every level, from the food on our plates, to farming practices and political policy.
Dr Roy Neilson of the James Hutton Institute agrees that soil health has much wider implications than its uses in agriculture. “On a global scale, soils deliver benefits such as water filtration, aeration, carbon sequestration and wider environmental benefits such as supporting pollinators and a whole host of cultural and societal benefits.
“It isn’t just about higher yields and crop rotation.”
Worming a way deep down to find a healthy biological solution
The key to improving soil health is understanding its make-up, and one Scottish project has come up with an innovative way to get a very accurate picture of what is going on beneath the surface.
The project, called Soilbio, claims to have used an integrated measure of soil biology, physics, and chemistry for the very first time.
Dr Roy Neilson, of the James Hutton Institute, says: “We were funded to develop – with industrial partners – a suite of tools which brings in the biological aspect using the whole soil nematode community.”
Nematodes are microscopic worm-type creatures that contribute, along with fungi, bacteria and protozoa, to the creation of soil.
Neilson says: “The reason we use nematodes is that we can classify them, by DNA sequencing, into different species, those that feed on bacteria, fungi or plants, those that scavenge or predate for example, so by knowing the relevant proportions of these groups we can get a proxy measure of the environment in the soil.”
The information can be collated and analysed to provide incredibly accurate information on the condition of the soil concerned.
Neilson says: “It is a leap forward. If you take a physical and chemical measure it is a short snapshot in time, whereas if you add in biological information it is more a measure of what has been going on in the soil over time, and potentially what is likely to happen.”
The Soilbio project was funded by the arms-length Westminster government body Innovate UK and was launched at the Royal Highland Show in June, with early adopters already taking it up.
Robert Ramsay, whose company Soil Essentials was partnered with the James Hutton Institute in developing Soilbio, says: “Up until now there was little way to measure the health of the soil and carbon storage, and so you couldn’t incentivise farmers to work towards that.
“This is a repeatable, reportable measure which isn’t down to opinion.”
He continues to say that understanding soil at this level has many applications: “It might be resilience against drought, another farmer might think high yields are more important, for some it might be storing carbon; if it is with Sepa it might be getting rid of nutrients before they get into the water course.
“There is a huge interest in regenerative farming but there are soil treatments already being used which may have no value at all.”
Neilson says: “Farmers are the environmental stewards of our land, and Soilbio is giving them another tool in their toolbox to protect their soils, produce healthy and productive crops but also to maintain the environment around them.”
Farmers can improve or restore their soils by:
Monitoring for management: You can’t figure out how to improve your soil if you don’t know how it is now. Start by digging a hole and pulling out a spadeful of soil. If it’s hard, like concrete, it’s compacted and you need to get air into it. Check the smell and colour. Send a sample to a lab to check acidity or alkalinity, phosphate and potassium levels and organic matter. Count your worms.
Increasing organic matter: Rotating between crops, and between crops and livestock, increases soil organic matter and prevents depletion. Add bulky organic matter like farmyard manure or compost, but how and what depends on the type of soil. Green manures can help in the shorter term.
Ploughing less often: Minimising soil disturbance has been shown to improve structure, and reducing machinery use can help prevent compaction. But compensating with herbicides will have a detrimental effect. The Soil Association report “To plough or not to plough” should help.
Intercropping, or companion cropping: Planting two different crops together can help prevent weeds, combat disease and pests, and improve soil health. Planting a cereal alongside a legume can help fix nitrogen in the soil and reduce the need for fertilisers.
Planting trees: Trees act as windbreaks and slow the run-off of water from farms, helping prevent soil erosion. The deep roots can help prevent nitrate leaching out of soils.
Restoring peatland: There are grants available for peatland restoration. Peatland covers just 20 per cent of Scotland but stores 25 times more carbon than the rest of the UK’s vegetation put together.
This article first appeared in The Scotsman’s autumn Vision magazine. A digital version can be found here.