Guest blog by Jane Rowling, Farm and Rural Liaison Officer, Calder and Colne Rivers Trust
Soil is something many of us take for granted. Unless we are dealing with plants, it is probably something we don’t think about very often. But soils do so much more than provide a place for plants to grow. At Calder Rivers Trust, we believe that healthy soils underpin a resilient and prosperous catchment. Soils are hugely important for supporting biodiverse environments, capturing carbon from the atmosphere and locking it away in the ground, improving our water quality, and for supporting flood resilience from the top of our catchment to the bottom.
A healthy soil is a dynamic living system with physical, chemical and biological qualities which are good for environmental quality and the health of the plants and animals within it.
Soils are made up of particles of different sizes. Some particles, like sand, are big enough to see with the naked eye if we look closely. Others, like clay, are so small that we cannot see the individual particles without a microscope. The proportion of different kinds of particles in a soil gives us the soil type. It also changes the amount of air and water that can be held within a soil. A soil with lots of small, clay particles will have very little space for air and water to pass through and so will drain slowly, whereas a very sandy soil, with relatively big particles, will also have big spaces between particles, as they cannot fit so closely together, so air and water is able to pass through very easily.
What makes up the soil, and how the particles of soil fit together is, therefore, really important in determining where the water is going to go, and how quickly. A healthy soil should have lots of vertical pores and fissures beneath the surface. This will allow water lots of space to filter into the soil. It also allows air and water to easily reach the roots of plants.
If the soil is unhealthy, we might see fissures going horizontally beneath the surface, we might find compaction at or below the surface, where all the soil particles are packed really close together, with very few pores at all, and we’re likely to find a lot of mud and puddles on the surface, showing us where the water is unable to pass down into the soil. Water which is prevented from soaking into the soil is much more likely to travel over the surface of the land. This water can travel quickly. We might see it running down tracks and roads. This means that it reaches watercourses very quickly and can contribute to rivers and streams overtopping their banks during a flood. If we can slow this flow down by getting water into healthy soil, we allow the rivers to rise and begin to fall again before this excess water reaches them. This reduces the risk of overtopping banks and creating floods.
When a soil is nice and uncompacted, air and water can get to the roots of plants to help them grow. This makes it better for growing crops and grass to feed animals. This is probably the first benefit we think of, when we think about why healthy soil is important, but there are lots more. In a healthy soil, the roots of all kinds of plant species, from clover to trees, can also get deep into the ground, and this helps to anchor the soil in place, making it less vulnerable to being washed away. When soil particles get into watercourses they cause lots of problems. Watercourses which become ‘silted up’ can hold less water, increasing flood risk. Silt can also overwhelm habitats, destroying spawning grounds for fish and reducing the invertebrate population. Soil particles also carry nutrients from the land into the water. Phosphates are a particular issue as they bond to the soil. When they reach the water, they can cause excess plant growth, blocking up channels, or even cause algae to bloom. Algae uses up a lot of oxygen from the water and blocks out light, making it impossible for other species to thrive there. It can also be very dangerous to people and animals who go into the water. If we can prevent silt from being washed into watercourses, by creating and maintaining healthy and well-structured soils, we also support healthy, species-rich watercourses which reduce flood risk.
The more roots we can get into the ground, permanently, the more carbon we can take out of the atmosphere. Well managed woodlands and ancient grasslands are really important for this, because they can support a huge variety of species. A variety of plant species creates habitat for wildlife of all kinds. It also has the effect of making the ground more rough. Imagine the difference between pouring water onto a smooth, hard slope, or onto a sponge with lots of crevices, gaps and air spaces inside it. The more vegetation of different sizes we have, the more sponge like the surface becomes, and the more water can soak in. This has the added benefit of filtering the water through layers of soil, gravel, even rocks. This means that anything which has been put onto the land, such as artificial fertilisers, animal manure, or herbicides and pesticides, is filtered out, rather than being carried straight off the surface of the land and into the river where it can damage in-river ecosystems.
What causes soils to become unhealthy?
Compaction is the main issue when it comes to the soil’s role in supporting natural flood management measures. Compaction means that the soil particles are pushed close together, losing its pores and fissures and becoming very hard and solid. This happens when wet soil is subjected to pressure, from tractors and other vehicles driving over it, from animals walking around on it, or even from people’s footfall. 80% of damage to soils is done during the first pass over the soil. Grey colours, rusty orange mottling, and horizontal fissures, as in the picture below, are all signs of damaged, compacted soil which cannot drain or filter water effectively.
How can we improve soil health?
There are lots of ways that we can help to maintain healthy soils in our catchment. If you have your own land, have a look at your soil. Look for an open, porous structure, with plenty of roots reaching deep into the earth. If your land borders a watercourse then make sure your banks are secure and undamaged, with a good grass cover. If you have livestock, consider fencing off the watercourse so that animals can’t break the banks down and create muddy, wet areas. High traffic areas like gateways can often get wet and muddy over winter, and this is very damaging to soil health. You might consider protecting these areas using hardcore or matting. This will also have a positive effect on animals’ foot health.
If you don’t have your own land, there are still lots of things which can help to reduce compaction. The most simple thing is to follow the Countryside Code.
We’ve all seen areas of footpaths where people avoid a little mud, and the path gets wider and wider as people walk around the edges, spreading the muddy patch into a larger area. By sticking to the footpaths and wearing suitable footwear in wet weather when out in the countryside, we can keep foot traffic on the footpaths, avoiding spreading soil damage and compaction out into the fields. Other good practices include taking your litter home with you, and using gates and stiles properly. This avoids potential harm to wildlife and livestock, reduces the chance of man made materials getting into watercourses and causing blockages in drains and culverts, and prevents damage to fences which could lead to livestock getting out.
If you have a garden, lots can be done to make your patch more water friendly. The most important thing is to have areas where rainwater can soak into the ground. Lots of ideas on how to do this can be found at: https://slowtheflow.net .Try to leave areas of lawn or flowerbeds rather than having everything paved or covered with artificial grass, if possible. Another great garden solution is having a water butt, which can collect rainwater and hold it temporarily.
Lots of small actions to slow the flow of water and preserve healthy soil in our catchment add up to a catchment which is more resilient to flood risk overall.
If you would like to know more about your soils, or opportunities to improve soil and water management on your land, contact Jane Rowling at firstname.lastname@example.org