Recent news headlines warn the state of our soil is now a serious threat to the environment. But they also say good-quality soil can help save the planet.
“No country can withstand the loss of its soil and fertility,” said Michael Gove in 2017, raising fears there are just decades of UK farming left. What are the powers and dangers of this dark material, and how worried should we be?
Soil is everywhere, in our parks, gardens, farmland, beneath our feet and under our pavements. But this extraordinary and valuable substance is often overlooked and dismissed as ‘dirt’.
We fundamentally rely on soil. It produces 95 percent of our food, be it the crops we eat, or grasses and other plants to feed animals for meat. And this is just one aspect of the goodness of the ground.
“Soil is one of the most underrated and little understood wonders on our fragile planet,” said Professor Bridget Emmett of the UK Centre for Ecology and Hydrology.
It is vitally important we take stock of this and, where we can, preserve this vital commodity.
To grow, plants need not only minerals from soil, but also carbon dioxide from air in order to make food by photosynthesis – and some of this carbon goes into the ground. Soil stores an extraordinary amount of carbon – three times the amount in the atmosphere and twice the amount in trees and forests. While soil can store or ‘sequester’ carbon, it can also lose it when degraded. The loss of the carbon in poor soils contributes to the rise of carbon dioxide in the atmosphere, one of the gases that causes climate change.
In just one gram of soil, it’s estimated there could be 50 thousand species of micro-organisms, and in a single teaspoon there are more individual micro-organisms than the world’s entire human population.
Crucially, this rich ‘soil-web’ of underground life creates an open structure. This allows rainwater to seep into the ground, storing moisture for plants to make crops grow well, even in times of drought. It also prevents flooding, an important function as global warming makes extreme and uncertain rainfall more prevalent in the UK and around the world.
We must be more careful in the treatment of our soils. It usually takes around 1000 years to produce an inch depth of topsoil by natural weathering processes. We can move literally tonnes in a matter of minutes using modern earth moving machinery, we just need to be more aware of the consequences of eradicating our precious soil resource.
Soils can vary in many ways, both physically and chemically on a local or regional scale. Many factors, including original parent material source, climate, weathering processes, topography or history of the land use influence their properties. This soil variability gives rise to all the different soil types universally classified by soil texture composition. Soil composition (soil texture) is determined predominantly by mineral particles and organic matter content and can be classified by the percentage of sand, silt and clay mineral particle content.
The strength and permeability of any soil is determined by its structure, soil type, drainage capacity and how well it is managed. Soils will perform differently governed by the amount of water, root mass and air there is in the soil matrix.
Determining soil texture can help you learn about possible restrictions and advantages of the soil. Soil texture is related to weathering and the parent material. The three basic texture classes are sand, silt, and clay, though many soils are a combination of these textures.
The terms sand, silt, and clay refer to relative sizes of the soil particles - sand, being the larger soil particle, feels gritty; silt, being moderate in size, has a smooth or soapy texture; clay, being the smaller size feels sticky.
Topsoils are complex arrangements of mineral particles, air, water, organic matter, living organisms and nutrients. The proportion of these elements is not always critical, however it is important that a soil contains all these elements in one form or another.
We need to find better ways of safeguarding our precious soil resources. We must not lose sight of its true immense value to the planet and begin finding better ways of protecting and manage this valuable resource for future generations.
Information displayed on the WWF website states, half of the topsoil on the planet has been lost in the last 150 years.
The effects of soil erosion go beyond the loss of fertile land. It has led to increased pollution and sedimentation in streams and rivers, clogging these waterways and causing declines in fish and other species. And degraded lands are also often less able to hold onto water, which can worsen flooding. Sustainable land use can help to reduce the impacts of agriculture and livestock, preventing soil degradation and erosion and the loss of valuable land to desertification.
We can undertake several steps to help preserve soil erosion these include maintaining permanent vegetation, reduce farming and gardening activities and planting cover crops. As the name suggests, cover crops provide a protective cover for soils in between the main plantings. Their function is the same as the function of permanent vegetation. They protect soils from rain and wind, slow down runoff and encourage water infiltration.
Mulching bare soils, increasing organic matter, controlling water runoff, sustainable grazing and afforestation, the planting of trees - all these activities over time will certainly reduce the loss and erosion of our precious soil.
With thanks to turf expert Laurence Gale for this blog.