The United Nations (UN) Food and Agriculture Organisation (FAO) made 2015 International Year of Soils to highlight the importance of soil.

Well managed and biologically active soils are fundamental to sustainable and profitable farming. Soils with a good structure, organic matter content and diverse soil biology will help to ensure good yields, reduce the risk of runoff and erosion, will help protect the environment, provide resilience to climatic pressures such as floods and drought, and can help to reduce inputs by ensuring nutrients and water are utilised correctly. Soils also play a key role in the carbon cycle.

Biota describes all the animal and plant life in the soil. A diverse biota is required to maximise soil health and crop potential, reduce reliance on artificial inputs and achieve better disease resistance in crops.

Without organic matter soil would just be a mixture of sand, silt and clay with limited ability to hold nutrients. Soil organic matter is made up of plant and animal matter which release nutrients into the soil as they decompose. This improves the porosity, workability, fertility and biota of soils as well as helping to maintain good structure. Where there are good levels of organic matter, the risk of capping, slumping and erosion can be reduced.

The burrowing, feeding and casting of earthworms plays a major role in decomposing and cycling organic matter and releasing nutrients. They can also improve soil porosity and aeration, water infiltration and conductivity, reduce surface crusting and increase root growth.

Levels of soil organic matter can be maintained or improved by retaining crop residues, growing green manures or cover crops, applying organic materials such as livestock manures, bio-solids or composts, introducing grass leys into an arable rotation, or by extending the length of time grass is managed in an existing rotation.

In an arable rotation, reduced cultivation techniques can be a good practice to help maintain soil organic matter, especially in the soil surface tilth.

The most important tool to help understand the condition of the soil on a farm is a spade. Whilst soil type and its key characteristics do not change, the soil structure will vary across the farm from year to year depending on things such as crop rotation, machinery use, livestock density and the weather. The best way to understand the structure is to dig holes across the farm and take a look. This approach also gives a feel for the organic matter content and begins to identify any compaction.

Compaction describes when soil has been compressed by, for example, machinery or livestock into a solid impermeable layer, either at the surface or within the topsoil. Root development can be restricted, which affects yield and plant health, and reduces drought resilience and crop nutrient response. The risk of runoff and nutrient loss will increase by 50 per cent.

A compacted soil has a higher risk of erosion as it is less porous, meaning it is less able to absorb water and resist surface runoff. Erosion removes soil, nutrients and pesticides from the field and, potentially to rivers.

On an arable farm, the shape of wheel imprints in tramlines (tracks used to minimise wheel damage to crops during operations such as spraying) channel rain water. If tramlines become compacted , this can create pathways for water runoff. Research has shown that 80 per cent of runoff in arable fields on sloping land comes from those compacted tramlines.

Maintaining land drainage is another essential tool for maximising the workability of soils and will help improve both crop development and soil quality by helping to improve aerobic conditions particularly in wet conditions. Where land is drained, extra care must be taken when applying fertilisers, manures and pesticides so that the field drain network does not act as a conduit for pollutants to water caused by these inputs.

Finally, soil testing helps to determine how many additional nutrients are required, allowing a more targeted approach to nutrient use, saving time and money, and optimising plant growth. Ideally you should test the pH and nutrient levels across the farm every three to five years, or more often if there is a known problem, such as a low nutrient index. Nutrient availability and crop growth can be limited in soils that have become acidic.

We all depend on maintaining the fertility of our land and International Year of Soils should have helped address growing concern by the farming industry for soil health.