Principles to improve soil health: Biological

Find out how organic matter, reduced tillage, and increased rotational diversity can improve soil biological health.

Key principles for improving soil health:

• Feed the soil regularly, through plants and organic inputs
• Move soil only when necessary
• Grow a diverse range of crops in your rotation, including mixtures

Soil organic matter is a key biological component and provides a direct source of energy/food for many soil organisms. It is the fuel in the soil food web.

Decomposition of organic matter increases nutrient cycling and improves the structure of soils.

Crops provide a valuable source of organic matter, and regular additions of organic matter (with diversity in organic material types), combined with reduced tillage, can help restore soil health.

Targeted use of organic matter inputs can also offset some of the negative effects associated with intensive tillage.

The system of tillage influences the periods where roots are active, and soil is covered by plants or residues. The system also changes the distribution of organic matter in the soil.

Soil organisms

Reduced tillage intensity is associated with increased fungal biomass. This includes arbuscular mycorrhizal fungi that colonise roots and increase crop access to phosphorus and water.

As reduced tillage stabilises habitats, it benefits many soil organisms.

Reducing the occurrence or frequency of disruptive tillage is also associated with increases in soil biological activity. Earthworm populations are a good indicator of these changes.

Rotations that lack diversity, especially monocultures, simplify the soil food web.

Such rotations can also build up pest, disease and weed problems. Maintaining a healthy, diverse and active soil population is key to preventing dominance by undesirable pathogens.

Increases in plant diversity, whether in space or time, often lead to greater species richness of soil biota. This happens through more diverse litter, exudates, rooting patterns and plant associations.

In arable and horticultural systems, diversification and/or the integration of green manures, cover crops and leys into crop rotations also has positive benefits for soil biota.

Increased resistance and resilience of soil functions, such as nutrient and water supply, appear to be associated with diverse rotations with no-till periods (e.g. ley-arable rotations) in particular.

Management of the farmed landscape, rather than fields, is also important. For example, field margins and hedges provide an important reservoir of a wide range of soil organisms.

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