Why grow cover crops?

Defining your main reason (objective) for growing cover crops is essential. This will dictate the best choice of species, timing of establishment, destruction and other management practices.

Your choice also needs to suit your farm in terms of climate, rotation, soil type and condition, and equipment.

Cover cropping is often a long-term commitment, and it may take several cycles to see the full benefits.

Reduce nutrient loss and leaching

Cover crops can reduce the risk of soil nutrient leaching (especially nitrogen). Deep-rooted cover crops are particularly useful catch crops because they can take up nutrients that have gone beyond the reach of shallow-rooted cash crops.

Reduce soil erosion and run-off

As cover crops bind soil and provide ground cover, they can help protect soil from erosion by wind and water.

Improve soil structure

Cover crops with vigorous root systems help loosen soils, improving access to water and nutrients. Roots create biopores and can break up compacted soil layers, enhancing subsequent crop root growth.

Improve soil fertility

When cover crops are incorporated and decompose in the soil, valuable nutrients are released. Cover crops can also add nutrients to the soil through biological nitrogen fixation.

Build soil organic matter and influence soil moisture

Organic matter is essential for the health of agricultural soils. When incorporated, cover crops help to increase the soil organic matter, improving the soil’s biological activity, moisture infiltration and retention, and nutrient-holding capacity.

Integrated weed, pest and disease management

Cover crops can suppress weeds and volunteers. They also provide habitats for beneficial insects.

Some species have soil-fumigating properties that reduce pressure from soil pests and nematodes.

Selecting non-host cover crop species can reduce soil-borne pathogen carryover.

Generate additional forage

Where a gap in forage supply has been identified, the strategic use of cover crops for livestock feed can be planned.

Lower greenhouse gas emissions

The longer ground is covered, the greater the potential to reduce net greenhouse gas emissions. While outcomes depend on cover crop species, management and soil type, the broader benefits are consistently positive.

Biodiversity benefits

Cover crops provide a diverse range of benefits to biodiversity.

Long-running experiments (up to ten years) demonstrate that using cover crops for multiple seasons delivers the strongest beneficial impact on soil functioning and microorganisms.

Above ground

• Autumn/winter flowering resources for insects that feed on nectar or pollen
• Provide habitat, shelter and protection for insects and animals (particularly during the winter months)
• Add to the diversity of vegetation, which can increase the abundance of natural enemies of pests

Take care to avoid ‘green bridges’ for pests and diseases of the following crop, especially when the cover crop and crop are closely related. For example, many plant species act as a host for aphids. Early termination may be beneficial to manage aphids.

Below ground

• Provide a food source for many soil organisms that carry out essential below-ground functions, such as the decomposition of soil organic matter (SOM) and transformation of nutrients into plant available forms
• Provide living plant roots and sugary exudates that serve as habitat and food for beneficial organisms, such as mycorrhizal fungi
• Support wider soil microbial communities and increase overall microbial biomass
• Increase macro fauna, particularly earthworms, which contribute to overall soil health (the effects depend on other factors, such as the tillage approach). More than 8 earthworms per soil pit represent an ‘active’ population for arable soils

Support measures (stewardship)

Cover crops can be used in agri-environmental schemes, provided they comply with the rules. The financial benefits of cover crops need to be considered across the rotation.