An introduction to cover crops

Find out about the different types of cover crops, their potential benefits, and how to grow and evaluate them.

What are cover crops, catch crops and green manures?

Cover crops, catch crops and green manures are non-cash crops that provide potential benefits to a rotation.

Typically, cover crops are grown over a single winter to cover bare soil and stubble. However, the duration of the cover can vary from a few weeks to several months or years, depending on the approach and the specific objective.

Although the terms cover crop, catch crop and green manure are used interchangeably, they can distinguish between different functions:

• Cover crops ‘cover’ the soil between the harvest and establishment of main (cash) crops
• Catch crops ‘catch’ available soil nitrogen and prevent nutrient losses (via run-off and leaching)
• Green manures improve nutrition for following crops through the capture and release of nutrients, and the addition of fresh biomass (organic matter)

Crops can deliver multiple functions.

For example, a relatively fast-growing winter green manure in an over-winter fallow field (before spring crops) can provide all three functions. However, a summer green manure grown in short (two- to six-month) blocks between crops provides a quick boost of nitrogen only.

Leys, made up of mixtures (including grass, clovers or herbs), can provide cover for relatively long periods (typically 12 to 18 months). These are often used in organic systems before nutrient-intensive crops, such as brassicas.

Why grow cover crops?

Incorporating cover crops into a rotation has many environmental and soil benefits. Carefully selected crops can help manage soil erosion, soil fertility, soil health, water, weeds, pests, diseases and biodiversity. The right choice depends on your objectives.

Types of cover crops

There are many types of cover crops. Each cover crop or species mix has different properties, so it is essential to select a suitable option. Your choice needs to fit in with farm practice, capabilities, expertise and equipment. It also needs to work with the system, including the rotation and soils. Critically, it must address your objectives.

How to establish and destroy cover crops

Good crop establishment and growth are essential to maximising benefits. As well as direct management of the cover crop, destruction and following-crop establishment should be considered.

How to evaluate cover crops – a five-step process

With diverse options of cover crops and systems, finding an approach that fits your farming situation is important. When considering a cover crop, follow these five steps.

Cover crop champions

The network provides evidence-based case studies in commercial settings to aid with the selection of cover crops and their husbandry.

Further information

Check out the Cover Crops Guide species selection tool to assess the suitability of brassica, legume, cereal and other cover crop varieties.

Each species is profiled for its winter hardiness, rooting depth, grazing potential, and nitrogen-fixing and nutrient-storing qualities.

The tool also includes information on sowing period and depth, and seed size and seed rate.