With the inclusion of cover crops in the CAP 'greening' measures there is a renewed interest in this idea. Cover crops can help improve soil structure and quality, provide a source of nitrogen, and potentially suppress weeds and pests.
The direct agronomic benefits are reason enough for farmers to at least consider whether to grow a cover crop. By using cover crops growers can reduce the use of some herbicides, therefore minimising the risk of increased resistance. Some cover crops are said to have an allelopathic effect. This is where the cover crop exudes chemicals into the soil that inhibit germination and growth of the weeds, this is currently under research.The more obvious benefit of cover crops for weed control is that many are fast-growing and can help with controlling weeds by simply out-competing them for light, nutrients and water.
A deep rooted cover crop will improve the vertical soil structure allowing the following cash crop a chance to produce an adequate root system to access moisture in dry conditions. The reliance on inorganic fertilisers and the associated costs can be lowered, whist increasing the organic matter content of the soil. This will then lead to an increase in the numbers of beneficial invertebrates thus helping to alleviate the burden of pests.
As soil biodiversity increases with improved levels of soil organic matter and lower inputs of pesticides, so will diversity further up the food chain. Many species of farmland bird are dependent on invertebrates for raising their young. During the winter months cover crops can provide much needed shelter for farm wildlife from harsh conditions. Retention of nutrients prevents leaching into the freshwater habitats that support a plethora of species.