The Benefits of Using a Cover Crop on The Veggie Bed Over Winter

Growing a cover crop, after finishing harvesting the vegetable garden in autumn, is an affordable and effective way to protect and enrich the soil. You can plant a green crop anytime, but, in summer the garden is often too full.

During the winter a living mulch will protect the soil from the compaction effects of winter rain, improves soil structure, increases organic matter, conserves moisture, suppresses weeds and is far better than leaving the soil in the bed bare or allowing weeds to grow and deplete nutrients and add to the seed bank.

In the spring the cover crop can be dug into the soil providing nutrients and organic matter, enriching the soil for the next season.

The Importance of Organic Matter:

Organic matter becomes humus. It feeds the earthworms as well as a wide range of soil micro-organisms, which in turn feed the plants.

Humus holds plant nutrients in the soil in a stable, slow release form, unlike water soluble chemical fertilisers which can acidify the soil.

Humus buffers pH changes.

Increased organic matter improves aeration and water holding capacity.

Organic matter improves soil structure - good soil structure is crumbly and is much easier to work with.

Why Sow A Cover Crop:

• To Improve Soil Structure: cover crops break up compacted soil, allowing for better root penetration.

• To Enhance The Organic Matter Level: as well as improving soil structure, and increasing microbial activity.

• To Improve Aeration: cover crop roots improve aeration by creating channels in the soil, aiding microbial activity and soil fertility.

• To Improve Soil Fertility: cover crop plants enrich the soil with nitrogen and other nutrients through fixation and accumulation preventing them leaching away. Deep-rooted plants bring minerals from the subsoil to the topsoil.

• To Improve Water Conservation: the cover crop reduces water runoff and evaporation, improves filtration and conserves the soil moisture-holding capacity.

• For Weed Suppression: a cover crop shades out and smothers weeds and other unwanted plants.

• To Improve Biodiversity: by providing habitats for beneficial insects, and soil-dwelling organisms.

• To Prevent Erosion: cover crops protect soil from wind and water erosion, their roots hold soil in place, preserving topsoil and reducing runoff.

• Financial Benefits: cover crops can increase yields and reduce the need for purchasing fertilisers and herbicides.

Common Plants Used as  Cover Crops:

The best cover crops for the home garden are:

• Legumes such as clover, peas, broad beans, lupins or vetch. These are nitrogen fixing. They have a symbiotic relationship with a Rhizobium bacteria which live on the roots and convert nitrogen in the air into a form that can be used by the plant. When the plant is dug into the soil it allows the nitrogen to be available for subsequent crops. Nitrogen is an important element for plant growth and development.

• Annual grasses like oats, barley, wheat and rye have large root systems reducing soil damage and water run off, hence improving soil structure. They capture any nitrogen remaining in the soil which is then returned when they are dug back into the soil in early spring. Grasses also produce a lot of biomass improving the organic matter levels in the soil

• Broadleaf plants like brassicas, daikon radish, mustard and buckwheat which grow rapidly and have roots that break up clay and compacted soil and allow water to penetrate deeper into the soil.

An ideal cover crop mix should include more than one type of plant that complement each other to provide a variety of benefits.

Method:

• Remove any spent plants from your garden at the end of the growing season, preferably 3 to 4 weeks before the risk of hard frost. Loosen the soil with a garden fork and rake it smooth.

• Sow the cover crop by scattering, the seeds throughout the garden bed. Rake the seeds gently into the soil and tamp them down. Water regularly until they are established.

• Well-spaced plants will grow faster and larger than overcrowded ones. But, the soil needs to be densely covered to crowd out the weeds. So it is a bit of a balancing act.

• Monitor the cover crops for growth and flowering. If it has been planted early in autumn it may be necessary to cut the crop back to prevent the plants from going to seed.

• Three to four weeks before planting vegetables in spring (around Late August, early September), cut the cover crop down at root level and dig the plant material into the soil with the roots. It is best to dig in plump, juicy stem, as once the plants flower they lose condition. If there is too much green stuff add some to the compost bin as well.

• Follow a rotation and don’t plant  brassicas into an area that had a cover crop like mustard.

A cover crop can be used for any sized garden bed, raised bed or even a container. If you can get the timing right, a new vegetable bed, built in autumn, can be planted with a cover crop through winter before being planted with veggies in the spring.