One of the most important tasks for organic polytunnel gardeners is protecting the soil in a polytunnel. We can protect the soil in a polytunnel through a wide range of gardening practices. One of these practices is the use of cover crops. It is important not to leave soil bare for extended periods. Leaving soil bare will not only encourage the colonisation of weed species, it can also degrade the soil.
We can use a range of cover crops as part of our crop rotation in order to improve soil quality in a polytunnel. Below are some of the cover crops that polytunnel gardeners may like to consider utilising as part of best practice in a polytunnel growing system:
Legumes and some other plants will facilitate the transference of atmospheric nitrogen to the soil, where it can later be taken up by your plants. Planting a cover crop that fixes nitrogen can be particularly beneficial where you will later by growing leafy, nitrogen-hungry crops. Nitrogen fixing cover crops include red or white clover, peas or beans.
Some cover crops act as green manures, which can be chopped and dropped and used to add organic material to improve the soil nutrient content and structure. Swift growing grasses such as rye can be ideal for use as a green manure cover crop. Brassicas such as mustard can also be chopped and dropped for this purpose.
Brassicas can also help as a cover crop by acting as biofumigants. They are believed to reduce the incidence of root pathogens in the soil, which could help the crops coming after. Buckwheat also suppresses root pathogens and can help to reduce the incidence of pests and disease in the soil of your polytunnel. Buckwheat is a good choice in poor soils, with low-fertility, and can grow quickly and outcompete weeds.
Cover crops can protect and even enhance the soil ecosystem in your polytunnel. There are a wide range of different cover crop options, which will be suited to different times of year and to different soil types and conditions. When thinking about incorporating cover crops into your polytunnel growing system, it is important to consider which problem or problems you would like to remediate before deciding which option or options to choose.