Warm weather is coming to an end, but that doesn’t have to be bad news for your garden soil. Over the winter months, soil can become waterlogged or compacted, especially during the wettest periods, so it’s important to keep it protected so that it’s ready for you once springtime arrives.
This means keeping the soil covered and maintaining a living root in the soil for as long as possible, which involves growing winter crops with appropriate mulches and using cover crops or green manures that will stay in place over the winter or alternatively, can be chopped and dropped in the spring.
Growing winter crops
For regions that experience winter temperatures that dip far below freezing, it may be impossible to maintain winter crops. But if you reside in a place that experiences a relatively temperate winter season, with the temperature rarely going below 14 degrees Fahrenheit (-10 degrees Celsius), then you may be able to grow some robust crops outside all season. You can also install an unheated polytunnel if you want to grow a variety of crops year-round.
If you do opt for a polytunnel, it’s especially important to protect the soil, because supporting good fertility with mulches is critical for areas that are used for growing year-round.
Top-dress the polytunnel beds with homemade compost or leaf mulch in the spring, and again in early autumn when summer crops are harvested and winter crops are sowed. Also, mulch fruit-bearing plants like tomatoes with comfrey and other dynamic accumulators when they’re flowering and fruiting. You can also add fall leaves as protective mulch.
One of the best ways to protect the soil is to practice crop rotation, especially if you have nitrogen-fixing legumes. They help to add nitrogen for the crops that will need it in the springtime.
You can also cover the soil under the polytunnel by growing other crops such as Asian greens, winter lettuces, mustards, and daikon radishes. Your soil will be protected because it hosts living roots and will provide you with some food during the winter months.
Winter cover crops or green manures
Field beans demonstrate better cold tolerance than fava beans, but like fava beans, they fix nitrogen. You can sow these on their own or between rows of edible crops like kale or winter cabbages in mid to late autumn.
Field beans can be grown as a winter cover crop alongside winter rye, which improves ground cover and suppresses weeds. Rye is also particularly useful because it takes up nitrogen, but can release up to 90 percent of what it’s lifted for the use of the next crop.
Vetches, also called winter tares (Vicia sativa), are another legume that you can use in a winter cover crop or as green manure, but it isn’t the best choice for dry or highly acidic soils. Plus, slugs, snails, and birds are partial to it, and once it’s chopped and dropped, you should avoid sowing in the location for about a month, because it releases a chemical that can inhibit the growth of smaller seeds like carrots, parsnips, and spinach.
Clovers are a good option to use as cover crops in the winter and can be grown as perennial ground covers in a forest garden. They can also be a useful addition to cover crops or green manures for annual growing systems.
Mustard adds organic matter that improves soil texture and moisture retention. Even if the foliage is damaged by frost, it can still be left as a soil-covering mulch, so you don’t need to worry about chopping and dropping it in the spring. If you plan to grow potatoes, planting mustard can reduce wireworm damage and suppress nematodes and pathogenic fungi.