The image above is a garden center of the UK.
Cover crops are plants that are grown in order to cover a bare patch of ground, anytime it’s not in use. Such as a backyard garden or an agricultural field. Cover crops help protect the land from the loss of water and soil. There are different types of cover crops, and each has advantages and disadvantages.
If you choose a leguminous cover crop, such as vetch, clover, peas, alfalfa, or beans, the cover crop will add nitrogen to the soil. Many people use nitrogen fertilizers, but keep in mind that those types of fertilizers are salts. If you use a legume cover crop, you’ll get organic matter plus nitrogen… and no salts added.
However, legumes do grow a bit slower than non-legume crops. This is actually because of their ability to produce nitrogen. Legume crops form a relationship with rhizobia bacteria in the soil, and it’s actually the rhizobia bacteria which “fix” nitrogen from the atmosphere (breaking apart the devilishly strong triple bond), making it available for the legume plant and other plants in the surrounding soil. In return, the plant provides some of its carbohydrates to the bacteria. So the legume plants often don’t grow as fast as other plants because they’re giving away some of their food to the bacteria.
However, nitrogen is needed by all plants and animals because it is “the building block of protein”. When nitrogen is present in sufficient amounts, plants grow better and often more quickly, their leaves are greener, the plant is healthier, and the crop produced is usually larger. Using legume crops as a cover crop, and turning it into the soil as green manure, would definitely be beneficial for your soil and your future garden.
There are other crops that are non-leguminous, such as rye, barley, oats, or buckwheat. You’ll notice that these are all grains. Grains are grasses and grow quickly. They provide a lot of organic matter and nutrients much more quickly than legumes. But they don’t fix nitrogen.
So it depends on what you’re going for… lots of organic matter, or some organic matter plus nitrogen? Either way, cover crops are a great way to protect your soil and improve it during the times of the year when you’re not growing anything else on it. And a green field of winter rye or clover looks a lot prettier than a bare patch of soil any time of the year.