Some Knowledge

A cover crop is a planting that puts a crop on soil that would otherwise be bare.  This can be a crop such as rye planted in the off season, or can be a crop that fixes nitrogen, like a legume.  There are several benefits to growing a cover crop.

One benefit of cover crops is that they prevent erosion.  The roots of the crop hold the soil, and the upper portions of the plant prevent rain from running in streams over the surface.  Erosion removes a significant proportion of farm soil each year.  A cover crop would be valuable if it were just for this purpose.

Legumes and clovers have the ability to fix nitrogen from the air and incorporate it into their tissues in the form of proteins.  When these plants are plowed into the soil, this nitrogen will be released as the plant tissues decompose.  Various kinds of legumes fix different amounts of nitrogen.  The ratio of carbon in the plant to nitrogen will determine the availability of fixed nitrogen as the plant decomposes.  This is because decomposition will take a certain amount of nitrogen to break down the cellulose and other carbon compounds in the crop.

Deep-rooted plants like alfalfa also transport a proportion of nutrients from the subsoil to the surface, where it can be used by subsequent crops.  The roots also break up compacted soils and hardpan and can improve the drainage of the soil.  Alfalfa is also a valuable forage crop rich in protein for animals.  All cover crops sequester a certain amount of plant nutrients in their tissues and are sometimes called “catch crops” because they keep the fertility of the soil from leaching away with the rain.

Another benefit of cover crops is that they incorporate a good deal of organic matter to the soil when they are plowed under.  As the tissues of the crop break down in the soil they turn into humus and other organic compounds that help the soil hold water, improve it’s texture or tilth, and provide a slowly-releasing source of nutrients for cash crops.  Organic matter in the soil also provides food for microbes, fungi, and worms which are beneficial to the growth of plants.

Cover crops used to be one of the common methods by which farmers improved the health of the soil.  These plantings can choke out and shade weeds, and in general make a better medium for the growth of plants.  As fertilizer and chemicals become more expensive, and as organic farming becomes more prevalent, cover crops will play an important part in the management of soil condition for the modern farmer.