Cover crops give back to your soil

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By Susan Brown, County Extension

People garden for many reasons.
When we garden, we are almost always focused on what is going on above the ground and think little about what is going on in the soil.
Many groups of organisms live in the soil. Earthworms and other soil-dwelling organisms contribute to soil fertility. Most of these creatures live in the root zone of plants. They range in size from microscopic (bacteria, nematodes, and fungi) to groups that are visible to the naked eye (earthworms and insect larvae). Scientists are still learning about these organisms and have even identified new organisms they did not know existed. When we add pesticides to our landscape, are we actually changing the soil chemistry? No one is sure.
One way to give back to your soil is to consider planting cover crops. A cover crop is a crop planted in a garden to protect the soil from erosion and to improve the soil structure.
Regular use of cover crops over a period of years slowly raises the organic matter content of the soil, increasing the activity of soil organisms such as earthworms and fungi. As these organisms break down organic materials, they help improve the soil structure, making the soil a more favorable place for root development.
Other benefits include using fertilizers less, improving the nutrient cycle, improving crop yields, protecting water quality, reducing the use of pesticides and weed suppression. Cover crops can provide habitats for beneficial organisms that are the natural enemies of crop insect pests. By lengthening a rotation through cover crops, crop pests (disease, nematode, insects and weeds) may become less problematic over time.
There are two types of cover crops: legumes and non-legumes. Legumes are associated with “nitrogen -fixing” bacteria. These rhizobia bacteria reside in the plants roots and capture or “fix” nitrogen from the air and make this nitrogen available to the legume. Non-legume cover crops provide less nitrogen but more organic matter. The type of cover crop and length of time it is growing determines how much organic matter and nutrients will be returned to the soil.
Cover crops should be selected to fill a need of your production system and fit well in your crop rotation. You must first decide what you want the cover crops function to be. Do you want the crop to provide nitrogen, suppress weeds, expand rotation or add organic matter?
Planning is important. Some gardener’s leave their vegetable gardens fallow for the winter. Why not plant a cover crop to add to the soil when the garden is not in use. Then the cover crop will need to be cut back so that the nutrients the plant creates can filter back into the soil. Then you are ready to plant your next crop whatever it may be. Mixed cover crop stands can be beneficial, especially grass/legume mixes.
Winter cover crops for North Carolina that are legumes would be hairy vetch, Austrian winter pea, crimson clover and red clover. Cover crops that are non-legumes would be ryegrass, rye, wheat, barley and oats. For more information on cover crops, visit http://www.ces.ncsu.edu/chatham/ag/SustAg/covcropindex.html.