A title like this may have many people thinking about their power bills, but I want to get your minds thinking about something even darker and dirty – your soil! Many summer crops have been or are being harvested leaving fields or gardens bare for the next several months. Your land is a very important asset and using cover crops is a sustainable agricultural practice that provides many benefits such as providing organic matter, nutrients, erosion control, weed suppression, and improves water infiltration. With recent rains, there should be enough soil moisture to allow for timely plantings of several cover crop choices.
Legumes, such as peas and clover, are plants that capture nitrogen from the air and convert it to plant-available nitrogen, providing a natural source of fertilizer. They are able to do this thanks to a beneficial relationship they have developed with a type of soil-dwelling bacteria called rhizobia. The main benefit of growing a type of legume as a cover crop is they increase nitrogen levels in the soil. Types of legumes commonly grown as winter cover crops include crimson clover, Austrian winter pea, and hairy vetch.
For best results, sow legume cover crops between mid September and mid October. If you are planting these crops in areas where beans or peas have not grown recently, you may get better results if you use a seed inoculant which contains the beneficial bacteria that helps legumes fix nitrogen. Some legumes, like clover, can be purchased with the inoculant already coated on the seed. Legume inoculants can be purchased from some garden centers or online, but make sure you purchase the correct inoculant for the legume species you want to grow. Only purchase what you need, because these living bacteria do have an expiration date.
Grains and grasses that are grown as cover crops include annual ryegrass, cereal rye, wheat, oats, and triticale. They can be planted a little later than legumes - October through mid November. Grains and grasses are the best cover crop choice for weed suppression, scavenging nutrients, and erosion control, especially when left on the soil surface rather than tilled into the soil. These cover crops are often seeded mixed with legumes as noted above.
Most brassica crops, like mustard or rapeseed, produce chemical toxins that can be used to help reduce soil pest such as nematodes, fungi, and weeds. They are particularly effective at reducing root knot nematodes, a destructive pest of many crops. There is no way to kill root knot nematodes, but growers can suppress them by planting resistant varieties and through practices such as incorporating nematode suppressive cover crops.
For gardens, plan to till these cover crops into the soil in early spring or to maximize nitrogen fixation, just as soon as legumes begin to flower. You can either till the crop directly into the soil or mow it first and then till it in. For no-till farming practices, the cover can be rolled with a crimper or desiccated with herbicides at least 2-3 weeks before planting directly into the residue.
For more information, please contact Mac Malloy, Extension Field Crops Agent with North Carolina Cooperative Extension, Robeson County Center, at 671-3276, by E-mail at mac_malloy@ncsu.edu, or visit our website at //robeson.ces.ncsu.edu/.
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