Cover Crops for Your Garden
Cover Crops for Productive Home Gardens
Will you have empty space in your garden that will remain bare and unplanted over the winter? Consider planting a cover crop in those spaces to build your soil’s productivity and prevent soil erosion. Cover crops are any crop that we plant but do not intend to harvest; they are planted during seasons when a “cash” or harvested crop is not growing. Once it is time to plant a cash crop again, the cover crop can be mowed and left on the soil surface, tilled into the soil, or removed and composted. The compost can then be added back to the garden soil. Cover crops are beneficial to any garden because they:
-prevent soil erosion by covering and “holding” the soil when a cash crop is not present
– catch extra nutrients or fertilizer that were not utilized by garden crops. The nutrients are then returned to the soil through the cover crop residues.
-help build organic matter in the soil, which improves water holding capacity of soil and fertilizer efficiency. Over the long-term, this means less fertilizer is needed to generate a productive garden, and soils will become more resilient during dry periods.
-provide habitat for beneficial insects such as ground beetles, and pollinators if left to flower.
-add diversity to our garden, which can disrupt pest and disease cycles.
Cover crops can also generate nutrients. For instance, plants in the legume family such as clovers, peas, and beans will fix nitrogen in their roots, thereby adding it to the soil for use by cash crops and reducing the need for fertilizer. In some instances, cover crops can and suppress weeds.
Choosing a cover crop
Choose a cover crop that aligns with goals you may have for your garden. A legume crop will add nitrogen to the soil which can be utilized by a subsequent crop. A grass or Brassicaceae family cover crop (such as a mustard or rapeseed) will scavenge leftover nutrients in the garden soil at the end of the season; brassicas can also suppress some diseases and root knot nematodes. Daikon radishes (also called forage radish) can break up hard or compacted soil and promote nutrient mixing through the soil profile. Certain species like cereal rye generate a lot of biomass when allowed to grow up in the spring, adding a substantial amount of organic matter to the soil when added back through mowing, tilling, or composting. Some species such as oats and field peas will die (i.e. winter-kill) in our climate most years. These are good cover crops for beds that will be planted in the early spring. Cover crops can also be grown in the summer between crops; buckwheat, millet, cowpeas, and sunn hemp are popular warm-season cover crops.
Planting a mixture of cover crops provides multiple benefits. Grass and legume, and grass-legume-brassica mixtures are popular. One popular mixture for winter is cereal rye and hairy vetch (an annual legume) or crimson clover: these mixtures produce a large amount of growth and fix a lot of nitrogen in a relatively short period of time.
Cover crop management
Cover crops can be planted as soon as a cash crop is removed from its section of the garden, or by “intercropping” (also called “relay cropping”), when cover crops are planted between rows of cash crops before they are removed.
Seed at recommended rates with a broadcast seeder, a precision seeder, or by hand. While broadcasting seed on the soil surface can be effective, this leaves them vulnerable to predation by birds, small mammals, and insects, so planting into furrows that are then covered with a planter or by hand is recommended. The best time to sow cover crops in this climate for good winter coverage is in September; however, sowing as late as early November is possible for certain species (like cereal rye), but fall growth and nutrient scavenging effects will be reduced.
Planting a cover crop requires an investment of time, planning, and money, so it is best to manage it well to reap the maximum benefit from your investment. An optimal cover crop stand may need to be fertilized, and irrigated to ensure germination and good growth, just as you would a cash crop. Legumes should be sown with inoculant to ensure nitrogen fixation. Cover crops can help us build much more productive gardens, lead to better crop performance in times of stress, and reduce the need for fertilizer and pest management inputs. They are a small investment with great potential for payback.
For more information on cover crop species selection and management, see https://growingsmallfarms.ces.ncsu.edu/growingsmallfarms-covcropindex/or contact our office at 828-757-1290.