Cover crops are so important for improving soil and protecting the environment that it’s public policy in Maryland to use federal funding to subsidize farmers to plant them. Nearly ½ a million acres across the state are enrolled in Maryland’s Cover Crop Program. Cover crops protect Maryland’s farm fields from soil loss over the winter and scavenge the soil for the fertilizer nutrients that weren’t used by corn and soybean crops and might have moved into groundwater and surface water.
Cover crops are typically planted from late August through October and include grasses like winter rye, winter wheat, barley, and oats and legumes like crimson clover and hairy vetch. Plants in the legume family, together with special soil bacteria, transform nitrogen from air into a plant-available form. Tillage radish (a type of daikon radish) and other plants are also grown as cover crops.
Cover crops improve soil health and help make soils more resilient to the climate crisis. They
- increase soil organic matter and carbon sequestration by feeding soil microbes with sugars and other root exudates
- improve soil structure and the strength of soil aggregates which lowers erosion risks
- increase water holding capacity which allows crops to withstand drought better
Cover crops use the sun’s energy (when food crops aren’t growing) to produce biomass- roots, shoots, and leaves. The cover crops are killed in the spring. Nutrients in the decomposing plants are eventually available for uptake by the roots of the vegetables and flowers we plant. This reduces the need for synthetic fertilizers, whose production requires fossil fuels.
What’s good for ag soils is also good for garden soils! 2022 is the Year of Soil Health for Grow It Eat It, the food gardening program of the UME Master Gardener program. This infographic by Jean Burchfield introduces the idea of planting cover crops, a key practice in building healthy soils:
If cover crops are so great for farms why don’t more gardeners plant them?
- You have to buy and plant seeds
- They take up space that could be used for fall vegetables
- You have to cut and smother them in spring to kill them
- Slows down the growing season. Once killed in spring (late April in Central MD), they need to decompose for 2 weeks prior to planting
After many years of growing cover crops in my garden, I am convinced of their value and more than willing to put in the time and effort. If you are cover crop curious, try them out in a small area sometime between now and mid-October in a bed where you plan to grow a warm-season crop in 2023, like tomato, squash, or eggplant.
- Clear the area of plant residues and mulch. Loosen the soil if needed and then smooth it with a metal rake
- Decide what to grow. It’s best to plant a mixture of at least one grass (grain) and one legume. If you plant a two-species mixture, use about 60% of the recommended amount of each
- Purchase seeds. Look for local cover crop seed at farm supply stores to save on shipping costs. I recently paid almost $20 to ship 14 lbs. of seed (I do it for the soil!)
Example: seeds to cover 100 sq. ft. of soil:
- Winter rye (also known as annual rye or cereal rye)- 4 oz. (1/4 lb.) = 1 cup (8 fluid oz.). A 10 lb. bag cost me $23.50 (about $0.60 for ¼ lb.)
- Crimson clover- 2 oz. (1/8 lb.) = 3.5 fluid ounces. A 2 lb. bag cost me $13.50 (about $0.85 for 1/8 lb.)
- Plant. If you are going with a mixture it’s best to broadcast the grain first, followed by the legume. Ideally, the seeds are covered with ½-in. to 1-in. of soil. Broadcast the seed as evenly as possible by hand or with a seeder. Gently raking the soil after planting and walking on the seeds will ensure good seed to soil contact.
- Water the area if rain is not expected. Watch it germinate and grow!
- Cut and terminate the crop in late April. Plant through residues (hope to cover all of this is in a spring blog post)
By Jon Traunfeld, Extension Specialist, University of Maryland Extension, Home & Garden Information Center.
Read more posts by Jon.