The Importance of Cover Crops

Author: Sandy Vanno, Master Gardener Warren County CCE

Cover crops have been in use for longer than you might have imagined. Ancient Romans knew the value of cover crops. A former legionary turned farmer, Lucius Columella realized how important legumes such as lupine, black medic, and vetch were too productive estates. He wished landowners, no matter how large or small, paid close attention to their soil. Even the founder of our country, George Washington was an early advocate for cover crops and extended rotations. In 1786, he wrote a letter looking for not just barley seed, but clover as well, to be used as a cover crop.“...I wish to divide my seed-time and am desirous of sowing clover and other grasses with barley in preference to other grain, I would gladly take fifty bushels ...”(University of Michigan Extension)

Farmers around the world grow cover crops to protect the soil and increase crop yields; it adds fertility to the soil without chemical fertilizers. It can be left on the surface as mulch or tilled while it is still green into the soil, becoming green manure. Farmers have used this technique for centuries. Green manures are crops that are grown not to be eaten by you, but to be turned into the soil and consumed by earthworms, insects, and microbes.

Cover crops are an excellent tool for home vegetable gardeners as well, regardless of garden size, and provide many benefits:

• soil erosion – the roots stabilize the root zone or surface of the soil, reducing the risk of erosion from wind and rain; the leaves and stems of the cover crop also decrease soil erosion by reducing the impact of rain and potential runoff.

• soil compaction – the root systems can be used to combat both shallow and deep compaction.

• soil organic matter – cover crop residues increase soil organic matter, providing numerous benefits to the soil and successive crops; increasing organic matter improves soil structure, soil water holding capacity and infiltration, and soil aggregate stability; decaying plant material contributes nutrients back to the soil to be used by future crops.

• weed suppression – cover crops can provide an incremental benefit of weed control by out-competing weeds for light, water, and nutrients.

• disease and pest management – according to the Virginia Cooperative Extension, many articles have been published recently about cover crops being another tool for use in disease and pest management; particular members of the brassica family, certain mustards and rapeseed varieties help control soil-borne pathogens such as root-knot nematodes and verticillium wilt.

• low maintenance – cover crops require very little maintenance, and additional nutrients are seldom needed to support them since cover crops scavenge nutrients already present in the soil, and may even “fix” additional nitrogen from the atmosphere.

Besides cover crops, gardeners can also improve the soil by adding compost or manure (when available) or other organic materials such as leaves, straw, or grass clippings. Earthworms, bacteria, fungi, nematodes, and other forms of life utilize organic matter to build healthy soil.

Vegetable production involves many practices that compromise soil health, and therefore limit productivity. New York soils are less forgiving of such practices than many other regions. Therefore, leading vegetable growers want to overcome this barrier to success with practices that maintain soil health. The Cornell Cooperative Extension document “Cover Crops for Vegetable Growers” provides recommendations for the results of the Cornell Soil Health Test. The report from that test often prescribes using cover crops, and this site will help identify the cover crop to use and how to use it effectively.

“Our soils support 95% of all food production, and by 2060, our soils will be asked to give us as much food as we have consumed in the last 500 years. They filter our water. They are one of our most cost-effective reservoirs for sequestering carbon. They are our foundation for biodiversity. And they are vibrantly alive, teeming with 10,000 pounds of biological life in every acre. Yet in the last 150 years, we've lost half of the basic building block that makes soil productive. The societal and environmental costs of soil loss and degradation in the United States alone are now estimated to be as high as $85 billion every single year. Like any relationship, our living soil needs our tenderness. ...”

From Living Soil: A Documentary

References:

http://covercrop.org/ “CCE Cover Crop Guide for NY Growers”

University of Minnesota Extension; “Using Cover Crops: A History of Green Manure”

Virginia Cooperative Extension; “Cover Crops”

University of Maryland Extension; “Protect and Improve Your Soil with Cover Crops”

CALS Cornell “Green Manure/School of Integrative Plant Science”

Last updated November 9, 2021