Cover Crop Innovation Center
New! We now have a new website for our project on winter-killed cover crops for no-till vegetable production: www.notillveggies.org. Please visit for blogs, photos and research updates.
Innovating with Cover Crops to Make Farming Better
Making the Land Pay 12 Months a Year.
Most farmers pay rent or taxes on the land 12 months a year. Yet many keep the land working for them only half the year. In terms of soil processes driven by growing roots and solar energy capture driven by plant leaves, a typical annual crop like corn is really using the soil and sun effectively - covering the land with green -- for only 3-4 months: June – July – August and part of September. Having only senescing crops, residues, weeds or nothing all on the land is a major waste of the farmer’s basic sun-soil-water resources. Cover crops can keep the soil humming for the other 7 to 8 months - accumulating organic matter, building soil structure, fueling the food web, capturing water and cycling nutrients.
Managing Plants to Improve Soils
Farmers are used to managing their soils to improve plant growth and crop yield. That’s why they fertilize, till and apply limestone to soils. Cover crops turn this idea on its head, giving farmer opportunities to manage plant to improve the soil. Because cover crops are not removed in harvest, their above and below ground biomass adds a bounty of organic matter to feed the soil food web. But this only the beginning. Some cover crop roots can ameliorate subsoil compaction. Some cover crop canopies can suppress weed seed germination. If given a chance, some cover crops produce deep root systems that can bring up nutrients from 2 or more meters deep. With the right choice of cover crop, these nutrients can be released to feed the next cash crop.
Freeing Farmers to Create Diversity
Ecological diversity aboveground is intimately connected to diversity belowground. Farmers are usually constrained to grow only crops they can profitably sell. The market place may dictate only corn and soybeans. Cover crops can free farmers from the tyranny of the market—freeing them to plant a wide variety of species without regard to what they can sell. With the adoption of cover cropping a corn, a corn-soybean-wheat farm can go from three plant species to a dozen or more, leading to much more diverse and vigorous belowground workforce, improving soil structure, water holding capacity, nutrient cycling and disease suppression.
Treating Cover Crops like Cash Crops
A sure way to fail with cover crops is to treat them as an after-thought. Careful selection, precision planting, timely establishment, possible starter fertilizer or irrigation will all help assure cover crops that pay.
Protecting water and soil from degradation
In Maryland much of the attention on cover crops for the past decade has centered on State government programs that subsidize cover crop planting for the purpose of reducing pollution of the Chesapeake Bay. Indeed, nitrogen capture to reduce leaching and soil cover to reduce erosion are two of the main environmental benefits that cover crops can provide. If the nitrogen captured is recycled in a way that the farmer’s crops can use and the soil saved is left on the farmer’s field, both the farmer and the environment stand to gain. The idea has been picked up by the popular press.
We began researching Brassica cover crops back in 2000. Forage radish is a unique Brassica cover crop that can capture large amounts of nitrogen and other nutrients in in fall and release them again early in spring, while loosening compacted soils and effectively suppressing winter/early spring weeds. Nearly a decade of lessons learned from research are summarized here Forage Radish Extension Fact Sheet (.pdf). The Weil lab is one of the foremost research groups for radish cover crop science and management practice.
No-till, no-herbicide planting of early vegetables:
Spring vegetable planting is often delayed because soils are too cold to plant and too wet to drive on or till. Most winter cover crops (like rye or vetch) can aggravate this situation by keeping soils cooler and wetter in spring. In contrast, we have found that in early spring, the soil after winterkilled forage radish is essentially weed free, has very little residue, and is drier and warmer and ready to plant earlier than soils under most other cover crops or just winter weeds. There appears to be no need for tillage or herbicides before you can plant.
Under a grant from Northeast SARE, our team of research scientists, extension agents and farmers from Maryland to Maine are working to see if it is practical to plant early crops directly into this seedbed without tilling it first – and without spraying a burn-down herbicide, either. A few of the questions the project will be asking are:
Will this work with conventional planters commonly used by small and medium-scale growers?
Will early crops be able to use the nitrogen (and other nutrients) released by the radish?
Will weeds be controllable once the crop is up?
Will early no-till planting result in earlier or bigger harvests?
How can a farmer best integrate this no-till technique into an overall vegetable cropping system?
For more information on no-herbicide no-till planting of early vegetables into a seedbed prepared by low-residue winter-killed cover crops, please visit the project website.
Cover Crop Field Day: Clarksville, MD 11/14/2013
Soil auger in hand, Natalie Lounsbury regales the group of about 65 farmers and ag professionals before heading out to the cover crop plots. The soil auger was later used to obtain samples from as deep as 80 cm into the soil beneath ground with cover crop and with only fall weeds.
Ray Weil (in the soil pit) discusses the below ground story of the winter killed cover crops. The soil pit was dug so as to cut into stands of phacelia (on the left) forage radish in the middle and no-cover crop (weeds) on the right.
Half the participants examine plots of winter killed cover crops including spring oat, forage radish and phacelia (left front).
The business end of the compaction-fighting forage radish. While the fat fleshy root is impressive (even tasty!), it’s the long, thinner taproot that blazes permanent pathways through the plowpan into the subsoil. This taproot seen on November 14 was less than two months old. It resulted from seed that was sown September 01, but only emerged in mid-September after it received some moisture.
Using the soil they augered from under the cover crop plots, the participants then measured the concentration of nitrate nitrogen in each 20cm thick layer. Soil (12.5 grams or about 10 grams on a dry weight basis) was weighed on a small but precise battery powered balance and shaken with 20 mL of calcium chloride salt solution to extract the nitrate, and then filtered (row of beakers with filter paper cones).
Natalie helps two farmer participants to measure the nitrate concentration in the soil filtrate by placing a few drops on the ion-selective sensor in the small green and white Horiba nitrate meter. The results (see table) were quite amazing (average of two replicate auger samplings), even considering that these field had a long history of manure and compost application.
In the soil (0-80 cm) under the weeds-only plots (no cover crop) the nitrate-N values added up to 384 kg N /ha (350 pounds nitrate-N/acre). Under the plots with forage radish cover crop the nitrate-N values added up to 27 kg N /ha (25 pounds nitrate-N/acre).
Zone planting of cover crops with spring oat growing in what will the tire tracks next spring and forage radish growing in what will be the planting beds. The idea is to produce a mulch in the tire tracks and a warm, drier, friable soil in the seedbed suitable for notill planting.
Ray Weil discusses the cover crop root growth exposed in a soil pit. The depth of penetration by the long, thin taproot did not appear related to the diameter of the fleshy part of the root. This cover crop contained well over 200 lbs N/acre in the plant tissue….nitrogen that had been brought up from deep in the soil profile and that will be deposited on and near the soil surface when the plant winterkill. Most of this captured N (along with substantial amounts of S, P, Ca, K and B) should be available to vegetable crops planted early in spring, rather than be on its way to the Bay.