Cover Cropping on the High Mowing Organic Seed Farm
I first heard the old adage of “no bare ground” while working for Gordon Tooley and Margaret Yancy at Tooley’s Trees in Truchas, New Mexico. Gordon espouses many philosophies on life and farming. However, the philosophy of “no bare ground” didn’t completely resonate with me in dry-land New Mexico. Not long after I started on the Seed Production Farm at High Mowing, our Seed Production Manager said the same sentence, “no bare ground”. I am not sure if Sir Albert Howard woke his wife Louise in her sleep, muttering this sentence. Or maybe the thought first crossed J. I. Rodale’s mind when pondering soil health and organic gardening. The idea of keeping ground covered, however, seems intuitive. A drive across the expanse of the Dakotas, Nebraska, Iowa or Kansas, through the middle of the country, through hundreds of thousands of acres of some of the world’s most productive landscapes crystallizes intuition. However, the invisible hand of herbicide forces the landscape into repose between plantings. These acres wait to be planted and while they wait, time has slowed and ecology is frozen. The land lies lifeless.
As organic seed producers, we annually propagate life to be lived again the next year. Every spring, mostly with seed we’ve saved, we begin the process of growing living vegetable seed. To grow strong living seed, we work to maintain and build a healthy living soil. Cover cropping serves as a key component to building healthy soil. We sow cover crops in spring and fall, with some cover spread in summer. Before sowing cover crop we run Perfecta cultivators over the ground to be cover-cropped. The Perfectas gently disturb the soil, overturning any weeds that are beginning to germinate.
Spring Cover Cropping
This year we are spring cover-cropping just over 10 acres. We spring cover crop with field peas and oats. We mix a 2:1 pea to oat ratio and sow the seeds with a PTO driven broadcaster seeder on the tractor. We spread rates of 100 lbs of peas and 50 lbs of oats per acre. According to the Northeast Cover Crop Handbook, a mature oat spring cover can produce 6,000-8,000 lbs of dry matter per acre; field peas can produce up to 5100 lbs of dry matter/acre. After the seeds are broadcasted, we cultivate with the Perfecta to better incorporate the broadcasted seeds into the soil. We have an old International Harvester grain drill that hopefully with enough love, WD-40 and elbow grease, we can make work.
Oats (Avena sativa) germinate well in cool weather, grow well easily, produce allelopathic compounds that suppress weeds, grow a fibrous root system that prevents soil erosion, and facilitates the upward growth of the companion planted legumes.
Field peas (Pisum sativum) and their associated beneficial bacteria fix atmospheric nitrogen into nitrogen compounds available to plants producing up to 172 lbs/acre of nitrogen. Both require minimal tillage to prepare a seedbed that was fall-tilled.
Fall Cover Cropping
Our fall cover crops are spread either on fields that were in summer seed production or in spring cover crop that was incorporated. We mostly plant cover crop in the fall with a mixture of winter rye, vetch, and crimson clover. We seed a per acre rate of: rye 30 lbs, hairy vetch 25 lbs, crimson clover 10 lbs.
Winter rye (Secale cereale) exhibits great cold tolerance, able to germinate in temperatures low as 34° F, and can take up excess soil nitrogen. Similar to oats, winter rye provides root structure below ground to hold soil and also above ground structure for legumes to utilize. Rye produces around 3000-4000 lbs of dry matter per season. Winter rye also exudes allelopathic compounds that inhibit weed growth. Hairy vetch (Vicia villosa) fixes nitrogen and provides weed suppression.
Crimson clover (Trifolium incarnatum) provides fall weed suppression due to its ground cover type growth habit. Crimson clover fixes nitrogen and does exhibit some shade tolerance enabling it to thrive under Hairy Vetch and Winter Rye. Crimson Clover and Hairy Vetch can fix approximately 200 lbs of nitrogen/season. We manage our cover crops while also spreading compost and other amendments in the spring and fall.
Patterns in Our Cover Crops
A theme prevails amongst our spring and fall cover crops. The monocots--oats and winter rye--provide a root mat to prevent soil erosion, exude allelopathic compounds that inhibit weed growth, provide above ground structure enabling the companion leguminous crops upright growth, and produce considerable biomass that can be incorporated into the soil therefore building levels of organic matter.
The legumes--field peas, hairy vetch, and crimson clover--importantly, form the symbiosis with beneficial bacteria that fix atmospheric nitrogen into nitrogenous compounds available to plants, forming a dense canopy shading out weeds both when living and after winter-kill, providing plant matter that can be incorporated into the soil.
Inadvertently, areas of the farm where we grow Brassica seed are cover cropped during seed harvest. Enough seed escapes in the dry seed harvest process that beautiful cover crops of mid-summer mustard greens take hold. Mustard greens suppress weeds, soil borne disease and release biofumigants into the soil that reduce numbers of predatory nematodes. Baby mustard greens also provide a tasty mid-day field snack.
Every season on the High Mowing Seed farm, like farms everywhere, our farming gets better. The evolution of our cover cropping practices hopefully will mature into a system with less tillage and less of a need for off-farm inputs. As long as we keep muttering to ourselves, “no bare ground”, we work toward a living landscape that yields a strong living seed.
- Clark, Andy. 2007. Managing Cover Crops Profitably. 3rd Edition. College Park, MD. SARE.
- Maguire, Andy. 2003. Mustard Green Manures. WSU Extension Bulletin EB1952E http://cru.cahe.wsu.edu/CEPublications/eb1952e/EB1952E.pdf
- Mohler, Charles L. & Sue Ellen Johnson, editors. 2009. Crop Rotation on Organic Farms: A Planning Manual. Ithaca, NY. Natural Resource, Agriculture, and Engineering Service Cooperative Extension.
- Sarrantonio, Marianne. 1994. Northeast Cover Crop Handbook. Emmaus, PA. Rodale Institute