Organic No-Till Cover Crops

 

Rye and hairy vetch cover crop. Photo Kathryn Simmons

Organic no-till cover crops are grown to flowering (or very close), killed without tilling or chemicals, and left to become dead mulch for the next crop. The food crops are planted into the dying residue. We have used no-till cover crops for Roma paste tomatoes, which are transplanted in early May. We don’t need early-ripening for these, making them a good no-till food crop. This method enabled us to have 1 year in 10 as a no-till year.

Four ways to kill cover crops without herbicides or tilling

  1. Winter-killed cover crops for early spring food crops
  2. Mow-killed cover crops.
  3. Crimped and rolled cover crops use special tractor equipment. A crimping roller is more successful than a smooth roller. I have also seen photos of an energetic human-powered method involving a T-post lying on the ground across a bed, with two well-coordinated people, one at each end of the T-post, lifting the post with a loop of rope or twine, setting the post back down a few inches further forward and stepping on it.
  4. Mowed and tarped cover crops, kept covered until the roots of the cover crop are dead. With this method, the cover crop or weeds can be killed at any stage of growth. I’m still learning about this, so I won’t say more this time.
We can no longer rely on our winter cover crop oats getting winter-killed. March photo by Pam Dawling

Organic no-till benefits to the soil

  • Soil is kept covered, reducing erosion.
  • Soil compaction is reduced by having fewer tractor passes. Labor, fuel and machinery costs are also reduced.
  • Soil layers are not inverted, the soil micro-organism habitat is undisturbed, the root channels of the cover crops are undisturbed, and the number of earthworms and microbes increases.
  • Soil structure improves, organic matter increases and the cover crop biomass is conserved, rather than burning up as quickly as it would if incorporated.
  • Soil can absorb and retain more water, making it more resilient in drought. Yields are higher under drought conditions than on tilled soil.
  • Soil retains cooler temperatures into the summer, increasing root growth.
  • No new weed seeds are brought to the surface.
  • Some pathogens and pests may be suppressed.
  • Mulch grows in situ – no need to haul and spread.
  • Legumes in the cover crop mix can provide all the nitrogen the next crop needs. The cost of N from vetch seed is half the cost of N from fertilizers.
  • Legumes are a slow-release fertilizer: 15% of the nitrogen in the vetch is in the roots, in position in the soil for the new transplants. 50% becomes available to the food crop as the soil warms in spring and early summer; 50% remains for the following season.
  • Hairy vetch activates plant genes that increase disease tolerance and plant longevity, giving tomatoes an extra 2 to 3 weeks of production
  • Use of agricultural plastics is reduced.
  • If spring is wet, it may be possible to mow, when you couldn’t till.
  • Crops such as pumpkins are cleaner than those grown on bare soil.
Hairy vetch cover crop.
Photo Southern Exposure Seed Exchange

Suitable cover crops for no-till

  • When choosing winter annual cover crops, consider cold-tolerance, the length of the growing season, and efficacy in fixing nitrogen and producing biomass. Do you want a winter-killed cover crop (oats, sorghum-sudangrass) or a hardy one (winter wheat or winter rye)?
  • Using a mixture of grasses and legumes helps limit the loss of N from the cover crop through leaching or denitrification. Generally, use a grass/legume mix in a 2:1 ratio, although you can use higher amounts of legumes, up to 1:1. Hairy Vetch, Austrian Winter Peas, Crimson Clover are all suitable.
  • There are advantages to including more than one legume in the mix – in unusual weather, one may struggle, while the other does better. 

No-till cover crops for early spring vegetables

  • Frost-tender cover crops can be used before early spring no-till food crops. Some growers say it is best to mow or roll the cover crop at around the first frost date, to provide a more uniform mulch in the spring. Weeds may be a problem and the soil will be colder than bare soil — this may work for cabbage and broccoli.
  • For the very earliest spring crops, forage radish, lab-lab bean or bell beans will die back and leave almost bare soil. While they are growing, they suppress weeds.
  • BUT fast-maturing spring vegetables will not do well with no-till cover crops unless you add N fertilizer, as they need nitrogen more quickly than can be got from no-till cover crops early in the year when the soil is cold.
Winter rye and crimson clover cover crop
Photo by McCune Porter

No-till cover crops before suitable late spring vegetables

  • A 1994 USDA trial of various no-till cover crop mulches for tomatoes found that hairy vetch (without added nitrogen fertilizer, and without any weeding) out-yielded plastic-and-fertilizer plots by about 25%, and out-yielded fertilized bare soil by 100%.
  • Late-spring transplanted crops such as late tomatoes, peppers, eggplant, Halloween pumpkins, or successions of cucumbers and squash can do very well after a winter-hardy legume-grass mix no-till cover crop.
  • I have read that transplanting eggplant into crimson clover (sown in the fall before) will reduce flea beetle outbreaks, but I have yet to try it. Mowing after early bud stage will kill crimson clover.
  • At the Coastal Plain Experiment Station in Tifton, Georgia, they have trialed peanuts planted into crimson clover.
  • If you have machinery or hand tools for seeding into no-till cover crops, direct seeded crops are possible.
Rows of Roma paste tomatoes, some on bioplastic, some no-till. Credit Bridget Aleshire

Our example: Paste tomatoes in a mow-killed no-till cover crop mix

  1. We find a plot that will be available in early September: Our spring broccoli and cabbage finish in early July. We follow them with a round of buckwheat summer cover crop.
  2. Then, on September 7–14, we sow winter rye, Austrian winter peas and hairy vetch. 5 oz HV, 1.5 oz AWP, 2.5 oz Rye per 100 sq ft (5 g HV, 5 g AWP, 8 g rye/m2.)
  3. It is vital to grow a solid stand of cover crops for high biomass. The goal is to have the vetch be about 4″ (10 cm) tall before hard frosts of 22°F (-5.5°C) stop growth.
  4. We do not till in this cover crop in spring, but in early May, we mow it very close to the ground using our hay mower (5/1-5/5), just before our tomato transplanting date. We want the cover crop to stay in long aligned stems, not be chopped up small. For small patches, a scythe is better than a weed-whip, for the same reasons
  5. This kills the cover crops. If mowed too early, they will not die. The vetch should be flowering. Rye should be at the soft dough stage – bite a kernel.
  6. We let the mulch wilt for a day, making it easier to work with, before transplanting. We measure and set out stakes and ropes to mark the rows.
  7. We transplant the tomatoes into the dying mulch with as little disturbance of the cover crop as possible.
  8. The vetch and peas (if plentiful) supply all the nitrogen the tomatoes need. We do not add any compost or other fertilizer. The peas reduce the incidence of Septoria leaf spot in the following tomato crop.
  9. In our humid climate the dead no-till mulch keeps weeds away for 6 -10 weeks, by which time it has mostly biodegraded. In climates that are drier or cooler than ours, the mulch will last longer.
  10. In July we roll hay between the rows, to top up the mulch. We plant the tomato rows 5.5 feet (1.7 m) apart and the plants are staked and woven, so we can snugly fit big round bales of hay down the aisles.
  11. This crop doesn’t finish until the frost, and we have all the posts to remove before we can sow a cover crop, so the winter following the paste tomatoes, we usually grow rye with Austrian winter peas.
The Roma paste tomatoes later in the year.
Photo Kathryn Simmons
Roma tomatoes in an earlier year, with rolled hay mulch. Photo Twin Oaks
Plentiful harvest of Roma paste tomatoes. Photo Twin Oaks COmmunity

Cautions about no-till planting

  • Cold-hardy cover crops need time in spring to grow to optimal size before mowing – they are not suitable for early spring food crops
  • Untilled soil in spring is colder than tilled soil: growth of anything you plant in it will be slower, and harvests delayed. Not good for warmth-loving crops such as watermelons!
  • The rate of nitrogen release from the cover crop will be slower than from an incorporated cover crop
  • Transplanting into untilled soil is harder work than planting into loose tilled soil
  • The timing of sowing, rolling or mowing and planting is critical. The wrong weather can jinx your plans
  • If the cover crop stand is poor, weeds will germinate – have a Plan B. Usually this will involve tilling, adding compost and then finding another mulch
  • There may be some regrowth of the cover crop, if mowing was too high, irregular or poorly timed. If needed, mow between the crop rows a couple of weeks later
  • There may be more fungal diseases and slugs
  • In arid zones, it is necessary to wet the mulch weekly to release the nutrients. Drip irrigation won’t do that
  • Hand-seeding into untilled soil is tricky – winter snow and ice can leave soil quite compacted. Unsuitable for small seeded, closely-spaced vegetables. Pumpkins and squash can be direct seeded in crimped and rolled (or mowed) winter rye.
  • Initial hopes for no-till cover crops – that it would be possible to grow vegetables organically without ever tilling again – were unrealistically high

No-till tractor equipment

  • For mowing cover crops, we use our hay mower/conditioner rather than our (rotary) bush-hog, as it cuts close to the ground and lays the cover crop down without chopping it into small pieces. This helps it last longer, and be easier to transplant into. Flail-mowers are recommended over lower-speed sickle-bar mowers, which can get tangled with long vetch vines
  • Roll-killing leaves a longer-persisting mulch than mowing, although there may be problems with re-growth. Adding a method of crimping the stems increases the effectiveness. Hairy vetch is harder to kill by rolling than crimson clover.
  • Ron Morse designed a No-Till and Reduced Till Planting Aid, consisting of a heavy coulter and shank assembly with a wavy coulter behind the shank to slice the mulch and leave a 2″-3″ (5-7.3 cm) strip of prepared soil, for planting in a separate operation.
  • Transplanters are available that are designed for use with thick organic mulches.
  • Direct seeding of large-seeded crops is possible using equipment to open a narrow slot deep enough for the seeds. No-till seeders are harder to find: an example has a toolbar planter, 15″ (38 cm) fluted disk blades to cut through the vetch mat, 15″ (38 cm) double disk opener, 12″ (30 cm) cast-iron closing disks, plastic seed pressers and extra weights.

More on no-till

At the Pasa 2022 conference I went to the workshop On-Farm Experience with Organic No-Till, by Sam Malriat from Rodale.

Sam pointed out that no-till methods sequester carbon in the soil, but simply never tilling does not improve the soil. He recommended we not be obsessive about no-till, but move towards reducing tillage. Sometimes shallow tillage can be a good choice, adding value by incorporating organic matter. OM and soil water capacity can be increased enormously by using cover crops, compost or manure, grazing, or a good crop rotation.

You need a very solid, heavy cover crop stand, to provide a thick mulch when terminated. There is a lot of difference in thickness of mulch from rye sown in August and in October. You also need a very competitive cash crop; a successful method of planting into the cover crop residue, and a back-up plan in case something goes wrong. For example, sowing corn into rolled and crimped hairy vetch does not work well, because corn is a heavy feeder and is not very competitive. A better idea is to undersow the corn at V5 or V6 (stages of vegetative growth) with white clover or crimson clover in September (in PA). It’s very important to get good seed to soil contact, and enough moisture. The clover grows after the corn dies. If the clover is left growing into the second year, cabbage can be transplanted into it.

Rye termination timing: When to successfully crimp

“Interested in no-till production, but unsure of how to manage cover crops so they don’t become a problem for the crop that follows?
The most common management concern is when to crimp your cover crop to get a good kill but prevent it from setting seed. Getting the timing right on crimping small grain cover crops like rye isn’t difficult, but it does take a little attention to its growth stage. See this three-minute video for a quick run-down on which stages to look for in order to get that timing right.”

Winter rye headed up. Mow or turn it under very soon! Don’t let it shed seed.
Photo Pam Dawling

Cover Crops for April: before the last frost.

 

Beds of young buckwheat.
Photo Bridget Aleshire

In January I shared some resources to give the Big Picture of Cover Crops, including a compilation of slides for SARE (Sustainable Agriculture Research and Education) and my slideshow Cover Crops for Vegetable Growers.

In February, I described limiting winter annual weeds by sowing oats in spaces without a cover crop and no planned food crop for 6-10 weeks. Six–ten weeks (depending on your climate) is long enough in early spring to get worthwhile growth from oats before prepping for the food crop. Also see February’s post for the Stale Seedbed and Tarping Techniques.

In March I wrote about some options for cover crops you might be sowing then, and alternatives like a fast-growing hardy leafy vegetable or mixed Eat-All Greens, an idea from Carol Deppe, a great idea if you have more than eight weeks before your main vegetable crop goes in the ground. This is where using transplants really helps increase your total food output. While the frost-tender transplants are growing indoors, you could be growing a “catch crop” outdoors in spaces that didn’t get a winter cover crop. I also talked in the March post about incorporating cover crops. Remember that if you incorporate fresh green cover crops into the soil, you will need to wait two or three weeks to sow, to give the cover crop time to break down in the soil before it can be available for your crop. Especially, wait three weeks after turning under winter rye before sowing, as it produces allelopathic compounds that can inhibit the germination and growth of small seeds. Transplants don’t suffer the same problem.

Potatoes, weeds and standing water. Until the soil drains, the potatoes cannot be hilled, and the weeds here are already large. The yield will be reduced by weeds out-competing the potatoes. Potatoes may be flamed at 6″–12″ (15–30 cm) tall, to kill weeds without damaging the potato plants. After that, flaming is not recommended.
Photo Bridget Aleshire

Once we get to April here, it is too late to successfully grow oats (they will quickly head up after making very little growth). But in climates like ours, we can sow winter wheat or winter rye in April – they will not head up, but will “wimp out” when it gets hot. That is, they will stop growing, so you won’t get a lot of biomass, but you will have some live roots in the soil, holding it together, taking care of the soil microfauna, and discouraging weeds form germinating. One April when our spring-planted potatoes got flooded, we transplanted potato plants to the drier end of the patch and sowed winter rye in the lower end, once the floods had subsided. This kept the soil covered, scavenged the compost we had spread for the potatoes, and was easy to deal with in July when we harvested the potatoes. It was also much more hopeful to look at an area of green cover crop than an area of green weeds!

April is too soon for us to rely on frost-tender cover crops, but by mid-April, we can sow a mix of oats and buckwheat. The oats will protect the buckwheat somewhat from the cold. if the season is warmer than average, the buckwheat will survive and smother weeds, provide pollen and nectar for beneficial insects

Here’s a lovely quote from Barbara Pleasant in SW Virginia:

“It’s April and the soil is warming up and drying out. After loosening a clump of fall-sown wheat with a digging fork, you pull up a marvelous mop of fibrous roots and shake out the soil. What crumb! The soil’s structure is nothing short of amazing! These are the moments an organic gardener lives for.”

Root systems of four grass cover crops at early stages of growth (two months in a greenhouse). From left: annual ryegrass, barley, triticale (winter biennials) and sorghum-sudangrass (summer annual). Photos by Joseph Amsili. From SARE

Depending on the stage of the year where you are, you could revisit any of the earlier posts. Here are links for each of the cover crop posts in the past year.

May: Buckwheat and Other Summer Cover Crops

June: Sunn Hemp, Soybeans, Southern Peas, and Partridge Pea, Senna Ligustrina

July: Millets and Sorghum-Sudangrass (Sudex)

August: Oats, Barley and Other Winter-Killed Cover Crops

September: Winter Wheat and Crimson Clover

October: Winter Wheat and Austrian Winter Peas

November: Winter Rye (with Austrian Winter Peas early in November)

December: Planning Winter Cover Crops

January: The Big Picture, Ponder and Plan Your Cover Crop Strategies for the Coming Year

February: Oats if you have a 6–10 Week Gap

March: Sowing Options and Incorporating Cover Crops

Perennial and Native Cover Crops

I attended a workshop at the VABF-SFOP Summit on cover crops led by Cerruti R2 Hooks, Veronica Yurchak, from the Department of Entomology, University of Maryland, and Hanna Kahl of UC Davis. The UMD Eastern Shore IPM Center has lots of useful programs and publications. They focus on the most important pest problems and make science-based information available to everyone who contends with pests. This workshop discussed how cover crops influence weeds, plant diseases and insects. Cover crops can smother weeds, augment weed seed predators (lifeforms that eat weed seeds), create a weed-suppressive soil microbe community, release allelochemicals that are toxic to weed seeds, release nitrogen into the crop germination zone, boosting crop growth, cool the soil and compete with weeds for resources.

Cover crops can decrease crop diseases by increasing the diversity of soil organisms, making soil more disease-suppressive; releasing compounds unfavorable to disease organisms; trigger plant immune responses; increase the number of beneficial organisms and forma physical barrier that reduces splash-back from the oil. A nice example is that sunn hemp interplanted in squash rows can cause aphids carrying virus particles in their mouth parts to drop them in the sunn hemp where they do no harm.

Sunn hemp at Nourishing Acres Farm.
Photo Pam Dawling

Cover crops can repel some insects and nematodes, as well as providing habitat, nutrients and protection from predators for the beneficial insects. This can help augment the population of beneficial insects. Cover crops can also act as trap crops for problem insects by being more attractive to them than the crop plants. Cover crops can also cause microclimate change within the crop, for example by acting as a windbreak.

The speaker gave examples with red clover, a short-lived perennial, sown in the previous fall between cucumber rows that were planted in spring. The population of striped cucumber beetles was lower, while populations of beneficials such as big-eyed bugs, minute pirate bugs and ladybugs were increased.

In November 2023, at the Carolina Farm Stewardship Conference, I went to an engaging workshop called On-Farm Cover Crops Research in the Carolinas by Justin Duncan from NCAT/ATTRA, Jason Lindsay from the Southeastern African American Farmers’ Organic Network, and Steve McAllan. See his YouTube  Cover Crops for Hot & Humid Regions. At the workshop, Justin Duncan explained Push-Pull Trap Cropping, invented in Kenya, combining a companion plant that repels a pest with a trap crop nearby that attracts it, making pest control easier.

Pigeon Pea as cover crop. Photo https://conservationist.wordpress.com/2008/11/03/pigeon-pea-as-cover-crop/

He advocated for pigeon peas (Cajanus Cajan) as a cover crop for warm droughty climates, that will also keep the soil cooler. When mean temperatures rise 1 Celsius degree, soils in warm areas burn up 10% of their OM, and cool areas lose 3%. Loss of water leads to loss of OM, leading to more water loss. Hot humid areas need twice as much OM as cooler ones to maintain fertility. No-till can cut the loss of OM by half compared to conventional tillage. Other cover crops Justin Duncan recommended include Perennial Peanut, good in orchards, Chamaecrista rotundifolia (round-leaved cassia) and Scarlet Runner beans. Cover crops are a way of growing Organic Matter in place.

Patrick Johnson, RVA Permaculture. Photo https://rvapermaculture.com/about-us/

Patrick Johnson, a Virginia permaculturist, also gave a presentation on native cover crops. See his Proposal and Project Overview:  https://projects.sare.org/sare_project/fs22-345/

And read the Feb 2024 SARE report Using a Native Legume as a Cover Crop for Soil and Vegetable Production Benefits in Small Scale Vegetable Production.

No-Till Cover Crops

I have not covered these yet, and don’t have much personal experience, apart from our one-year-in-ten growing of paste tomatoes in a mow-killed rye, hairy vetch and Austrian winter peas dying mulch. I’ll make a separate post for next week about combining cover crops and no-till methods.

Cover Crop Training Videos from SARE

See SARE for a series of ten training videos.

Weeds Next

For my next annual series of blogposts, starting at the beginning of May, I will cover Weeds of the Month.

2023-2024 Conference Tips 3 – Climate Change, less usual edible plants

Carrots under shade cloth in summer.
Photo Pam Dawling

2023-2024 Conference Tips Part 3 – Climate Change, Less Usual Edible Plants

I reported earlier on good tips I got from the CFSA Conference and the VABF-SFOP Summit.  Here I’ll continue the theme.

At the VABF-SFOP Summit, I also attended workshops on Meeting the Climate Challenge with Mark Schonbeck, and Eating and Marketing the Whole Plant with Chris Smith. I’ll tell you more about those now, then move on to the Pasa Sustainable Agriculture Conference.

Meeting the Climate Challenge: Sharing Stories, Co-Creating Solutions with Mark Schonbeck

Mark’s slides and handout will be available soon on the VABF website. In our region we are experiencing hotter summer nights, which are hard on plants (and livestock, I’m sure). At 95F (35C) most crops close down completely or slow their growth. For every 1.8F (1C) in warming, 3-10% of the Organic Matter is lost (burned up) and nitrous oxide emissions may increase 18-28%. Daffodils are flowering up to 5 weeks earlier, fruit trees are budding out earlier, risking losing the fruit to freezing nights. In the spring we are getting later cold snaps below 10F (-12C) in March.

We are having a longer frost-free period, with more generations of bugs. Downy mildew of cucurbits is spreading further north than previously.

Our kale beds after heavy rain. Photo Wren Vile

In Virginia we are getting more intense and heavier rains, with more flooding. The erratic nature of the rains means we can experience flash floods, followed by droughts and wildfires. Heavy rainfall leads plants to grow shallower roots, which then die if a sudden drought follows.

Keeping living roots in the soil will increase climate resilience, as will other ways of building healthy soils, such as diversified rotations, and varied agricultural enterprises. Here’s Mark’s list of

6 Organic Principles of Soil Health:

  1. Keep the soil covered
  2. Maintain living roots
  3. Return organic residues to the soil
  4. Minimize soil disturbance
  5. Diversify crops
  6. Integrate livestock.
Teff cover crop.
Photo Wikipedia

Increasing the use of cover crops will help with 1, 2, 3 and 5. Teff can be considered as a summer cover crop in alleys between plastic mulched beds. Mixing with clover gives better soil coverage. I have not yet tried this myself. Oats/barley/peas/mustard sown in March will grow big by June, adding lots of biomass. Oats/radish/legume cover crop mix will winter-kill. Silage tarps and landscape fabrics can help hold the soil in place.

Installing terraces, berms and swales will help with water management. Installing drip irrigation will help manage droughts. Protected growing, in hoophouses or caterpillar tunnels, will help protect from many kinds of extreme weather. There are steps we can take to mitigate climate change, and more information is becoming available.

Eating and Marketing the Whole Plant with Chris Smith

Chris is the author of The Whole Okra, and part of his presentation was about the many uses of okra, beyond cooking the pods. Okra leaf chips are the latest thing he has tried. The leaves are used for soup in Nigeria. The flowers can be eaten or dried for tea. The oil from okra seeds is nutty, citrusy, a bit like olive oil, although the yield is small, at 9-20%. The oil presscake can be ground for defatted flour.

Book Edible Leaves of the Tropics by Franklin Martin, Ruth Ruberte and Laura S Meitzner

Chris showed us a remarkable book Edible Leaves of the Tropics, by Franklin Martin, Ruth Ruberte and Laura S Meitzner. Plants for a Future  has a database of 8000 plants, including edible plants.  The Book of Greens by Jenn Louis and Legume Species as Leafy Vegetables by Robert P Barrett (online) are also valuable resources on edible plants.

DIYseeds.org educational films on seed production

Go to https://www.diyseeds.org  then search for info on growing seeds.

Male squash flowers can sell at $1/flower for an 8-week season. Winter squash yields can increase if some of the early male flowers are removed! Wisteria, redbud and black locust flowers are edible. Kudzu offers many food options (eat it up!) Roots of dandelion, burdock, thistle, sassafras, daylily, dahlia, runner bean and chayote are all edible.

Soil Health, Climate Adaptation and Mitigation Planning, Rachel Schattman, Sara Keleman and Nic Cook

In February 2024, I participated in the Pasa Sustainable Agriculture Conference.  The first session I attended there was Soil Health, Climate Adaptation and Mitigation Planning, with speakers from the University of Maine Climate Science department. They reported that the NE has seen a 15% increase in Growing Degree Days since 1948, and the frost-free growing season in Maine has increased by 14 days since 1895. California has seen a 40-50 day increase in that period. In Maine the temperature changes are greater in winter than in summer. Since 2012, half of the US has shifted to the next warmer winter-hardiness zone. It is helpful to watch indicator species to determine when to plant particular crops. (See my post on Phenology). Warmer temperatures mean that the air holds more water (7% more for each C degree). This means slower storms, more storms heavier rainfall. They also experience droughts, and distinguish between agricultural drought, meteorological drought, and hydrologic drought – be sure which kind your conversations are about.

Young blueberry plant in snow. Photo Bridget Aleshire

Sea level rise is dramatic on the East coast because of past glaciation. The other main impacts they are seeing on agriculture include False Spring (fruit bud kill after a “warm snap”), winter soil erosion and rain ponding, and new pests, diseases and invasive species, warm season heat stress including crop quality deterioration, greater irrigation demands and needs for shade and ventilation (drought can decrease yields 30%), storm intensity including hail and high winds, longer power outages, soil compaction and nutrient runoff, increased rainfall leading to delayed planting and crop losses. These are all possibilities to prepare for. The silver lining is that there may be new crops we can grow, or longer seasons of familiar crops. NRCS, Extension and other resources are available. Climate-Smart Farming and Marketing is a program for farmers from Maine to South Carolina, offering financial support and technical help to farmers implementing climate-smart practices such as cover cropping, agroforestry, reduced tillage and prescribed grazing.

Prescribed grazing is the intentional use of ruminant animals (hoofed herbivores such as cows, sheep, and goats) on the landscape. Unlike conventional grazing, prescribed grazing utilizes a grazing plan that dictates the location and duration of graze periods. This plan is informed by the ecology of the grazing area.” (Community Environmental Council).

Garlic beds next to rowcovered broccoli beds, under a stormy sky.
Photo Wren Vile

We were helped through an 8-stage planning process:

  1. Risk Assessment (prioritizing which aspect of climate change to deal with first). Heavier rains, then high temperatures, wildfire and smoke, plant diseases.
  2. Vulnerability (looking at your system, climate, location, and seasonal time period). Consider both Exposure to the risk and your farm’s Adaptive Capacity.
  3. Option ID. Consider all of small, medium large and total transformation of your farming. Divide your options up into 4 quadrants on axes of cheap-expensive, difficult-easy; low Greenhouse Gas-high GHG, reducing risk-increasing risk; low impact-high impact, quick to install-takes a long time.
  4. Evaluate tradeoffs (financial, ecological, social). Rank your options and select one that meets as many of your priorities as possible.
  5. Try to meet several goals with one solution. Consider seeking advice or funding.
  6. Monitoring and assessment. How will you measure the improvements?
  7. Revising/tweaking. Reflect and assess. Consider success at each stage.
  8. Share what you learned. Don’t expect perfection, or that others will expect that from you.

Next followed a section on funding. Currently there is lots in Inflation Reduction Act coffers for efficiency increases, renewable energy, conservation practices. Try REAP (Rural Energy for America Program), USDA, NRCS, Rural Development Office for your state, SARE funding for experimentation and trials, state agriculture departments, advocacy organizations, regional non-profits, Chesapeake Bay Trust, Farmer Resource Network, county grants, Beginner Farmer grants, grants for historically under-served farmers, Ambrook Accounting software for American farms..

Take a buddy with you to the offices!

Farmer Resource Network

Cover Crops for March: Sowing Options and Incorporating Cover Crops

In March, where we undersowed clovers in the broccoli patch in August, the old broccoli trunks are surrounded by a sea of green clover.
Photo by Kathryn Simmons

In December I wrote about Cover Crop Planning for Next Year, including 5 steps of cover crop planning for all opportunities. I have a slideshow Crop Rotations for Vegetables and Cover Crops, which I find to my surprise that I haven’t posted here since my 2014 version.

Here it is now

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In January I shared some resources to give the Big Picture of Cover Crops, including a compilation of slides for SARE (Sustainable Agriculture Research and Education) and my slideshow Cover Crops for Vegetable Growers.

In February, I described limiting winter annual weeds by sowing oats in spaces without a cover crop and no planned food crop for 6-10 weeks. Six–ten weeks (depending on your climate) is long enough in early spring to get worthwhile growth from oats before prepping for the food crop.

This month I will include some options for cover crops you might sow in March (in central Virginia and similar climates), and then talk about incorporating cover crops, which surely you will be doing this month!

Cover crops to sow in March, and other options

Purple stemmed mizuna. Mizuna and other frilly mustards are fast-growing crops, attractive to the eye and the palate.
Photo Pam Dawling

Depending on the stage of the year where you are, you could revisit any of those posts.

  • In early March the oats plan still works for us.
  • In early spring, the air and the soil are cold, and sowing a fast-growing vegetable crop will not be successful with a gap of less than eight weeks. Crops take too long to grow at this time of year.
  • If you have more than eight weeks you could try those fast-growing vegetables: kale, spinach, Tokyo bekana, radishes, chard, lots of salad crops, senposai, mizuna, tatsoi, land cress. Or try Eat-All Greens, an idea from Carol Deppe. Patches of carefully chosen cooking greens are sown in a small patch. When it reaches 12″ (30 cm) tall, Carol cuts the top 9″ (23 cm) off for cooking, leaving the tough-stemmed lower part, perhaps for a second cut, or to return to the soil.
  • In late March or April in climates like ours, we can sow winter wheat or winter rye – they will not head up, but will “wimp out” when it gets hot. That is, they will stop growing, so you won’t get a lot of biomass, but you will have some live roots in the soil, holding it together and taking care of the soil microfauna, and discouraging weeds form germinating. One year when our spring-planted potatoes got flooded, we transplanted potato plants to the drier end of the patch and sowed winter rye in the lower end, once the floods had subsided. This kept the soil covered, scavenged the compost we had spread for the potatoes, and was easy to deal with in July when we harvested the potatoes. It was also much more hopeful; to look at an area of green cover crop than an area of green weeds!
  • Once we get to March 31 here, it is too late in the year for us to sow oats (they will quickly head up after making very little growth) and too soon to rely on frost-tender cover crops. See the section in February’s post on the Stale Seedbed and Tarping Techniques.

    Tarping beds to kill weeds.
    Photo Cornell Small Farms Unit
  • By mid-April, it is an option to sow a mix of oats and buckwheat. The oats will protect the buckwheat somewhat from the cold. I’ll come back to that idea next month.

Incorporating cover crops, or not

See Barbara Pleasant: How to Take Cover Crops Down. Gardeners working with small tools can start by mowing their live cover crops, grazing poultry on them, or scything them and hauling them aside to use later for mulch. On a very small scale, you can pull your cover crop plants, although I think it is valuable to leave the roots in the soil. On a larger scale, you can graze larger animals, or cut the cover crop down. If the cover crop was winter-killed, the stems will easily disintegrate, so you can skip the cutting down part of these instructions.

If you plan to incorporate the cover crop, choose a mowing method that cuts the plants into small pieces, making them easier and faster to incorporate. On a small scale, this could be a weed whip or a lawn mower; on a larger scale a bush hog. If you plan to use the cover crop for mulch, cut it in a way that leaves the stems as whole as possible. On a small scale this means a sickle or scythe, on a bigger scale, the kind of machinery you might use to cut hay.

Cover crop of rye, vetch and crimson clover in March.
Photo Kathryn Simmons
Rows of Roma paste tomatoes, some on bioplastic, some no-till. Credit Bridget Aleshire

After getting the cover crop down, you could tarp for a minimum of three weeks (allow for more), or you could work the residue into the soil, with a chopping hoe or by digging it in, or using a walk-behind two-wheel tractor such as BCS with a rototiller or a power harrow, or a four-wheel tractor and discs. Cornell has posted a webinar Pairing Tarping with Cover Crops, by Brian Marr.

If you incorporate the cover crop into the soil green, you will also need to wait two or three weeks (or more in early spring) to plant or sow, to give the cover crop time to break down in the soil before it can be available for your crop.

Winter rye produces allelopathic substances that can temporarily inhibit the germination and growth of small seeds. Wait three weeks after turning under before sowing. Transplants don’t suffer the same problem. Oats, wheat, and other cereals also have this tendency, but to a much smaller degree, usually small enough to ignore. Sorghum-Sudan grass hybrid incorporated fresh in the soil hinders the growth of tomatoes, lettuce, and broccoli, but that’s a summer cover crop you won’t need to think about for several months.

I still haven’t got to my Conference notes on cover crop workshops, 2023-2024, but this is enough for one post!

Vegetable Growing Tips from Conferences, Winter 2023-2024. Part 1 CFSA

 

A Spacemaster cucumber plant in our hoophouse on April 23.
Photo Pam Dawling

I love learning new things and getting tips for improving our vegetable production. My events page tells you about recent and upcoming conferences. After I get home from conferences, I usually need to dive back into work, and am in danger of ignoring things I learned. Hence this blogpost. I’ll pass tips on, and extract the gems from my hand-written notes, making it more likely I’ll do something useful with them!

CFSA SAC 2023 banner

In November 2023 I took part in the Carolina Farm Stewardship Conference. I went to an engaging workshop called On-Farm Cover Crops Research in the Carolinas by Justin Duncan from NCAT/ATTRA, Jason Lindsay from the Southeastern African American Farmers’ Organic Network, and Steve McAllan, a last-minute substitute. I’ve got a blogpost brewing about native cover crops in vegetable production, so I’ll save the content for that post. Patrick Johnson also gave a presentation on native cover crops, which I’ll include more about in the promised post.

https://www.youtube.com/c/clem’sorganicgardens

I also participated in a workshop on Advanced Organic Weed Management for Vegetable Growers, given by Clem Swift of Clem’s Organic Gardens, from Pisgah Forest, NC, where they have 8 acres in field production of vegetables. I hadn’t realized the workshop was mostly machinery-focused, but I learned actionable tips anyway! I watched his video on potato planting, cultivation and harvest, which is similar to the way we grow potatoes. I learned a way of covering the edges of plastic mulch by walking backwards with one foot on the plastic to tension it, hoeing soil up onto the plastic. That sounds easier than our method using shovels, but sounds like it does require looser soil than we sometimes have where we use plastic. Clem has a well-organized system of first removing perennial weeds, then cultivating early and often to deal with annual weeds, including using a double-wheeled wheelhoe with a scuffle on either side of the row. Perhaps like one of these:

Double-wheeled double-scuffle wheelhoe. Hoss Tools
Double-wheel double-sweeps wheelhoe. Sweeps available as a conversion kit from Earth Tools.

Johnny’s Selected Seeds has a Wheelhoe Selection Guide in their Tool Library

Next I attended Precise Nutrient Management for Small-Scale Farms by Kyle Montgomery of Advancing Eco Agriculture. Kyle’s goal was to help us answer the question: How could marketable yields be significantly increased with minor changes to a fertility program? Plants have different nutrient requirements at different stages of growth. Sap analysis can show what the plant is taking out of the soil. In each 24 hour period, we want all soluble nitrogen to be converted to stable forms. This was something new for me to think about. I didn’t bring away anything specific to work on.

South Wind slicing cucumber.
Photo Common Wealth Seed Growers

High Tunnel Cucumber Production by Joe Rowland, CFSA’s Organic Initiatives Coordinator, covered preliminary findings from year one of CFSA’s SARE-funded organic high tunnel cucumber project. They trialed 6 varieties of cucumbers grown on 2 different trellis types (drop lines vs Hortanova netting) to compare disease occurrence and severity and marketable yield. Three participating farms replicated the trial to see what works best throughout the region.

Excelsior pickling cucumber. Photo Johnny’s Seeds

Their standout varieties were Itachi, an Asian white slicer (low yield but good disease resistance), and Excelsior pickler (highest yield).

Itachi white Asian slicing cucumber. Johnny’s Seeds

Poniente (a parthenocarpic European slicer) had the most disease of the 6 in the trial; Shintokiwa had the least disease, but was a slow producer, with low yields. The dropline system uses a single leader, more clips, more pruning and twirling than the Hortanova, where two “rows” could be made per bed, training two leaders from each plant in a V. This gave good airflow, slowed down the height-increase compared to single leader plants, and enabled herbs to be intercropped. We grow a succession of five or six plantings of cucumber, mostly outdoors, sprawled on the ground. Only for the early crop does it seem worthwhile to us to grow them in the hoophouse. But I’ve no idea how our yield compares with trained high    tunnel cukes, and perhaps measuring it would lead me to a different plan!

 Poniente cucumber. Territorial Seeds. Note trellis.
Shintokiwa cucumber High Mowing Seeds

Cover Crops for February: Oats if you have a 6–10 week gap

Oats Cover Crop, Steve Groff farm, Holtwood PA. SARE Soil Health Resources

Cover Crops for February: Oats if you have a 610 week gap

In February, you’ll hopefully have made your crop plans and maps. Perhaps you’ve discovered some beds with no winter cover crop, that you are not using for early spring crops? Those winter annual weeds, chickweed, dead nettle and henbit, will shed lots of seeds if you let them.

If food crops were harvested too late to sow any winter cover crops, in early spring you will be looking at weeds, or “spontaneous vegetation” as I’ve heard them euphemistically called. The first year I gardened in Virginia I had lots of beds in April with purple flowers (henbit, purple dead nettle, some ground ivy) and I couldn’t think what to do – I didn’t need those beds for a few more weeks, so I wasn’t ready to till them. Oh, so wrong! I had squandered an opportunity to improve the soil as well as deal with weed seeds.

Now, when we have the crop plans made, we tag any beds that won’t be used for six weeks or more, till in the weeds and sow oats. In February or March here, with a last frost date of April 30, six weeks is just enough time here to make enough growth to out-compete the weeds and add to the organic matter in the soil.

Examples of crops in our gardens that occupy beds too late for us to sow winter cover crops include late cabbages, the last lettuce, leeks and fall Asian greens. Examples of late spring crops the next year include eggplants, peppers, tomatoes, edamame and chard. In some cases, we might even have no food crop planned until August or the beginning of September.

Six–ten weeks (depending on your climate) is long enough in early spring to get worthwhile growth from oats before prepping for the food crop.

Once we get to March 31 here, it is too late in the year for oats (they will quickly head up after making very little growth) and too soon to rely on frost-tender cover crops. See the section below on Stale Seedbed Technique.

Oats Cover Crops Steve Groff farm, Holtwood PA SARE Soil Health Resources

I wrote about oats as a winter-killed cover crop in August.

Will oats work as an early spring cover crop for you?

Large oat plants will be killed by three nights at 20°F ((–7°C) or by a single plummet to 6°F ((–14°C). Oats seedlings die at 17°F (–8°C). Consider your likely nighttime low temperatures during the period in question, and how likely your seedlings are to die. Oat cover crops of a medium size die around 10°F (–12°C). If they die after growing to adolescent size, no worries – just till them in before planting your next crop.

The minimum soil temperature for germination of oats is 38°F (3°C), and the time required to grow to a worthwhile height in cool weather is 6–10 weeks.

If you are in zone 8 or warmer, oats will not winter-kill, and can be grown in winter too – they may not reliably mow-kill, but are relatively easy to incorporate.

Oat plant and seeds. SARE

Pros and cons of oats as a cover crop

Like most cover crops, oats add biomass and nutrients, increase the biological activity of the soil, smother weeds, reduce soil erosion (their fibrous roots anchor the soil) and absorb and store rainfall. Oats are easy to establish, are fast-growing and particularly good at shading out germinating weed seeds and at salvaging any nutrients (especially nitrogen) left from the previous crop and making them available to the following crop.

In early spring you won’t get as much biomass as from a fall oat cover crop, when you can get. as much as 2000–4000lbs per acre (2240–4480 kg/ha. Certainly not enough to be a no-till cover crop for your next food crop. Oats provide some allelopathic effect (producing biochemicals which inhibit the growth of other plants) although less than winter rye. Like most plants, oats form arbuscular mycorrhizal associations (fungi penetrate the plant’s cell walls and help capture nutrients from the soil) – a mutually beneficial relationship, although probably not a big feature when conditions are cold.

Oats are not as good as some other cover crops at breaking up compacted subsoil, although they do loosen the upper layers of topsoil nicely. (Just where you are going to sow.) Oats do not add nitrogen, and unlike flowering cover crops, they do not attract beneficial insects (assuming they are turned under or mowed before heading up and shedding pollen).

Common Oats. Buy Organic and avoid GMO canola seed inclusions

Buying oats, sowing rates

We used to buy “horse oats” (feed oats) locally and not worry about organically certified seed. But I noticed canola sprouting along with the oats, and I don’t want GMO canola going feral in our gardens! We plan ahead and order extra Organic spring oats in summer when making our big cover crop seed order.

Oats will grow in soils with a pH range of 4.5–7.5, and even do OK in soils without great fertility. They have some tolerance to flooding, but not much to heat or drought (although more than rye).

The sowing rate for drilled oats alone is 80–100lbs/ac (90–123 kg/ha). The broadcast rate is 110–140lbs/ac (123–155kg/ha). On a small scale, this is 4–6 oz/100 sq ft (12–20gm/sq m). Aim to cover the seed to a depth of about 1″ (2.5 cm).

Oats grow to a height of 2–4 feet (0.6–1.2 m) if not killed before then.

Stale seedbed technique and tarping

If you have less than 8 weeks until you need to plant the food crop, you are better off mowing when you can, or weed whipping, to prevent weeds seeding.

Tarping beds to kill weeds.
Photo Cornell Small Farms Unit

You could mow and tarp. I don’t yet have much experience of tarping, but there are good directions in The Lean Micro-Farm and The Market Gardener. There are also online videos. The basic idea is to mow the bed, cover it with a black plastic silage tarp, weight down the edges to get good soil contact and stop the tarp blowing away, and wait till the plant matter has disintegrated, or until you need to use the bed. This will take several weeks in cold weather, (although only a few weeks in summer). If you have a late-finishing fall crop, you could mow and tarp as soon as the crop is finished, and leave the bed tarped until spring. Weeds germinate under the tarp, but then die without light.

For a stale seedbed technique without tarps, you could mow, till several weeks before planting, water (if it doesn’t rain) to germinate weeds, and hoe off those weeds once a week. This can really help reduce the weed seedbank in the soil. It is particularly useful before sowing small seeds of slow-growing crops, such as carrots.

What not to sow in short gaps in early spring

Other quick cover crops, like buckwheat and soybeans, are not at all frost-hardy, so wait until after your last frost date to sow those.

In early spring, the air and the soil are cold, and sowing a fast-growing vegetable crop will not be successful with a gap of less than eight weeks. Crops take too long to grow at this time of year.

 Spring gaps longer than eight weeks

If you have more than eight weeks you could try those fast-growing vegetables: kale, spinach, Tokyo bekana, radishes, chard, lots of salad crops, senposai, mizuna, tatsoi, land cress. Or try Eat-All Greens, an idea from Carol Deppe. Patches of carefully chosen cooking greens are sown in a small patch. When it reaches 12″ (30 cm) tall, Carol cuts the top 9″ (23 cm) off for cooking, leaving the tough-stemmed lower part, perhaps for a second cut, or to return to the soil.

Young spinach seedlings.
Photo Pam Dawling

Undersowing oats in spring

Another way we have used oats in spring is between rows of peas (grown on the flat, not in beds). We sowed the oats the same day as the peas, and lightly tilled the oats in. We mowed the oats as needed during the pea training and harvest period to make access easy. This reduced the number of weeds, and we quite liked the “lawn” underfoot!

Green fallow (Full year cover crops)

If you have a bed with no crop planned for the whole season, you could grow a Green Fallow. You can plant long-term cover crops to replenish the soil. Start with oats or one of the more cold-hardy grasses, and once we get to warm weather, after the frosts, till that in (or mow if it mow-kills) and sow warm weather cover crops.

Reasons not to do no-till food crops in spring

Untilled soil in spring is colder than tilled soil, and growth of anything you plant in it will be slower, and harvests delayed. You could consider broccoli or cabbage, perhaps, but not warmth-loving crops. You may get more slugs and/or more fungal diseases with no-till. The cover crop could try to regrow, or you could get some weeds anyway.

Also, if you are planting by hand, transplanting into untilled soil is harder work than planting into loose tilled soil. Hand-sowing into untilled soil is tricky – winter snow and ice can leave quite compacted soil. If the notion of organic no-till appeals to you, experiment on a small-scale the first year. Reduced tillage is another option. Till out narrow strips in the oats for your plantings of large food crops normally grown on a wide row-spacing.

Using a push seeder for cover crops

EarthWay push seeder.
Photo from EarthWay

You can drill cover crop seeds using a push seeder. See VABF Using Manually-Operated Seeders for Precision Cover Crop Plantings on the Small Farm. Don’t worry if the seed ends up deeper than ideal. It will still germinate.

 

Cover Crop Planning

My book Sustainable Market Farming has a chapter on cover crops and 9 pages of charts about particular options.

The book Managing Cover Crops Profitably (third edition) from the Sustainable Agriculture Research & Education Program (SARE), is the best book I know on the subject. You buy the book or download it as a free PDF from SARE.

Cover Crops in January: The Big Picture

Winter rye and crimson clover cover crop
Photo by McCune Porter

Since May 2023 I have written a post at the beginning of each month about cover crops. In most parts of the US,  January is too late to plant any cover crops, and too early to terminate any  in preparation for sowing(except winter-killed ones!). This is a great time to ponder your cover crop strategies for the coming year, and perhaps plan some changes or tweaks.

I found a great treasure trove of cover crops resources from SARE (Sustainable Agriculture Research and Education). The Resources and Learning tab led me to the Cover Crops Topic and the four page publication Cover Crops for Sustainable Crop Rotations.  

My search for slideshows didn’t immediately turn up the collection I had saved previously, but there is plenty there to usefully inspire you on a rainy day, when you’re all caught up on the accounting and the tool repairs! Or even sooner.

Here’s a compilation of slides I made from SARE’s materials. There are slides on reasons to grow cover crops, some beautiful photos of some good “starter” cover crops, factors to consider when choosing cover crops, information of planting equipment options and opportunities, and several slides of further resources.

Sit back and enjoy the show!

SARE Cover Crops Materials Digest

 

I can also give you to the most recent version I have of my own cover crops slideshow

Cover Crops for Vegetable Growers 2023 60 mins

 

Cover of Managing Cover Crops Profitably book from SARE

Happy New Year , and all the best for a great 2024 growing season!

Cover Crops for December: Planning for Next Year

Our asparagus patch mulched for the winter.
Photo Kathryn Simmons

 

Keeping the Soil Covered all Winter

Don’t plant cover crops in December, unless you live in a warmer place then Zone 7a. Weeds will be our cover crop for the next few months! You can mow the weeds anytime you see lots of flowers and seed heads. For us, it’s usually one mowing in November, then no more until early February.

If you are later than 3-4 weeks past your average first frost date, leave the weeds or crop remains growing. It’s too late to sow a cover crop, and you’ll do more harm than good tilling up the soil.

Having plants growing through the winter, or at least into the winter until they get killed by cold temperatures, will improve your soil both physically (the roots hold the soil in place, preventing erosion, and they open up channels that improve the drainage) and biologically (the soil micro-organisms thrive when they have active plants to cooperate with, exchanging nutrients).

If you are less than 3 weeks past your first frost, see my post Cover Crops for November. It is still worthwhile to sow a few cover crops up to three weeks past your average first frost. If the area is ready for cover crops up to 10 days past the frost date, sow winter wheat or winter rye and hairy vetch or Austrian winter peas. Two or three weeks past your first frost, you could sow winter rye. Winter rye is hardier than any other cover crop and can take later planting dates. If you don’t have winter rye, don’t till! Leave the weeds.

You could mow and tarp, to kill the weeds before spring. I’m not sure what the soil life thinks about that, though!

If you don’t have weeds, but only almost bare soil, and it’s too late to sow cover crops, find some kind of organic mulch. Cardboard weighted down with bricks or rocks is much better than nothing.

Be prepared to act early in spring, so you don’t get weed seeds. You could mow in early spring, or till and sow oats, if you won’t be planting a food crop in the following 8 weeks, giving the oats time to make respectable growth before turning them under.

This rye cover crop is still small in early March, but will soon make rapid growth.
Photo Pam Dawling

Plan Cover Crops for Next Year

Our other cover crop related task is planning for next year, and ordering seeds. See Planning Winter Cover Crops, a post that includes my Short Simple Guide to Winter Cover Crops.

Choosing the “perfect” cover crops can be confusing, but any is better than none, so I encourage you to experiment and keep records, so you can improve your choices each year. It helps to know your average first frost date, and your winter-hardiness zone (the lowest temperature your garden is likely to encounter).

Create a crop rotation for vegetables that includes good cover crops

If you haven’t yet made a plan for next year’s cover crops, a good time to do it is when planning the crop rotation for your vegetables. You can tweak your plan to maximize your cover crop opportunities.

Here’s 5 steps of cover crop planning:

  1. Identify your opportunities for cover crops (When, how long, how warm, crops before and after)
  2. Clarify your cover crop goals for each opportunity (check list of benefits above)
  3. Shortlist suitable cover crops for each situation (consult books and charts)
  4. Make a decision from among the options to match your main goals and some secondary goals
  5. Record your decisions and results, and review for possible changes next year.
Sunn hemp cover crop at Nourishing Acres, North Carolina.
Photo Pam Dawling
Step 1 – Cover crop opportunities
  • In fall after food crops, for the whole winter – the easiest place to start
  • In late winter or early spring, if the area will not be planted with a food crop for 6 weeks or more.
  • In spring, summer or fall, whenever you have 4 weeks or more between one vegetable crop and a later one
  • Undersowing at last cultivation (usually 4 weeks after planting the vegetable crop)
  • To replace a crop failure, smother weeds, make use of the compost you provided for the failed crop.
  • Year-round cover crops (green fallow) if you have a space you will not be using for vegetables in the coming year.
Step 2 – For each opportunity, clarify your cover crop goals

Which cover crop benefits are your main priorities and your secondary goals at that site?

  • Smother weeds, prevent them growing and seeding
  • Add organic matter and nutrients
  • Increase the biological activity in the soil
  • Reduce erosion by using actively growing roots to anchor the soil
  • Improve the tilth of the soil and the sub-soil structure
  • Improve soil drainage
  • Improve the soil’s ability to absorb, hold water
  • Salvage leftover nutrients
  • Fix nitrogen to feed the next crop
  • Attract beneficial insects
  • Bio-fumigation for pest or weed control
Step 3 – Choose cover crops matching your goals
  • Smother weeds: sorghum-sudangrass, pearl millet, winter rye, wheat, barley, oats, buckwheat, brassicas, lupins, red clover, subterranean clover, berseem clover, soybeans, southern peas
  • Add organic matter, improve the soil’s ability to absorb, hold water: bulky grasses and legumes, sorghum-sudangrass, millets, winter rye, velvetbean, southern peas, sweetclover, sunn hemp (Crotalaria)
  • Increase the biological activity in the soil – use varied mixes
  • Reduce erosion: (good roots) grasses especially rye, barley, oats; also sweetclover, southern peas, sub clover,
  • Improve the tilth of the soil, the sub-soil structure, soil drainage: sorghum-sudangrass, sunflower, daikon, sweetclover, crimson clover, alfalfa, lupins, southern peas, forage radish, sugar-beet or forage-beet
  • Scavenge leftover nutrients: (non-leguminous cover crops) grasses, brassicas (pest and rotation problems), annual ryegrass (danger of it becoming a weed)
  • Fix nitrogen: (legumes) clovers, vetches, peas, southern peas, soybeans, lentils, sunn hemp.
  • Attract beneficial insects: (flowers) buckwheat, peas, beans, clovers, brassicas, phacelia, sunn hemp
  • Pest control: rye, brassicas, sorghum-sudan, sunn hemp, white lupins, sesame.
  • Kill nematodes: Pacific Gold mustard, white lupins, Iron and Clay southern peas, OP French marigolds, sesame
Iron and Clay southern peas flowering in September. Photo Pam Dawling
Step 4 – Choose cover crops for the fall and for the summer

Work back from your farm’s first frost date, to see what options you have in the fall. In the summer work with the length of time that plot has before you need it for another food crop.

Here’s my 7 steps of crop planning:

  1. Figure out how much area is needed for each major crop (the ones needing the largest amount of space).
  2. Measure and map the land available
  3. Divide into equal plots big enough for any one of your major crops
  4. Group compatible crops together to fill out each plot not yet housing a major crop
  5. Set a good sequence, maximizing cover crop opportunities
  6. Include best possible cover crops at every opportunity
  7. Try it for one year, then make improvements

For more details, see my slideshow Crop Rotations for Vegetables and Cover Crops on SlideShare.net

Cover Crops for November: Winter Rye and Austrian Winter Peas

Cover Crops for November: Winter Rye (with Austrian Winter Peas early in November)

Winter rye headed up. Mow or turn it under very soon! Don’t let it shed seed.
Photo Pam Dawling

The first half of November is the last chance to sow winter cover crops in central Virginia

Our average first frost is October 14-20. If yours is later, see my post Cover Crops for October. It is still worthwhile to sow a few cover crops up to three weeks past your average first frost, and I’ll tell you about those, with ideas on what to do if your climate is past that point.

If the area is ready for cover crops up to 10 days past the frost date, sow winter wheat or winter rye and hairy vetch or Austrian winter peas.

See Planning Winter Cover Crops, a post that includes my Short Simple Guide to Winter Cover Crops and my slideshow Cover Crops for Vegetable Growers.

Last Chance Cover Crops in November: Rye

Rye grows impressive roots that improve the soil. Kauffman Seeds

Winter rye can still be sown in the mid-Atlantic in the first half of November. Winter rye is the cereal grain rye, not ryegrass. Ryegrass comes in annual and perennial forms, but neither is a good winter cover crop here. They don’t produce as much biomass as cereal rye, and can become weeds in our climate.

Winter rye is hardier than any other cover crop and can take later planting dates. Some people do sow winter wheat in early November rather than winter rye, so if you don’t have rye seed, use wheat. It can be tricky to have the cover crop seed you want, without risking buying more than you need. Sometimes it pays to use what you already have, as it may not give good germination if saved over to next fall.

Winter rye has an allelopathic effect (inhibition of germination) on small seeds, that lasts three weeks or more after rye is turned under. This means you will need to be fairly confident that the weather will allow you to till the rye in with three weeks to go before sowing carrots, spinach or other spring crops with small seeds. Transplants are not affected in the same way. If necessary, reconfigure your crop rotation plan over the winter. Plan for the next food crops after winter rye to be ones planted after late April, such as late corn plantings, winter squash, transplanted watermelon, sweet potatoes, tomatoes, peppers, June-planted potatoes, fall brassicas, and second plantings of summer squash, cucumbers, beans.

A field of winter rye with a strip of crimson clover in early May.
Photo Bridget Aleshire

Other key features of winter rye cover crop

  • Rye grows 5′-7′ (1.5-2.1 m) tall.
  • Mow-kills at flowering, but not earlier.
  • Suppresses weeds (especially lambsquarters, redroot pigweed, ragweed).
  • Adds lots of organic matter if grown to full size.
  • Improves the soil’s ability to absorb and store water.
  • The roots hold the soil together and greatly reduce erosion.
  • Can be used to scavenge nutrients left over from a previous legume crop or to hold onto nutrients applied for a crop that failed.
  • Sow from 14 days before to 28 days after first fall frost.
  • Don’t sow before September in zone 7 – it may set seed.
  • Rye makes little growth in mid-winter, but very good growth once spring arrives.
  • Rye can be sown in the spring, although when incorporated, oats break down quicker.
  • Can be undersown in sweet corn or in fall brassicas in early September, and left as a winter cover crop.
Cover crop of rye and winter peas with flowering crimson clover. Photo Bridget Aleshire.

Include Austrian Winter Peas if possible in the first week of November

See my September post for more about the benefits of including legumes with winter cover crops grasses. Also how to inoculate legume seeds with the nitrogen-fixing bacteria. Austrian winter peas can be sown later than other legumes. See my October post for more about those. See Working with the time you have left for options if you are in another climate zone.

A key to success with legumes is to sow early enough in fall to establish before winter halts growth, and to plan not to need that plot next year until flowering time for that legume. Austrian winter peas bloom here at the end of April (about a week later than crimson clover, and a week earlier than hairy vetch). (If you have a legume that doesn’t reach flowering, you get less nitrogen for your money, and will need to add some compost or other source for the following food crop.) Suitable crops for following Austrian winter peas are ones planted after May 1: winter squash, melons, sweet potatoes, tomatoes, peppers, middle sowings of sweet corn, June-planted potatoes. This is pretty much the same list as crops that can be planted after winter rye.

Austrian winter peas
Photo https://www.uaex.edu

October 15 (our average frost date) is our clover/peas watershed (legume-shed?). Before that date we use crimson clover; after it (until 11/8, 3 weeks after our average frost date) we sow Austrian Winter Peas, along with winter rye or winter wheat.

Austrian winter peas winter-kill in zone 6, but are hardy in zone 7. Hardy to 0°F (-18°C). Sow Austrian winter peas at least 35 days before first hard freeze (25°F/-4°C) – in zone 7, that’s a 50% chance on 11/8. See Weatherspark.com for info on your location, or Dave’s Garden.

Last Chance cover crop

In the second week of November, we sow winter rye alone as our last chance cover crop. It is too late for any legumes.

Grain seed will store OK for the next year, but peas and beans really lose viability fast. If you still have Austrian winter pea seed from last year, I’d say throw it in this November rather than keep it for a third year, even if you are past the usual date. Germination rate goes down to 50% after a couple of years, and the plants won’t be sturdy.

Barbara Pleasant tells us two other ways cover crops can improve soil: Rhizodeposition and bio-drilling.

Rhizodeposition is a process whereby plants release sugars and other substances through their roots. The root tips host colonies of helpful microorganisms that go deeper as the roots grow deeper.  For rye, this depth can reach 6 feet (2 m)!

Bio-drilling is what happens when cover crop roots “drill” into compacted subsoil. Oilseed and daikon radishes are cover crops famous for this action. The roots push deep into tight subsoil. Bio-drilling also happens when deeply rooted cover crops penetrate the subsoil and then die. With winter rye this can happen when the headed-up rye is mowed close to the ground in spring, or the rye is tilled into the top soil, severing the roots below till level. The next crop can follow the root channels made by the cover crop. This gives access to nutrients (including dead roots and microbes) left behind by the cover crop.

How to protect the soil over the winter if it is too late for cover crops

Carrot harvest cart. Our Danvers carrots have plenty of sturdy leaves to protect the soil over winter. Photo Mari Korsbrekke

Sowing cover crops too late means you don’t get enough growth in the fall, and the soil is not adequately protected from erosion or from weed growth over the winter. Try really hard not to leave bare soil over the winter.

If it’s too late to sow cover crops, but you do have a healthy growth of weeds, mow them at the beginning of November and then leave everything alone until early spring. The weed roots will hold the soil together and the above-ground growth will protect the soil from heavy rain. Having live plants will provide food for the microbial life in the soil.

If you don’t have weeds, but only almost bare soil, and it’s too late to sow cover crops, find some kind of organic mulch to cover the soil. When we harvest our storage carrots in November, we return the cut tops to the soil surface. Another seasonal option is tree leaves (sometimes conveniently left in bags by the curb). Best to ask the “owners” before lifting them. Other ideas include straw or hay. Woodchips or sawdust will work for winter protection, but don’t till them in when spring arrives. Rake them off and compost them nearby. If turned under, they use up a lot of nitrogen decomposing, and your crops will be starved.

More resources on cover crops

My book Sustainable Market Farming has a chapter on cover crops and many pages of charts about particular options.

Cover of Managing Cover Crops Profitably book from SARE

The book Managing Cover Crops Profitably (third edition) from the Sustainable Agriculture Research & Education Program (SARE), is the best book I know on the subject. You buy the book for $19 or download it as a free PDF from SARE.

Cover Crops for October: Winter Wheat and Austrian Winter Peas

Austrian Winter Peas

Focus Cover Crops for October: Winter Wheat and Austrian Winter Peas

In August I wrote about cover crops such as millets, southern peas, buckwheat which are frost-killed. For most of us in the mid-Atlantic, it’s too late for those.

October is too late to sow winter-killed cover crops in central Virginia

Our average first frost is October 14-20. If yours is later, and you still have 40-60 days to your average first frost, you can still sow oats to winter-kill. If possible add a legume (soy and spring peas are easy, and will be killed by the frost, so they won’t complicate food crops next year). For us, the cut-off date for oats is September 15 if we really push it. Sowing too late means you don’t get enough growth in the fall, and the soil is not adequately protected from erosion or from weed growth.

Oats winterkill completely at 6°F (-17°C) or three nights at 20°F (-7°C. Fall-sown barley (Hordeum vulgare), grows even faster than oats, and dies at 17°F (-8°C).

There are still three weeks here when it is worthwhile to sow cover crops (up to a month past first frost), and I’m going to write about those here.

See Planning Winter Cover Crops, a post that includes my Short Simple Guide to Winter Cover Crops and my slideshow Cover Crops for Vegetable Growers. Oats, barley, wheat and rye sown too early can head up and seed before you get to winter, making them less useful, and more of a weed problem. Once we’ve reached mid-October, this is no longer an issue here.

Winter rye cover crop headed up in early May.
Photo Pam Dawling

Winter-hardy grass cover crops to sow in October

Winter rye and winter wheat can be sown in the mid-Atlantic in October. Wheat has less of an allelopathic effect on small seeds, the inhibition of germination that lasts three weeks after rye is turned under. Wheat doesn’t produce as much biomass as rye, so there’s the tradeoff. We sow wheat if the area is ready for cover crops 20-40 days before frost, allowing us to make faster use of those plots in the spring, compared to plots sown to rye.

Winter wheat prevents erosion, suppresses weeds, scavenges excess nutrients, adds organic matter, encourages helpful soil microorganisms, and the fine root system improves the tilth. It is less likely than barley or rye to become a weed; easier to kill than barley or rye; cheaper than rye; easier to manage in spring than rye (less bulk, slower to go to seed); tolerates poorly drained, heavier soils better than barley or oats.

The challenges of wheat are that it does not have good tolerance of flooding, and is a little more susceptible than rye or oats to insects and disease.

For us wheat is a good, trouble-free winter cover crop. The later it gets towards our cover crop cutoff date of November 15, the more likely we are to choose rye. Also, of course, if we have already used all our wheat seed! Winter rye is hardier than any other cover crop and can take later planting dates. More about Last Chance Cover Crop next month. Then I will also write about how to protect the soil over the winter if it is bare.

Austrian Winter Peas graphic

 

 

Secondary cover crops in October: Include legumes where possible

See my September post for more about the benefits of including legumes with winter cover crops grasses. Also how to inoculate legume seeds with the nitrogen-fixing bacteria. See Working with the time you have left for options if you are in another climate zone.

Another key to success with fall sown legumes is to sow early enough to establish before winter halts growth, and to plan not to need that plot next year until flowering time for that legume. If you have a legume that doesn’t reach flowering, it’s not the end of the world, you just get less nitrogen for your money, and won’t be able to supply all the N needs of the following food crop. Crimson clover flowers in central Virginia 4/16-5/2, most usually around 4/20. Austrian winter peas bloom at the end of April, and hairy vetch in early May.

October 15 (our average frost date) is our clover/peas watershed (legume-shed?). Before that date we use crimson clover; after it (until 11/8, 3 weeks after our average frost date) we sow Austrian Winter Peas, along with winter rye or winter wheat.

Austrian Winter Peas. Photo UAEX Edufarm Ranch Resource Library

More about Austrian winter peas

Austrian winter peas can be sown later than other legumes.

  • Hardy type of Field Pea. (Black peas)
  • Winter-kill in zone 6, hardy in zone 7. Hardy to 0°F (-18°C). (Canadian/spring field peas are hardy to 10-20°F (-12° to -7°C))
  • Can sow several weeks later than clovers
  • Sow at least 35 days before first hard freeze (25°F/-4°C). In zone 7a, 8/10–11/8
  • Optimum temperature for germination is 75°F (24°C), minimum germination temperature 41°F (5°C)
  • Good at emerging through crusted soil
  • Tolerate a wide range of soil types
  • Make rapid spring growth in cool weather
  • Suppress weeds, prevent erosion
  • High N-fixers – a good stand can provide enough N for the following food crop when incorporated
  • They fix as much, or more, nitrogen than crimson clover
  • More dry matter than hairy vetch (which produces more than crimson clover) in the SE
  • Can be mixed with grasses for vertical support, more biomass and better weed suppression
  • Suppresses Septoria leaf spot in tomato crops the next year
  • Blooms late April at Twin Oaks, before hairy vetch
  • Flowers attract beneficial insects (especially honeybees) and reduce aphids
  • The tendrils and shoot tips make a nice addition to salads or stir-fries in early spring
Winter rye with Austrian Winter Peas. Photo Cindy Conner

Cautions with Austrian winter peas

  • Pea seed cannot be stored long. The germination rate could be only 50% after 2 years. Run a germination test if you have seed you are unsure about.
  • Seeds are large and heavy – high sowing rates (compared to clovers). Cost/area is fairly high, a little higher than vetches
  • If you haven’t grown peas or beans on that plot for some years, inoculate the seed.
  • Winter-killed in zone 6, at 0°F (-18°C). For the best chance of winter survival in cold areas, choose your sowing date to get plants 6-8″ (15-20 cm) tall before the soil freezes. (Hairy vetch is more cold-tolerant than AWP.)
  • Sowing in a mix with a winter grain will improve cold weather survival by reducing soil freezing and heaving.
  • May not do well if sown in spring – require a cold dormant spell.
  • Not tolerant of flooding, drought, high traffic, salinity, heavy shade, long cold spring weather below 18°F (-8°C) with no snow cover, or hot (or even warm) weather.
  • Do not regrow after mowing or grazing once blooming starts.
  • Peas on their own do not add much organic matter to the soil – the vines break down quickly.
  • May increase 39 species of pest nematodes, so if you are already having trouble with those, this is not a good cover crop for you.
  • Susceptible to Sclerotinia crown rot, which can completely destroy crops during winter in the mid-Atlantic. One reason not to grow pea crops on the same land two years running.
  • Can also be host to Sclerotinia minor, Fusarium root rot and Ascochyta
Cover of Managing Cover Crops Profitably book from SARE

More resources on Cover Crops

My book Sustainable Market Farming has a chapter on cover crops and many pages of charts about particular options.

The book Managing Cover Crops Profitably (third edition) from the Sustainable Agriculture Research & Education Program (SARE), is the best book I know on the subject. You buy the book for $19 or download it as a free PDF from SARE.