Tag: undersowing cover crops

Cover crops for August: Oats and Barley

From the USDA Barley Plant Guide

Note: I edited this post in September when I found I was mistaken in believing barley was less cold-hardy than oats.

Focus Cover Crops for August: Oats, barley and other winter-killed cover crops

In August we are looking ahead, thinking about how our cover crops will be impacted by future cold weather. In July I wrote about hot weather grass cover crops, including Sorghum-Sudan hybrid (Sudex), and the millets, which are not frost-hardy.

German/Foxtail and Japanese millets are day-length sensitive. Growth is considerably less if they are sown after the summer solstice, so they are likely to be of limited use as cover crops once we reach August.

Browntop Millet could be useful in August in the mid-Atlantic. Proso/Broomcorn Millet I’m not so sure about. Pearl/ Cattail Millet is not day-length sensitive. To winter-kill and avoid seed formation, sow 60-85 days before your expected first frost.

See Working with the time you have left in the post Cover Crops in Summer. See No-Till summer cover crops in that same post (Soy, southern peas, foxtail millet). Also there, see Five Easy Summer Cover Crops that Die with the Frost (buckwheat, sorghum-sudan grass, soybeans, southern peas and sunn hemp.)

Buckwheat cover crop in flower.
Photo Pam Dawling

Buckwheat can be sown up to 28 days before the first frost.  See my article about buckwheat. Soybeans can be sown up to 45 days before frost. A mix of sunn hemp, soybeans or southern peas and other frost-tender cover crops can be grown during August (60-80 days before frost) before planting garlic in mid-fall. This method will work more easily if you mow the cover crop around your frost date, so that it is easier to make furrows in the soil. Forage radish, lab-lab beans or bell beans sown now will die back and leave almost bare soil. This is a boon for the very earliest spring transplants or sowings.

Or, instead of sowing a cover crop now, you could sow a fast-growing vegetable crop. Kale, spinach, Tokyo bekana, radishes, chard, lots of salad crops, senposai, mizuna, tatsoi, or land cress. Try Eat-All Greens, an idea form 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.

Twin Oaks Eat-All Greens on October 19.
Photo Bridget Aleshire

Winter-killed, not frost-killed, cover crops

In August, we can sow winter cover crops to be winter-killed for easy soil cultivation before early spring vegetables. Oats and barley are in this category. Oats will be killed by three nights of 20°F (-7°C) or a single night of  6°F (-14°C). Sow oats 5-8 weeks before your average first frost to get good size plants before they get winter-killed. We sow in late August and early September in Zone 7a. See Cover Cropping Your Garden by Chris Blanchard in 2002:

“Inexpensive and easy to grow, oats are a standard early fall cover crop in the northern and middle sections of North America.  A quick-growing, non-spreading grass, oats will reliably die in Hardiness Zone 6 and colder, and often in zone 7.”

It used to be nine years out of ten, here in Louisa County, VA, but our climate is shifting to be too warm in winter to reliably kill oats. This past winter (2022/2023) oats did not die. They were cold-damaged, and set back, but definitely not dead.

We can no longer rely on our winter cover crop oats getting winter-killed. March photo by Pam Dawling

Fall-sown Barley (Hordeum vulgare), grows even faster than oats, although not as fast as winter rye, and it won’t die as early in the winter as oats. Barley dies at 17°F (-8°C). It usually will die in Zone 7 and colder regions. The dead barley residue protects the soil through the winter, and dries into what Barbara Pleasant calls “a plant-through mulch” in spring in cold zones.

See Planning Winter Cover Crops. If the area has been fully harvested of food crops by 60-80 days before frost, sow a frost-killed cover crop or even a fast-growing food crop.  In central Virginia, it’s a mistake to sow rye as early as August, as it can set seed.

Winter-hardy cover crops to sow in August

Not all winter cover crops can be sown as early as August in the mid-Atlantic. Don’t sow winter rye, or it may head up before winter and drop seeds. Only sow oats or barley if you are sure you can get them turned under or killed by cold winter weather before they seed. They will not mow-kill. Be careful buying feed-grade seeds (rather than seed-grade), as they can contain weed seeds including GMO canola.

Clovers can be sown in August (provided you can supply enough overhead irrigation). September is a better time to sow clovers here, if you are sowing them in bare ground. They will make some growth in our climate before winter, and then a lot more once spring arrives.

Secondary Cover Crops in August: Undersowing for more cover crops

  • Choose vigorous food crops, but cover crops that are only moderately vigorous.
  • Timing is critical: Sow the cover crop late enough to minimize competition with the food crop, but early enough so it gets enough light to grow enough to endure foot traffic when the food crop is harvested. Often the best time is at the last cultivation.
  • The leaf canopy of the food crop should not yet be closed. With vining food crops, sow the cover crop before the vines run.
  • Ensure a good seedbed and a high seeding rate.
  • Irrigate sufficiently. The food crop will have good roots by then, but the cover crop seed will be just below the surface and will need some help to germinate.

 Green fallow (Full year cover crops)

Fall broccoli undersown with a mixed clover winter cover crop.
Photo Nina Gentle.
  • Our main use of clovers is to undersow fall brassicas such as broccoli and cabbage, with a mix of Crimson clover, white clover and medium red clover in August, to form a green fallow crop (all-year cover crop) for the following year, replenishing the soil and reducing annual weeds.
  • 2 weeks after transplanting the brassicas (August), we hoe and till between the rows, or wheelhoe.
  • We repeat at 4 weeks after transplanting, and broadcast a mix of clovers (late August-early September): 1 oz (30 g) Crimson clover, 1 oz (30 g) Ladino white clover and 2 oz (60 g) Medium red clover per 100 sq ft (9 m2)
  • In March, we bush hog the old brassica stumps and let the clovers flourish, mowing once a month to prevent the crimson clover and the annual weeds from seeding.

See my Mother Earth News post: Late summer and fall intercropping of cover crops in vegetable crops, aka undersowing.

If you have difficulty getting even coverage when broadcasting clovers or other cover crop seeds, try seeding half the crop walking in one direction, and then seed perpendicularly across your original path

In mid-August, we undersow our last sweet corn planting with oats and soybeans, as the winter cover crop, which winter-kills, leaving a plot that is easily worked up next spring. Our 6th sweet corn is sown 7/16. 4 weeks after seeding, we cultivate and sow oats and soy. In mid-March we follow with our spring potatoes. Both oats and soybeans have some tolerance for shade and for foot traffic (harvesting corn!).

Late season sweet corn undersown with oats and soy
Photo Kathryn Simmons

Sweet corn can be undersown with clover rather than soy or oats in some climates. We tried clover but found it harder to germinate in hot weather, and harder to keep the tiny seed damp. Buckwheat can be undersown in corn as a short term summer cover, but according to Sue Ellen Johnson, (co-editor of Crop Rotation On Organic Farms: a planning manual, it grows rather straggly in the shade of the corn. Soy has the advantages of tolerating shade as well as foot traffic.

We tried an idea from NY State, or undersowing winter squash with buckwheat and tilling it under just before the vines run (that was June), but here in the south, the vines ran too fast. We ended up having to wade in among the vines to pull up the buckwheat by hand!

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. On a small scale, you can sow by hand, either broadcasting and raking in, or in close rows using a hoe, as if sowing

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 for $19 or download it as a free PDF from SARE.

Planning Winter Cover Crops

 

A cover crop mix of winter rye, hairy vetch, Austrian winter peas and crimson clover.
Photo Bridget Aleshire

If you haven’t already made a plan for winter cover crops, this is a good time to do it. 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 microorganisms thrive when they have active plants to cooperate with, exchanging nutrients). Cover crops will also reduce the number of weeds you have next year, because they crowd out weed seedlings. In some cases they even inhibit weed seeds from germinating.

I have some slideshows about cover crops, and am including one at the end of this post.

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 first frost date, and your winter-hardiness zone (the lowest temperature your garden is likely to encounter). A two-week delay in sowing can seriously reduce the effectiveness of the cover crop, so follow these guidelines if you can.

A cover crop of overwintered oats the year they didn’t die.
Photo Pam Dawling

Short Simple Guide to Winter Cover Crops

  1. If the area has been fully harvested of food crops by 60-80 days before frost, sow a frost-killed cover crop or even a fast-growing food crop. Buckwheat, soy, cowpeas, spring peas, sunnhemp, Japanese millet, sorghum-sudangrass will frost-kill. Forage radish lab-lab bean or bell beans will die back and leave almost bare soil. Don’t sow a winter cover crop yet. If sown too early, oats head up in the fall and even drop seed.
  2. If the area is clear of vegetable crops by 40-60 days before frost, 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 with a first frost date of October 14, the cut-off date for oats is September 7. This would be after growing early sweet corn, spring broccoli, cabbage, spring-planted potatoes or early season spinach, lettuce, beets, carrots. Oats will winterkill completely at 6°F (-17°C) or even milder than that, leaving the plot quick to prepare for early crops next year. So plan to put your early crops where you had oats in the winter. See the slideshow for more about oats.

    Crimson clover cover crop in flower.
    Photo McCune Porter
  3. If the area is ready for cover crops 20-40 days before frost, sow winter wheat. Add a legume such as crimson clover, if you won’t need to prepare the area before it flowers (in central Virginia 4/16-5/2, most usually around 4/20). You get the most nitrogen from the legumes if they reach the flowering stage before you kill them off in spring. 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. It is too late to usefully sow cover crops that are not frost-hardy, or even oats, which won’t make enough growth before getting killed.

    Cover crop of winter rye, hairy vetch and crimson clover.
    Photo Kathryn Simmons
  4. 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. Winter rye is hardier than any other cover crop and can take later planting dates. But it is a bit harder than wheat to incorporate in the spring. Austrian winter peas can be sown later than other legumes.
  5. If you are up to 3-4 weeks past your average frost date, (we choose November 7 here, where our average first frost is October 14), sow winter rye alone. It’s too late for any legumes.

    Cover crop of winter rye still small in March, but holding the soil together.
    Photo Pam Dawling
  6. 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. You can mow the weeds anytime you see lots of flowers and seed heads. The weed roots will hold the soil together and help feed the soil microorganisms until early spring. Be prepared to act soon in spring, so you don’t get weed seeds.
Quick Guide to Winter Cover Crops.
Pam Dawling

More Options for Each of These Time-frames

  1. 60-80 days before frost: You could follow a frost-tender cover crop with an over-wintering cover crop, for best effect. If you leave the dead tender cover crops in place, in early spring the winter weeds will start growing in the open space, so be ready for fast action. For the very earliest spring crops, forage radish lab-lab bean or bell beans will die back and leave almost bare soil. While still 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.
  2. 40-60 days before frost: Austrian winter peas, crimson clover, or red clover are other options for legumes, but they won’t die when the oats do. They are relatively easy to incorporate in spring. Frost-killed cover crops can also be combined with oats. Or for a cover crop to survive the winter, sow winter barley or winter wheat with Austrian winter peas, crimson clover, hairy vetch, red clover, fava beans. Hairy vetch takes a few weeks longer than crimson clover to reach flowering. Which you choose will depend what you want to grow there next spring and when you need to plant it. After oats or other winter-killed cover crop, we like to plant our early spring food crops, peas, cabbage, broccoli, carrots, March-planted potatoes, spinach and the first sweet corn.

    Cover crop height and thickness in late April.
    Photo Kathryn Simmons
  3. 20-40 days before frost: Winter rye, or winter barley are also options for the cereal grain part of the mix, if you have those seeds on hand. In central Virginia, it’s a mistake to sow rye as early as August, as it can set seed. Austrian winter peas, or red clover are other legume options if that’s what you have. Sometimes it pays to use what you already have, as it may not give good germination if saved over to next fall. Winter rye needs 3-4 weeks after tilling in, in spring, to break down and to disarm the allelopathic compounds that stop small seeds germinating. Plan for the next food crops to be ones planted after late April, such as late corn plantings, winter squash, transplanted watermelon, tomatoes, peppers, sweet potatoes, June-planted potatoes, fall brassicas, and second plantings of summer squash, cucumbers, beans.
  4. Up to 10 days past the frost date: it’s too late for clovers. Austrian winter peas winter-kill in zone 6, but are hardy in zone 7. Hardy to 0°F (-18°C). AWP bloom in late April at Twin Oaks, before hairy vetch. Suitable crops in the year before using Austrian winter peas are the late-finishing winter squash, melons, sweet potatoes, tomatoes, peppers, middle sweet corn, June-planted potatoes. The same group of crops are suitable for following AWP, as they are planted after May 1. You can sow AWP several weeks later than clovers, but at least 35 days before first hard freeze (25°F/-4°C) – in zone 7, 8/10–10/24 (11/8 is sometimes OK)

    Winter rye headed up. Mow or turn it under very soon! Don’t let it shed seed.
    Photo Pam Dawling
  5. Up to 3-4 weeks past your average frost date: no really, it’s too late for any other cover crop. If you don’t have winter rye, don’t till! Leave the weeds, see below.
  6. Later than 3-4 weeks past your average first frost date: no, really, do not till! You could mow and tarp, to kill the weeds before spring. I’m not sure what the soil life thinks about that, though! You could mow again 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.

Create a crop rotation for vegetables that includes good cover crops

If you include winter cover crops when planning a crop rotation for your vegetables, you can tweak your plan to maximize your cover crop opportunities. Here’s the steps:

 Figure out how much area is needed for each major crop (the ones needing the largest amount of space).

  1. Measure and map the space available
  2. Divide into equal plots big enough for your major crops
  3. Group compatible crops together to fill out each plot
  4. Set a good sequence, maximizing cover crop opportunities
  5. Include best possible cover crops at every opportunity
  6. Try it for one year, then make improvements

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

Advanced Options for Winter Cover Crops

Sweet corn with undersown soybean cover crop. Photo Kathryn Simmons

Undersowing

Sometimes you can undersow the cover crop between the rows of a growing food crop, to take over after the food crop dies of frost or mowing. We do this with our last planting of sweet corn, and with fall broccoli and cabbage.

Timing is critical: Sow the cover crop late enough to minimize competition with the food crop, but early enough so it gets enough light to grow enough to endure foot traffic when the food crop is harvested. The leaf canopy of the food crop should not yet be closed. Often the best time is at the last cultivation, often about a month after planting the food crop. With vining food crops, it’s important to sow the cover crop before the vines run.

Choose vigorous food crops, but cover crops that are only moderately vigorous. Ensure the seedbed is clean and the soil crumbs small enough. Use a high seeding rate, whether broadcasting or drilling, and irrigate sufficiently.

A no-till cover crop mix of winter rye, hairy vetch, Austrian winter peas and clover.
Photo Bridget Aleshire

No-till Winter Cover Crops

In the spring, kill the cover crop without tilling it in, and plant food crops into the dying residue. There are three ways to kill cover crops without herbicides:

  1. Winter-killed cover crops for early spring food crops
  2. Mow-killed cover crops.
  3. Roll-killing (but it usually requires special equipment).

We have had one year in 10 as a no-till year. We use no-till cover crops before 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. The soil under no-till cover crops stays colder than tilled soil, slowing the plant growth down.

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.

To be an effective mulch, you need to get a thick sturdy stand of cover crops, which means sowing in plenty of time, and being generous with the seed. To make the timing work, you need a previous food crop that finishes before the sowing date 4-5 weeks before the average frost (that’s September 7-14 for us).

Timing is also critical in the spring. For maximum N, the legumes in the mix will be flowering right when you need to plant the food crop. Mow the cover crop mix close to the ground, and plant right into the stubble. Transplants or big seeded crops work well. The ground will be relatively hard – you probably can’t make a furrow for small seeds).

It’s not all over with the weed-prevention after that. In our humid climate the no-till mulch biodegrades after 6-10 weeks. In July we roll hay between the rows, to top up the mulch.

Cover Crops for Vegetable Growers 2019 60 mins

Summer Reading: Mother Earth News, Organic Broadcaster, Finding a Place to Grow

Fall broccoli undersown with a mixed clover cover crop. Photo Nina Gentle.
Fall broccoli undersown with a mixed clover cover crop.
Photo Nina Gentle.

Here’s some leads to some summer reading on gardening and farming. First, my blog post on the Mother Earth News Organic Gardening blog. It’s my third post in a series about intercropping (planting a second crop around or beside a first, to take over after the first crop finishes. In this case, I’m writing about undersowing cover crops in vegetable crops.  We like to undersow our fall broccoli and cabbage about 4 weeks after transplanting, with a mix of crimson clover, medium red clover and Ladino white clover. First we remove the rowcover or ProtekNet we have been using to keep the bugs off the crops, then cultivate with our BCS tiller or our Valley Oak wheelhoe. And hand hoes in the row. Then we broadcast the clover and hope for rain. (Huh! We’ve had plenty so far this summer!). If no rain, we use overhead sprinklers every other night for a week.

The MEN blogpost includes other examples, advantages, challenges and so on.

 

broadcasterlogowebI just received the July/August edition of the Organic Broadcaster. Good thoughtful articles on keeping organic livestock healthy; why organic certification doesn’t have the same attractiveness it once had and what can be done to re-energize enthusiasm for the guarantees that certified organic brings; inspiring stories of mentors who are contenders for the MOSES Organic Farmer of the Year award; advice about getting crop hail insurance; dealing with pesticide drift, using mob grazing of cattle; strengthening the bonds between women farmers by holding potlucks; a review of Jean-Martin Fortier’s The Market Gardener; news about an open-source network of seed growers, plant breeders and researchers; an article about how climate change is impacting agriculture and lots of news snippets about resources, opportunities, reports, and tools for organic farmers; classified ads (bargains!),and an events calendar. This paper is free, in either the electronic or the paper format. It’s based in the Mid-west, with information relevant to us all.

R1IsO4E6fviHqxAg8gx8rIJ42tz3oOygTkNRzqXDhapu5gfQta-a7McKdqgJEFZDDTtYP-F9DxxOKJEbHn5ymsHdGn-CCdiW=s0-d-e1-ftI recently heard from the Piedmont Environmental Council about a publication containing  eight stories of beginning farmers and landowners working together to craft affordable leases that enable committed new farmers to establish themselves in farming, and landowners to put land they are not using into good hands. You can read the stories online or Download the PDF.

Finding a Place to Grow: How the Next Generation is Gaining Access to Farmland.

land_leasing_stories_web_banner_2000xThe biggest hurdle for beginning farmers is usually finding land they can afford. This publication encourages us to think more broadly about what might be possible. The eight stories include

  • land slated for housing development that became instead an incubator farm for half a dozen small farming enterprises (Each tenant negotiates his or her own rent with the landowner, maybe starting out with a reduced rate and building up to what is affordable and realistic as the business grows);
  • another new farm is building up their herd by leasing cattle to make full use of the acreage, until they can afford to own their own big herd;
  • others leased form like-minded farmers who needed to take a break from the intensity of full-time farming;
  • others farm on a public nature preserve owned by a non-profit (as part of the deal, the farmers serve as caretakers for the property, keeping the paths cleared for visitors);
  • another started by using family land that had not been actively farmed, then added leases on neighbors’ lands to expand the farm;
  • Waterpenny Farm has been the model and the training ground for many new farmers (they started their lease by paying the landowner in sweat equity, restoring a house);
  • another leaser points out the advantages of having like-minded people around, and a landowner who wants them to succeed;
  • and finally there’s the story of Willowsford, a planned neighborhood including a working farm to grow food for the development’s residents and others.

So, if you or your friends are hoping to start in farming but can’t afford to buy land, here are ways to farm without ownership – although still with commitment, hard work, variable weather and all the ups and downs of dealing with real live plants or animals.