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!

Stale seedbeds, triage farming, vertical farming

This week I have for you several sources of information related to small-scale sustainable farming.

Hoe the small weeds in this bed of young lettuce soon, and the closing canopy of the lettuce will shade out most weeds after that. Photo Bridget Aleshire

Triage Farming

Growing for Market has posted Triage Farming by Matt S. as a free article on their website

Matt tells of becoming farm manager on a new piece of land, with terrible drainage problems and lots of grass weeds.

“There are five spheres in which a farm can be challenged. Most farms deal with serious disadvantages in one or two of these. We were handicapped in four.” The five are location challenges, site challenges, infrastructure and equipment challenges, institutional challenges (dealing with the bureaucracies), human challenges. They didn’t have human challenges!

As a response to kicking around dried mud-balls full of grass bristles, Matt invented Triage Farming. Triage (from the French trier ‘separate out’) was a concept that came into wider use during WW1 as medics had to sort injured soldiers into three groups: those that would be OK without treatment really soon, those that were going to die whether they had treatment or not, and those who would get the most value from immediate treatment. In farming it means prioritizing using your limited resources to their maximum effect when it’s impossible to accomplish all you hoped to do.

This is not a sustainable way to farm (or live). It’s a way to preserve sanity and be most effective when things have got out-of-control. It doesn’t leave a feeling of satisfaction. But nor a feeling of despair. It can be ruthless, sloppy and minimalist.

Maybe you have never had such moments, but I have. If you have, then I recommend this article. Keep a copy handy, especially in the heat of the summer. You’ll likely not agree with every decision Matt made, but the article will help you raise your head and look around, rather than keep pushing on the task at the top of the schedule you made back in January.

Matt helps with deciding which crops to grow, and how much, if you know it’s likely to be a difficult year (new site, brand new crew, etc). He works through each of the five challenge spheres he identified and explains his response to that aspect: suitable crops for different location challenges, suitable equipment, approaches to weeding (timely, untimely, and “carnage weeding”), tools and equipment for different situations, dealing with various bureaucracies, and how to delegate to other workers.

Matt has an uplifting style, which also helps when the going gets tough.

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False and Stale Seedbeds

Future Farming Center Banner

I just read a very clear 25-page publication about using false seedbeds and stale seedbeds, including flaming. False and Stale Seedbeds: The most effective non-chemical weed management tools for cropping and pasture establishment. Dr Charles N Merfield, 2013. Lincoln, New Zealand: The BHU Future Farming Centre www.bhu.org.nz/future-farming-centre

Screenshot 2023-07-31 at 13-45-27 False-and-stale-seedbeds–the-most-effective-non-chemical-weed-management-tools-for-cropping-and-pasture-establishment-2015-ffc-merfield.pdf

“False and stale seedbeds are based on three rules:

  1. most weed seeds are dormant,
  2. tillage is the most effective means of germinating weed seeds, and
  3. most weeds only emerge from the top 5 cm / 2” of soil.
  • Both false and stale seedbeds work by the very simple process of germinating the weeds then killing them and then growing the crop.
  • False seedbeds use tillage/cultivation to kill the weeds.
  • Stale seedbeds use thermal weeders or herbicides to kill the weeds.”

Both false and stale seedbeds are made by preparing the bed 7-10 days before you plan to sow your crop, watering if the conditions are dry, then killing the carpet of emerged weeds, by very shallow tilling, hoeing or flaming. Getting the tillage correct is critical, including having a good weather-eye. Flaming will kill broad-leaved weeds, but only set grasses back by about a week. Alternatively, cover the prepared bed with a tarp to germinate and kill the weeds.

The 5-15% of weed seeds that are non-dormant are mostly in the top 5 cm/2” of the soil, and germinate very quickly. These can be very effective techniques, and this publication explains them well, and has good photos of crops, and machines such as the milling bedformer and the roller undercutter, and some fancy flamers and steam weeders, which might be equipment to aspire to, while working with spring tine weeders and shallow tillage. The explanations help with getting a better understanding of weeds seed germination, and so how to succeed with pre-plant tillage and post-crop-emergence cultivation. Timing is important, as is having the right tools for the job.

There’s also a good relevant article in Growing for Market:

Tools and strategies to reduce time spent weeding by Sam Hitchcock Tilton

Definitely read this if you are spending a lot of time weeding, or your crops are over-run by weeds. Work towards reducing your weed population each year, by preventing weeds from seeding. “Realize that one lamb’s-quarters or kochia or bindweed or galinsoga plant going to seed can be a much bigger problem next year than 10 or even 100 non-reproducing plants are now. So marshal your precious weeding resources smartly.”

Timely hoeing, while weeds are tiny and quick to die, can prevent the need for pulling weeds by hand, if you are working on a quite small scale. If your scale needs other tools, here you can learn about equipment to physically control weeds as part of your cropping system. If you are using a 4-wheel tractor, consider hillers, mini-ridgers, finger-weeders, Spyders, beet knives (L-blades), tine weeders, basket weeders.

A Thiessen walk-behind tractor cultivator, with Spyders up front, with the front of the Spyder angled towards the crop row (to pull soil away from the row), and torsion weeders at the back to weed in the crop row.

The article includes some equipment for 2-wheel walk-behind tractors, such as the Thiesson cultivator, Buddingh and Tilmor basket weeders, Even wheel hoes have weeding attachments.

Sam also describes stale seed-bedding, and advises rolling the prepared bed before tarping or watering, to provide the weed seeds good contact with the soil.

Sam’s article includes excellent photos, a tailored-for-beginners’ explanation of which tool does what and many links to other website and videos.

As Ben Hartman points out in The Lean Farm, hand-weeding is in a sign of failure to act sooner, that has led to a time-wasting scramble to correct the situation. read my review of The Lean Farm.

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Here’s an article from USDA on Killing the Crop Killers—Organically

As an alternative to bromide fumigation to kill pest nematodes, and other pests, try anaerobic soil disinfestation (ASD), an organic treatment that temporarily removes oxygen from the soil, is inexpensive and easy to apply. This method involves using a source of carbon, such as orchard grass, or mustard seed meal, tilled into the soil


Lean Times Hit the Vertical Farming Business.

Vertical farming is a code for a type of high tech hydroponics. See this article on the BBC website. Yes, hydroponics uses a large amount of energy to grow the plants. Yes, growing plants takes skill and attention. Yes, growing only a few crops is risky: people will only eat so much lettuce. Aerofarms has filed for bankruptcy, and several other “vertical farming operations” have hit financial troubles too.

Balance that with this post by Lee Rinehart from ATTRA:

Real Organic: Reflections on “The Deep Roots of Organic in Soil” by Paul Muller.

Soil is complex, with a universe of microorganisms, and cycles of carbon, nitrogen, hydrogen and many other elements. Farmers are part of the cycle. Organic farmers are seeking to make continuous improvement to the life in the soil, by observing patterns and lifeways, mimicking the native systems. We are not the center of the universe. Wendell Berry says “We don’t know what we are doing because we don’t know what we are undoing.”

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Plastic in the Organic Supply Chain Conference Report

From Modern Farmer

In early May, the Organic Center and the Organic Trade Association held the Organic Confluences conference about Reducing Plastic Across the Entire Organic Supply Chain. “While plastics serve many practical purposes on organic farms as well as for packaging and distribution, plastic production, use, and disposal cause massive amounts of pollution, which disproportionately affects low-income people and communities of color in the United States and around the world. At the conference, farmers, researchers, policymakers, wholesalers and retailers, nonprofit organizations, government agency staff and many others gathered to define the challenges in reducing plastic use, identify research needs, highlight success stories, and discuss what needs to be done to solve this growing problem.” Read a report about the conference on the eOrganic website here, with links to the conference program and slide presentations.

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Young spinach seedlings.
Photo Pam Dawling

Spinach Trial Underway to Inform Organic Seed Production

The Organic Seed Alliance is evaluating 272 spinach accessions from the USDA-ARS Germplasm Resources Information Network (GRIN) seed collection at their research farm in Washington State to assess timing of bolting and seed yield potential as part of a NIFA OREI funded project. This fall, they will share the trial results as well as their knowledge on spinach seed production and seed cleaning techniques through a webinar hosted on eOrganic, but meanwhile, read more about the project on their blog post here!

The seed production trial information is a part of an effort to aid in developing better varieties for organic farmers. “Research on the role of soil microbes on nutritional content, nitrogen use efficiency, and abiotic stress such as extreme temperatures is also underway by the project lead researcher Vijay Joshi at Texas A&M, and Ainong Shi and Gehendra Bhattarai at University of Arkansas. Together with the results of the seed production trials this project will help inform organic spinach breeders and farmers, and anyone working with seed from the USDA-ARS Germplasm Resources Information Network (GRIN) seed bank.” Results will be posted on the eOrganic project website.

eOrganic logo

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Tomato Breeding Project Fueled By Over 1,000 Backyard Gardeners

 

Some of the Dwarf Tomato Project’s diverse harvest. Courtesy of Craig LeHoullier

This 12-minute segment from Science Friday is an interview with Craig LeHouiller, who is a gardener/garden writer / tomato breeder in North Carolina. He is the author of Epic Tomatoes. In this segment he talks about the open source Dwarf Tomato Project. He and collaborator Patrina Nuske-Small aimed to preserve the flavor and beauty of heirloom tomatoes, without taking up too much space. They started crossbreeding heirloom tomatoes with smaller dwarf tomato plants. They signed up over 1000 volunteers across the world. They now have over 150 varieties of dwarf tomatoes, everything from cherries to beefsteaks, in every color. You can buy seeds from Victory Seeds, who have dedicated themselves to offering every dwarf variety produced.