Cover Crops for Vegetable Growers

Cover crops feed and improve the soil, smother weeds, and prevent soil erosion.

Select cover crops to use opportunities year round. Fit cover crops into the schedule of vegetable

production.

©Pam Dawling 2016

author of Sustainable Market Farming

www.sustainablemarketfarming.com

www.facebook.com/SustainableMarketFarming

What’s in this presentation A. Five steps of cover crop planning

B. Reliable cover crops at Twin Oaks

C. Winter cover crops we use at TO

D. Spring and summer cover crops we use

E. Cover crops for pest control

F. Cover crop mixes

G. Small scale equipment and methods

H. Resources

So many possible cover crops to choose from!

No single solution suits all situations and all times of year – make careful and informed choices

Experiment with different ideas, take notes

Be flexible about your plans, to take account of the weather, the crops, the weeds and your schedule.

Have back-up plans in case the weather prevents you from following your original plan

5 steps of cover crop planning 1. Identify your opportunities for cover crops

2. Clarify your cover crop goals for each opportunity

3. Shortlist suitable cover crops for each situation

4. Make a decision from among the options

5. Record your decisions and results, and review for possible changes next year.

Crimson clover and bumble bee. Bridget Aleshire

Step 1 - Cover Crop Opportunities

In fall after food crops, for winter – the easiest place to start

Frost-seeding of small seeds such as clover, when ground is frozen.

To replace a crop failure. Year-round cover crops/green

fallow 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, 4 weeks or more between one vegetable crop and a later one

Undersowing at last cultivation (oats and soybeans in sweetcorn shown here, photo by Kathryn Simmons.)

Step 1- Identify a specific opportunity

• When does the window open?

• When does it close?

• What are the ambient temperatures during that time? Will there be frosts?

• Will irrigation or rainfall be restricted?

• What is the preceding food crop (avoid the same family)?

• What is the following food crop (avoid the same family)?

Broccoli Mustards Kale

Step 2 - Clarify your main goals Which cover crop benefits are your priorities 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

Step 2 - Clarify your secondary goals

Salvage leftover nutrients

Fix nitrogen to feed the next crop

Attract beneficial insects

Bio-fumigation for pest or weed control

Kill nematodes

Step 3 Shortlist suitable cover crops

Consult charts and other local growers. Cover crops divide into 6 groups: • Cool-season grasses • Cool-season legumes • Cool-season broadleaved crops • Warm-season grasses • Warm-season legumes • Warm-season broadleaved crops

Step 3 – Consult Cover Crop Charts The 9 pages of charts in Sustainable Market Farming will help you find cover crops suitable for your climate, time of year and time-window.

The SARE book Managing Cover Crops Profitably is the best book on the subject.

Step 4 Fit your cover crop with the season (fall)

Work back from your farm’s first frost date, to see what options you have.

• 80-120 days before frost - buckwheat, soy, cowpeas, Japanese millet, sorghum-sudangrass, or a fast vegetable crop.

• 60-80 days before frost - buckwheat, soy, cowpeas, Miami peas, Japanese millet, sorghum-sudangrass to winter-kill; or oats with Austrian winter peas, crimson clover, or red clover to grow into winter.

• 40-60 days before frost - oats with soy beans or Miami peas to winter-kill; or winter barley or winter wheat with Austrian winter peas, crimson clover, hairy vetch, red clover, fava beans to survive the winter.

• 20-40 days before frost, winter rye, winter wheat, or winter barley, with crimson clover, Austrian winter peas, red clover or (40 days before frost) hairy vetch. Too late to usefully sow crops that are not frost-hardy.

• 10 days past the frost date - winter rye or wheat + Austrian winter peas.

• Up to a month past your average frost date - still OK to sow winter rye.

Fit your cover crop with the season (summer)

• If you have only 28 days until the patch is needed for a food crop, you can grow mustards or buckwheat. Or weeds, if you’re careful not to let them seed!

• If you have at least 45 days, you can grow soy or Japanese millet.

• If you have 50–60 days, Browntop millet is possible.

• In the right climate, sunn hemp can mature in 60 days.

• With 60–70 days, Sorghum-sudangrass, German foxtail millet, pearl millet and some cowpeas will mature.

Step 4: Choose cover crops matching your main goals

Smother weeds: sorghum-sudangrass, pearl millet, winter rye, wheat, barley,oats, buckwheat, brassicas, lupins, red clover, subterranean clover, berseem clover, soybeans, cowpeas

Add organic matter, improve the soil’s ability to absorb, hold water: bulky grasses and legumes , sorghum-sudangrass, millets, winter rye, velvetbean, cowpeas, sweetclover, sunn hemp

Increase the biological activity in the soil – use varied mixes Reduce erosion: (good roots) grasses especially rye, barley, oats

sweetclover, cowpeas, sub clover, Improve the tilth of the soil, the sub-soil structure, soil drainage:

sorghum-sudangrass, sunflower, daikon, sweetclover, crimson clover, alfalfa, lupins, cowpeas, forage radish, sugar-beet or forage-beet

Choose cover crops matching your secondary goals

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, cowpeas, soybeans, lentils, sunn-hemp.

Attract beneficial insects: (flowers) buckwheat, peas, beans, clovers, brassicas, phacelia

Pest or weed control: rye, brassicas, sorghum-sudan, sunn-hemp, white lupins, sesame.

Kill nematodes: Pacific Gold mustard, white lupins, Iron and Clay cowpeas, OP French marigolds, sesame

Step 5 - Record decisions & results; Review for possible changes next year

• Keep notes on how well your cover crops work for you, and if something goes wrong, what might work better.

• Winter can offer time to reconfigure planting schedules to make more future windows for short-term summer cover crops, or to include legumes with winter cover crops.

Reliable cover crops at Twin Oaks, Central Virginia, Zone 7a

Winter cover crops

Grasses:

• Spring Oats

• Winter Wheat

• Winter Rye

Legumes:

• Hairy Vetch

• Crimson Clover

• Austrian Winter Peas

Summer cover crops

Grasses:

• Sorghum-sudangrass

• Japanese millet

Legumes:

• Soy

Broadleaved crops:

• Buckwheat

Create a crop rotation for vegetables that includes good cover crops

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 the major crops

4. Group compatible crops together to fill each plot

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 all the details, see my slideshow

Crop Rotations for Vegetables and Cover Crops on SlideShare.net

Winter cover crops at Twin Oaks 1. Winterkilled cover crops

2. Under-sowing

3. Wheat and Rye – hardy grasses

4. No-till cover crops

5. Including winter-hardy legumes

Rye, crimson clover, winter peas. Photo Bridget Aleshire

1. Winterkilled Cover Crops - oats Winter-killed cover crops

smother weeds and grow biomass to provide a dead mulch to cover the soil and hold it in place until early spring. The dead material is more easily incorporated in spring than a green cover crop, making the soil ready for planting earlier.

We sow oats in the areas where we plan to plant the early spring crops next year.

Needs a crop rotation that clears those patches before the end of the previous August.

AFTER GROWING early sweet corn, spring broccoli, cabbage and spring-planted potatoes

Sow OATS in August

NEXT YEAR, PLANT peas, cabbage, broccoli, carrots, March-planted potatoes, spinach and the first sweet corn

When to sow oats for a Winter Cover Crop

5-8 weeks before your average first frost to get good size plants before they get winter-killed.

For us, that’s 8/5-9/17 (our average first frost is 10/14).

If sown too early, oats head up in the fall and even drop seed.

If sown too late, they won’t provide much biomass before they are killed.

A 2 week delay in sowing can seriously reduce the effectiveness of the cover crop

Photo Oklahoma Farm Report

About Oats

Low-cost, easy to establish, fast-growing - provided the temperatures are right - minimum soil temperature for germination is 38F (3C)

Grow to a height of 2-4 feet (0.6-1.2 m) if not killed before then.

Will grow in a wide pH range, and even do OK in poor soils If sown in August/early September, reliably winterkill in

zone 7a - average annual minimum temperature range 0-5F (-18C to -15C).

Seedlings die at 17°F. Large oat plants will get serious cold damage at any

temperature lower than about 20F (-7C) and will die completely at 6F (-17C) or even milder than that.

Benefits of Oats

If they die, they are simple to till in; if they don’t die, they are still easy.

Some tolerance to flooding

Add lots of biomass

Very good at shading out germinating weeds

Very good at salvaging any nutrients (especially nitrogen) left from the previous crop and making them available to the following crop.

Oats increase the biological activity of the soil, reduce soil erosion (their fibrous roots anchor the soil) and absorb and store rainfall.

Limitations of oats as a cover crop o Oats are not as good at breaking up compacted subsoil as

some cover crops, but they do loosen the topsoil nicely. o Less allelopathic effect than winter rye. I suspect that if the

crop is winter-killed, little allelopathy remains in the spring. o Not much tolerance to heat or drought (more than rye). o Oats do not add nitrogen, but often you can add a

nitrogen-producing legume in with the oats. o Unlike flowering cover crops, they do not attract beneficial

insects (assuming they are winter-killed before heading up and shedding pollen).

o Beware GMO canola from feed store “horse oats.” You don’t want GMO canola going feral! Buy organic!

o Spring oats can be sown in late summer, early fall or early spring.

Other Winterkilled Cover Crops During August and September, other warm-weather cover crops can be used for areas that will be planted early the next year:

1. Frost-tender sorghum-sudangrass hybrid, buckwheat, soy, cowpeas, Miami peas, sunnhemp and millets.

2. Crops which winter-kill at 5-20°F include oats, barley, berseem clover, Lana vetch, purple vetch, fava beans, Canadian/spring field peas, oil and fodder radish.

They can be used before early spring food crops.

Sorghum sudangrass hybrid. Photo by Bridget Aleshire

2. Under-sowing (inter-seeding) for more winter-killed cover crops

• Want more areas in winter-killed cover crops? Under-sow. (Most of our food crops are not finished in August.)

• Cultivate the food crop in August 2 weeks after planting.

• Repeat after 2 more weeks and sow cover crop between the rows of the vegetable crop while it is growing.

• Remember to irrigate if nature doesn’t. 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.

• The cover crop continues to grow after the food crop is finished - you have your winter cover crop in place early and you don’t need to invert the soil again.

Sweet corn under- sown with soy. Kathryn Simmons

Example of undersowing oats • We undersow our 6th sweet corn (sown 7/16) 4 weeks

after seeding, with oats and soy in mid-August, a perfect time for oats.

• Soybeans are also winter-killed in our climate, so they make a good companion for the oats.

• Oats and soy are both somewhat shade-tolerant.

• They also tolerate foot-traffic when it’s time to harvest.

• It’s important not to till between rows of large food crop plants – it damages their roots. With corn, it’s wise not to till after the crop is knee-high.

• We do not mow down the corn after harvest, but just leave it until early spring. It incorporates pretty easily by then.

• We follow this combination with our spring potatoes, planted mid-March.

(Under-sow summer cover crops too!) • Buckwheat or white clover can be under-sown in a

spring vegetable crop, to take over after the food crop is finished.

• Buckwheat can be undersown in winter squash, watermelon or sweet potatoes, and mowed or tilled as soon as the vines start to run. Once we tried buckwheat between our squash rows to keep the weeds down, but failed to mow or till it in, and had to wade in and pull it by hand.

• One trial of undersowing buckwheat in corn reported that if sown the same day as the corn, the buckwheat outcompeted the crop; if sown at the eight-leaf stage of the corn, the buckwheat did not get enough light.

Green fallow at Twin Oaks • Full year cover crops (green

fallow) can build soil fertility. • We discovered a “spare” plot! • In August, we under-sow our fall

brassicas with a clover mix - to form a green fallow crop for the whole of the following year, to replenish the soil and reduce 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.

• Then (late August-early September), we broadcast a mix of clovers

Clover green fallow in July. Photo by Bridget Aleshire

Clover fallow details • 1 oz crimson clover, 1 oz Ladino white clover and

2 oz medium red clover per 100 sq ft.

• Crimson clover is the fastest growing in the fall, and the others gradually take over in the spring and summer of the next year.

• White clover: 3 main types - the large (12-15”) type, Ladino, produces the most biomass and the most N. It is not as durable or as heat-tolerant as the intermediate types, and is later to flower. The lowest growing type (Wild White) is used for high traffic areas like orchard alleys; the intermediate-height range (up to 12”) includes Dutch White and New Zealand White.

• Red clover: get medium, multi-cut red. Don’t use mammoth if you want to mow regularly.

• Don’t till the seed in. Use overhead irrigation to get the clover germinated - aim to keep the soil surface damp for the few days until germination. Usually watering every two days is enough.

Broccoli with clover under-sown. Photo Nina Gentle

Green Fallow Decision Points We plan to keep the clover growing for the whole next year. Back-up plan:

• In spring, we bush hog the old brassica stumps and let the clover flourish.

• If the plot is not too weedy, we keep the clover, mowing once a month or so to prevent the crimson clover and the annual weeds from seeding. I have often been surprised at how a patch that is thin and weedy in March and April can look really good by May, and lush by the end of June.

• In late April, we assess again. If there are too many perennial weeds, or the clover isn’t growing well enough, we disk and plant warm weather covers, (buckwheat, soy, sorghum-sudangrass hybrid) until frost.

• In July, if the weeds are bad we disk in the clovers and sow sorghum-sudangrass mixed with soy. While this deals effectively with the weeds, it is a poor crop rotation, as the next year’s crop in that patch is early sweet corn, which is related to sorghum-sudan.

• In August, if the weeds are gaining the upper hand, we disk and sow oats (perhaps mixed with soy). If the clover is still growing well (as it usually is), we leave the green fallow to overwinter.

• We disk it in February, a year and a half after sowing, for early sweet corn.

Keys to success with undersowing • 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. 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. Buckwheat, millets and cowpeas all have their fans for summer use.

• Ensure the seedbed is clean and the soil crumbs small enough.

• Use a high seeding rate, whether broadcasting or drilling. • Irrigate sufficiently.

Location, location, location Some things that work in New York state don’t work in Virginia

• Kale undersown with rye and hairy vetch, rye alone, or oats in mid-late August

– in Virginia, winter rye sown in August goes to seed the same year.

– we overwinter kale, and cover crops would compete too much.

• Winter squash and pumpkins undersown with red or crimson clover when the vines are just starting to run.

– in central Virginia this was a hopeless failure - the vines grew so much faster than the clover and smothered it.

• Sweet corn undersown with crimson clover:

– In the South, corn grows too fast compared to clover.

– It is difficult in Virginia to get the clover to germinate in the heat and dryness of June and July. Soy is easier and cheaper.

3. Winter wheat

Winter wheat. Photo USDA

Winter wheat prevents erosion suppresses weeds scavenges excess nutrients adds organic matter less likely than barley or rye to become

a weed is easier to kill than barley or rye cheaper than rye easier to manage in spring than rye

(less bulk, slower to go to seed) fine root system improves tilth tolerates poorly drained, heavier soils

better than barley or oats Can be sown in spring – it will not head

up, but “wimps out” encourages helpful soil microorganisms

Challenges o Not good tolerance of

flooding o a little more susceptible

than rye or oats to insects and disease

Winter Rye/Cereal Rye Rye grows 5-7' tall.

Mow-kills at flowering, but not earlier.

Suppresses weeds (especially lambsquarters, redroot pigweed, ragweed).

Sow from 14 days before to 28 days after first fall frost, but makes little growth in mid-winter

Rye can be sown in the spring, although oats break down quicker.

Don’t sow in August in zone 7 – it may set seed.

Can be undersown in sweet corn or in fall brassicas in early September, and left as a winter cover crop.

Rye needs 3-4 weeks after tilling in, in spring, to break down and to disarm the allelopathic compounds that stop small seeds germinating.

Kauffman Seeds

Cover Crops for Fall

September

Before 9/15, oats Any time in September:

winter rye, winter wheat, winter barley, hairy vetch, crimson

clover, red clover, Austrian winter peas.

October

Before 10/14, winter wheat with crimson clover or red clover.

After 10/15, winter wheat or winter rye with Austrian winter

peas

November

Before 11/8, winter wheat or winter rye, Austrian winter peas

From 11/9 to 11/15 (a month past our average

frost date) winter rye alone

Only include legumes if there will be time in spring for them to flower

4. Organic no-till cover crops

Kill the cover crop without tilling, and plant food crops into the dying residue.

3 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 is another option, but usually requires special equipment.

Photo Rye, hairy vetch, crimson clover. Kathryn Simmons

Organic no-till benefits to the soil Soil is kept covered, reducing erosion. Soil compaction is reduced by having fewer tractor passes. 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.

Other organic no-till benefits Reduced use of agricultural plastics.

If spring is wet, it may be possible to mow, when you couldn’t till.

Fewer tractor passes - labor, fuel and machinery costs are reduced.

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.

Crops such as pumpkins are cleaner than those grown on bare soil.

Legumes in the 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

Suitable cover crops for no-till Which winter annual cover crops to choose ? 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

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. 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 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.

No-till cover crops before late spring vegetables

No-till cover crops are grown to flowering, killed by mowing or rolling, and left to become mulch for the next crop.

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%.

We have 1 year in 10 as a no-till year. We use no-till cover crops for our 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.

Suitable food crops for no-till • 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.

• If you have machinery or hand tools for seeding into no-till cover crops, direct seeded crops are possible.

• At the Coastal Plain Experiment Station in Tifton, Georgia, they are trying peanuts planted into crimson clover.

Steps of mow-killed no-till cover crops 1. Find a plot 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. Austrian winter peas are said to reduce the incidence of Septoria leaf spot in following tomato crops, so we include those. 1.5 oz HV, 1.5 oz AWP, 2.5 oz Rye per 100 sq ft

Winter rye, hairy vetch and Austrian winter peas. Photo Bridget Aleshire

Mow-killed no-till steps continued 3. Grow a solid stand of a cover

crop for high biomass. The goal is to have the vetch be about 4” tall before hard frosts of 22°F stop growth.

4. The next year we do not till in this cover crop but mow it very close to the ground using our hay mower (5/1-5/5), just before our transplanting date.

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.

Winter rye and hairy vetch. Photo Kathryn Simmons

Mow-killed no-till continued

6. Plant the food crop into the dying mulch with as little disturbance of the cover crop as possible. Transplant, or seed using equipment to open a narrow slot deep enough for the seeds. We transplant paste tomatoes.

7. The dead mulch keeps weeds away for 6 -10 weeks in our climate.

Flowering hairy vetch with rye at mowing stage. Photo by Bridget Aleshire

No-till cover crops continued

8. The vetch and peas (if plentiful) supply all the nitrogen the tomatoes need.

9. In our humid climate the no-till mulch does biodegrade. In July we roll hay between the rows, to top up the mulch. We plant the tomato rows 5.5 feet apart and the plants are staked and woven, so we can snugly fit big round bales of hay down the aisles.

Cautions about no-till planting o Cold-hardy cover crops need time in spring to grow to

optimal size before mowing - not suitable for early spring food crops

o Untilled soil in spring is colder than tilled soil, and growth of anything you plant in it will be slower, and harvests delayed. Not good for watermelons!

o Transplanting into untilled soil is harder work than planting into loose tilled soil.

o Hand-seeding into untilled soil is tricky – winter snow and ice can leave soil quite compacted. Unsuitable for small seeded, closely-spaced vegetables.

o Initial hopes for no-till cover crops - that it would be possible to grow vegetables organically without ever tilling again - were unrealistically high.

Challenges with organic no-till • The timing of sowing, rolling or mowing and planting

is critical. The wrong weather can jinx your plans.

o 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.

o 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.

o There may be more fungal diseases and slugs.

o In arid zones, it is necessary to wet the mulch weekly to release the nutrients. Drip irrigation won’t do that.

o The rate of nitrogen release from the cover crop will be slower than from an incorporated cover crop.

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 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” strip of prepared soil, for planting in a separate operation.

• Transplanters are available that are designed for use with thick organic mulches.

• No-till seeders are harder to find: an example has a toolbar planter, 15” fluted disk blades to cut through the vetch mat, 15” double disk opener, 12” cast-iron closing disks, plastic seed pressers and extra weights.

5. Including winter-hardy legumes

Crimson clover flower, Photo Kathryn Simmons

For maximum N, mow and incorporate cover crops when they start to flower.

A good legume stand can provide all the N the following crop will need. We only spread compost for our late crops if we had poor luck with the legumes.

Include legumes in cover crop mixes whenever possible, to add nitrogen to the soil.

Austrian winter peas can be sown later than clovers.

Hairy Vetch Very widely-adapted, cold-hardy to

−15°F

Needs a minimum soil temperature of 60°F to germinate

Sow 40-60 days before the first 28°F frost

Grows quickly in fall

In spring it reaches a height of 2' alone or 6' if mixed with tall cover crops.

In zone 7, 9/7–10/10 is ideal for sowing. Don’t delay - over 1100 Growing Degree Days are required in the fall to make enough growth.

Hairy vetch and winter rye. Photo by Kathryn Simmons

Hairy Vetch Benefits and Challenges Benefits:

Drought tolerant once established.

Suppresses yellow nutsedge, lambsquarters.

Challenges:

o Vines can be tangly.

o Can be invasive if it sets seed.

o Seed is poisonous to poultry.

o May harbor pest nematodes.

o Not tolerant of shade or flooding.

Hairy vetch Photo Southern Exposure Seed Exchange

Clovers Many types of clover - used to

discourage weeds, add nitrogen and biomass to the soil and prevent erosion.

Clovers attract beneficial insects and reduce aphids.

Main uses : as overwinter cover crops; green fallow (full year cover crops); under-sown in existing food crops, no-till or reduced-till crop sowings in standing clover.

Best planted with a grass crop. Alone they sprawl.

“Frost Seeding” - broadcast clover seed on prepared soil, early in the morning after a hard frost. The thawing will wet the seeds and pull them down into the soil. (2/15-3/15 in central Virginia).

Field of crimson clover. Photo Bridget Aleshire

Crimson Clover

Deep-rooting annual, hardy to 0°F (-18°C).

In zone 7, 9/1–10/14 is ideal time to sow.

Establishes earlier than hairy vetch in fall, so suppresses weeds better.

Fall-sown crops make fast growth in spring

Grows to 18" or 36”with a supporting crop.

Flowers a few weeks earlier than hairy vetch.

Mow at early bloom (in central Virginia 4/16-5/2, most usually around 4/20).

Provides about 2/3 as much N as hairy vetch.

Can also be sown in very early spring, but will not make much growth before flowering (in our climate at least).

Benefits: Shade tolerant. Attracts beneficials, including assassin bugs which eat Colorado potato beetle. Suppresses Italian ryegrass. Can be undersown in fall crops for winter cover.

Crimson clover, Photo Kathryn Simmons

Over-winter crimson clover in our rotation

sweet corn, June-planted

potatoes, watermelons

and sometimes tomatoes and

peppers

Crimson Clover sown 9/20-10/15, with

wheat. Turned under in late

April

Later corn plantings,

winter squash, transplanted watermelon,

tomatoes, peppers, sweet potatoes, June-

planted potatoes, fall

brassicas

Vegetable crops cleared by end of September/ mid October

Vegetable crops planted after late April

Photo Crimson clover Bridget Aleshire

White clovers Perennials used as winter annuals in the South.

Hardy to −20°F. Generally hardier than red clovers, and smaller.

Can be frost-seeded in early spring

Or sow in fall, at least 6 weeks before a hard frost.

Only sow in summer if you can keep the soil damp.

Water frequently until established.

Competes poorly with weeds until well established.

Good for all-year cover, tolerates foot traffic. Drought tolerant.

Has stolons, so good at re-growing after mowing.

The dwarf type is not a good choice to mix with grasses.

White clover. Photo Kathryn Simmons

Red clovers

Short-lived perennials.

Cheap. Best incorporated after a full season of growth (needs time to grow - 24-36” tall)

Good weed suppression.

Tolerates shade and poor drainage (not flooding).

Fairly cold tolerant (not as hardy as white clover).

Attracts beneficial insects.

In the S, sow in fall or spring, 30 days before first fall frost, and 30 days before last spring frost. In the N, from 45 days before last frost, up till 30 days before first frost. In warmer weather, sow with a nurse crop (rye, buckwheat or oats). Ensure sufficient water.

Mammoth is easier to establish in dry soils than Medium, faster growing, bulkier, but not good at re-growing after mowing.

Subterranean clover (Sub clover)

Re-seeding cool season annual. Best suited to areas with dry summers, mild wet winters. Thick, low growth, good for long-term orchard floors, living

or dying mulch, erosion control. Survives close mowing. Strong seedlings, good weed suppression. Dormant in winter, regrows in spring. Seeds, then dies in summer. New plants germinate in the fall. In hardiness zone 7 and warmer, sow in the fall. In colder

zones, sow in spring.

Berseem clover/Egyptian clover

(Bigbee, Multicut), grows 24” tall. Very productive, vigorous annual white clover.

Does best in hot moist conditions, tolerates wet soil. Mow to 3", not less, when 7–20" tall. Excellent weed suppression. Sow in spring, or late summer if water is adequate. Sow with oats as a winter cover before early spring vegetable crops. Frost seeding is not very successful. Hardy to 15°F. If it winter-kills, it leaves a friable seedbed needing

minimal spring tillage, if any. Oats and berseem clover have a good write-up in Managing Cover

Crops Profitably.

Sweet clover Grows up to 6ft tall.

White Hubam variety is an annual, winter-kills at 19°F.

Other sweet clovers are biennial.

Yellow sweet clover is not easy with small scale equipment, and can be difficult to incorporate. (White is much easier.)

The yellow is earlier than the white, but less productive.

Yellow sweet clover seed is cheap, white is expensive.

Mow high for maintenance, e.g., if inter-seeded between crop rows.

Deep rooted.

Requires 17" of water per season.

Sow late summer for heavy growth next spring.

Spring sowings make growth by early summer.

Can be frost-seeded in late winter.

Cautions with clovers

o Clovers do not winter-kill in our zone 7 climate.

o Consider avoiding legume cover crops ahead of legume food crops, to reduce the likelihood of spreading pests or diseases. We haven’t seen any problem that we can directly blame on a poor rotation, and until that happens we’ll likely continue to add legumes frequently, to increase the soil organic matter, feed the soil microorganisms and support the nutrient cycle.

o Beware red and crimson clovers, (and some peas and beans, beets, buckwheat) before white potatoes, as these can host Rhizoctonia and scab.

Austrian Winter Peas– a cold-hardy leguminous cover crop

Hardy type of Field Pea. (Black peas)

Winter-kill in zone 6, hardy in zone 7. Hardy to 0F (-18C). (Canadian/spring field peas are hardy to 10-20F (-12 to -7C)).

Can sow several weeks later than clovers

Sow at least 35 days before first hard freeze - in zone 7, 8/10–10/24 (11/8 OK)

Optimum temperature for germination is 75F, minimum germination temperature 41F.

Good at emerging through crusted soil

Tolerate a wide range of soil types

Make rapid spring growth in cool weather

Suppress weeds, prevent erosion

Austrian winter peas

Benefits of Austrian Winter Peas

Austrian winter peas with winter rye. Photo Cindy Conner

High N-fixers - a good stand can provide enough N for the following food crop when incorporated.

As much, or more, 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.

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 the spring.

Austrian Winter Peas in our rotation La

te f

inis

hin

g c

rop

s winter squash, melons, sweet potatoes, tomatoes, peppers, middle sweet corn, June-planted potatoes

Sow

Austrian Winter Peas

Oct 1-Nov 7

With winter wheat or rye C

rop

s af

ter

May

1st

winter squash, melons, sweet potatoes, tomatoes, peppers, middle sweet corn, June-planted potatoes

Photo by Cindy Conner

Cautions for Austrian Winter Peas o 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.

o Seeds are large and heavy - high sowing rates (compared to clovers). Cost/area is fairly high, a little higher than vetches

o If you haven’t grown peas or beans on that plot for some years, inoculate the seed.

o Winter-killed in zone 6, at 0°F. For the best chance of winter survival in cold areas, choose your sowing date to get plants 6-8” tall before the soil freezes. (Hairy vetch is more cold-tolerant than AWP.)

o Sowing in a mix with a winter grain will improve cold weather survival by reducing soil freezing and heaving.

When Austrian Winter Peas are unsuitable.

o May not do well if sown in spring - require a cold dormant spell. o Not tolerant of flooding, drought, high traffic, salinity, heavy

shade, long cold spring weather below 18°F with no snow cover, or hot (or even warm) weather.

o Do not regrow after mowing or grazing once blooming starts. o Peas on their own do not add much organic matter to the soil -

the vines break down quickly. o 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.

o 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.

o Can also be host to Sclerotinia minor, Fusarium root rot and Ascochyta blight.

Early spring cover crops we use at Twin Oaks

In February or March we sow oats, where we have winter weeds, no cover crop, and will not be planting a food crop for 8 weeks. That is sufficient time for growth to out-compete weeds and add to the organic matter in the soil.

March 31 here is too late in spring for oats (they will quickly head up after making very little growth)

In late March or April, we can sow winter rye, which “languishes” here once it gets hot. One year when our spring potatoes got flooded we transplanted potatoes to the drier end of the patch and sowed rye in the lower end, once the floods had subsided. This kept the soil covered, and was easy to deal with in July at potato harvest time.

In early April, too late for oats, but too soon to sow frost-tender cover crops, we might just till and make stale seed beds (till 2 or more weeks ahead of time, prepare beds, hoe once a week to kill weeds)

Late spring and summer cover crops at Twin Oaks In late April (close to our average last frost), we sow frost-tender

cover crops like buckwheat or soy, mixed with a grain such as winter rye or wheat for insurance and some shielding from harsh weather.

When summer gaps occur between the end of one vegetable crop and the planting of the next, we sow a short-term cover crop

After our corn planting date, if a food crop fails, or we “discover” some space, we grow sorghum-sudangrass for the remainder of the warm season.

Unlike our winter cover crops, we often only plant summer cover crops in small areas each time, so we broadcast and till-in with our walk-behind BCS tiller.

Buckwheat flowers. Photo NRCS

Sorghum-sudangrass Fantastic summer cover crop Huge amounts of biomass Very good at smothering weeds Sow during corn-planting season Takes 60-70 days to full height When it reaches 4-5 ft (1.5m) tall,

mow to a foot (30cm) high, and let regrow

Some of the roots die to balance the needs of reduced top growth, leaving channels in the soil

The tops regrow and new roots grow – improving soil texture

Dies with frost Allelopathy inhibits germination of

small seeds, such as weeds. o Does need large machinery

Sorghum-sudangrass shown here after mowing. Photo Kathryn Simmons

Meet the Millets German foxtail millet

grows to 3'–4' (1–1.3 m),

Japanese millet to 3'–5' (1–1.6 m)

Pearl millet gets much taller, at 5'–10' (1.6–3.2 m).

Of the millets, pearl millet and German foxtail millet will mow-kill after heading (not before), but Japanese and browntop millets will not reliably mow-kill.

Pearl Millet Non-copyrightable image courtesy of the USDA-ARS

Warm weather legumes - soy beans

• Soy has been a handy legume for us, because Twin Oaks has an organic tofu business. We can get organic beans at wholesale price.

• Almost all non-organic soy grown in the US is genetically modified, so if you don’t want to add to the problems caused by GMOs, buy organic, or if you are not certified organic, Identity Preserved.

• See the Organic and Non-GMO Sourcebook for a searchable database of non-GMO suppliers.

Sweet corn with undersown soy cover crop. Photo Kathryn Simmons

Warm weather legumes - cowpeas

• Most cowpea varieties mature in 60-90 days and will be killed by the first frost. (Oats may provide temporary protection).

• Iron and Clay cowpeas are often used to break up compacted soil

Iron and Clay Cowpea. Photo Southern Exposure Seed Exchange

No-till cover crops for fall vegetables For fall vegetables such as broccoli, (and winter vegetables in hot climates):

• A mix of soybeans or cowpeas and foxtail millet can be grown over the summer and mow-killed before planting.

• Frost-killed Sorghum-sudangrass and sunnhemp could also work. (Beware allelopathy of sorghum-sudangrass)

Foxtail millet

About Buckwheat

This warm-season broadleaf annual germinates in just a few days,

Takes only 30-50 days to grow to full size - a height of 2-3' Sow from around the last frost date to late summer (50

days before first frost). Incorporate 7-10 days after it starts flowering. A useful cover crop in case of crop failure or early end of a

food crop.

Buckwheat flower. Photo NRCS

More about Buckwheat Use to prepare land for perennials or to bring neglected land back into production.

• Till the field, up to 2 weeks before the last frost,

• Cultivate after 10-14 days to kill new weeds.

• Sow buckwheat thickly, let it flower and seed (8 weeks). Sow early to reduce winter weeds

• Till again, let the volunteers grow, to reduce warm-weather weeds.

• Either incorporate in the fall or let the buckwheat frost-kill

• If for perennials, plant in late winter or early next spring

• If reclaiming neglected land, sow winter cover crops into the bare soil or no-till drill into the dead buckwheat.

Young asparagus patch with self-sown buckwheat “weeds”. Photo Kathryn Simmons

Benefits of Buckwheat Can be left to self-seed if there is time for several

sequential plantings of buckwheat. (Cheaper than buying more seed.)

If the soil is too wet to disk or till, it can be mow-killed or rolled.

Almost 3 times as good as barley in scavenging phosphorus, and more than ten times better than rye (a poor Phosphorus scavenger).

Not related to any of the common food crops - simple to include in rotations.

Quick to incorporate, easy with manual or small-scale equipment.

Photo NRCS

Strengths of Buckwheat Buckwheat does a good job of suppressing weeds,

especially ragweed and purslane. Improves the soil tilth (aggregate structure) with its

fibrous roots, and extracting K, Ca and P from the soil Mowing will kill buckwheat in full flower, but non-

flowering plants may re-grow from lower nodes. Open-faced flowers attract many beneficial insects

including honeybees, hoverflies, lady beetles; caterpillar-predatory wasps and tachinid flies; aphid and mite predators; minute pirate bugs and insidious flower bugs (which feed on small insects and insect eggs such as corn earworm eggs).

Photo NRCS

Weaknesses of Buckwheat o No tolerance of frost, drought or flood - seed can rot in

waterlogged soil.

o Little tolerance to salt, shade or compacted soil.

o Only fair at reducing soil compaction and erosion; poor at scavenging nitrogen.

o The summer weeds most likely to grow in gaps in a stand of buckwheat are redroot pigweed, lambs-quarters and barnyard grass.

o Provides relatively little biomass – decomposes fairly quickly if cut and left on the surface. Thick sowing can overcome this, but warm weather grasses, forage radish or lupins will provide more value for money spent on seed.

o May harbor root lesion nematodes (not root knot nematodes).

Summer Cover Crops in the Hoophouse • Hoophouse growing burns up the organic matter

in the soil at a fast rate. In summer you could grow cover crops to replenish the OM, ready for your next fall plantings.

• Buckwheat, soy, and cowpeas all work well. • If you don't have harlequin bugs, brassicas may be

a good choice. But if you grow winter greens, brassica cover crops would be a poor rotation.

• Short term, manageable, fast-growing cover crops are needed: – Clovers are too slow. – Winter cereal grains won't grow in the

summer. – Beware of huge hot weather grain crops, like

Sorghum-sudan. We grew Sorghum-sudan one year, and it grew all too well!

– The shorter millets are manageable

Buckwheat photo credit Southern Exposure Seed Exchange

Brassica cover crops for pest control • We tried a forage brassica

(canola/rape), before a new strawberry planting, but it encouraged too many brassica pests, harlequin bugs being the worst.

• We decided brassica cover crops are not for us. In areas where they work, try daikon, forage radish, mustards or canola. Do this when the soil is 45°F–85°F (7°C–30°C). That’s up until early October for us.

• Aim to get 6-8 leaves before a 28°F frost.

• Brassicas produce allelopathic compounds that inhibit weeds and biotoxins (glucosinolates) that kill pests.

Photo Kathryn Simmons

Biofumigation with mustards When solarized, mustards release volatile compounds very effectively. Different mustards do different jobs. Mighty Mustard offers 3 varieties: • Kodiak (Brassica juncea): Suppresses soilborne fungal pathogens and

nematodes, produces more biomass than other varieties • Pacific Gold (Brassica juncea): Reduces soilborne fungal pathogens,

nematodes • IdaGold (Sinapis alba): Suppresses weeds. Photo Mighty Mustard

Root Knot Nematodes • Peanut Root Knot Nematodes popped

up in sections of our hoophouse in 2010-2013.

• 64°F is the threshold soil temperature for nematode reproduction

• We have grown nematode-suppressing cover crops, wheat and white lupins, OP French marigolds, sesame, from September to June.

• We solarized from June to September • Our current approach is to have 2

years of resistant crops, followed by 1 year of somewhat-susceptible crops

• Resistant crops: Kale, Yukina Savoy, other Juncea mustards and radishes in winter, West Indian gherkins, Mississippi Silver or Carolina Crowder cowpeas in summer.

Photo Credit University of Maryland Plant Diagnostic Laboratory

Cover crop mixes – general points • Mixes can give the advantages of each of the components. • A mix of several cover crops species will provide more resilience in

the face of extreme weathers. • Extension.org recommend first selecting 1-3 cover crop species that

serve your major goals, then identifying “missing services” and choosing 1 or 2 cover crops that provide this service to add to the mix. Increase the number of species you mix as you gain experience. Don’t bedazzle yourself with 57 varieties and fail to learn anything.

• Mixes can generally be sown at a depth of 1” (2.5 cm), regardless of seed size. Up to 3” deep will be OK.

• When legumes and grasses are mixed, sow in the grass date range. • When 2 grasses are mixed, the seeding rate of each is reduced by a

third (not a half), • Do not reduce the seeding rate of legumes by much in mixtures.

Use at the same rate as a pure stand, or reduce the legume seeding rate by a maximum of 25%.

Cover crop mixes - specifics • In mixes with oats, reduce the amount of oats to as little

as 30#/ac (34 kg/ha) so that the highly competitive oats don’t out-compete the other crops.

• We sometimes use a mix of rye, crimson clover and AWP if the date is borderline for crimson clover and the weather uncertain, especially if we have the seed on hand and don’t want to use it the next year when the germination rate and seedling vigor will be less good.

• Most mixes include some crops that attract beneficial insects and some legumes to add N.

Ingredients for mixes

Spring mixes

• Main ingredients could be oats and peas, 3 oats:7 peas

• Minor ingredients could include hairy vetch, radish, turnips and red clover.

Summer mixes

• Major ingredients could include soy, cowpeas, red clover and buckwheat.

• Lesser ingredients could include pearl millet, proso millet, radish, turnips, sunflowers and sunn hemp.

Nurse and patient mixes • Oats can also be used in an

August/September sowing as a nurse crop for a winter legume cover crop, such as crimson clover.

• Sow the mixed legume and oats, expecting the oats to die in the winter and the legume to survive into spring and reach flowering before terminating it.

• The oats protect the legume plants from initial chilly temperatures, cover the soil faster and suppress weeds, and also provide a scaffold for vining legumes to climb.

• This is a way to get a better stand of clover than is possible if the clover is sown alone, because clover is slow-growing and weeds can take over.

• Buckwheat can work well as a nurse crop to protect late-fall sowings of winter-hardy crops in locations where timely frost-killing of the buckwheat is certain.

• Oats, clover and buckwheat mix

Using manual seeders for small-scale production

You can use an Earthway-type seeder for small areas of cover crops; information about this, including which plates to use for which crops, can be found in the VABF Infosheet Seeders: Using Manually-operated Seeders for Precision Cover Crop Plantings

Make rows about 6” apart.

For crimson clover use the #5 (beet) EW plate. For other clovers use the #8 (light carrot) plate Austrian winter peas need the #14 (pea) plate, For winter rye, oats, soybeans, cowpeas and hairy vetch, use

the #22 (beets, okra) plate.

Small scale production

• We broadcast and till in small areas of cover crops with our walk-behind BCS tiller.

• For slightly larger areas, a spin seeder can be used (easier on the arm than manual broadcasting). Incorporate the seed using a rototiller.

• For small vegetable plots, mow cover crops with a sturdy walk-behind mower, or use a nylon line trimmer or scythe for smaller patches.

• A 30” roller crimper for a walk-behind BCS 732-948 is available for around $1000 at Earth Tools in Kentucky. There are YouTube videos of it in action.

BCS 722 Photo from Earth Tools BCS

Incorporating Cover Crops into the Soil • If possible, grow to early bloom for max biomass, and with legumes,

max nitrogen • Incorporate before plants set seed • Mow with a rotary mower (eg bush hog) which chops the plants into

small pieces. (Sickle-bar mowers and scythes leave long strawy plants). On a small scale, use a nylon line weed whip.

• Till shallowly, put cover crop where soil life is most active, not deeper. • If direct-sowing the next crop, incorporate cover crop (especially

winter rye) 3-4 weeks before sowing date in spring. A cover crop of rye, hairy vetch and crimson clover. Photo Kathryn Simmons

How available is the Nitrogen? • The amount of nitrogen that will be available to the next crop

depends on the C:N ratio in the cover crop.

• Soil microbes have a C:N ratio of 10:1. When a cover crop is incorporated into the soil, they use the C and some of the N to make more microbes, tying it up until they die - it is not immediately available to the next crop.

• If the cover crop has a C:N ratio of 50:1 (like sorghum-sudan), the microbes will need to find extra N to make use of all the C. They will use N from the soil, tying it up until they die. Hence any crop following immediately after a high C:N ratio cover crop will need a different source of nitrogen.

• Legumes have a lower C:N ratio (from 30:1 down to 12:1) and when they are incorporated, soil N is unlikely to be tied up, so is available for the next crop. This is explained in the North Carolina Extension Service Horticulture Information Leaflet 37 cited in the Resources.

Planning for Nitrogen availability • Incorporate high-C cover crops a few weeks ahead

of planting the following crop. This also allows time for any cover crop allelopathy to subside.

• If cover crop residues are left on the surface rather than incorporated, the rate of decomposition is slowed. Although some N is lost to the air (denitrification), the increased organic matter can boost the diversity of microorganisms at the surface.

• Some of the carbon from cover crops is below the top 8”(20 cm), where almost all soil data are collected. Remember the value of the roots!

How to chart your rotation plan In 1996, inspired by

Eliot Coleman’s New Organic Grower, we used cards to represent each major crop.

We modified Eliot’s method, and put the cards in a circle, like a clock face with “hours,” and set about imagining a good sequence.

Crop rotations are a cycle, and a circular design makes more intuitive sense to us, than a linear format.

Squash

Corn

Potatoes

Corn

Broccoli Cabbage

Tomatoes

Water

melon

Corn

Potatoes

Winter Squash

Late Corn undersown with oats (1/2). Sweet

Potatoes (1/2)

March-planted Potatoes, followed

by fall-planted broccoli & cabbage,

undersown with clovers

All-year Green Fallow

Early Corn followed by

fall Garlic (1/2) and oats (1/2)

Garlic followed by Carrots (1/2). Spring Broccoli

& Cabbage, then rye & vetch (1/2)

No-till paste Tomatoes

Water-

melon

Mid-season Corn, then rye

& crimson clover

June-planted

Potatoes

Having the rotation in a useful format

We drew up our ten year rotation on a piece of card with a small central disk (naming the plots) attached by a brass paperclip so it can rotate each year to show which crops will be planted in which plots. We call this our Rotation Pinwheel

We are still using the same piece of card we made in 1996, even though we started our second ten year sequence in 2006. It has seen quite a bit of White-Out!

For my book, the publishers’ re-drew it tidily.

Year 1. Winter Squash followed by Rye and Austrian Winter Peas

• Winter squash are sown in late May, so there is time for a legume winter cover crop to reach flowering before we need to prep

• Winter squash finishes on our farm on Halloween, early enough to include Austrian Winter Peas in the following cover crop mix with rye

• Photo of butternut squash. Kathryn Simmons

Year 2. Late Sweet Corn and Sweet Potatoes

• Our last corn sowing and our sweet potatoes are both planted late in the season. Having them share a plot works in terms of allowing the preceding Austrian winter pea cover crop to flower.

• Late corn can be under-sown with oats and soy to provide a winter cover crop that is easily incorporated before next spring’s potato planting.

• The sweet potatoes finish in October, too late to sow oats before next year’s spring potatoes. So we follow the sweet potatoes with wheat.

Sweet potatoes and late corn. Photo Bridget Aleshire

Year 3. Spring Potatoes Followed by Fall Brassicas

• The plot is disked in February.

• We harvest the March-planted potatoes in early July, till in compost and immediately transplant our fall broccoli and cabbage.

• We undersow the fall brassicas with a mix of clovers (white, red and crimson) about a month after transplanting. This becomes Year 4’s All Year Green Fallow.

Potatoes emerging in spring. Photo Kathryn Simmons

Year 4. All Year Green Fallow The clover sown under the

fall brassicas grows all next year, if all goes well.

We monitor the success of the clover mix in March, May, and August.

If the clover isn’t doing well, we turn it under and sow oats or sorghum-sudangrass depending on the season.

If all goes well, we leave the clover growing over the winter.

Fall broccoli under-sown with clovers

Year 5. Early Sweet Corn, Half Followed by Garlic

• We get two food crops in year 3 and none in year 4. The Green Fallow is disked in March in year 5 to plant our first sweet corn.

• After the early corn, we sow oats and divide the plot.

• We mow one half from time to time until late fall, then disk and plant garlic in early November.

Sweet corn under-sown with soybeans. Photo Kathryn Simmons

Year 5-6. Sweet Corn → Oats →Garlic →Buckwheat →Carrots

A tight rotation: We harvest the garlic in June of

year 6, sow buckwheat and soy,

Then sow fall carrots in late July or early August.

We harvest in mid-November, usually too late for a cover crop.

That half-plot grows 3 food crops in 2 years.

We keep the other half of that

plot for spring broccoli in year 6.

Garlic harvest, Photo Marilyn Rayne Squier

Year 6. Spring Brassicas in the Other Half.

• The oats are turned under in mid-February. • Spring broccoli and cabbage can be followed by rye, hairy

vetch and Austrian winter peas sown in early September, in good time to grow a thick stand for no-till tomatoes in year 7.

Photos Kathryn Simmons

Year 7. Paste Tomatoes and Peppers • We transplant paste tomatoes and peppers into dead no-

till mulch in early May.

• This crop doesn’t finish till the frost, and we have all the posts to remove before we can sow a cover crop, so it is usually rye with Austrian winter peas.

Year 8. Watermelon • Watermelons are not planted till mid-May, so the Austrian winter

peas have time to flower before we disk the cover crop under in preparation for planting.

• We have finished with watermelon harvesting by late September, so we disk and sow wheat or rye with crimson clover for the winter cover crop. Crimson Sweet watermelon. Photo Nina Gentle

Year 9. Mid-season Sweet Corn • Mid-season corn is sown in early June. The crimson clover has time

to flower before we disk that plot.

• The corn is finished in time to establish wheat or rye and crimson clover, which will do well and produce lots of nitrogen and biomass before we need to plant the June potatoes in year 10.

Three varieties of sweet corn sown on the same day, to extend the harvest. Photo Kathryn Simmons

Year 10. Summer Potatoes • Our second round of

potatoes are planted in mid-June, giving the crimson clover plenty of time to flower before we need to disk and plant.

• To combat the heat of summer, we hill and mulch the potatoes immediately after planting.

• They are ready to harvest in October, and we follow with wheat or rye and crimson clover or Austrian winter peas.

June-planted potatoes. Photo Kathryn Simmons

Resources - General ATTRA attra.ncat.org Many helpful publications

SARE sare.org -A searchable database of research findings

SARE Managing Cover Crops Profitably. Buy the book or download the free pdf from their website sare.org/Learning-Center/Books/Managing-Cover-Crops-Profitably-3rd-Edition

SARE Cover Crop Topic Room: No-Till sare.org/Learning-Center/Topic-Rooms/Cover-Crops/Cover-Crops-No-Till

SARE Crop Rotations on Organic Farms, A Planning Manual, Charles Mohler and Sue Ellen Johnson, editors. sare.org/Learning-Center/Books/Crop-Rotation-on-Organic-Farms Buy or download

articles.extension.org/organic_production The organic agriculture community with eXtension. Publications, webinars, videos and trainings.

Growing Small Farms: growingsmallfarms.ces.ncsu.edu click Farmer Resources. Debbie Roos keeps this site up to the minute. Click Farm Planning and Recordkeeping to download Joel Gruver’s spreadsheets.

VABF www.vabf.org/information-sheets Seeders: Using Manually-operated Seeders for Precision Cover Crop Plantings by Mark Schonbeck/RonMorse

Resources - Books The Market Gardener, Jean-Martin Fortier, New Society Publishers

The Complete Know and Grow Vegetables, J K A Bleasdale, P J Salter et al.

Knott’s Handbook for Vegetable Growers, Maynard and Hochmuth. Online at http://extension.missouri.edu/sare/documents/KnottsHandbook2012.pdf

The New Seed Starter’s Handbook, Nancy Bubel, Rodale Books

The New Organic Grower, Eliot Coleman, Chelsea Green

The Organic Farmer’s Business Handbook, Richard Wiswall, Chelsea Green

Sustainable Vegetable Production from Start-up to Market, Vern Grubinger,

Grow a Sustainable Diet: Planning and Growing to Feed Ourselves and the Earth, DVD/CD set Develop a Sustainable Vegetable Garden Plan Cindy Conner.

Crop Planning for Organic Vegetable Growers, Daniel Brisebois and Frédéric Thériault (Canadian Organic Growers www.cog.ca)

SARE Crop Rotations on Organic Farms, A Planning Manual, Charles Mohler and Sue Ellen Johnson, editors.

Northeast Cover Crops Handbook Marianne Sarrantino

Jeff Moyer Organic No-till Farming http://rodaleinstitute.org/shop/organic-no-till-farming/

Resources - slideshows Many of my presentations are available at www.Slideshare.net. Search for Pam Dawling:

Cold-hardy Winter Vegetables; Crop Planning for Sustainable Vegetable Production; Crop Rotations for Vegetables and Cover Crops; Fall Vegetable Production; Feed the Soil; Fall and Winter Hoophouses; Spring and Summer Hoophouses; Succession Planting for Continuous Vegetable Harvests; Sustainable Farming Practices for New Growers and this presentation

Planning the Planting of Cover Crops and Cash Crops, Daniel Parson www.slideshare.net/parsonproduce/southern-sawg

Cover Crop Innovation by Joel B Gruver www.Slideshare.net

Cover crops for vegetable cropping systems, Joel Gruver

www.slideshare.net/jbgruver/cover-crops-for-vegetable-crops

Finding the best fit: cover crops in organic farming systems. Joel Gruver, Some overlap with previous slideshow. www.slideshare.net/jbgruver/cover-crops-decatur

http://vabf.files.wordpress.com/2013/02/tom-peterson-farm-planning-for-a-full-market-season.pdf Tom Peterson Farm Planning for a Full Market Season

Cultural Practices And Cultivar Selections for Commercial Vegetable Growers Brad Burgefurd www.slideshare.net/guest6e1a8d60/vegetable-cultural-practices-and-variety-selection

Conservation Systems Research, USDA-ARS Auburn University, Cover Crops for the Southeast slideshow https://www.ars.usda.gov/ARSUserFiles/60100500/SlideSets/SS01.pdf

Impacts of plastic and cover crop mulches http://www.slideshare.net/greenjeans76/weaver-fieldday-ziegler20120810?from_search=1

Mark Cain Planning for Your CSA: www.Slideshare.net (search for Crop Planning)

Resources – Cover Crops 1 CEFS Organic Production: Cover Crops for Organic Farms, https://cefs.ncsu.edu/wp-

content/uploads/covercropsfinaljan2009.pdf?3106e7

eOrganic Agriculture Resource Area of the eXtension website, Cover Cropping in Organic Systems http://www.extension.org/pages/59454/cover-cropping-in-organic-farming-systems#.Uk7Z7CRJOv8. (many useful documents.)

Extension.org, in the eOrganic section, http://articles.extension.org/pages/72973/making-the-most-of-mixtures:-considerations-for-winter-cover-crops-in-temperate-climates Making the Most of Mixtures: Considerations for Winter Cover Crops in Temperate Climates

USDA/ARS Cover Crop Chart, download at ars.usda.gov/main/docs.htm?docid=20323 The crop “tiles” can be clicked to access more information about 46 cover crops

USDA project Multifunctional Cover Crop Cocktails for Organic Systems. http://agsci.psu.edu/organic/research-and-extension/cover-crop-cocktails

Sequester soil organic carbon http://news.aces.illinois.edu/news/cover-crops-can-sequester-soil-organic-carbon

Mark Schonbeck http://www.carolinafarmstewards.org/wp-content/uploads/2012/12/1-Schonbeck-Principles-of-Sustainable-Weed-Management-in-Organic-Cropping-Systems.pdf

See plans by Greg Bowman for a roll-kill roller at http://www.croproller.com/ or build your own http://www.newfarm.org/depts/notill/features/2006/0506/drawings.shtml

http://www.extension.org/pages/18526/what-is-organic-no-till-and-is-it-practical#.Uk7a1iRJOv8 A Sub-surface Tiller-Transplanter designed by Ron Morse.

Resources – Cover Crops 2 asi.ucdavis.edu/programs/sarep/research-initiatives/are/nutrient-mgmt/cover-crops-

database1 University of California Davis, Cover Crops Database Cornell University, Cover Crops for Vegetable Growers, covercrops.cals.cornell.edu

nysaes.cornell.edu/hort/faculty/bjorkman/covercrops USDA-ARS Auburn University, Cover Crops for the Southeast (also see Slideshows)

ars.usda.gov/southeast-area/auburn-al/soil-dynamics-research/docs/fact-sheets/ Rodale Organic No-till roller-crimper http://rodaleinstitute.org/our-work/organic-no-till/ NCSU Department of Horticultural Sciences Horticulture Information Leaflet 37, Summer

Cover Crops, ces.ncsu.edu/depts/hort/hil/pdf/hil-37.pdf In Sustainable Production of Fresh-Market Tomatoes and Other Vegetables with Cover Crop

Mulches, Aref Abdul-Baki and John Teasdale found that rye with hairy vetch and crimson clover produced 22% more biomass than just rye and hairy vetch. https://www.ars.usda.gov/ARSUserFiles/oc/np/SustainableTomatoes2007/TomatoPub.pdf

Cornell Buckwheat Cover Crop Handbook (not organic) hort.cornell.edu/bjorkman/lab/buck/handbook/main.php

Buckwheat for Cover Cropping in Organic Farming – eOrganic Agricultural Resource Area of the eXtension website. extension.org/pages/18572/buckwheat-for-cover-cropping-in-organic-farming

tranq3.tranquility.net/~jefferson/Cover%20Crop%20Guides/Buckwheat%20Guide%20Sheet.pdf Buckwheat Cover Crop Guide – Jefferson Institute

How to De-hull Buckwheat with the Country Living Mill http://countrylivinggrainmills.com/grainmill3.html

Sources for seed: Seven Springs Farm, Floyd, VA, 7springsfarm.com; Lancaster Ag products, PA, lancasterag.com; Adams Briscoe Seed Co, Jackson, GA, (770) 775-7826

Resources – Crop Planning AgSquared online planning software: agsquared.com

COG-Pro record-keeping software for Certified Organic Farms: cog-pro.com

Free open-source database crop planning software code.google.com/p/cropplanning.

Mother Earth News interactive Vegetable Garden Planner, free for 7 days: motherearthnews.com/garden-planner. Also as an app: http://www.motherearthnews.com/grow-planner-gardening-app

The Twin Oaks Harvest Calendar by Starting Date and by Crop are available as pdfs on my website in this post: sustainablemarketfarming.com/2013/11/07/growing-for-market-articles-2/

Target Harvest Date Calculator: johnnyseeds.com/t-InteractiveTools.aspx

Jean-Paul Courtens, Roxbury Farm www.roxburyfarm.com. Under the Information for Farmers tab you’ll find great stuff.

Mark Cain www.drippingspringsgarden.com under the CSA tab, you can download their Harvest Schedule. Notebook-based system.

Cover Crops for Vegetable Growers

Cover crops feed and improve the soil, smother weeds, and prevent soil erosion.

Select cover crops to use opportunities year round. Fit cover crops into the schedule of vegetable

production.

©Pam Dawling 2016

author of Sustainable Market Farming

www.sustainablemarketfarming.com

www.facebook.com/SustainableMarketFarming