COVER CROP GARDENINGSOIL ENRICHMENT WITH GREEN MANURES

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Cover Crop GardeningCONTENTS

Meet the Green ManuresBenefit 1. Buy Less FertilizerBenefit 2. Cut Nitrogen PurchasesBenefit 3. Stop Those WeedsBenefit 4. Improve Your Soil StructureBenefit 5. Increase the Life in Your SoilBenefit 6. Save Time and EnergyBenefit 7. Stop Wasting NutrientsBenefit 8. Growing Healthier PlantsBenefit 9. Improves Soil’s Ability to Hold WaterBenefit 10. Make Your Garden More AttractiveGreen Manuring MethodsHow to Plant ThemWhen to Turn Under a Green ManureHow to Turn Them UnderThe Best Tool for Green ManuringBuckwheatA Fast-Growing Crop for Poor or Weedy SoilRyegrassThe LegumesAlfalfaThe VetchesCloversSweet CloversDouble Duty Green ManuresKalePlanting Cover Crops of Beans and PeasGreen Manuring in Small GardensLupineSmall GrainsOther Good Soil-Conditioning CropsWhere to Get SeedThe History of Soil-Improving CropsOther Storey Titles You Will Enjoy

Meet the Green ManuresGreen manuring — the growing and turning under of crops to fertilize and improve the soil — is anage-old practice that is gaining popularity again.One reason has been the rising costs of chemical fertilizers.Even more important is the development of equipment that has made the task of turning under cropsan easy one. Once gardeners turned these under with spades. It was hard work, and time-consuming,but many gardeners thought it was worth it, even then. Now the gardener can quickly chop up a crop— and that speeds decomposition — and mix it with the soil, using equipment designed for the job.But why raise green manures? Why plant cover crops, or catch crops? The answer is simple. All thesecrops will improve the soil. They add something valuable to it, or prevent something valuable fromdisappearing.As you read this bulletin, think of these crops as closely related, and having a single purpose — toimprove the soil. Green manures add huge amounts of organic material to the soil, cover crops preventerosion, catch crops prevent the leaching away of nutrients, and all overlap in their contributions.A Vermont gardener has summed up the benefits he has seen: “Gardening is easier now that I’mraising green manures. It’s easier to get the soil right for planting, easier to keep the weeds out ofthe garden, easier to get good crops, and easier to clean up the garden and get it ready for winter.â€‌He and others find these green manure crops are simple to raise, and their contribution to the garden,once turned under, is quickly apparent. Like them, you will find the next crop you raise after greenmanures will be improved.Let’s look more closely at the benefits you can expect from these crops. Turn this page and beginreading about them.

Benefit 1.Buy Less Fertilizer

If you are an experienced gardener, you know that you can’t have rich, productive soil unless you putsomething back into it. For many, chemical fertilizers have been the answer, and an increasinglyexpensive answer.By growing green manures you can improve the soil and cut your fertilizer needs in half at the sametime.Green manuring is a way to speed up the natural system of creating rich soil. Soil has been built up overthe centuries as natural vegetation died and decomposed. By raising crops, then chopping them up andtilling them under, this same process is accelerated, and the benefits to the soil are much more quicklyapparent.The result is that the amount of fertilizer you have to buy and use can be reduced sharply.Green Manures Help Unlock Soil NutrientsLarge supplies of nutrients may be locked up in insoluble rocks or minerals. Green manures can helpunlock some of this supply.One way that green manures can make more of these nutrients available is by increasing the activity ofmicrobes in the soil.These microbes produce weak acids that eat away at soil minerals, causing them to release nutrients forplants to use.Some green manure crops can extract nutrients from insoluble minerals. Rye, buckwheat, and sweetclover can extract phosphorus from some insoluble minerals. When crops like these are grown in poorsoil and turned under, the phosphate they mine from the earth is released to plants grown later in thesame area.

Benefit 2.Cut Nitrogen Purchases

Nitrogen is one of the most plentiful elements. It’s in the air we breathe. Tons of it hang in the airover each acre of our gardens, free for use if we can get it down into the soil.At the same time, nitrogen bought through commercial channels has shot up in price, becauseproduction of it demands use of expensive petroleum products.There is a way to get this nitrogen free, and in large quantities. You can plant legumes as greenmanures. Legumes — alfalfa, beans, peas, and vetch are some of them — have the ability to hostbacteria that can fix nitrogen in the air. The legume seed is inoculated by coating it with a strain ofnitrogen-fixing bacteria suited for the particular legume, then planted. This inoculant is widely availablein seed stores. When the seeds sprout and grow, the bacteria enter the developing root hairs, takenitrogen from the air and fix it in nodules on those root hairs.Alfalfa, the best of the nitrogen-fixing crops, can add as much as 200 pounds of nitrogen per acre.That’s the same amount of nitrogen you would get from spreading a ton of 10-10-10 commercialfertilizer on that acre. And think of the extra organic material you are adding to the soil and thusenriching it.The Force of a Raindrop Splash

A drop of rain striking bare soil is like an explosion. Small particles of soil splash into the air and scatterin all directions. On bare ground which has poor soil structure, one hard rain can move tons of soil peracre. On a slope, most of this soil will land downhill from its original location, and it can cause even moreerosion than flowing water.Green manures can help this problem in several ways. They shield the soil from the force of a drivingrain. The plants absorb the force of the raindrops and the water flows gently into the ground. The rootshelp hold the soil in place and there is almost no loss to erosion.

Benefit 3.Stop Those Weeds

If weeds are your problem, and you think weeding or poisonous, expensive herbicides are the onlyanswer — read on.Green manures, particularly buckwheat and ryegrass, are effective against weeds by making the weedsknow they’re not wanted. You till the soil, preparing it for a planting of a green manure. This exposesthousands of weed seeds that have been waiting for light and warmth to begin growing. And begin togrow they do, but so does that green manure crop, and the green manure grows so fast that it soonoverpowers the weeds and crowds them out. It’s that simple.Peas and beans, broadcast or planted in wide rows, will do this, too, and they have the advantage ofproviding a crop for your dinner table.Thus, every time you grow a green manure crop and till it under, you are reducing the number of weedseeds in your soil. A few such crops and the weeds will no longer be a problem.Buckwheat Halts Nut GrassNut grass can be a serious pest in a garden because it grows from little “nutsâ€‌ or tubers that spreadrapidly underground. Hoeing and cultivation won’t kill these tubers, and it’s difficult to pull themout, since the roots break off so easily.

Dick Raymond, a well-known garden specialist, got rid of a heavy crop of this weed this way: first, heplanted a crop of buckwheat in the spring. Then, six weeks later, Dick tilled that buckwheat under andplanted a second crop. Then finally, in late summer he tilled that under and planted annual ryegrass. Thenext spring — no sign of nut grass.

Benefit 4.Improve Your Soil Structure

Pick up a handful of good soil. It is soft, dark and has a spongy “give.â€‌ Smell it. Not unpleasant at all.Rich.Examine it closely. Notice how it separates into small granules. These are called “aggregatesâ€‌ andexplain the soil’s looseness. Clay particles, microscopic in size, fit together very tightly, leaving littlespace for air, water or roots. When the soil is well aggregated, these clay particles are molded intorounded granules that have spaces between them. They fit together loosely like a pile of pebbles ratherthan tightly like bricks. Water and roots can penetrate those spaces between the granules.Green manures play a big role in the formation of these granules. First the plants protect them frombeing shattered by raindrops. When the crop is turned under, the micro-organism population isincreased many fold. And it is this population that produces polysaccharides, the glue that holdstogether the material in each aggregate. A good green manure can produce several thousands ofpounds per acre of this glue.Hidden BenefitsA gardener sees only the leaves and stems of the green manure crop, and this vegetation is only part ofthe plant’s contribution to the soil. Don’t forget the root system.

Few realize how large a root system can be. A scientist grew a single rye plant in a box for four months,then measured the roots. His findings were almost unbelievable — nearly 14 million roots with acombined length of 387 miles. This means roots reaching down, loosening soil, and bringing up minerals.It means, too, hundreds of pounds of organic material decaying in the soil.

Benefit 5.Increase the Life in Your Soil

By turning under lush green manure crops, you can create conditions so that the millions of organisms inyour soil will flourish.And the list of jobs they will do for you is tremendous:

They decompose organic matter in the soil and release nutrients that plants can use.They create humus, organic matter that helps the soil to hold water and retain nutrients.They help dissolve nutrients tied up in the insoluble minerals of the soil.Some of them even take nitrogen from the air and make it available to your crops.

Help the Earthworms Help YouThe green manure gardener provides ideal conditions for earthworms. He offers them food in largeamounts as he tills under those green manure crops. He gives them protection, too, a cool, protectedsoil in the summer, and insulation during the fall, when a sudden frost across bare ground would killthem before they could move deep into the earth.

What does the gardener get from them for this food and protection?More than he gives. Earthworms will increase in numbers. They will eat and eat, and pass more than 50tons of materials per acre through their systems.The product of this is castings, and compared with topsoil, castings are exceedingly rich, containingtwice the calcium, ½آ2 times the magnesium, five times the nitrates, seven times the phosphorus andeleven times the potassium of topsoil.

Benefit 6.Save Time and Energy

Composting and green manuring are alike in that both are excellent ways to improve the soil in yourgarden. And the greatest difference between them is the amount of work required to achieve this.Composting is one of the most valuable tools of the gardener, providing him with rich and nutritiousfood for his garden. But it is hard work. You must select a site and build an enclosure. You must find theproper materials to compost, providing a source of carbon as well as a source of nitrogen, on a ratio ofabout 15 to 30 parts of carbon to one part of nitrogen. The pile must be built up, and should be turnedseveral times.Compare this with green manuring. The seed bed is prepared, the seeds are sown and covered, then thegardener waits until the crop has grown. He turns it under, an easy task with tractor-drawn disks andplows, or rear-tined rotary tillers.The only carrying involved was carrying that seed to the garden. In composting, materials must becarried to the pile, and the compost carried to the garden and spread.Green manuring provides uncounted pounds of inexpensive organic material, and it grows right whereyou need it.Think of green manuring as a way of composting on a large scale. Instead of making piles of compost,you are turning your whole garden into an efficient compost pile.

Benefit 7.Stop Wasting Nutrients

When the growing season is over, a lot of nutrients are left in the soil. What will happen to them?Some, of course, will remain in the soil until next season. But much of that goodness may be leachedaway and lost.To avoid this loss, plant green manures, and this time call them catch crops, to underscore their abilityto catch and hold nutrients that might otherwise leach out of the soil, or cover crops, if they are leftover the winter.This approach is particularly valuable in the south, where soil life stays active all winter, breaking downorganic matter and releasing nutrients. In such areas of mild winters with heavy rainfall, nutrients thatwould be lost can be caught and held until needed.Planting these crops is a way to store safely over the winter the soil nutrients, because they can’t belost while they are a part of growing plants or undecayed plant material.Escaped Nutrients Are DangerousRunoff and leaching of nutrients is wasteful, and can be harmful to our environment as well. Oneproblem is that phosphates and nitrates from fertilizer often end up in lakes and waterways.

Lakes that have remained pure and clear since the Ice Age suddenly become scummy and stagnant.Ultimately the fish die, the water smells, and the lake can reach the stage where it is “too thin toplow and too thick to drink.â€‌Nitrates can also leach through the soil into well water, becoming a health hazard.Gardeners, of course, contribute less to these problems than large farms do, but they also have fewerexcuses for waste.

Benefit 8.Growing Healthier Plants

Here’s the real reason for any activity in the garden — to grow healthier plants that produce thetastiest crops.Most gardeners have noticed that a combination of good soil, adequate moisture and sunny, warm dayswill result in healthy plants, and that the threats to garden plants, such as pests and disease, seem toavoid crops that are healthy. Green manuring, by its contributions to improving soil, thus helps toprovide good conditions for healthy plants.Green manures seem to contribute even more. They seem to suppress plant diseases carried in the soil,doing this by encouraging the beneficial soil life. Diseases develop when the balance of power is upsetand the disease organisms outnumber and overpower the good organisms. By growing a green manurecrop and turning it under, we can often increase the beneficial organisms so they regain control. Potatoscab and snap bean root rot are examples of diseases that can be eliminated with the right greenmanures.

Green Manures Help Fight NematodesRoot-knot nematodes are a threat to gardens, particularly in the South. These microscopic wormsinvade the roots of many vegetables, produce knots or lumps on the roots, and stunt the growth of theplants.It’s difficult to eliminate a buildup of nematodes in the soil. Green manures can help you avoid themand may even help you to reduce their population if they are already a problem.Green manures help by encouraging natural predators of nematodes, such as nematode-trapping fungi.Under the right conditions, the fungi can multiply faster than the nematodes. Turning under largequantities of organic matter in the form of green manures provides these conditions.

Benefit 9.Improves Soil’s Ability to Hold Water

The gardening books say that most crops should have “moist but well-drained soil.â€‌ Fine, but whatdo you do if your soil is sandy, and so dries out quickly, or if it is clay and crusts when drying?The answer: Green manures.In the sandy soils the green manures turned under will increase the amount of organic matter in the soiland greatly increase its ability to hold water. With clay, the soil structure will be improved by the greenmanures, enabling the water to soak in much more readily.Compacted subsoil called hardpan may prevent water from draining down through or from workingback up to the surface by capillary action. Grow a crop with strong, deep taproots, such as alfalfa orclover. These taproots penetrate into the subsoils and loosen them. When the crops are turned under,the roots decay, leaving columns through which water will travel.Grow Your Own MulchDon’t overlook the possibility of cutting a green manure crop and using it as mulch in another part ofyour garden.

By doing so you can transfer benefits of the green manure crop immediately to that part of the gardenwhere you are growing food crops.The mulch will conserve moisture, smother weeds, encourage soil life, improve soil structure, andprevent erosion.

Benefit 10.Make Your Garden More Attractive

Vegetable gardens can be a pleasure to view in the summer, and an eyesore in the fall.You can change that by growing green manures.Most gardens, after the crops have been collected, have a bare and desolate look. Some are a mass ofblackened squash vines, posts on which tired tomato plants still cling, and weeds in unlikely patches.Others are bare, with the gardener having raked and removed the trash, and left the soil exposed to theerosive blasts of winter.Then there’s the garden that is soft with a thick mat of green. It belongs to the green manuregardener. You’ll notice some patches which are green are higher than others. That’s because hedoesn’t wait to plant his whole garden with green manures, but fits them in when and where he can.He will harvest a row of vegetables, and quickly spread seed. Or he may even plant between rows whilethe crops are still growing.Gardeners in the north can have a green garden right up to the first snow by planting a crop such asannual ryegrass. A heavy, rich growth will appear in only a few weeks.Southern gardeners have a much bigger variety from which to choose. Crimson clover and blue lupineare two good selections. Vetch, field peas, annual sweet clover and bur clover are others. In both thenorth and south, a wide band of kale can be grown to provide a contrast, and to offer good eating formany months.

Green Manuring MethodsUse your imagination in planting green manures and cover crops. There’s sure to be a crop that willfit into your situation. If you have lots of room and good tilling equipment, you have a greater choice ofapproaches, but there are possibilities for even the smallest areas. Here are three basic methods forgreen manuring. Try them, experiment a bit, and find out what works best for you.A. RotationFor a two-year rotation divide your garden into two plots. Plant garden crops in one, and manures forthe entire season in the other. Switch uses of the two plots the next year. A three-year rotation worksthe same way except that only one-third of the garden is planted to green manures each year. Eitherway, perennials such as asparagus and berries are kept in a separate part of the garden.

B. Winter Cover CropWinter cover crops protect the soil from erosion and temperature extremes, and add organic matterwhen they are turned under in the spring.Annual ryegrass is good in the north for space where you will plant early crops the following spring.Hairy vetch, kale and winter rye will resume growth in the spring, so plant where later crops, such ascorn, squash and melons, will be planted. Choices in the South include crimson clover, bur clover, yellowsweet clover, vetch, field peas, lupine, rye, oats, barley, and wheat.

C. Spot PlantingWhen there’s a bare spot in your garden, fill it with a green manure, possibly an edible one such asbeans or peas. In the fall, after the last cultivation, plant between the rows. Cowpeas, buckwheat, andryegrass are fast-growing and quickly fill vacant spots.

How to Plant Them1. Prepare SoilTurn under crop residues and weeds, and let them decompose. Rototill soil to fine texture. Add fertilizerand lime if they are needed.

2. Sow SeedBroadcast by hand. See chart to determine amount of seed needed.

3. Cover SeedRake it in, or go over area with rear-mounted rotary tiller set at a very shallow depth. Roll it or simplywalk on seedbed.

4. Water If DryIf weather is hot and dry, water the plot so the seeds are moist until they put down roots.

Soil Test RecommendedDoes your soil need fertilizing before you plant green manures? Is it too acid? A soil test will give you the

answers. It is available through the Agricultural Extension Service as well as from private laboratories.It’s either free or inexpensive, and can result in better crops.

When to Turn Under a Green ManureHere are some guidelines for determining when green manures should be turned under, to getmaximum benefit from them.One rule is: Don’t let them go to seed. A crop of buckwheat is an excellent soil conditioner, but if it ispermitted to go to seed, and that buckwheat comes up again in a vegetable crop, suddenly thebuckwheat looks and acts suspiciously like a weed, since it is a plant growing where it is not wanted.Another rule is to plant a vegetable crop soon after turning under the green manure. In that way youavoid loss of the nutrients.Are you trying to add minerals to your soil? Then turn under the crop while it is still fairly young, greenand succulent. The acids produced as the green material rots will free locked-up soil nutrients. The soilwill be ready for planting in as little as two weeks.Do you want to build up the organic material in your soil? Then let the crop mature. The woody materialwill last in the soil much longer, and assist you to increase the humus in the soil. If you do this, youshould wait six or eight weeks before planting another crop.

How to Turn Them UnderYou can use any method that will chop up the green manure crop, then get it down into the soil whereyou want those nutrients to be. Choose the one that best meets your needs.By HandIf you are energetic, or if your garden is fairly small, turning by hand works well. Use a shovel or spadingfork. The job is easier if you cut the crop first with a power mower or a scythe.With a TractorThe crop can be disked or plowed into the soil if you have a tractor, or you can hire someone to do it foryou. This method can be used for several acres. Tractors tend to compact garden soil.A Front-End Tiller?Front-end tillers, designed to cultivate the soil between rows, aren’t good for this job since theywon’t dig through a heavy plant cover into the ground. Also, the tines tangle.

The Best Tool for Green ManuringA rear-mounted rotary tiller is ideally suited for turning under a green manure crop in either a large orsmall garden.The forward motion of the tiller is controlled by the wheels so it takes little effort to operate.Since the tines turn many times faster than the wheels, tangling is not a major problem. Crops that aretwo or more feet high can be tilled under in just a few passes.A rotary tiller is better than a plow for turning under green manures. A plow slices off a long strip ofearth and turns it upside down or on its side. This leaves the vegetation in a mass, not mixed with thesoil.A rear-mounted tiller chops up the plants and mixes the material with the topsoil, together with plentyof air. Since the organic matter is more uniformly distributed through the soil this way, it will decay andrelease its nutrients much more quickly.The tiller can handle small sections of the garden that would be difficult to get at with larger equipment.Also it is light enough so that soil compaction is no problem.From beginning to end, each step of a good green manuring program is made more easy by the tiller.It is good for preparing the seedbed, since it leaves a smooth surface, ideal for sowing seed. By settingthe tiller to a shallow depth, it will cover those seeds.Finally, its big job comes when it is time to till under those green manures.

Buckwheat

A Fast-Growing Crop for Poor or Weedy SoilIt’s hard to beat buckwheat as a green manure that answers many requirements. It will grow in wetor dry areas. It can be planted in soils from which almost all nutrients have been depleted, and, whilethe crop won’t be outstanding, it will start the soil back to a more healthy state. Buckwheat isespecially good for loosening up tough sod and discouraging weeds in a new garden area.Wait until after the last spring frost before planting it. You’ll see it emerge a few days after planting.Within a week it will begin to shade the soil. It comes up so quickly weeds don’t get a chance to getstarted. It will even smother out quackgrass, if the quackgrass is tilled thoroughly before the buckwheatis planted.Give the buckwheat a full season and it will prepare a new garden site for you. Till the area in the spring,then plant the buckwheat. Wait until it blossoms, then till it under. Wait about three days, then plant asecond crop. When this blossoms, then till it under. Wait about three days, then plant a second crop.When this blossoms, till it under and plant an annual ryegrass. The next season you will have an idealgarden site.Or you can let that second crop of buckwheat reach maturity, then mow it. The seeds will germinate andgrow the following spring. Till the crop under when you wish to use the space.

Ryegrass

One of the Best Crops for Winter ProtectionThe most versatile of the winter cover crops is annual ryegrass. It grows fast in home gardens whenplanted after garden crops are harvested and will keep growing until the cold of winter hits it. While it iskilled by extreme cold, the grass forms a heavy mat that will continue to protect and insulate the soil. Byspring it can be tilled under in time to plant early crops such as peas.

Get the annual variety of ryegrass rather than the perennial variety which is longer lived but doesn’tgrow as rapidly. Also, don’t confuse ryegrass with rye, which is a grain. Both have their places amongthe green manures, and winter rye will be discussed later.Don’t delay too long in the fall before planting the ryegrass cover crop, since you want it to havegood growth before being killed by the cold. Garden residues should be turned under soon after thecrops are harvested, and while those residues are still green. Plant ryegrass between the rows of late-bearing crops, such as those in the cabbage family, or carrots.Consider using annual ryegrass among your perennial garden crops. It can help in many ways, such asadding humus to the soil and cutting back on the weeding you must do. One way to try this is to plant itin your asparagus bed after the last harvest. The thick growth will eliminate the need for weeding forthe rest of the summer the ryegrass will die in the winter and will not interfere with the asparagusshoots that come up the following spring.

The Legumes

Remember: Legumes will increase the amount of nitrogen in your soil. A special kind of bacteria,rhizobia, lives in nodules on their roots and can take this plant nutrient out of the air and fix it in a formthat plants can use. Peas, beans, alfalfa, clover, and vetch are some of the well-known legumes.Nitrogen will be fixed only if the right bacteria are in the soil. Make sure they’re there by coatingthem on the seed in the form of an inoculant. These inoculants are available in most seed stores, andare bought as black powders that are mixed with water. Be sure to get the right one for the crop thatyou are planting. For example, all soy beans are inoculated with one type of rhizobia, while another typeis associated with most of the clovers.

Alfalfa

Alfalfa is a high-protein forage crop to consider if you use rotation plans for green manures. It is aperennial that can add much to your soil, and it should be allowed to grow for at least a year beforebeing turned under. This pays off, because a year-old growth of alfalfa can supply up to 200 pounds ofnitrogen as well as tons of organic material per acre, when it is turned under. Many gardeners cut itwhile it is growing, and use the cuttings for mulch elsewhere in the garden. This makes excellent mulch,and provides nitrogen to the soil as it decays.Alfalfa has a high proportion of root growth, with those roots reaching as much as thirty feet down intowell-drained soils. The roots mine nutrients from the subsoil, and make alfalfa very droughtresistantbecause they can draw moisture from great depths. When the crop is turned under, these roots add awealth of organic matter and improve the soil far below normal tilling depth.Alfalfa has two requirements: the soil should be well-drained and not too acid. The pH level should bebetween 6 and 7.5.In the north, plant alfalfa in the spring and turn it under the following spring. Many plant it in the fall inthe south. Do this early enough so that the plants are established before winter, but late enough toavoid the summer’s heat and drought.

The Vetches

Several varieties of this viney legume are valuable soil-improvement crops. Since they are annuals andlike cool weather, they make good winter cover crops for the Southeast and the Pacific Coast. Hairyvetch is the only variety hardy enough to survive northern winters. Vetches will grow in a wide variety ofsoil and do not require as much lime as most legumes. They demand a fairly fertile soil and adequaterainfall because they are shallow-rooted and not very drought resistant. They make a good cover cropbecause they form a large mass of roots in the surface soil and will yield a lot of nitrogen.Hairy Vetch is the most widely used because of its winter hardiness. Even in the south it is often thebest choice because it doesn’t begin growth during temporary warm spells in winter, only to bekilled by severe freezing later. Vetch is susceptible to root-knot nematodes and either should not beplanted where these are a problem, or should be planted late enough to avoid these parasites.In the North, hairy vetch can be planted later than any other legume. The best time is from August tothe middle of October, depending on your latitude. It is a slow starter, so don’t look for much growthin the fall. Plant it with a nurse crop such as winter rye or oats which will control the weeds until thevetch is established. The nurse crop will also protect the vetch against the cold of northern winters. Thiscombination makes an excellent green manure that does well in both sandy and clay soils. Don’t soweither crop too thickly, or one may choke out the other.Common Vetch can’t be grown where temperatures drop below .F°آ10 It grows well on the PacificCoast, does poorly in light, sandy soils.Hungarian Vetch is between the two previous vetches in winter hardiness. It does better than both inheavy, poorly drained soils.Purple Vetch is the least winter-hardy, and its growth is limited to the Pacific and Gulf coasts. It willgrow all winter and thus its large mass of green material can be turned under early in the spring.

Clovers

Excellent Deep-Rooted Soil-Improvement CropsIf your ancestors were gardeners or farmers, they knew it for generations back: plant clovers to improveyour soil. This was practiced for years before the chief reason for its contribution was understood, thatclover, like other legumes, could absorb nitrogen from the air and thus enrich the soil.Clover is still one of our best green manures, with species for many purposes.Most of the clovers grown for green manures are planted in the spring and allowed to grow a full year.Crimson clover, an exception, is an annual that can be planted in the fall where winters are mild, thenturned under in the spring.Red Clover. A perennial that grows one or two feet high and once was the most common forage plantin this country. If not cut before it sets seed, it will usually die the year it is planted. It prefers well-drained soil that is not too acid. Because it won’t tolerate as much heat and dryness as alfalfa, it ismainly a northern crop. It has a strong taproot, with many branches. Red clover will produce a largemass of green material, plus nitrogen.Alsike Clover. this clover looks much like red clover except that its flowers are pink or white. It is aforgiving crop, since it will grow in poorly drained areas and in soil too acid or alkaline for red clover. Itsroot system is less extensive, but it’s a strong nitrogen producer.White Clover. The usual white clover plant is a low, creeping perennial often found on lawns. However,one variety, Ladino, is much larger and has been used increasingly in the North as a forage crop. It is agood green manure, tolerating excessive moisture, demanding heavy feeding and producing rich organicmatter.Crimson Clover. This clover is popular where winters are mild, and where it is planted in the fall. Itmakes rapid growth in the spring, and decomposes rapidly when it is turned under, so it contributesmuch organic material to land that is quickly ready for such warm season crops as corn, beans, melonsand squash.

Sweet Clovers

Excellent Soil-Improvers with Powerful TaprootsLook below the surface of your garden when putting a value on those biennial legumes, the sweetclovers. Their root systems work in many ways to improve your soil.The sweet clovers have a strong taproot that will dig its way into hardpan and subsoils. This means theplants are bringing up for use minerals not reached by other plants. And when the plants are turnedunder, those roots decay quickly, leaving deep channels filled with organic material.The sweet clover roots, too, have a greater ability than most crops to extract nutrients from insolubleforms of phosphorus and potassium, such as rock phosphate and feldspar. Later crops will benefit fromthe sweet clovers when they use these nutrients. And as with other legumes, the roots of sweet clovershouse the bacteria that can extract nitrogen from the air.Sweet clover has one requirement: It wants a pH above 6.0, so you may need to add lime. It will tolerateboth wet and dry conditions, and extremes of cold and heat.The two common varieties are white and yellow sweet clover. The white-flowered variety usuallyproduces a greater bulk of green material, while the yellow will grow under drier conditions. Both areusually planted in the spring, and in the first year develop a single branched stem and a strong taproot.The following spring many stems come out of the buds that remain dormant on top of the root throughthe winter.The best time to turn it under is in the spring when this second growth reaches six to eight inches tall. Byturning it under at this time you get 75–80 percent of its potential soil improvement value and at thesame time you clear the way to plant the warm-season crops.If you turn it under in the fall, till it thoroughly. Otherwise many of the dormant buds will survive thewinter and sprout in an unwelcome fashion in the spring.There are annual varieties of sweet clover such as the Yellow Annual, sometimes called sour clover. Thisis used as a winter cover crop in the south and is not winter hardy in the North.

Double Duty Green ManuresIf your space is limited, or you’d like to get more than soil enrichment from your green manures, trythe double-duty varieties. They produce food for the table as well as for the soil, and include peas,beans, and kale. Other possibilities are soybeans and cowpeas. With most of these crops, the trick is toharvest as early as possible, then turn them under. Peas are especially suited for this, being an earlycrop. It is easy, in most areas, to till under the pea vines, then have ample growing time for a variety ofcrops in the same space.

Kale

The Wonder CropKale, the hardiest member of the cabbage family, can be grown through the winter south of New Jersey,and well into the winter north of that line. Thus it makes a good cover crop in a broad area of thenation.It’s a nutritious food, and its fresh greenness is welcome when no other leafed plants are available inthe garden. Most persons cook it like spinach, and the more hardy aren’t bothered by its coarsenessand cut it into salads. Its color and crispness make it a fine garnish.Kale is particularly high in vitamin A, and offers vitamins B1, B2 and C as well. Its flavor is improved bythe cold weather; and fast growing lessens its toughness.Kale should be planted about six weeks before the first frost in the northern areas, and can be plantedinto the winter in the South.For the best crop, thin it (and dine on those thinnings) so that the plants are as much as a foot apart,with the dwarf varieties about six inches apart. A heavy mulch placed around the plants will extend thegrowing season in the North as heavy frosts threaten.

Planting Cover Crops of Beans and Peas

Beans and peas are excellent cover crops and equally good eating. For a cover crop, they are planted inwide rows. Both are legumes, so add nitrogen and organic material to your soil.If you use a rear-mounted tiller, broadcast the seeds, trying to spread them so they are about twoinches apart. Set the tiller so that it tills about two and one-half inches deep, then run over the plot inhigh gear. This will cover the seed.If you are doing the work by hand, broadcast the seeds in one strip, cover them with soil from theadjacent strip, then plant that strip, and cover, getting the seeds under about an inch and a half of soil.Next, in both cases, firm the seedbed, either rolling it or walking on it. Water if it is dry. You won’thave to thin the plants and they should be thick enough to crowd out the weeds.

Green Manuring in Small GardensHere’s an easy way for the small gardener to use green manures without taking sections of hisgarden out of production.Divide your garden into three sections, and plan to plant green manures in successive sections during athree-year period.In section one, plant peas the first year, in rows up to six feet wide. Pick the yield, then turn under thepea vines, and plant snap beans, soybeans or cowpeas, broadcasting these seeds. You are now addingnitrogen to the soil, as well as discouraging the weeds by shading them out. After gathering these crops,till under the plants and plant a winter blanket crop such as annual ryegrass, in the section andthroughout the garden if possible.The following year, select another section for the green manuring cycle and use the first section forsmall-seeded crops, such as onions, lettuce, and carrots, to take full advantage of the weed reduction.The third year plant the third section to green manures, use the first section for large-seeded crops suchas melons, corn and potatoes, and the second section for the small-seeded crops. Continue this rotation,year after year.

Lupine

Large showy flowers make lupine a colorful winter cover crop for the Deep South. This deep-rootedlegume has been used as a soil-improvement crop in Europe for more than 2,000 years. It grows onlywhere winters are very mild, but in these areas it can produce more green material to turn under thanany other winter cover crop. Planted in October or November, it may yield as much as twenty tons ofgrowth per acre by the middle of March.The common varieties of lupine are white, yellow, and blue. White is the most winter hardy, but itrequires fairly fertile soil with a nearly neutral pH. It can be grown as far north as Arkansas. Yellow is theleast winter hardy, but can grow on moderately acid, sandy soils of low fertility. Blue falls between theother two in both winter hardiness and pH and fertility requirements.

Small Grains

Rye, oats, wheat, and barley are among the small-grained or cereal plants that can be used as covercrops. All have both spring and winter varieties. The winter varieties are planted in the fall and makeexcellent winter cover crops. The best is winter rye. It can survive extreme cold and will grow in almostany soil. Winter wheat ranks second in cold tolerance while winter oats is the least hardy of the four.Although winter rye and wheat can survive northern winters, they grow very little during cold weather.Plant them before hard frosts in the fall or allow them to make their growth in the spring, to get the bestyield of organic matter to turn under. All produce a lot of green manures to be turned under before it istime to plant late crops, and all make excellent mulches if they are cut and collected before the stubbleis tilled in.

Other Good Soil-Conditioning CropsHairy Indigo is resistant to root-knot nematodes and may help reduce the number of them in infestedsoil. A legume, it does well on poor soil. Grown during the summer in the Deep South.

Lespedeza is a legume valuable in the South for restoring poor land. It will tolerate an acid soil. Twovarieties are Common and Korean. Both are usually planted between February and April, and can beturned under in time to plant a fall garden.

Smooth Brome grass is a good winter cover crop in the North. It has a dense root system and a fine topgrowth that decomposes quickly when turned under. A good crop for improving soil.

Bur Clover is a good winter cover crop for the South and the Pacific Coast. If you plant it once and allowit to go to seed once every five years, it will return each fall without being replanted. This happensbecause bur clover has hard seeds that can survive for a long time in the soil, and it germinates onlyunder exactly right conditions in the fall. Be sure you want it for many years before you plant it.Pearl Miller is fast growing grass with a dense root system. It can smother out weeds with its bulk oforganic matter.

Weeds. Nature’s original cover crop, this one grows if nothing else is planted. Advantages: Protectsthe soil from erosion, sends roots deep into the subsoil, and the seeds come at bargain rates.

Where to Get Seed

Most of the green manure crops in this bulletin are common field crops. Seeds for many of them shouldbe available at your local farm supply store.Baker Creek Heirloom Seeds417-924-8917www.rareseeds.comComstock, Ferre & Co.800-733-3773www.comstockferre.comThe Cook’s Garden800-457-9703www.cooksgarden.comFedco Seeds207-873-7333www.fedcoseeds.comHarris Seeds800-544-7938www.harrisseeds.comHeirloom Seeds412-384-0852www.heirloomseeds.comJohnny’s Selected Seeds877-564-6697www.johnnyseeds.comNichols Garden Nursery800-422-3985www.nicholsgardennursery.comPinetree Garden Seeds207-926-3400www.superseeds.comW. Atlee Burpee & Co.800-333-5808www.burpee.com

The History of Soil-Improving CropsThe idea of using crops to improve the soil is not a new one. The Chinese word for green manure is“miao fenâ€‌ and Chinese gardeners have been using green manures for nearly 3,000 years. As farback as the fifth century B.C., one Chinese writer described several crops that were used for soilimprovement and wrote that “they are broadcast in the fifth or sixth month and plowed under in theseventh or eighth month … Their fertilizing value is as good as silkworm excrement and well-rottedfarm manure.â€‌The ancient Greeks and Romans practiced green manuring extensively. One Roman writer, Varro(116–27 B.C.) wrote: “certain plants are cultivated, not so much for their immediate yield, as withforethought for the coming year, because cut and left lying, they improve the land.â€‌By the seventeenth and eighteenth centuries, green manuring began to be common in Germany andEngland. It was slow to spread to the United States because of the abundance of fertile, virgin land, butthe colonists were not totally ignorant of it.The benefits of cover crops took a little longer to be recognized. The first person to really advocate themwas Richard Parkinson. He said, “… it is seen how earnest my wish is that the surface of the groundshould at all times, winter or summer, be well covered, whenever it possibly can be accomplished.â€‌It was only about a century ago that scientific explanations for the benefits of green manures began tobe discovered, as agronomists learned about the ability of legumes to fix nitrogen and about theimportance of microorganisms in the soil. Soon afterward, the practice of green manuring began to beovershadowed by the massive use of chemical fertilizers.

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