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​Cover Crops and Green Manures

Learn about benefits of cover crops, where to buy seeds, where and how to direct seed and three ways to use the organic matter in your garden. Get growing guidelines for both winter and summer varieties for Central Texas.
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In this video we give you 7 reasons to plant cover crops in your garden. At the end we also give tips on how to harvest and compost “green manure.”
​WHAT ARE COVER CROPS
A cover crop is a crop you grow for the soil, and not necessarily for your plate. The practice of growing specific crops just for fertilizing and building the soil dates back to Roman ages. Another name for cover crops is green manure. 
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WHY PLANT COVER CROPS
  1. Soil Carbon Sequestration: Cover crops are an important soil carbon sequestration strategy. The roots and shoots of cover crops feed bacteria, fungi, earthworms and other soil organisms, which increases soil carbon levels over time.
  2. Reduced erosion and runoff:  Cover crops reduce the impact of rain on the soil surface, reducing soil erosion and runoff . 
  3. Increase Organic Matter:  Overtime, planting cover crops increases organic matter, leading to improvements in soil structure, stability, moisture, and nutrient holding capacity. Therefore improving the overall quality of the soil.
  4. Fertilize soil:  Cover crop stores nutrients from compost, mineralized organic nitrogen until the next crop can utilize them, reducing nutrient runoff and leaching. Certain cover crops, such as clovers, field peas and beans, add nitrogen to the soil, reducing the need for nitrogen fertilizer.
  5. Reduced soil compaction: Deep tap roots of some cover crops such as Daikon Radish penetrate compacted soil layers, improving drainage while conducting more moisture deeper in the profile.
  6. Suppressed diseases, pests and weeds: A cover crop provides a natural means of suppressing soil diseases and pests. It can also serve as a mulch or cover to prevent weed growth.
  7. Source of Food: While some cover crops provide an actual source of food for you, they also provide a source of food  for beneficial insects and wildlife.

WHERE TO PLANT COVER CROPS
So based on all of these benefits, choose an area in your garden, for a new area that you want to garden that.
It is also a good crop rotation strategy. We will be planting cover crops where we grew corn, which uses a lot of the nitrogen in the soil. Additionally we will be planting cover crops where we grew sweet potatoes. This will ensure that we control any potential nematode problems. 

WHEN TO PLANT COVER CROPS
​Early Fall and Late Spring. Scroll for growing guides and a list of cover crop varieties.

HOW TO PLANT COVER CROPS
Seeding
Rake the soil surface to break up clumps. You can wait until you've harvested the existing crop, or sow it a few weeks before the season ends, to protect the soil after harvest. Scatter the seed as evenly as you can, then tamp the soil down. Try to time the sewing of seeds with the waxing gibbous moon cycle and with forecasted rain. If you don't get rain while the seeds are germinating, water lightly daily. As the seedlings get bigger, water more deeply and less often.

Harvesting and Decomposing Organic Matter
If you plan to leave the manure crop on through the summer or winter, mow or cut it each time it begins to flower, letting the clippings fall to the ground. That way, it can't go to seed and create a weed problem. Although, some quick cover crops like buckwheat you can allow to seed and cycle up to three times.

NEVER, uproot your crops because you want to not upset the soil ecosystem or pull up the organic matter and nitrogen nodules that are in the roots of the plants.

Here are three ways to harvest and use the cover crops.
  1. Chop and Drop:  A few weeks before you plan to plant your garden, use a scythe, sheers, weed eater or mower or other tool to chop the leaves and stems, or mow with a mulching mower, or weed eater. It will be easier to work the manure into the soil if you first let it dry for a few days. You can use the organic matter as mulch anywhere in your garden.
  2. Trench Composting: You dig a trench in your garden and compost the organic matter or add it to your compost bin. When you turn the manure under the soil depends on the results you want. Grasses and other non-legumes add mostly nutrients if you turn them under when they are young and tender. When they are older, they become a better source of organic matter. Mature legumes add more nitrogen than young ones, but can be harder to cut and turn under the soil.
  3. Double Dig Method If you cover only a small area with cover crops, you can turn it under with a spade using the double dig method. Tough plants such as old alfalfa may require a few passes.

Accelerate Decomposition
If you want to speed up the breakdown of the green manure, recycled mushroom blocks, add animal manure, compost, or another well-balanced organic fertilizer after chopping, trenching or turning under.

WINTER COVER CROPS FOR CENTRAL TEXAS
Annual ryegrass (Lolium multiflorum Lam.)
Annual ryegrass dies out after one year, although some of the seed planted the first year may come up for the next two or three. Use it when you need a green manure that germinates quickly, loosens the soil, and prevents soil erosion. Annual ryegrass won't tolerate flooded conditions for long. Annual ryegrass germinates well in cool soils. It does well in a wide range of soil pH and textures, but prefers loamy or sandy soils. Annual ryegrass releases substances toxic to other plants. That trait makes it good for weed control, but means you can't plant small-seeded crops such as lettuce and radishes just after turning annual ryegrass under. Transplants and large-seeded crops aren't affected.
Growing Guidelines: Plant in the fall. You can plant it along with a legume. Scatter 1.5-3 ounces of seed per 100 square feet, or 1-2 pounds per 1000 square feet. Cover with about half an inch of soil, then tamp down the soil.
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Winter Rye (Secale cereale) Because winter rye grows early in the spring and produces toxins that kill seedlings, it's ideal for smothering weeds. Like other grasses, its fibrous root system and succulent leaves add organic matter. Winter rye prefers a well drained soil.
Growing Guidelines: Plant in the late summer or fall at a rate of 4 ounces per 100 square feet or 2.5 pounds per 1000 square feet. Grow transplants or large-seeded plants after turning it under; small seeded plants can't tolerate the toxic substances.

Winter Wheat (Triticum aestivum) Use winter wheat, an annual grass, as a short-term green manure that you sow in the fall and turn under in the spring. Winter wheat prefers a fertile, loamy soil and a neutral pH.
Growing Guidelines: In the late summer, plant 3-6 ounces per 100 square feet or 2-3 pounds per 1000 square feet.

Alfalfa (Medicago sativa) Alfalfa is the best legume for fixing nitrogen, if the soil is adequately fertile. Because it's deep rooted, alfalfa draws nutrients from the subsoil, which are returned to the topsoil when you turn the plants under. It is high in protein, minerals, and vitamins. It's a perennial grown for one year. Alfalfa needs a deep, well-drained soil, a pH near neutral, and adequate amounts of phosphorus, potassium, calcium, and sulfur.
Growing Guidelines: Before planting, apply an inoculant. Sow in the spring, planting 1.5 ounces per 100 square feet or 1 pound per 1000 square feet.

Soybeans (Glycine max) Grow soybeans, a summer annual legume, to add nitrogen to poorly drained soils. Soybeans are often grown with a grass such as buckwheat. Soybeans do best on a well-drained soil, with a moderate amount of moisture, but will tolerate poor drainage.
Growing Guidelines: Apply an inoculant to the soil before planting. Plant 3-5 ounces per 100 square feet or 2-3 pounds per 1000 square feet in the spring or early- to mid-summer. Cover with an inch of soil.

Crimson clover (Trifolium incarnatum L.) Crimson clover is a adapted to shady areas and grows well at low temperatures. It's often left in place for a year. Crimson clover can grow in both sandy and well-drained clayey soils if they're not extremely acidic. The germinating seeds and young seedlings need to stay moist. Crimson clover won't tolerate calcareous soil (soil high in limestone), and needs a good supply of phosphorus and potassium.
Growing Guidelines: Apply an inoculant before planting. Sow in October. Scatter 0.5 ounces per 100 square feet or 1 pound per 1000 square feet. Cover with a half inch of soil and tamp down. Keep the soil moist while the plants are young.

Sweet clover (Melilotus spp.) Sweet clover is the best legume for improving poor or disturbed soils that aren't acidic. It adds phosphorus, nitrogen, and large amounts of organic matter to the soil. Its deep roots loosen the soil and draw nutrients from the subsoil, which return to the top soil when you turn the green manure under. Sweet clover requires a well-drained soil with a pH near neutral. It absolutely won't tolerate acid soils.
Growing Guidelines: Sow in the spring or summer at a rate of 0.75 to 1.5 ounces per 100 square feet or 0.5-1 pound per 1000 square feet.

Ladino Clover Ladino clover is a tall variety of white clover. Because it dies during the winter, you can more easily turn it under in the spring than regular white clover. It produces more organic matter than white clover.
Growing Guidelines: Apply an inoculant to the soil before planting. Plant in the fall, sowing 0.75 ounces of seed per 100 square feet or 0.5 pound per 1000 square feet. Turn under in the spring.

Vetch (Vicia spp.) There are several vetch species, including common vetch, hairy vetch, and purple vetch. All are vining annual legumes that are often planted with grasses. Use them as a winter annual to add nitrogen and organic matter to any well-drained or droughty soil. Hairy vetch grows in most soil types, while common vetch needs a fertile, loamy soil. All prefer well-drained soils. The vetches are drought-tolerant.
Growing Guidelines: Apply an inoculant to the soil before planting. Plant in the late fall unless you're growing common or purple vetch in the North, in which case you should plant in the spring. Plant 3 ounces per 100 square feet or 2 pounds per acre. Cover with 0.75 inch of soil.

SUMMER COVER CROPS FOR CENTRAL TEXAS
Buckwheat  (Fagopyrum esculentum)
Use buckwheat, a broadleaved non-legume annual, to quickly smother summer weeds. It matures in two months; you can plant a second crop for full summer coverage. Buckwheat builds organic matter and adds phosphorus to the soil. This plant steals soil nitrogen from its neighbors, tricking interplanted southern peas into fixing more nitrogen. Buckwheat grows in most soils, including infertile and acidic ones. Buckwheat is very attractive to honeybees, hover flies, soldier beetles, parasitic wasps and parasitic flies and predatory insects including assassin bugs, shield bugs, and predatory stink bugs. Buckwheat has a short growing cycle and will reseed and grow three cycles through spring and summer. 
Growing Guidelines: Plant 5 ounces per 100 square feet or 3 pounds per 1000 square feet in the spring or summer.

Sudangrass (Sorghum bicolor) Grow this tall grass during the summer to choke out weeds. This crop is unrivaled for adding organic matter to worn-out soils and the roots grow very deep.These tall, corn-like stalks, fast-growing, heat-loving summer annual grasses can smother weeds, suppress some nematode species and penetrate compacted soil.Sudangrass has a dense root system that makes it well suited to erosion control and adds organic matter. Sudangrass survives drought well but performs better with more water, especially in the Southwest. It adapts to poorly drained soils.
Growing Guidelines: When the soil is warm, plant 1.5-3 ounces per 100 square feet or 1-2 pounds per 1000 square feet.

Pearl Millet (Pennisetum glaucum L) is a tall, bunching grass that can get up to 12 feet high. The heads of some varieties of millet resemble that of a cattail. It is best suited for mid-summer plantings. The pearl millet has good nitrogen scavenging qualities, prevents erosion, Foxtail millet and pearl millet are the two with the popularity for cover crop use. 
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Southern Peas (Cowpea) are relatively drought tolerant and come in varieties that grow on vines or as a bush. As a legume, they provide a good source of nitrogen. We love purple hull peas and California cowpeas. Here's a link to the growing guide with varieties that grow well in Texas.

Sunflowers (Helianthus) can attract predatory insects such as big-eyed bugs, wasps, lady beetles and predatory bugs. Sunflowers have a deep taproot breaking up some of those soil layers and bringing more different kinds of beneficial bacteria, fungi and microbes. 

WHERE TO BUY
Check your local garden store. We have bought organic seeds at Callahans, Natural Gardener. You can also find organic, non-gmo blends online. We like this blend of Winter Cover Crops from True Leaf Market.

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