By: Heather Rhoades
Cover crops for the garden is an often overlooked way to improve the vegetable garden. Oftentimes, people consider the time between late fall to winter to early spring to be a time where the vegetable garden space is wasted. We think our gardens rest during this time, but this is not the case at all. During cold weather there’s something you can be doing to help improve your garden for next year and this is by using cover crops.
A cover crop is anything that is planted in order to literally “cover” a piece of land that is not in use. Cover crops are used for a wide variety of reasons, from green manure to soil improvement to weed control. For the home gardener, the question of where to plant cover crops comes down to what part of your garden will be empty during the cold weather.
Cover crops are most often planted as green manure. Nitrogen fixing cover crops are much like sponges that soak up nitrogen as well as other nutrients that might otherwise be lost to weeds or washed away by rain and snow melt. Even non-nitrogen fixing plants will help to ensure that many of the nutrients in the soil can be returned to the soil when the plants are tilled under in the spring.
Cover crops are also a wonderful way to help maintain and even improve the condition of your soil. While planted, cover crops prevent erosion by holding the top soil in place. They also help reduce soil compaction and help the beneficial organisms in the soil, like worms and bacteria, to flourish. When the cover crops are worked back into the soil, the organic material they provide increases how well the soil can hold onto water and nutrients.
Lastly, when you plant a cover crop, you are growing plants that can compete with weeds and other undesirable plants that would like to take up residence in your garden while it is empty. As many gardeners can speak to, often a vegetable garden left empty over the winter will be filled with cold hardy weeds come mid-spring. Cover crops help to prevent this.
There are many choices for cover crops and which is best for you will depend on where you live and your needs. Cover crops tend to fall into two categories: legumes or grasses.
Legumes are beneficial because they can fix nitrogen and tend to be more cold hardy. However, they can be a little harder to establish as well and the soil must be inoculated for the legumes to be able to properly take up and store the nitrogen. Legume cover crops include:
Grass cover crops are easier to grow and can also be used as wind blocks, which further help prevent erosion. Grasses tend not to be cold hardy and cannot fix nitrogen though. Some grass cover crops include:
Winter cover crops can help you improve and make use of your garden year-round. By using cover crops for the garden, you can be sure that you will be getting the most out of your garden next year.
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Read more about General Vegetable Garden Care
When it comes to low maintenance gardening, nothing can quite lend a hand like planting no-till garden cover crops.
No-till garden cover crops play a major factor in eliminating weeds from your garden!
Do you want to eliminate nearly all of your weeding woes next year?
Would you like to plant your vegetables next spring with ease, and without the hassle of a rototiller?
And, does the thought of fertilizing your garden 100 percent naturally appeal to you?
Well, if you plant soil-charging, weed-eliminating, no-till garden cover crops this fall, you are well on your way to all three and more!
There are three main categories, depending on their properties and options for use: grasses, legumes, and broadleaf non-legumes. In most cases, they combine several functions at a time, like preventing erosion, improving soil quality, serving for grazing, among others.
Many gardeners have used cover crops to help keep soil from blowing away over winter. An added benefit of raising cover crops is that the foliage and root growth can be tilled under in late winter to help loosen heavy soils and improve overall soil structure and fertility. Also known as “green manure,” these cover crops can be especially valuable in preparing a new site for gardening or for rehabilitating a heavy or compacted site.
Cover crops are generally sown in late summer or early fall. In established gardens, wait until after summer vegetables are harvested. The type of crop to grow will depend on the desired function, as well as availability. Winter rye, buckwheat, hairy vetch and winter wheat are ideal for use as cover crops and are among the most commonly available through garden centers and mail-order catalogs.
The amount of seed to plant will vary with the species, but, in general, winter cover crops are seeded at a rate of 2-3 pounds per 1,000 square feet. Till or spade the soil, and scatter the seed over the area to be covered at a depth corresponding to the size of the seed. Large seeds should be covered with one-fourth to one-half inch of soil or compost. Small seeds can be left on the surface and lightly raked. Apply a thin layer of loose straw to protect the area from wind and runoff from heavy rains.
Fertilizing is generally not necessary, especially for established garden beds. Some members of the Legume family of plants, most notably alfalfa and hairy vetch, actually facilitate the fixing of nitrogen in association with certain soil-borne bacteria. The bacteria colonize in nodules of the legume’s roots.
The root growth of the cover crops will help loosen heavy or otherwise compacted soils, and the addition of the dead foliage later in winter or spring will improve aeration, water-holding capacity and nutrient status. The cover crop should be plowed under several weeks prior to spring planting time to allow the vegetation a chance to break down a bit. For plants that have a large volume of top growth that tends to get tangled in the tiller tines, mow the tops first, then till under.
Feed Soil Life. Think of cover crops as little solar-energy factories using sunlight to transform water and carbon dioxide into leaves and roots, which release carbohydrates and other compounds to sustain the soil microbes, earthworms and other fauna that make soil fertile. Nutrients constantly cycle through plants and back into the soil cover crops keep this cycle going when you aren’t growing other crops.
Protect Soil Life. Without plant cover or mulch for protection, beneficial soil microbes can be killed by ultraviolet radiation and extreme temperature swings.
Prevent Erosion. Bare soil also is vulnerable to erosion. Even on relatively flat ground, winter rains still can wash away topsoil.
Prevent Weeds. Fast-growing fall cover crops out compete late-season weeds like quack grass and chickweed.
Cover crops are grown outside of the cash crop growing season, usually seeded in the fall and killed before spring planting.
Keeping living roots in the ground year-round can improve water management, soil protection and nutrient scavenging, but they need to be given the same attention as a cash crop to ensure success.
Try cover crops on a small scale at first, and look into cost-share from state and local governments.
Some of the best opportunities are with early-harvested cash crops like corn silage, small grains, and canning crops like beans and peas, as you’ll get more vigorous fall growth if you plant in late summer and early fall.
In fields where wheat was just harvested, simply allowing the wheat to reseed itself without tilling the land would work as a cover crop. But cover crops can work with standard corn-soybean rotations as well.
For a quick way to get started, Minnesota cover crop recipes provide step-by-step guidance to some of the lowest-risk starting points for cover crops. These recipes don’t cover all possibilities, but they can help beginners get most pieces in place to incorporate cover crops into a farm operation.
Cover crops reduce erosion in a few different ways.
Cover crop root systems create large channels through the soil to allow increased infiltration. This effect is especially significant for species that have large taproots, but increasing infiltration is reported for other cover crop species as well.
Cover crops can also help soil store water by building structure and creating a network of large and small pores.
Soil nitrate reduction is well-established in Minnesota for a variety of cover crops.