By Kimberly Oxley, Gardner Community Garden Education Chair
As fall hits in the Midwest and the vegetable garden is cleaned out, some may think that’s it until next Spring. Why not take advantage during this rest time in your garden and add much-needed nutrients back into your soil? One way to accomplish this is to plant a fall/winter cover crop in your garden.
What is a cover crop or green manure?
As I talked about cover crop in the article “Love Your Garden Soil, it will Love You Back”, a cover crop (or green manure) helps feed your soil by building fertility, improving structure, prevent soil erosion, reduce weeds and provide a habitat for beneficial insects. This practice has been around for over 100 years. The roots in the soil will create open paths as it decays to improve air and water movement. The cover crop feeds your soil by incorporating macronutrients (nitrogen, phosphorus, potassium) as well as many micronutrients. The residue becomes a “holding tank” for these nutrients. As it breaks down and becomes incorporated as organic matter, the nutrients are released. Examples of cover crops are rye, buckwheat, and oats.
Other cover crops such as legumes require an inoculant (Rhizobium bacteria) when planted into your soil for the first time. They increase nitrogen levels in the soil by a bacteria (Rhizobium spp.) that lives in their roots. This inoculant is available at most garden supply centers. Examples of cover crop legumes include winter pea, hairy vetch, and clover.
Planting cover crop is a simple procedure. If needed, gently break up the soil to help assist in good seed to soil contact. For a home gardener, using a broadcast seeder is affordable. Once the seed distributed, rake it in. Raking will establish a good soil to seed contact. It will also protect from birds and wildlife from having a snack. You need to allow time for the seed to germinate and become established. Plan to plant the cover crop four weeks before frost to enable good germination. One exception is rye, which can be planted up to the first frost.
5 Easy to Grow Fall Cover Crops
Crimson clover is grown as a winter cover in the Midwest. It is cold tolerant, good nitrogen-fixing capability and is moderately drought tolerant. To kill this crop in the spring, mow close to the ground before full bloom to prevent reseeding.
Hairy Vetch has an excellent cold tolerance, moderate nitrogen-fixing capability and is drought tolerant. It also can tolerate a wide range of soil pH and fertility levels. Vetch needs to be planted 40 days before the first freeze to establish a good stand and be able to survive the winter. About a month before planting your crop, terminate the vetch by mowing or trimming it to the ground. It will eventually die down, where you can plant your vegetable crop in the dried mulch
Austrian Winter Pea
Austrian Winter Pea is moderately cold tolerant and has a good nitrogen-fixing capability. It can rapidly establish a good stand. Plant mid to late September is possible.
This grass can take drought conditions and is cold tolerant. It is easy to till or incorporate into the soil the following spring season.
Winter Wheat or Rye
This rye is a tall growing grass that can be planted late into the season that overwinters well. It provides excellent erosion control. It is also easy to till or incorporate into the soil the following spring season.
A Good Combination
Certain legumes and grasses, when combined, provide good nitrogen capacity and adds a significant amount of organic matter into the soil. The grasses provide a structure for the legumes to grow on during springtime and reduce the chance of matting. The cover crop can be mowed and incorporated back into the soil leaving a residue. Examples are vetch and rye, pea and oats, pea and rye.
Terminating Your Cover Crop
There are a few ways you can take down your cover crop. Traditionally, cover crops are plowed or tilled into the soil. Many gardeners will mow, cut or pull them and lay them down as mulch for the fruit or vegetable plants. If you mow or till, it is recommended to wait two weeks before planting your crop to avoid any negative reactions from the residue.
Search seed catalogs for cover crops and find the right one for you in your area. As you start your cover crop rotation in between your crop planting, you will slowly build up a healthy soil and feed your gardens soil food web. Healthy soil = heathy plants!