Author: Natalie Hoidal
Fall cover crop planting is right around the corner, and this blog post is full of resources to help you with species selection, seeding rate, and seeding methods.
Choosing a cover crop
The first step to choosing a cover crop for fall is knowing when you'll be able to plant it. Some crops like oats, peas, and tillage radish are better suited to early fall planting since they die over the winter and need some time to get established before a hard freeze. Others like winter rye, winter wheat, hairy vetch, and red clover survive the winter and grow in the spring, so they can be planted a bit later.
For an overview of each of these cover crops and their pros and cons in a vegetable production system, check out our page titled Cover Crop Selection for Vegetable Growers.
Another great resources is the Midwest Cover Crop Council Decision Tool. To use this tool, select the county you farm in and (if you'd like) your goals for the cover crop. The tool will then give you a list of cover crops with ideal planting windows, ranked according to your goals. If you click on the cover crop you're interested in planting, the guide provides information about the crop, including the ideal seeding rate for drilled or broadcast seeding.
Mixing cover crops
There are many benefits to planting multiple cover crops together in the same field to achieve multiple types of benefits. In particular, mixing a legume with a non-legume is a practical way to achieve an optimal blend of ecosystem services. A high biomass grass will boost organic matter in the soil, suppress weeds, control erosion, and scavenge excess soil nitrogen, while legumes provide nitrogen.
While mixes with multiple species can offer multiple benefits, pre-made mixes are often not designed with vegetable growers in mind. Many cover crop mixes contain plants in the Brassica family, which can be hosts for pathogens that infect broccoli, cabbage, cauliflower, many Asian greens, mustard, arugula, turnips and radishes. Take care to avoid planting a mix that contains cover crops in the same families as your cash crops.
Remember to account for your nitrogen credit
Cover crops provide nitrogen to your next cash crop in two ways:
- Cover crops in the legume family form relationships with soil bacteria called rhizobia, and together they convert nitrogen from the atmosphere into soil nitrogen. This process can provide 50 - 200 pounds of nitrogen per acre, depending on the species of cover crop and how well it establishes
- Even non-legumes help with nitrogen. Nitrogen is very mobile in the soil and can easily wash away as water moves through the soil. Keeping a living plant in the soil helps to hold the nitrogen in place. So, while non-legumes do not add nitrogen in the soil, they keep it from leaving your farm.
This video provides step-by-step instructions to calculating how much nitrogen your cover crop is providing. You can subtract this from next year's nitrogen needs, which can help to reduce your fertility costs.
Dig deeper
Do you want to learn more about cover crops? SARE has an excellent free book (the online version is free) called Managing Cover Crops Profitably. Check it out here.
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