The healthy-sized nodules on the roots of these field peas indicate that the plant has been fixing nitrogen in the soil. (Photo credit: Becky Maden.)
I can tell you all the reasons why it is best for my body to eat well, sleep well, and exercise, but many days, my task-oriented brain takes over and I shove self-care to the bottom of my list. Similarly, while most vegetable growers are familiar with the reasons why they should cover crop—to protect against erosion, to cycle nutrients, to fix nitrogen, to boost organic matter, to suppress weeds—it can be hard to make cover cropping a priority in the midst more pressing demands on a vegetable farm. Plan Cover Crops in Advance Perhaps the most critical first step in becoming a committed cover cropper is to integrate cover crops into your crop plan. This means that when you decide where your onions, potatoes, and eggplant are going, you should also decide what cover crop will immediately follow each cash crop throughout the season. Including cover crops into your crop plan also means ordering cover crop seed before the season starts, just as you do for your vegetable seeds. This is particularly important for certified organic growers since organic seed can be tough to source and may sell out quickly. Once the season begins, you are less likely to spend the time or money ordering seed. (Just remember to store it in a space secure from rodents!) As you consider next year’s crop rotation, cover crops can play a critical role in correcting some of the issues from this season. Below are a few items to observe as you wrap up the current season and suggested cover crops for helping to balance things out:
  • Make note of where this season’s weed pressure was particularly high or where you are currently seeing weeds go to seed. You will want to plant a smother cover crop on this field, and may even consider multiple successions of cover crops. To ensure the smother effect you want, your seeding rate should be slightly higher than suggested just to make sure you don’t leave a crack of light for those weeds to germinate. Also be sure to seed at a time when you are guaranteed to have good germination (like right before a gentle rainstorm). Some good candidates for fall smother crops are oats or winter rye. During the summer, buckwheat and sorghum-sudangrass (“sudax”) can suppress weeds.
  • Note where you noticed nutrient deficiencies during the current season. If you are cover cropping after a heavy feeder, seed a legume. Field peas or hairy vetch are good candidates if you plan to grow on this field next year.
  • Note where you applied significant amount of nutrients (including compost). You will want to plant a cover crop to “mop” up these excess nutrients—and you should get this cover crop established as soon as you can to prevent the nutrients from leaching.
    • Suggested cover crops are rye (if fall or winter), oats (if late summer), or sorghum-sudangrass (if midsummer). Note that seeding a legume into a nutrient rich field doesn’t make much sense since your goal is to cycle the existing nutrients, NOT fix more nitrogen.
Integrating Cover Crops Into Your Crop Rotation
Cover crop between beds of melons. (Photo credit: Becky Maden.)
A simple way to plan your cover crops is to base your decisions on the timing of cash crops, loosely grouped as follows: early spring crops, warm season crops, and fall crops. By managing your fields in blocks based on harvest time, you can free up sections that can quickly be seeded into a cover crop at any time of year. Below are some cover crop suggestions based on the harvest times of your cash crops: In field(s) where you’ll plant early spring crops some options are: Oat/Pea Mix. Drill at 20-40 lb/acre oats plus 100 lb/acre field pea. Broadcast at 40 lb/acre oats plus 120 lb/acre field peas. Seed before end of August. Straight Oats is a better option for very late August/early September.  Drill at 80-110 lb/acre. Broadcast at 110-140 lb/acre. Oats and peas will winter kill; residue is relatively easy to incorporate in spring for early plantings. Tillage Radish. Drill at 10 lb/acre. Broadcast at 13 lb/acre. Great for breaking up compaction, scavenging nitrogen, and adding biomass. Seed before September 1. Can be seeded in combination with oats or oat/pea mix. Note: Tillage radish is not recommended as a cover crop following, preceding, or adjacent to a Brassica cash crop, as it can harbor the same insects and diseases.
Danielle Allen at Root 5 Farm in Fairlee, VT stands in a lush field of oats and field peas. (Photo credit: Becky Maden.)
In field(s) where you’ll plant warm season crops in late May/ June some options are: Winter rye plus hairy vetch. Drill 70 lb/acre rye plus 20-30 lb/acre vetch. Broadcast 80-90 lb/acre rye, 30-40 lb/acre vetch. Seed early to mid-September. Best if cash crop will be planted before mid-May, since vetch needs most of May to put on decent growth. Rye-oat-vetch mix. Broadcast 60 lb rye, 50 lb oats, 30 lb vetch per acre. Reduce rates by 20% if drilling. Seed early to mid-September. Oats will winter kill leaving a less dense mat of winter rye in the spring, and more room for vetch to establish itself. In field(s) where you’ll plant fall crops in July/August some options are: Straight Winter Rye. Here are guidelines for planting dates and seeding rates, adjusting for reduced growth when planted later in the fall: 9/15    Drill 60 lb/acre. Broadcast 85 lb/acre. 9/22    Drill 100 lb/acre. Broadcast 140 lb/acre. 10/1    Drill 140 lb/acre. Broadcast 200 lb/acre 10/15    Drill 180 lb/acre. Broadcast 250 lb/acre. Additional Resources & Links: Cornell Cover Crop Guide for Vegetable Growers: http://www.covercrop.net SARE’s Managing Cover Crops Profitably: http://www.sare.org/Learning-Center/Books/Managing-Cover-Crops-Profitably-3rd-Edition Cover Crops – New England Vegetable Management Guide: https://nevegetable.org/cultural-practices/cover-crops-and-green-manures Effect of Planting / Terminate Dates on Cover Crop Biomass: http://www.hort.cornell.edu/extension/organic/ocs/reports/Cover%20Crops%20Planting%20and%20Termination.pdf Cover Crop Mixtures and Planting Dates: http://www.hort.cornell.edu/extension/organic/ocs/reports/Cover%20Crops%20Planting%20and%20Termination.pdf Managing Cover Crops Profitably: http://www.sare.org/publications/covercrops.htm Cover Crop Periodic Table: http://www.ars.usda.gov/Main/docs.htm?docid=20323