by Olivia Saunders, UNH Extension Field Specialist in Vegetable & Fruit Production, Carroll County.
As a grower, you likely already know the benefits of incorporating a cover crop into your rotation. From mopping up excess fall nutrients, to improving crop yield, or suppression of root rots, nematodes and weeds. At a recent cover crop training in Maryland we were presented with new research showing that growing cover crop mixes, or cocktails, will diversify the benefits provided by a cover crop in a single season, without diminishing any single benefit. If you only grow winter rye (the real work horse in the cover crop world) you’re receiving one, maybe two benefits, soil cover and additional soil carbon. Growing a multi species cover crop will provide your soil with more, without changing your management too much.
We already understand the advantage of a rye/hairy vetch (75%:25%) mix with considerable carbon contribution from the rye and nitrogen fixation from the vetch. The challenge is, what benefits might we see if we grow a four, five, or even six species mix? And how do these mixtures perform in New Hampshire?
If you’re considering growing a cocktail, think through what your main goals are. If the cover crops fill the same niche, they will make a poor mix. Something like Clover/Radish/Oat all fill specific goals, of nitrogen contribution, infiltration/reduced soil compaction and physical soil building, plus carbon contribution and weed suppression from the oat. If your goals are to suppress weeds we know you need to grow a crop that jumps out of the ground quickly, AND that an established fall crop that winter kills will keep weeds suppressed in the spring (oat, radish, buckwheat). If your goals are to supply & retain nitrogen, seed in the fall a mix with a winter kill and spring growing crop. This may look like clover with Australian winter pea. Australian winter pea can sustain temps of 10 degrees, and likely will not over-winter well in most parts of New Hampshire, however, plowing in a green manure of winter pea can supply 90-150 lbs of N per acre. If your goals are both weed suppression plus N-retention/N-supply, a Cereal Rye/Oat/Red Clover mixture might be for you. If established early enough in the fall (Aug 1-sept 14 depending on location) a nice stand of oats will suppress weeds, with Rye/Clover creating a fertile field the following spring.
As we learn more about the role cover crops can play, it’s apparent mixtures will become more important and popular in the future.
Resources to help you learn more:
The Cornell University Cover Crop Decision-Making Tool for northeast vegetable growers. This is an excellent tool that is worth checking out to help you decide which cover crops may fit your specific system. One tip I have found to get more “hits” is to leave the “planting time” and “duration” fields blank. Simply select your goal, and see what pops up.
Watch this 3-minute video of Farmer Steve Groff, as he talks about Cover Crops on his Pennsylvania Farm https://www.youtube.com/watch?v=a9hTumFPiBA&feature=youtu.be
The Cover Crop Bible, A SARE published text is also available for free online here: “Managing cover crops profitably”