Q&A

DEAR NEW FARM:

We're in our fourth year of organic CSA farming, and we've managed to really wear out the soil in our oldest set of rows. We have incorporated composted cow manure every year and cover cropped with oats twice. It's also had a thick layer of hay mulch incorporated through tillage in most places. What's the best cover crop we could put on it this winter to improve matters? We're considering putting it to rest for all of next year as well, so we could till something in next spring and crop again with something else. Vetch? Rye? I worry about something that doesn't winter kill or easily till becoming a weed problem, as these rows are hard to get our bigger equipment onto (hillside).

Any advice would be appreciated!

Thanks,
Camela Decaire
Wisconsin

DEAR CAMELA:

We know from our own research and from stories from other farmers that carefully managed organic farming regenerates the soil year over year. For some specifics on your situation, we asked The Rodale Institute’s own research agronomist, Dave Wilson. Here’s what Dave had to say:

First determine if you need to produce nitrogen with your cover crop for the subsequent crop in your rotation. If the next crop to be planted in the rotation is a legume (peas, beans), you don't need to produce nitrogen (they will fix their own nitrogen). If you want to add nitrogen with your cover crop, then you want to grow a legume. If you have plenty of nitrogen from manure or compost, you may not need to use a legume; you can use a cereal-grain cover crop that overwinters, such as winter rye, winter wheat, winter barley or a brassica.

Hairy vetch and spring oats or hairy vetch and winter cereal rye are good options. Hairy vetch is a winter annual legume. Spring oats or winter rye planted with the hairy vetch will act as a nurse crop for the legume. Both the spring oats and rye will germinate quickly and grow until the first killing frost; spring oats will winter kill but the winter rye won't (the spring oats will die and still leave some residue over winter). Hairy vetch seed will take longer to germinate than the oats and will grow slower initially in fall compared to small grain until the killing frost; then the vetch will go dormant over the winter. Hairy vetch should be planted at least 40 days before the first killing frost, and it will make it through the winter better. Starting about mid April and through May, the vetch will grow prolifically, producing a lot of biomass and fixing nitrogen. In June the vetch can be tilled under as a green manure, or it can be flail mowed, or, if you have the equipment. it can be rolled down (tomato sets can then be planted into the mulch).

Another option is to plant winter cereal rye with the hairy vetch. Cereal rye is also a winter annual and will overwinter and grow more in the spring along with the hairy vetch (the vetch tends to grow up the rye tillers in the spring). Grown in combination, the two cover crops produce more biomass than the vetch alone.

Winter cereal rye is usually the most inexpensive and available winter grain to use as a cover crop. Winter wheat, winter barley, winter spelt, or triticale can all be substituted for winter rye. Rye typically produces the most biomass, then triticale, spelt, wheat and barley.

Some seed companies have cover crop mixtures designed for green manure plow down, or you can mix your own (such as 60-percent red clover, 20-percent yellow-blossom sweet clover and 20 percent ryegrass). Another good combination is yellow-blossom sweet clover, red clover and white clover in a 2:2:1 ratio by volume.

Another option is to plant a brassica cover crops, oilseed /forage radishes, rapeseed or mustard. These cover crops do not fix nitrogen like the legumes do, but they will take up excess nitrogen left in the field and help prevent it from leaching over the fall-winter-early spring months. They grow tenacious taproots that penetrate the soil deeper than the cereal crops or legumes.

Hope this helps,
Dave Wilson

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