Cover Crops for Beginners

What to do this week

The first frost is still (I hope) a while away but parts of the garden are starting to look tired and tapped out. As the harvest moves through the garden, it’s important to clean up as you go. It’s time to pull up or till under those weeds that escaped your scrutiny, along with the withered pea vines and bolted lettuces.

Not to say you should leave those areas bare, however. This is the time of year to get serious about cover crops. Especially given our increasingly erratic winters, with unseasonal rains and flooding, cover crops are an important tool to slow erosion and nurture the soil. There’s a reason they’re also called ‘green manures.’

Cover Crops in Small Grain stubble, Brookings County, SD. (Photo by USDA NRCS South Dakota Colette Kessler, Pierre, SD, 2013, Public Domain, via Wikimedia Commons)

Cover Crops in Small Grain stubble, Brookings County, SD.
(Photo by USDA NRCS South Dakota Colette Kessler, Pierre, SD, 2013, Public Domain, via Wikimedia Commons)

You can tailor the cover crop to the effect you’re trying to achieve. If you are trying to alleviate compacted soil, try oilseed or tillage radish seed. It isn’t as effective as others for combating weed pressure, but its deep tap roots, sometimes as long as a meter, can force their way even through hardpan. Once winter-killed, they will leave those lovely spaces in the soil full of organic matter. William Dam and T&T Seeds have seed available by mail order in small or large quantities.

If you have been struggling with a quack grass problem, I personally can recommend a green manure of kale, sown any time after the middle of August. Brassicas actually suppress the soil mycorrhizae. Normally you want to encourage these microscopic organisms but quack grass loves them too and sometimes you have to choose which to deal with.

You can buy forage kale in large quantities from the Country Co-op on Keltic Drive, but you may have to order it in as they don’t keep it in stock. The 25 kg bag is a lot to purchase but the seed will keep well for a number of years if you store it in a lidded bucket. As an added bonus, you can eat the kale or feed it to your very appreciative chickens.

If your quack grass is under control and you want to encourage those vascular mycorrhizae, any of the small grains will build up their numbers. Many people sow winter rye because it can add such massive amounts of organic matter to the soil. You have to be diligent about turning it under in the spring, however, or it can itself become a weed.

You can also sow annual rye, wheat, barley or oats. I prefer to use oats as a cover crop. Sown late enough (after August 1st but before mid-September) it won’t produce viable seed to become a problem, and will winterkill nicely. The leaves and roots hold the soil well during winter rains and rot down quickly in the spring to make planting easier.

For weed control, you can’t beat a summer cover crop of buckwheat followed by another of fall oats. It is too late now for sowing buckwheat but keep it in mind for next year. You must be prompt about mowing the buckwheat before it sets seed or you will be fighting it as a weed for years to come. The bees love it, though, so for the most part, I tolerate the volunteers that come up.

Soy beans coming up in rye cover crop. (Photo by Photo by Lander Legge, Soil Conservation Technician, USDA Natural Resources Conservation Service, Elk Point, SD, via Wikimedia Commons)

Soy beans coming up in a rye cover crop. (Photo by Photo by Lander Legge, Soil Conservation Technician, USDA Natural Resources Conservation Service, Elk Point, SD, via Wikimedia Commons)

If you like to get multiple uses from your cover crop, as I do, you can also feed those oats to your livestock, starting at the milk stage, where the green seed gives out a milky droplet when crushed. Chickens love it, as do sheep and cows, and the stalks become part of the bedding. I cut small quantities with a sickle, larger amounts with the whippersnipper and just throw it in their run. Leave the stubble in the field to hold the soil, though.

Barley and wheat can also be used as cover crops, but they need more heat than oats and so aren’t as suitable for fall planting. I have tried winter wheat, but it doesn’t like our wet falls and seed is more expensive. For seed oats the cheapest way is to buy a bag of feed oats – the kind they give horses. The germination won’t be as good as certified seed and it isn’t a registered variety but that doesn’t matter with a home garden or small farm.

You can undersow green manures while the main crop is still being worked. Throw seed around under well-established plants just before a good rain. The tall plants provide a nice little nursery for the seedlings and when they are cut down or taken off, the seedlings will shoot up quickly. In the case of that buckwheat and oats combination, the buckwheat can just be mowed down and left on top of the seedling oats.

If you want to boost the nitrogen in your soil, you can sow yellow sweet clover. It will fix nitrogen from the air and add lots of organic matter. It will regrow if mown the first year, but if you mow it just when it begins to flower the second year, it won’t come back. It also has a nice large root system helpful for breaking up soil. It is neutral as far as mycorrhizae are concerned.

Terminating a cover crop is usually accomplished by mowing, but some growers use the crimping-rolling technique. This is basically knocking down the plants and crushing the stems so they don’t regrow. I have seen some growers do this with a piece of angle iron screwed on to a length of two by four. The sharp edge of the angle iron crushes the stem as they move the plank around the garden and stomp on it. There are other home-made crimpers you can find on the internet, if you are handy with a welding torch. Me, I use my trusty sickle and brush cutter.

Remember that cover crops take a little time to get established, so for best results, plant them in the next few weeks if you can. Once in a while, you can take a chance and plant later but it is more often than not a waste of seed.

Featured image: Cover crops by USDA NRCS South Dakota, CC BY-SA 2.0, via Wikimedia Commons

Market gardener, farmer, workshop leader, seed-saver, political candidate and mother, Michelle Smith has spent over 30 years coping with the challenges of our bioregion and in the process has built a store of practical and technical knowledge. The Inverness resident has served on the board of Seeds of Diversity Canada and represented Alternative Producers with the Federation of Agriculture but can do nothing about her hair. She is pictured with a head of Club Wheat, a seed that shares her approach to hairdressing.