Cover Crops, Nurse Crops, and Biological subsoilers

I have mentioned “cover crops” before, but I have not given any clear examples. Cover crop is a phrase used to describe many kinds of plants that are grown for “cover” and not for their produce. For example, one can grow Wheat in order for it to mature and dry and then harvest the grain. This would be an ordinary crop of Wheat. A cover crop use of Wheat would be to plant it, usually in the fall, and then terminate it in the spring, leaving its residue on the soil to improve soil conditions. Termination can be by many means: usually herbicide application, mowing, or tillage. A newer and intriguing technique developed by the Rodale Institute is roller crimping, which I think is the future of cover crop termination.

 In fact, one doesn’t necessarily need to terminate a cover crop. I planted winter Barley in September. It came up in early spring and I rolled over it as gently as possible with a disc harrow. I then broadcast Sweetclover into it. The Barley came right back and provided a “nurse crop” for the Sweetclover, which I felt would benefit from some nursing. The slight tillage of the soil I thought provided a looser surface for the Sweetclover seeds to lodge into and germinate. It turns out this was probably of very little benefit. The Sweetclover grew nearly as well in the places I missed with the disc. I think timing, weather, and species are more important variables with seeding this way than soil surface preparation. FYI: Sweetclover broadcast seeds well, but not as well as true clovers (Red, White, Alsike).

In the name of science I mowed half the Barley in the early flowering stage to see if it would kill it. I let the other half continue to grow. Mowing didn’t kill it. In fact, by mid May one could hardly tell I mowed half of it. They both began setting seeds at nearly the same time, though the mowed part was shorter on average. When it was dry, I cut some of it down with a sickle, yes a sickle, because I had a delusion I was going to make beer out of it. In truth, it was an experience proving in my mind the superiority of our ancestors. I think I burned more calories collecting the grain than I would have gained from eating it. Anyway, I had enough to at least plant again, but it was infected with loose smut (why Barley historically hasn’t been grown in humid Southern Indiana), so I am pretty sure my kids just made a mess with it or fed it to chickens.


(the back heads are smutty)

Alas! At least this was a demonstration that fall planted winter crops can be used as nurse crops in the spring, which to me is an advantage, since the fibrous roots of Rye or Wheat (probably the best choice for nursing a spring crop) are holding the soil over the winter.

Though I have not tried it, the use of Spring Oats as a nurse crop for establishing Alfalfa is commonly known. Alfalfa, like its close relative Sweetclover, is not very vigorous or competitive when young. Weeds can get ahead of them. Red Clover, by comparison, is much more vigorous and rapidly shades out most weeds, and I think would benefit very little from being “nursed” by some grass (Wheat, Rye, Oats, Corn, Barely, Sorghum are all annual grasses). Of course, this doesn’t matter much to the modern farmer, which has Roundup Ready Alfalfa at his disposal. As long as he can get the Alfalfa to grow, he just sprays on the Roundup and watches all the weeds die except Johnsongrass, Marestail, Palmer Amaranth, and some other rapidly evolving bastard weed.

There are, of course, some other very good uses for cover crops. One I am most impressed with I call “Biological Subsoilers.” Daikon Radishes (called “tillage radishes” by my neighbors) are brassicas that have almost unbelievable seedling vigor, enormous penetrating taproots, and a waxy cuticle on their leaves that makes them surprisingly drought tolerant. Like most brassicas and Oats, they die at about 20 F. Once they die and  begin to decompose your property will smell like an enormous fermenting sauerkraut crock on warm days in the winter, and giant “macropores” into and sometimes through the subsoil layer will be left by the decaying roots. Supposedly these decaying roots are good food for earthworms! I cannot confirm this, but I can confirm two things about these radishes: they improve surface drainage considerably and cattle do not eat them readily. This means that if you have a pasture or hayfield with some drainage issues, and you don’t want to rip a subsoiler through it, you can simply broadcast radishes into the sod and they will come up, the cattle will leave them alone, and they will die in December or whenever it gets cold enough to kill them, giving you much of the benefit of subsoiling with a fraction of effort, fuel consumption, and time expenditure. Also, Daikon radies make good people food. The roots make as good or better real, fermented sauerkraut as any store-bought cabbage. My kids eat “radish pickles” like candy.


This is a wet spot I missed when I was broadcasting radishes and oats. There are a few of them in the upper right. The grass you see is Perennial Ryegrass and the clover you see is White Clover. Oh, and a Marestail stalk is visible in the lower right. 


This is a wet spot that I got enough radishes on. This photo was taken on the same day as the photo above it in late December after a hard freeze in the single digits. All the radishes died and flopped over. This spot is very near the one above it, demonstrating how effective radishes are at improving drainage.

The radishes I used came in pre-mixed bags from Cisco. The 50-pound bags were 91% VNS Oats and 9% Scavenger or Buster variety radishes. I seeded into a first year seeded pasture sod (so it was thin in places) on August 21st at a rate of one bag an acre approximately by broadcasting. I then rolled over about a third of it with a cultipacker, a third of it with a borrowed chain harrow, and a third of it I just ignored. (The top bar of this blog is a picture of me cultipacking in this experiment). There was no apparent difference in the three groups by October, but I think the cultipacked seeds came up a bit faster. We did have an unusually wet August, which I think helped enormously. In the end, the radishes fared much better than the oats. A few oat plants grew up, mostly in the places where the sod was very thin, and were eaten with relish by Lizzy. Radishes, even though seeded at 1/10th the rate of the oats, came up everywhere, even the gravel and concrete driveway where I spilled some on the way to the field. In the future, I am not going to even bother with the oats in a sod. But radishes sure work. I suspect that turnips would work like this too, however, turnips are quite palatable to cattle, and one would have to keep them off the pasture while the turnips were growing.

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5 Responses to Cover Crops, Nurse Crops, and Biological subsoilers

  1. Pingback: More Than Just a Cover Crop | A Contrarian's Guide to Grass and Guns

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