W.R.
Minnesota

Answer: Thank you for contacting ATTRA for information on converting a pasture to organic grain crops without using herbicide or tillage.

This is a tricky question. Obviously, you have figured out that you want to keep the soil structure that good pasture provides, but are a bit stuck, since much of organic weed control depends on tillage.

Be aware that no perfect organic no-till system has been developed. You will probably have a lot of trial and error to figure this out. Rodale is really the leader in developing an organic no-till. However, even in their system, there is some tillage. So it might be better called “minimum till.”

Here’s some of my thoughts. I would start by reviewing some of the innovative work being done by the Burleigh County Soil Conservation District near Bismarck, North Dakota. They are not organic, but are doing some innovative things with cover crops in a no-till rotation. I was just out there this past summer. They have a website with some interesting PowerPoints. The one I would suggest is Bringing CRP Into A No-Till Cash Grain System. You can find the website at: http://www.bcscd.com/. The presentations are in the Soil Health category. This particular presentation talks about Glenn Bauer in Regan, ND.

He started preparing the ground in the fall. He sprayed with RoundUp and then hayed off 2/3 of the residue. He then combined the remaining 1/3 of the residue and used the spreaders to get an even distribution of the residue. Next he did 3 passes with a disc. But it’s important to note that the disc only ran on the surface and acted more like a leveler to smooth out the bumps. (There is an illustration of this in the PPoint.) You wouldn’t want the disk to really rip into the soil… this would break down the beautiful soil structure that developed with the pasture years.

In the spring he did a light harrow operation, then a roller pass. Next he seeded field peas with a roller pass after seeding. (He recommends a deeper seeding depth in expired CRP than in a normal field.) After seeding he had 2 herbicide applications. A week after harvesting the pea, he seeded a cover crop cocktail of about 8 species. This cover crop was predominately low C:N species to help with further residue breakdown. In addition, he had some forage radish and turnip to help with infiltration. (The details of the mix are in the PPoint.) I believe that this cover crop terminated with winter kill and no herbicide was used.

This spring he planted no-till corn into this field and it looks great.

Now, the big question for you is… how can you do this in an organic system? This is the big unknown. Some suggestions… Obviously, you’re not going to use RoundUp for termination. But the haying, residue spreading, and discing are still workable options. Also, I would consider planting a different crop than field peas the first spring. I’m not sure that peas would be competitive enough. Also, I am making the assumption that your pasture was predominately grasses. Is this correct? If so, you will want to be putting in as many broadleaf crops at first to help with this residue breakdown. And, since grassy pasture can tend to be nitrate deficient, you would want most of those to be legumes.

So… the trick is to find the highest competitive legume that you can. I’m not sure there would be time to get a fall-seeded legume in due to all the disc operations required in the fall. However, a fall-seeded species would give you that extra jump on the growing season. The fall vs. spring seeded would be a question you would have to answer.

Would hairy vetch do the trick? Alternatively, is there a mix of species that would outcompete everything else? My guess is that by planting an annual mix of about 7 or 8 species you could get canopy cover at all levels, which would really help to choke out any weeds. You could then use a swather and lay down the cover crop residue in an even layer (not windrows), or try the roller crimper.

As you may know, the roller crimper is not a perfected technology. Burleigh County tried it on a mix of pea and oats. The pea terminated, but the oats bounced back. This year they rolled a crop of only peas and it worked very well. Notice that you wouldn’t want to hay off this cover crop, because you would want all of the residue to feed the soil biology.

Another option for termination would be to do some intensive fall grazing. The advantages of this strategy are that you kill the cover crop, feed your livestock, and get manure value. Stocking rates need to be relatively high to get an even kill and an even distribution of manure.

After you terminate your first cover crop off, you would want to seed your fall cover crop right away for soil building and weed control. The fall cover crop could all be species that winter kill. Again, I would recommend using a mixture of species. Your residue levels will determine the mix of species in this crop.

In addition, I would highly recommend doing some baseline soil tests for nutrients and organic matter. Make sure you don’t have too much residue to tie up the nitrogen. I would advise that you not plant a cash crop the first year after a grassy pasture, so that the nutrients in the residue have a chance to cycle into the soil. It might be that you could get your first cash crop in 2012 if you begin your transition this fall. That would really depend on the condition of your soil, the weed pressure, and the soil test results.

Dr. Pat Carr at the Dickinson research station might also be a good contact as he is doing some work on developing organic no-till, although his research his in drier climates than Minnesota. His number is: (701) 483-2348 x.143