A discussion in the Organic Grain Resource and Information Network (OGRAIN) email group started with a question about interseeeding clover into soybeans. Several no-tillers proceeded to discuss the topic and how timing of planting could dramatically affect the outcome. Read the full discussion below. To post to the OGRAIN listserv email discussion group, send an email to: ograin@g-groups.wisc.edu. To subscribe, send an email to ograin+subscribe@g-groups.wisc.edu .  

Has anyone ever interseeded clover into soybeans? I'd imagine if you do it too early it won't survive or will cause issues at harvest... but if you do it too late, it won't get much growth.

-Rye Carlson, Mora, Minn. 

Response:This past fall we hired a local farmer with a modified Miller sprayer to drop a mix of 4 clovers (medium red, balansa, crimson and persian) into soybeans in late September when the beans were starting to turn yellow. Here is a link to some pics: https://photos.app.goo.gl/JSmBNybGiUKqzKNr8 Multiple species of clover established last fall but didn't grow much. It will be interesting to see what greens up in the spring.

-Joel Gruver, Professor of Soil Science, School of Agriculture -- Western Illinois University 

Response: Thank you! I'd like to give this a try. 

-Rye Carlson, Mora, Minn.

Response: In the future, I will probably try to overseed clover into soybeans a few weeks to a month earlier but that was not an option last fall. Even with the late planting last fall, I am optimistic that we will have enough clover this spring to provide some benefit to corn. Hopefully observations this spring will shed some light on which species of clover and soil surface environments (we dropped clover into both conventional till and no-till bean fields) work better.

-Joel Gruver, Professor of Soil Science, School of Agriculture -- Western Illinois University

Response:Joel, what date are you targeting? I wonder if July would be too early. I'd have to drive through the crop before it gets too bushy.

-Rye Carlson, Mora, Minn.

Response: We tried spinning on a clover mix in late July/early August onto a harvested oat field where we left the straw instead of taking it off. We did plant clover at the same time as the oats but due to operator error the seed was used up after several trips around the perimeter of the field.  So the attempt was to get clover into the interior of the field. We ended the season in the D2 drought and saw very little clover when walking the field in late September. Would you assume this was more water related or shading related from leaving the straw or both?

-Kim Andersen, Andersen Seed and Supply, Brighton, Iowa

Response: Kim, Biggest negative was probably the dry conditions. Did you then till this field in the fall?  The clover would likely have been able to come anyway the following spring if left undisturbed…  I’ve often found that “time” and patience can be your greatest ally…. “Leave ‘em alone, and they’ll come home, wagging their tails behind them”. Your “context” however may not allow for that.

-John Meyer, Rock Dell Forage Farms, Stewartville, Minn.

Response: Here in Central Illinois we frost seed red clover in February and this has worked for me for many years. 

-Bernard Hand, Central Illinois

Response:As I’ve said before here on Ograin, I PREFER to frost seed (SE Minnesota), and I also have done it in February, if the snow is reasonably gone …more for the right conditions for my drill to function (as I want it to, as opposed to how the manufacturer intended for it to be used and function) than anything else.  I PREFER to use a regular old grain drill (JD8300), and I PREFER to drill my mix on right through like 3-4” of snow if I can get that timing right. The drill is mostly for even distribution of seed, and to generate just the smallest of a “seed trench” (more of a slight cut on the surface of the soil) into which the seed is dropped. As the snow melts and spring rains come, the seeds are pressed down onto the soil surface and that little trench fills back in around them. Seed is kept moist through that spring thawing/rains/warming up process, and it works great. I just never worry about red clover once I put the seed out there. I’d be much more concerned about trying to start it in a good green crop of firmly canopied soybeans too early in the summer during dry and heat than I ever would about it making it through winter from a fall started seedling, or with frost seeding even in the dead of winter.

-John Meyer, Rock Dell Forage Farms, Stewartsville, Minn.

Response: Do you let the clover grow a whole year then? My goal is to get enough growth that I can plant corn the next year after soybeans and have a decent amount of clover to disc in. Our springs are pretty short and late up here in east central MN.

-Rye Carlson, Mora, Minn.

Response: Lately, yes, and even more than a year. I haven’t yet determined when I will “terminate it” because I’ve converted my whole operation to either pasturing (AMIG), or growing harvested forages for my animals for winter, or both. But that doesn’t change the parameters of trying to establish a good crop of “red clover." For example (I seed a multi-species blend now).  I typically prefer to seed this blend onto soybean stubble ground (more exposed soil with less residues, so more opportunity for better seed to soil contact especially when just “putting it on top”), but I have done it on unchopped, untouched cornstalks too. And I USED TO BE a “grow it in the fall, and terminate it in the spring” operator.

In your case, because you’re planning to go from soybeans in the current year, to corn the next, I personally would suggest putting some red clover along with some winter rye out in mid-late August, by air seeder distribution (Tru-Spread), aerially, or with a dual spinner broadcast spreader (in my experience, a single spinner throws much too unevenly, unless you are willing to really narrow up your “planned” width of spread or to spread in opposing directions).  It's important to get that clover established early enough that it will be flourishing as a young plant by bean harvest. And if it was me, especially if operating organically, I’d still come back and put BOTH out immediately following bean harvest with a NT drill…  get that winter rye rate up good and heavy for the weed control benefit the next spring, and for the biomass it can produce.  THAT will all depend on how you are comfortable managing that rye of course.

Here’s the problem though...

1. You’ll get the clover established… it will be there and green at bean harvest, but still small, because of competition with the beans. And you’ll want it to be small, so you don’t have a full crop of clover going through your combine. So the only REAL opportunity THAT YEAR for it to establish a healthy amount of N fixing is following the harvest of the beans. How early can you get them off? The earlier the better, without question, for the sake of the clover and its desired benefits. If you can harvest those beans in early September, you’ll have about a month (maximum really) for the clover to get growing again… that’s huge. Remember that the days are getting shorter, colder, and the sunlight is getting weaker with every day that passes. Growing plants have been designed to realize these are the signals that winter is coming and they automatically will work to build root reserves to survive. You just tapped that root reserve it had been struggling to achieve (struggling previously because of sunlight competition with the beans when the sun was still stronger) by cutting that clover off very close to the ground, eliminating most of its photosynthetic abilities!  It IS going to fight at all cost to build that back before winter hits, so it can survive… it’s a perennial… so it won’t be growing new plants from seed that it grew and dropped, the next spring.  Without those photosynthetic receptors, it will have no choice but to tap into its root reserves to grow new ones, before it can start to “refill the bank” in its roots. The more growth it can achieve before winter, the more prolifically it will be able to grow the next spring, because of reserves it has been able to build back in the plant and root mass. DAYS MATTER HERE… I have seen where even just 12 hours late in the fall season can make a visibly noticeable difference on growth the next spring! And that applies to ANY kind of over-wintering plant that you’re attempting to get established in the fall.

2. How long will you be willing to wait to terminate/plow under the clover in the spring? Most “alfalfa operations” for dairy here in Minnesota want to be cutting that first crop around May 15-20… at early bud stage. The plant isn’t mature enough to have accomplished all of its growth stages, and therefore, it hasn’t been able to fully develop its N fixing capabilities, OR its root reserves for regrowth. The plant itself USES nitrogen for much of its early growth stages. It fixes N in its nodules to its highest level once it begins to prepare for setting seed. Are you willing to wait that long? If you’re plowing the green growth under, the N that’s in the plant material of course will also be broken down by biological processes in the soil pretty quickly and be made available by this digestion process… “green manure”. Of course, the more tons of green biomass you can deliver to the biology, the more N that will be made available in the soil from it. So “how long” is optimum for you? You’ll have to decide that one. If you could leave it growing for a whole year and manage it appropriately so that you avoid tapping that root reserve, and allow the plant to “optimize," you’d achieve more benefit FROM THE CLOVER…but of course, you’d give up a year of benefit from the corn crop. That’s why the “old school” crop rotations worked well in the past… 2-3 years of “mixed hay” that wasn’t managed for “optimum forage quality yield” (2-3 cuttings instead of 5), followed by 1-2 years at most of corn, with the second year of corn requiring supplemental N of course (which could be primarily supplied by the manure from livestock that the forage was fed to). Managing so intensively for that “optimum forage quality yield” is also why the “hay crops” no longer last.

This then all gets back to context…  What are YOUR goals. You have to prioritize them, to determine what’s important to YOU on YOUR operation. Obviously, the longer you’re able to allow a clover plant to do what it is that you want it to do, the more potential benefit it will be able to supply you.

-John Meyer, Rock Dell Forage Farms, Stewartsville, Minn.

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