By Bill Kleiman
If you are trying to turn a low diversity cool season grass pasture into high diversity prairie should you just seed the recently prescribed burnt sod? Or first apply glyphosate herbicide or grass herbicide, then burn it, then seed it?
This long term experiment tests this. Here are our year two thoughts.
Above is the “before” photo of the pasture. Almost all simply cool season grass sod and a few weeds.
Fall 2021, October 15 and 18, we sprayed one plot with clethodim grass herbicide, one with glyphosate, and the third we left alone. We only did one application of herbicide.
All three plots were then burned November 11, 2021.
Next, the plots were all seeded by Bernie Buchholz. The first seeding was a few weeks after the prescribed fire of the plots. This was with about 27 pounds per acre of seed from 117 species. Then in April another 27 pounds per acre of 55 species was over-seeded. So 54 pounds of seed per acre were planted before the first growing season. This is a lot.
May 22, 2022: Above is First spring of the “control” plot where we did not apply either herbicide.
May 22, 2022: Above is clethodim pasture looking about the same as the control with the grasses looking weaker and maybe some weedy forbs coming up.
May 22, 2022: Above is the glyphosate pasture looking very similar to the clethodim with the grasses looking weaker and maybe some weedy forbs coming up.
October 10, 2022: Above, by fall of the next year, so one growing season, is the control plot where we did not spray the pasture, but only seeded it. On the left you can see the glyphosate plot.
October 10, 2022: Above is the clethodim grass herbicide plot looking wild and weedy after one season. It looks very different from the control. The seedlings would be an inch or two tall and very hard to find in there.
October 10, 2022: Above is the glyphosate herbicide plot also looking wild and weedy after one season.
July, 2023: Above, on left is unsprayed but seeded control, and on right is clethodim grass herbicide treated and seeded. With Bernie Buchholz doing some weeding. On right grass is less dense and there are more weedy forbs, but what was seeded are mostly seedlings.
July, 2023: Above, no spray but seeded on left, glyphosate and seeded on right.
July, 2023: Above, Bernie Buchholz finding small seedlings of his planted species in the second year of the restoration in among the tall weeds.
Here are Bernie’s thoughts about what he is seeing on year two of this long term study:
“Now in the second growing season, both herbicide treated areas have dramatically more stems of native species, easily 20 times more. And the volume of the biomass in treated areas is significantly higher than untreated areas.
The glysophate treated area seems to have the greatest number of native species, including more little bluestem.
It’s hard to imagine the untreated area catching up to the treated areas over the coming years, but that’s what we are trying to learn.
The only significant non-native (or some would say low value native) species in the treated areas is the thousands of yarrow. One of the major downside risks to treating a pasture planting with herbicide is the potential to release difficult species like white and yellow sweet clover. Our favorable results are our good fortune. Had we released otherwise dormant weed species, the untreated areas might have seemed more favorable and certainly would require less management.”
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So the Clethodim area showed about the same native species in year two as the Glysophate area but more little bluestem.?Not clear if that is the results and why. What of anything was being killed by spraying Clethodim initially as it is unclear with other grasses to me if it actually kills anything. I think it is a wonderful experiment but I am always trying to find the best use of Clethodim. This is not a wet area I presume. I rarely use Clethodim except for RCG and that is almost all wet areas. Craig Annen’s papers on Clethodim refer to it being photosensitive and losing 50% effectiveness in sunlight so between the fact that it only kills down to the point of growth then the RCG re sprouts, not being able to use in wet areas, costs three times as much as Round up and the photosensitivity it just made sense to use Aquatic Round up to me and know I killed it once. My understanding of using Clethodim is to give surrounding quality species the opportunity to go to seed around it and potentially squeeze out RCG. Is this working? Which leaves the question what to do in the wet areas where you can’t spray Clethodim?
I will let Bernie answer which was showing more species.
On the use of clethodim. I heard the new formulations are not photo sensitive. Glyphosate is cheaper. I think a single application of clethodim weakens the grass sod and lets other plants emerge. Don and Espy Nelson report good control of reed canary with a carefully made mix clethodim with ammonium sulfate, surfactant, and crop oil.
A single application of glyphosate looked the same with a weak grass sod, but still there. In the past I have sprayed a pasture three times over a growing season and then seeded that in the fall. That seemed to work too but it took a few years to show prairie plants dominating.
There are many good opportunities for study on this topic.
John, I haven’t done a count of species, but my impression is that the glyphosate treated area has more species. I’m looking forward to September when the presence/absence of little blue will be much easier to determine.
What are your burn plans or other management?
Though on a much smaller scale we have seen a terrific change only after year 4-5 years and with some annual additions of seed. (Route 66 Prairie LItchfield).
Henry, Can you elaborate on the “…terrific change only after….” Do you mean seeding into pasture without spraying first? Or did you use a spray?
My main point was about recruitment timelines.
We were dealing with areas that had been damaged and seriously compacted during a construction event. We primarily got foxtail, barnyard grass, ragweed and others the first 2 years and almost no natives that we could tell. It started to improve then and we have a dense and varied matrix of natives this year, including many native annuals.
That makes sense. It often takes several years to see seedlings.
That is a huge upside to the method, you can basically add seed over time for as long as you want in conjunction with very frequent dormant (fall to very early spring) fire to keep that thatch out. I’ve seen quite a few examples of this now, including Mounds View, where they tested these methods side by side and with replication and have applied the technique over large plantings, which are now old enough to appreciate.
This has been experimented with formally at Mounds View Grassland (glyphosate killed grass next to untreated grass). The latter comes through better after 8-10 years with structure much more like old growth prairie. Success requires enough antecedent burning to thoroughly eliminate thatch and weaken cool-season grass (often 2-3 seasons prior to seeding), and annual burning during the first decade or more after seeding (seeding is also usually spread over a couple years). More of the low stature and/or more conservative species (blue-eyed grass, wood lily, edible valerian, false toadflax, wood betony) come in better (though slowly as is their nature) under the weak cool-season grass than the big weed flush. Sowing into cool-season grass (perhaps with sublethal glyphosate to weaken grass in richer areas) has become standard practice there with astounding success. This method is not worth doing without annual or near-annual burning. Treated areas do come in faster initially, but look less like old-growth prairie and have less expression of conservative species in the long-term. Another consideration is that often pastures have 5-20 species the steward would want to keep, sometimes a few very good ones…and many out there providing advice to private landowners don’t see those things. Anyone interested in this that hasn’t seen this presentation should watch it: https://www.youtube.com/watch?v=hvMy–MMM2c
Another factor (and there are many) is what the dominant cool-season grass was. The no treatment method works better in old brome fields than it does in bluegrass dominated fields. In addition to annual burning, mowing multiple time in the first few years is advantageous. How frequently do you mow these plantings? Was the seed drilled or broadcast? That was a very dense seeding that is likely out of the possibility for most people that are doing plantings.
I will ask Bernie what grasses he sees in there. I remember a mix of cool season grasses. We don’t usually mow plantings until early winter to take down the tall weeds so we don’t have eye-pokes the next field season. At least for plantings in ag fields the growing season mowing did not seem to be doing anything. Our best ag field plantings were not mowed. But I have heard of repeated mowing to try to support seedling establishment. This may be good for this situation, although hard on nesting wildlife. Another need for a controlled study for one of us to do. This long term study has its limits and these are initial view.
The site was primarily brome but with heavy concentrations of quack grass. I did not notice much blue grass. The planting was mowed once in June 2022. The seed was broadcast.
I’m not aware of many of the interseeding into cool-season plantings also mowing early on–just burning. Did you on yours? I don’t think that’s the case for most of the Mounds View plantings or others I’ve seen. My impression regarding bluegrass fields was the opposite, so long as they will burn and aren’t over-vigorous. In pasture situations, that’s where there are more likely to be several or more good remaining forbs and rosette panic grasses too. Long ago I had great success seeding into bluegrass, but that was a case where a spray had to occur in dry weather and didn’t kill anything, but modestly set back the brome that was over top it…under an old WHIP contract.
If the soil was not mechanically disturbed, then what was the mechanism that encouraged the yarrow to dramatically emerge in only two of the three test fields? Also what is the size of each test field?
There were three large plots, about 100 feet by 300 feet. One was sprayed with clethodim grass herbicide and seeded. One was sprayed with glyphosate and seeded. The “control” was not herbicided but it was seeded. The two plots with herbicide applied came up with yarrow and other weedy plants because the grass sod was much decreased by the herbicide.
While I don’t know about yarrow specifically, but many short lived or otherwise early successional species’ germination is triggered by nutrient pulses (this would occur if a fraction of the vegetation were killed as happened here), increased temperature fluctuations in the upper soil profile from a more open canopy, or shifts in red-far red ratio due to more open canopy. That’s why one can get a weed flush without soil disturbance, but it is muted if a site remains vegetated.