What is in this article?:
- Panel discussion at Pigposium discusses on-farm methods, costs, suggestions for control of glyphosate-resistant pigweeds.
- How deep into the fall should a farmer chop pigweeds?
- How to keep ditch banks clean?
Has anyone tried a moldboard plow?
“Yes, we’ve had research for the past couple of years,” said Norsworthy. “The idea is to (deal) with a small patch of pigweed — half an acre, 1 acre — before it spreads across the farm. (To do that, maybe) we can deeply bury the seed.
“We tried it on a silt loam in Marianna, Ark., and it works a lot better in soybeans than in cotton. In cotton, we see a 50 to 60 percent reduction just by going out in the fall with a moldboard plow. This is something you want to use only once, not annually.
“The problem with a moldboard plow in cotton is when you run hippers back through to re-bed, we seem to be pulling back up a good amount of seed.
“In soybeans, (a moldboard plow) works better. Then, we come back in with a field cultivator, lightly run over the field to level it and drop back in the following spring with drill seeding.
“There, we were seeing upwards of 90 to 95 percent reduction in pigweed emergence. When I say ‘90 to 95 percent’ that’s actually a combination of treatments. We’re actually … working the moldboard plow, then we plant wheat — essentially double-cropping soybeans — or rye on top of the moldboard plow.
“Doing that appears to be very, very effective. But it isn’t foolproof. You’ll have to use some residual herbicides to carry it on out. But there are definitely some benefits.”
What about burning the residue?
“I’ve gotten that question two or three times already today,” said Scott. “If you can burn that seed, great. But when it falls to the ground and it’s moist or wet, we don’t always get enough heat” to destroy the seeds’ viability. “We’ve been burning fields and stubble for years and still have barnyardgrass and other weeds. By burning, you’ll get some of it — but not the seed on the wet ground. It just doesn’t get hot enough, in my opinion.”
Norsworthy agreed with Scott. “Several weeks ago, we initiated some plot research at Keiser, Ark. We are looking at fall management programs. One of those is burning the stubble. We’re in the process of quantifying what was actually removed.
“One thing we’ve done is to try and windrow soybean stubble. We took the straw-chopper off the combine … and successfully burned it. But, at this point, we’re not sure to what extent we reduced the seed going through the combine.
“This is something they’ve done in Australia. There, they try windrowing it and burning it. They’re also catching the chaff as it comes through the combine.
“I’ve told that to people in Arkansas and they say ‘that’s crazy. No way will I ever do that.’ But in some of these fields we’re confronted with, you’d be surprised at what you’d do to try and reduce the amount of pigweed going into the soil seed bank.”
I have wheat that I want to plant soybeans behind. Do I burn the straw or no-till into it?
If you burn that straw and … have ash on the soil surface, you’ve essentially taken yourself out of using a residual herbicide without tillage,” said Norsworthy. “Because the ash is there, if you place a residual on it, it will tie up the herbicide…
“The other option is to try and control those weeds extremely early with post-emergence herbicides. But the options are very limited.”