Using plot work last growing season Ronnie Helms left and Jim Groves checked the effects of glyphosate and sodium chlorate on drained rice The results were surprising

Using plot work last growing season, Ronnie Helms, left, and Jim Groves checked the effects of glyphosate and sodium chlorate on drained rice. The results were surprising.

How safe is your rice after draining?

Drained rice and glyphosate studied. Common beliefs mistaken regarding when rice crop safe?

Here’s the scenario: you’ve babied your rice crop all growing season and it’s now down to the last few weeks before harvest. With the rice drained, yield is set and you no longer have to worry about glyphosate drift, right?

Wrong, says fresh plot work research from Lodge Corner, Ark., farmers Ronnie Helms and James Grove.

Here’s the main point: rice that’s been drained is still susceptible to glyphosate,” says Helms. “That wasn’t conventional wisdom before. You know, ‘The rice has been drained, the crop year is over, and grain yield and milling quality is set.’ Well, no they aren’t.”

The plot work shows glyphosate is actually “extremely detrimental to rice from when it’s just emerging to some point just prior to harvest. There may be 20 to 25 days of susceptibility that we didn’t think was there before. That’s very important because you don’t want to be set up for a 190-bushel crop and, all of a sudden, someone comes in who doesn’t know that glyphosate can yank away 30, 40, 50 bushels even if the rice has been drained.

“This work showed how susceptible rice is to glyphosate even when it’s drained. We used to believe there was little damage that could be done to rice at that point. Well, this work shows that assumption just wasn’t true.”

In a nearby soybean field, “You might have someone spraying an insecticide and some glyphosate. Maybe he’s spraying for stinkbugs and it’s drifted towards the rice field a little bit and thinks, ‘It’s not a big deal, that’s drained rice over there.’”

What was the impetus for the research?

“Some guys we know around here were cutting rice in the high 180-bushel range,” says Helms. “They got to other fields and yields dropped off to 110 to 125 bushels.

“They really started paying attention to a yield monitor wherever there were soybeans half a mile or a mile away. When they’d sprayed those beans the wind was blowing out of the south towards the rice. By yield mapping as they harvested, they noticed where trees had blocked some of the spray application drift. The rice yields were very good but where there was an open area to the soybean fields rice yields were dramatically reduced.”

The discovery was all due to the maps.  Otherwise, the rice field “looked fine. I went out to the field and could see no damage whatsoever.

“Over the years, we’ve heard — and have had it happen on our own farm — about things like a farmer cutting four fields and three of the fields cut great rice. Then, there’s one field that inexplicably has a yield that is 40 bushels off. It isn’t soil variability or we’d have seen the beginnings of that years earlier.”

Now, it may not be glyphosate damage every time. However, “it would certainly explain a lot of those types of incidences,” says Helms. “It should at least stay as a potential reason for that rice yield variability.”


The men, who also do contract work for agriculture companies, had some extra research plots and decided to look into this. “We do this sort of thing whenever we get a wild hair,” says Groves.

Helms nods in agreement. “No one sponsored the work, no one asked us to do it. When we started, we had no intention of presenting the data or anything like that. It was just a matter of trying something out for the sake of it.”

So what happened in the plots?

Following treatment, “some of the rice grains in the plots had a yellow cast to them — the flag leafs were fully extended,” says Helms. “One of the symptomologies of glyphosate on rice if the crop is at boot, the head won’t exert itself from the flag leaf sheath and the flag leaf will be short and accordion-like.

“When we sprayed the plots, it was way past that. The flag leaf was out and sitting there. The heads were out and the top of the panicle had the yellowish colored grains but all the grains weren’t dried down completely.”

What really is interesting, says Groves, “is that a half-ounce rate of glyphosate knocked the rice yield back 11 percent. We never thought that’d be the case. That’s a dramatic number and seems to surprise a lot of folks.

“There’s also been some surprise from (university and company) researchers that no one has ever looked at this before. Obviously, they’ve looked at glyphosate on rice earlier in the growing season. But they haven’t looked at what it might do late-season.

“You have to ask: at what point in the rice crop is it safe to have glyphosate drift on it? We still don’t know. Is it ever safe? Hopefully someone will look at that and other questions this raises.”

“Yeah, you figure glyphosate is so common that every little scenario had been looked at somewhere,” adds Helms. “That wasn’t the case.”

When the men presented their data at the recent consultant’s meeting in Little Rock, “it kind of stirred some folks up,” says Helms. “Consultants really wanted to be updated on what this means and how to tell their producers what to do and be careful with glyphosate around rice. With this research we continue to understand how much damage glyphosate can do to rice, even when the rice has just been drained.”

“There will be a bunch of rice planted in Arkansas this year. Pencil it out and rice is the best of the worst — especially if you can pick up a PLC payment.”

Drained rice response to glyphosate

  • Variety: RiceTec CL745
  • Rice drained: Aug. 30
  • Application date: Sept. 1
  • Harvest date: Sept. 29
  • Untreated check: 154 bushels per acre with a milling quality of 61/72.
  • 32 ounces per acre: 115 bushels (a yield hit of 25 percent) with a milling quality of 45/67.
  • 16 ounces per acre: 124 bushels (a yield hit of 19 percent) with a milling quality of 54/69.
  • 8 ounces per acre: 126 bushels (yield hit of 18 percent) with a milling quality of 57/71.
  • 4 ounces per acre: 135 bushels (yield hit of 12 percent) with a milling quality of 62/72.
  • 2 ounces per acre: 138 bushels (yield hit of 10 percent) with a milling quality of 60/71.
  • 1 ounce per acre: 141 bushels (yield hit of 8 percent) with a milling quality of 59/71.
  • 0.5 ounce per acre: 143 bushels (yield hit of 7 percent) with a milling yield of 60/71.

Sodium chlorate

The research didn’t end with glyphosate. Helms and Groves also checked out the effect of sodium chlorate — used as a dessicant — on rice.

“What happened is a friend of mine, a rice farmer, was spraying some milo with sodium chlorate and his boom messed up,” says Helms. As a result, “he sprayed it on some of his rice. He wanted to know what to do to document it.

“I said, ‘Just leave some out there. We’ll go out and measure it, take a weigh wagon and weigh the areas with the sodium chlorate versus areas without it.’ Turns out there were some big differences.

“So, we came back and did the same kind of plot work we tried with the glyphosate. We went down to an 8-ounce rate but should have done a 4-ounce and a 2-ounce rate. But this was all new — we were just seeing what would happen.”

Groves says the men suspected at 8 ounces “the yield would start curving back up. But even at 8 ounces the crop was still losing 16 percent of its yield.”

What this shows “is you want nothing — not glyphosate, not sodium chlorate — on your rice after draining,” says Helms. “Farmers need to keep all this in mind as we move into the summer.”

Drained rice response to sodium chlorate

  • Variety: Rice Tec CL745
  • Rice drained Aug. 30, 2015
  • Application date: Sept. 1, 2015
  • Harvest date: Sept. 29, 2015
  • Untreated check: yielded 154 bushels per acre with a milling quality of 61/72.
  • 128 ounces per acre: 104 bushel yield (32 percent yield hit) with a milling quality of 46/63.
  • 64 ounces per acre: 120 bushels yield (22 percent yield hit) with a milling quality of 48/65.
  • 32 ounces per acre: 123 bushel yield (20 percent yield hit) with a milling quality of 52/68.
  • 16 ounces per acre: 125 bushels yield (19 percent yield hit) with a milling quality of 55/69.
  • 8 ounces per acre: 130 bushel yield (16 percent yield hit) with a milling quality of 59/71.
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