It’s a question Alan York gets every year: “I lost a crop, what can I plant there next year?"
For the most part, the question comes from cotton and corn producers, explains York, professor of crop science at North Carolina State University. “The tobacco people are going to reset tobacco, and peanut guys are going to want to plant peanuts, and soybean people are going to replant soybeans,” York says.
Speaking at the North Carolina Agricultural Consultants Association annual convention in Raleigh Dec. 3, York said the big question is: “I lost my corn or my cotton stand, do I replant to that same crop or am I going to plant something else?”
In essence, York advises farmers to replant the same crop if they are concerned about herbicide issues.
The question farmers need to address is what kind of herbicide program is needed after the first crop failed. If the herbicide failed on the first crop, what will be the impact on the crop a farmer wants to replant?
York cites research by Stanley Culpepper, Extension agronomist at the University of Georgia, on the guidelines for replanting cotton behind cotton that received a treatment of the herbicide Warrant. If a farmer strip tills, he needs to wait at least 14 days after the first Warrant application to replant, according to Culpepper’s research. If a grower no-tills, he needs to wait at least 21 days to replant after the first Warrant application, Culpepper’s research shows.
When these guidelines are used, stunting shouldn’t be a problem, York said. If not, severe stunting could be an issue.
“It’s my observation that we have very good tolerance of cotton to Warrant. The exception is when the cotton took 10 days to two weeks to come up; that’s when we get severe stunting,” York said.
The weed scientist explained that stunting may occur because Warrant uses an encapsulated formation where the herbicide is contained in egg shells. “What likely happens is those little egg shells popped opened and released more of the Acetochlor than that little plant could handle. I think that’s where we got the injury. If the cotton comes up quickly like you want it to, I’ve not seen an issue,” York said.
Another question farmers need to consider is the application of additional herbicides after replanting the same crop. York notes that this turns out to be a judgment call in most situations.
How much time has lapsed since the first herbicide?
“There are some things you can think about,” Yok said. “What did I use the first time? How long is the residual on it? Is it pretty long or pretty short? If it’s short, maybe I need to think about putting down something else. What is my crop tolerance to that first one I put down? If it’s good tolerance, maybe I’ll put some more. If it’s a little touchy on tolerance, I don’t want more.”
Farmers need to consider how much time has lapsed since the first herbicide application and consider the weed pressure in a particular field and how much herbicide is needed. Considering post application options is critical, York advised.
“If I have some good post options, I’m less likely to want to apply more herbicide when I replant. It all depends how timely a grower will be with those post options. If he’s not going to get there on time, then I am more inclined to put some herbicide on when I plant that second time,” York said.
When replanting the same crop and the original herbicide was broadcast applied, a farmer may consider another herbicide with a different mode of action than the original compound applied. “For example, if I had Reflex and Warrant on my first planting, and I lost a stand, instead of more Reflex and Warrant, maybe on the replant I’ll think about some Diuron or Fluometuron,” York said
Herbicide management becomes more tricky when a farmer plans to replant a different crop.
York said the first thing to consider when replanting a different crop is whether the herbicide used on the first crop is registered for the replacement crop. If the herbicide is registered for both crops, York said the decision is fairly easy.
For example, the herbicide Warrant is registered for cotton, soybeans and sorghum, so planting soybeans or sorghum after cotton should not be a problem if a farmer wants to use Warrant in his weed management program.
“If the herbicide you put out for the first crop is not registered for the replacement crop, that’s when the questions come in. I think the first thing you need to do is take a hard look at the rotational restrictions on the labels from the first product,” York said. “My official recommendation when you want to replant, if the herbicide on the first crop is not registered on the replacement crop, your smartest strategy is to follow the rotational restrictions.”