October 30, 2002 | By: Laura Skillman

As the harvest season winds down in Kentucky, farmers begin thinking about next year’s crop and part of their thoughts deal with weed control.

Using herbicides in the fall to control cool season weeds is a practice on a number of farms in the state and it can have its place. But it is not for everyone or for all fields, said Jim Martin, a weeds scientist with the University of Kentucky Cooperative Extension Service.

“Many of our acres in Kentucky should not receive fall applications because of the risk of soil erosion,” he said. “The goal is to reduce the amount of weedy vegetation going into the spring and most of these are cool season weeds, and those weeds help hold soils together.”

There are places with distinct advantages for using fall herbicide applications, Martin said, specifically, where soils tend to be wet and producers can’t get on them early enough in the spring to kill the weeds for no-till. So by the time a farmer can get on the field the weeds are pretty big and healthy and it slows the process in getting them killed off enough so that it can be planted.

But during an extremely wet season the vegetation can act as a sponge to help dry the field more quickly than without any vegetation, he said.  However, that is a rare occurrence, he noted.

“Some people like fall herbicides as a means of keeping the vegetation down, particularly in soybean fields where glyphosphate resistant varieties have been planted and there is essentially no soil activity – no residual herbicide aspect. By the time the soybeans are taken off, some weeds may have gotten a head start.

“It is mostly directed at cool season weeds and I don’t see it giving us much extended control into the growing season,” he said. “It is mostly to allow us to get in and get the stuff planted and may allow the soil temperature to warm up more quickly.”

Martin said he sees fall herbicide application also as a means of helping control some weed problems such as Italian ryegrass. It is pretty easy to control in the fall but it can be a real problem once it over winters and initiates multiple tillers, he said.

It may end up costing a farmer more in chemical costs,” he said.

“But when you look at the advantage of being able to get in early and get your crop planted while others had to wait, you can’t place a dollar value on that and can be worth a lot of money. Likewise, it may eliminate a chemical application in the spring and that could save time in a busy time of year.”

But, farmers need to use caution in areas were land is erodible. Dealing with gulleys is not fun, Martin noted.

Contact: 

Jim Martin, (270) 365-7541