Don't Delay Burndown Herbicide Application In No-Till Fields

Don't Delay Burndown Herbicide Application In No-Till Fields

ISU weed specialists say forgoing herbicide application prior to planting is a risky proposition.

So, you think you'll save time this spring by skipping your burndown herbicide application and getting the corn planted as quickly as possible? Think again. Planting this spring is getting off to a later-than-anticipated start, due to cold, wet weather in April. The late arrival of spring has everyone ready to hit the fields running when fields finally dry out.

"Some farmers will be tempted to forgo applying herbicides prior to planting, to make sure fields get planted in case another wet period arrives," observes Bob Hartzler, an Iowa State University Extension weed management specialist.

APPLY THAT BURNDOWN HERBICIDE: With a later-than-expected start on planting this spring, it's tempting to go ahead and plant corn and skip the burndown herbicide application. "Some farmers try that and plan to come back and apply burndown treatment before the crop comes up. But it can start raining or you get busy and don't get the burndown herbicide applied before the crop begins emerging," says ISU field agronomist Paul Kassel.

"This is an exceptionally risky proposition for no-till fields because it provides weeds a head start on the crop and a competitive advantage for the rest of the season," says Hartzler. "If everything falls in place perfectly, this practice can be successful. But any delay in getting back into the field to apply the burndown and residual herbicides can have a big impact on the success of weed control and, therefore, on crop profits."

Scout fields now to determine what weeds are present, and choose the right burndown herbicide to apply

Selection of an appropriate burndown treatment is the first step in a successful no-till weed management program, he points out. Fields should be scouted to determine what weeds are present. The addition of 2,4-D to glyphosate improves control of many winter annual weeds and any glyphosate-resistant weeds such as horseweed/marestail.~~~PAGE_BREAK_HERE~~~

NOTE: A seven-day interval between application and planting is required with 0.5 pounds acid equivalent per acre (0.5 pints per acre of a 4 pound per gallon product) for both corn and soybeans, he says. Farmers wishing to plant immediately following the burndown application can substitute Sharpen herbicide (or other Kixor product) for 2,4-D to maintain effectiveness of horseweed control. An MSO (methylated seed oil) surfactant and nitrogen source is required when using Sharpen for burndown purposes.

Don't overlook importance of early season weed control, watch fields closely

Whether you are a no-till farmer or not, it's important to scout fields and control weeds early, says ISU field agronomist Paul Kassel, to start corn and soybean crops off right. Especially on soybeans research has shown weed competition with the crop can begin even with weeds as small as 2 to 4 inches. It's very important for corn as well as soybeans, but especially soybeans, to have that preemergence herbicide down to protect yield potential even early in the season.

Farmers are watching soil temperatures to decide when to start planting. The advice is to plant corn when the soil temperature at the 4-inch depth is 50 degrees F and the weather forecast shows a warming trend. At this date, in late April, Kassel is more concerned about the field conditions, make sure the soil isn't too wet to begin planting.

This time of year if there are areas of a field still saturated or are still slightly wet and you go in and plant, the corn is never going to be able to recover from sidewall compaction or other types of soil compaction. So giving that field another day or two to dry out is very important, partly because of the fact corn can make up growing degree units as the season progresses. Once you plant after the first of May the corn actually needs less heat units, approximately 6.8 less GDU's per day, to reach black-layer stage in the fall. Corn can compensate and help make up for the time on these somewhat later planting dates. "Don't push it and get in and plant when soil isn't ready," says Kassel. "Let that field dry out an extra day or two because we're going to make that up during the season."

TAGS: USDA Extension
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