Think Through Burndown Strategy Carefully

Some products require wait before planting.

Published on: Apr 21, 2010
Remembering the nightmare than ensued last year when constant rain and cool weather nearly wiped out planting until late may, one central Indiana farmer made it a priority to knock down weeds when a dry spell opened up a few days ago. In fact, he followed a three-prong approach to help make sure he won't be dealing with big weeds later, should this season also turn wet before he can complete planting.

First he had about half his fields sprayed last fall. That's proven to be a successful way to get clean fields headed into spring, he notes. The only problem last fall was that wet days and the priority to complete harvest, and the lateness of harvest in some fields, made it less than ideal for application of herbicides on some cases.

Second, once soils were dry enough recently, he field-cultivated soybean ground left alone over winter one time, primarily to knock down green vegetation. That will knock back weeds if rainy weather returns. It also helps reduce the possibility that cutworm moths coming up from the Gulf of Mexico will find his fields attractive fro laying eggs. Fields that remain covered with green vegetation longer into the spring tend to be more likely candidates for black cutworm activity.

Third, he sprayed stalk fields that will likely be no-tilled to soybeans that weren't sprayed last fall with 2,4-D. That's the leg on the three-legged stool approach he followed which can become troublesome if one doesn't adhere to the label. When he was applying the chemical, he was likely weeks away from no-tilling beans. However, if you're thinking about that practice today on ground not yet disturbed that will go to no-till beans, be aware of plant back restrictions as you move closer to prime planting dates for soybeans.

Glenn Nice, a Purdue University weed control specialist, recently noted that the 2,4-D label states that if you apply one pint per acre of 2,4-D or less as a burndown ahead of soybeans, you must wait seven days before planting soybeans. But if the rate is more than 1 pint per acre of 2,4-D, then the label requires that you wait 30 days as a preplant interval. Note that requirements on some labels of individual products may vary slightly. Also note that the rates given here are for the product, not the active ingredient.

If you're talking about active ingredient, then if you use less than 0.5 pounds per acre of active ingredient of 2,4-D, most labels require waiting seven days to plant soybeans. If you apply more than 0.5 pt. active ingredient of 2,4-D, then the wait is 30 days.