The difference a day makes

Published on: 17:35PM Apr 06, 2010
Gordon Vail
Controlling weeds early in the season is critical – because not controlling weeds in time is costly. How costly? Some excellent research from Michigan State University shows what a difference a day can make in controlling weeds in corn and soybeans.

A four-year study examined how long it takes weeds to grow to a certain height. They found that, in general, weeds grow from 4 inches to 6 inches in just two to four days. Then they looked at crop yields based on when weeds were controlled. The results are fascinating.

According to the data from Michigan State, controlling weeds in 15-inch soybean rows when weeds were 4 inches tall resulted in a 5 bu/A yield loss. Waiting a couple more days to control weeds when they were 6 inches tall resulted in a 10 bu/A yield loss. That’s a lot of yield in just a couple days – up to 2.5 bu/day.

In corn, the difference was even more dramatic: Controlling weeds at 4 inches tall resulted in no yield loss, but waiting to control weeds when they were 6 inches tall resulted in an 18 bu/A loss. That’s a loss of as much as 9 bu/day. 

This research backs the Syngenta recommendation to control weeds in both corn and soybeans by the time they are 4 inches, or to rely on pre-emergence residual herbicides so early season competition isn’t an issue.

There are good pre-emergence residual options in both corn and soybean. What are you using to protect yield from weed competition this spring?