Row spacing, preemergence herbicides reduce early season weed competition

INDIANAPOLIS — May 12, 2014 — What do weeds want? They want their space.

Weeds aggressively fight for water, light and nutrients, crowding crops. But growers can prevent weeds from taking up precious space by planting narrower rows and using a preemergence herbicide program.

Weeds begin robbing yield early in the growing season, according to a study from the University of Nebraska.1 The study found that weeds can begin causing yield loss as early as the V1 growth stage in soybeans planted in 30-inch rows. Yield loss started in the V2 stage in 15-inch rows and at the V3 and V4 stages in narrower rows of 7.5 inches. The study confirmed that row spacing and the timing of weed control significantly influenced weed growth.

Combining the use of narrowly planted rows with a preemergence herbicide program can greatly reduce early season competition and give soybeans a clean start, says Joe Armstrong, field scientist, Dow AgroSciences.

“Once growers lose crop yield to weed competition, it can’t be recovered, even if the crop is kept weed-free for the rest of the season,” Armstrong says. “Timing is everything, and because weeds rob yield so early in the growing season, using a preemergence herbicide to reduce competition is that much more important.”

If a grower uses an effective preemergence herbicide, it delays the starting point for weeds, giving crops the full use of moisture, sunlight and nutrients, says Armstrong.

“If soybeans get the right amount of nutrients and moisture in the beginning because they aren’t competing with weeds, they can get that much closer to canopy closure before the preemergence herbicide wears out and weeds start to emerge,” Armstrong says. “When the canopy closes, it blocks sunlight from reaching the soil, impeding weed growth.”

Sonic® herbicide and Surveil Co-pack herbicide feature multiple modes of action that tackle high-anxiety weeds preemergence, including marestail, Palmer amaranth and waterhemp, says John Chase, portfolio marketing leader, Dow AgroSciences.

“Sonic and Surveil offer the residual control necessary to curb early season weed competition in soybean fields,” Chase says. “Reducing competition early can lower growers’ stress levels later in the season.”

Sonic and Surveil can be used preplant, premergence or within three days after planting to provide powerful weed control.

For information on weed control in soybean fields, visit and

1Knezevic, S.Z., S.P. Evans, and M. Mainz. 2003. Row Spacing Influences the Critical Timing for Weed Removal in Soybean. University of Nebraska. Weed Technology. 17:666-673.

About Dow AgroSciences
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