By Scout Nelson
Weed control in soybeans is a key part of successful farming. While herbicides remain essential, research from the SDSU Extension Weed Science program shows that using narrow row spacing can make herbicide programs even more effective.
The study compares 30-inch and 15-inch row spacing with a strong herbicide plan. Fierce EZ, a mix of Valor and Zidua, is applied at planting. When weeds grow to about 6 inches tall, Enlist One and Liberty are applied. Both row spacings provide excellent weed control, but narrow rows show added long-term benefits.
In narrow rows, the canopy forms more quickly, shading the soil between plants. This limits sunlight, making it harder for late-season weeds to grow after rain and heat. These later weeds may not hurt the current crop’s yield, but they can still drop seeds, leading to more weeds in future seasons.
This research shows that 15-inch rows—and even 7.5- or 20-inch setups—can help stop future weed problems. For farmers using 30-inch rows, a post-residual herbicide like Dual Magnum or Warrant can help manage weeds until the canopy closes.
Not all farmers have the tools to plant narrow rows, but this study helps them understand how spacing choices affect weed growth. Using cultural practices like row spacing, along with herbicides, gives farmers more control and helps protect their fields long term.
Photo Credit: south-dakota-state-university
Categories: South Dakota, Crops, Soybeans