Most soybeans in Tennessee are now planted in 15 to 7.5” rows. This can help on weed control as the soil is shaded more quickly. Shaded soil will reduce weed seed germination rates. A good PRE-applied herbicide coupled with narrow rows and effective POST applied options is a very sound weed management strategy.
However, in fields where Palmer amaranth is resistant to POST over-the-top herbicides, planting in wide rows and using a cultivator or hooded herbicide application can be an effective weed management option.
Metribuzin and Gramoxone both have labels for shielded application in soybean. In soybeans planted in wide rows a tankmix of those two herbicides applied with a hooded or shielded sprayer can be an effective way to control large Palmer amaranth and grasses.
Hooded Application for Palmer Amaranth
Paraquat (Gramoxone SL 16 to 20 oz/A) + Metribuzin 5 oz/A.
Advantages: This is the most consistent mixture to control large Palmer (>12”)
Considerations: Needs to be applied carefully! Use 0.25% COC for best results on large Palmer (>6”). As always with paraquat, be mindful of mix order and water pH.
Planting soybeans early could help get a jump on pigweeds in regards to canopy closure. We usually don’t begin seeing pigweed seedlings until the soil is warm enough to plant cotton (60+ degrees).
At planting (Enlist trait beans): Gramoxone + Presidual, First post: Liberty + Zidua, Last post: Enlist + Powermax on 20” row beans worked well for me.