By Mark VanGessel, Extension Weed Specialist; firstname.lastname@example.org
This is an article written by Dwight Lingenfelter and Bill Curran from Penn State and modified for Delaware.
As more farmers use vertical tillage to manage crop residues or to mellow the seedbed prior to planting (especially soybeans), questions have arisen about possible impacts of using these types of tillage operations in combination with certain soybean herbicides. The PPO herbicides (Group 14) in particular are drawing attention in these discussions. The soil applied PPOs include flumioxazin (Valor SX, Valor XLT, and Envive); sulfentrazone (the Authority family lineup and Sonic), fomesafen (Prefix, Reflex); and saflufenacil (Sharpen, Verdict, Optill). In general, if a vertical tillage operation is done before the PPO herbicide application, residual weed control will typically not be negatively affected. However, if the PPO herbicide was applied before the tillage operation then weed control could be compromised. In particular, flumioxazin and saflufenacil-containing herbicides can be affected the most. In this case, any tillage after herbicide application disrupts the uniform layer of herbicide potentially causing weed escapes or patchy weed control.