By Jeremy Kichler
I have received this question a couple of times this week from growers and retailers with indeterminate soybeans. According to the soybean weed control section of the 2022 UGA Pest Management Handbook, paraquat can be applied to soybeans based on the following instructions. The paraquat rate according to this reference is 0.25 lb ai per acre which is 16 oz of 2 lb formulation.
Indeterminate Varieties: Apply when at least 65% of the seed pods have reached a mature brown color or when seed moisture is 30% or less.
Determinant Varieties: Apply when soybeans are fully mature (full pod development, 50% leaf drop, and the remaining leaves are yellow).
Mature cocklebur and drought stressed weeds are not adequately controlled by this treatment. Do not apply to immature soybeans. Add a nonionic surfactant at 0.25% v/v. May be ground or aerially applied. Tank-mix with Aim if annual morningglories are also a problem (except smallflower).
Source : uga.edu