Using multiple practices to suppress Giant Ragweed in Soybeans

A field study was conducted by WiscWeeds Graduate Research Assistant Guilherme Chudzik in 2022 and 2023 at the Rock County Farm, Janesville, WI, to evaluate the impact of soil management practices, soybean planting time, and PRE-emergence (PRE) herbicide application on giant ragweed management and soybean yield.

Study treatments consisted of:

  • Four soil management strategies: i) conventional tillage (chisel-plow in the fall and field cultivator in the spring), ii) no-till, and fall-planted cereal rye treatments terminated at two different times: iii) cereal rye early terminated (10-14 days before planting) and iv) cereal rye late terminated (‘planting green’; within three days of soybean planting).
  • Two soybean planting times: early (early to mid-May) and late (late-May).
  • Two PRE herbicide treatments: no PRE and yes PRE (Sonic @ 6.45 oz/acre) at soybean planting time.

To simulate common practices adopted by Wisconsin soybean growers, Enlist One (2 pts/acre) + Roundup PowerMax (2 pts/acre) + AMS were applied postemergence (POST) when ~50% of giant ragweed plants within a specific treatment reached ~4 inches in height. Giant ragweed density at the time of POST application and soybean yield data were collected in this study and are discussed.