EXPERT VIEW: Maximize yield potential with soybean herbicide

By Eric Smith, United Cooperative area seed and agronomy specialist

Due to low commodity prices and net returns over the past two to three years, a large amount of time and “expert” comment has been focused on what areas of a crop management plan to cut. This article gives you a few reasons why NOT to hit the easy button on soybean chemistry.

Waterhemp has been a huge topic of discussion for the past few years, driving the importance of using residual chemistry on your soybeans. While pre emerge treatments and post residuals are extremely important in waterhemp management, they are also important in helping us maximize soybean yield potential. The average yield loss from a moderate infestation of giant foxtail, velvetleaf and waterhemp, all at 2 to 4” heights, is 4 to 6 bushels per acre. At $9.50/bushel soybeans, that’s $38 to $57/acre of lost revenue! This can be prevented with the use of a pre emergent herbicide application that has an upfront investment of 1 to 1.5 bushels per acre, and will typically help keep a soybean crop clean through the late vegetative stages or early reproductive stages. Aside from the direct benefits of the start clean, stay clean system and yield preservation from early season weed control, there are other benefits to a pre emerge residual application.

Pre emerge herbicide applications also give us the opportunity to scout for insects like soybean aphids and spider mites ahead of the second pass and tank mix an insecticide to eliminate these critters. The timing of a second application also gives the agronomist a chance to pull tissue samples ahead of the reproductive stages to let the soybean plant tell us what it’s lacking. Year after year, a large percentage of the tissue samples indicate Zinc and Mangenese deficiency in area soybean fields.

A post emerge application of a residual herbicide has been most beneficial in areas with waterhemp pressure. The battle faced with waterhemp is the 250 to 300 thousand seed/plant that it produces, which survive at least four years in the soil, while germinating through mid August. We MUST be using a post applied residual after a pre emerge if we want to control this monster!

We have covered a variety of benefits to the use of residual herbicides on soybeans in this article. If you have any additional questions, please contact your United Cooperative agronomist.



This picture shows early season weed control (32 days after application) from a pre emerge applied chemical.