Soybean School: Weed control in a dry year

Does it pay to invest in weed control in a dry year?

When soil moisture is scarce, one way to help conserve it is to prevent weeds – they can rob the precious resource from emerging and growing plants. On this episode of RealAgriculture’s Soybean School, we travel to the BASF research and development site in Winkler, MB, to talk weed control with Jeanette Gaultier, the company’s senior technical service specialist.

Despite the light soil and lack of moisture, the soybeans that Gaultier is standing in look quite good, having benefited from effective weed control using a two-pass system.

Gaultier says making that decision to commit to a pre-emergent application can be challenging, especially in dry conditions when weed competition doesn’t appear significant, but weeds emerging with the crop will steal valuable moisture and also provide competition that will impact yield. (Story continues below video)

Gaultier does note that there has been a move away from residual herbicides for soybeans in BASF’s western Canadian portfolio. Multiple modes of action for resistance management and a Group 2 with a bit less residual within the two-pass program, sets weed control up well, with open re-cropping options.

“It’s probably a good idea to review what Group 2s have been used throughout a rotation,” says Gaultier, and there are some sustainability guidelines around using this mode of action, from BASF — including using only one application of a Group 2 in a field per year, maxing out at two applications of a Group 2 in four years.

Looking at the dry conditions across the Prairies, the moisture required to drive the microbial and chemical breakdown of a Group 2 herbicide in soil, just isn’t there this year.

It’s not just Group 2s that can affect next year’s cropping decision under low rainfall, says Gaultier, there are other products that have residual — for soybeans specifically, some Group 4 products used in wheat or canola can impact a soybean crop.

Gaultier says to use rainfall data from the time the application was made, to about September 1 as a starting point, for cropping decisions.