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Soybean field

Residual herbicide activity keeps IP soybeans weed free

When it comes to soybeans, research shows the mere presence of weeds cues stress-induced adaptive responses which have a rapid and irreversible negative effect on the yield.

As weeds grow and proliferate, so does their influence on profitability. This is particularly true for Identify Preserved (IP) soybean varieties, where herbicide options are more limited, and staining due to the presence of weeds at harvest can have a serious impact on quality as well as yield. Indeed, staining is one of the main causes of rejection at the elevator, and a problem which can be exacerbated by moisture.

Knockout weeds early

Knocking weeds down early – and keeping them down – is critical.

A go-to strategy begins with a pre-plant incorporated or pre-emerge application to eliminate germinating weeds up to the V3 growth stage. Fields should be scouted for escapes, with subsequent applications post-emergence being altered based on the weed spectrum identified. If a one-pass strategy is the only option, soil-applied herbicides can control escapes and performance issues easier than post-emergence applications.
Cleaning up escapes the year prior to planting IP soybeans can also pay huge dividends at  
harvest. In fields where kochia, redroot pigweed, lamb’s-quarters and waterhemp are common, growers need to be even more mindful prior to planting, since effective control in IP systems can be difficult to achieve.

Mopping up

Regardless of the strategy employed, using pre-emergent herbicides with extended residual control is key. These products establish a protective barrier at or just below the soil surface, killing both emerging weeds and those soon to emerge. Because IP varieties are generally grown for the export market, however, growers also have to ensure they are using products which fit the production specifications (notably allowable residue levels) of the buyer.