Managing soil-applied herbicide injury in soybeans

What can growers do to reduce crop injury in soybean fields where they rely on soil-applied herbicides for weed control?

Ontario Ministry of Agriculture, Food and Rural Affairs weed management specialist Mike Cowbrough sees this type of injury every year in soybean fields, but he says there are always other factors at play including untimely rain, compaction and carryover.

In this video report from 2021 Ontario Diagnostic Days, Cowbrough offers tips on how growers can best manage soil-applied Group 14 and Group 15 herbicides to avoid injury in soybeans. He looks at environmental conditions that contribute to injury and describes plant damage caused by each group or a tank-mix combination. He also describes the plant’s ability to bounce back and grow out of injury with help from axillary buds.

Cowbrough acknowledges that Group 14 and 15 products are “hotter” and have the potential to cause greater crop injury, but these two modes of action are needed control problem weeds, especially in IP soybeans. He notes that growers can take precautions to reduce injury — he recommends avoiding use of these products on course soils with lower organic matter levels.

Crop injury often occurs, however, because of environmental conditions beyond the grower’s control that take place after application. From Cowbrough’s perspective, the best approach for growers is to understand that they are likely to see some injury. “What you hope for in situations like this is the value that those herbicides bring in terms of clean fields out-weighs the risk of crop injury.”

In the report, Cowbrough looks back at 10 years of research on Group 14 and Group 15 herbicides. He notes that data indicates that tank-mixes could produce higher crop injury in any given year, but they produced more than double the yield when compared to the unsprayed check. He also explains that Group 14/15 yields were equivalent to herbicide programs that might have had better crop safety, but were less effective at killing weeds.

Click here for more Ontario Diagnostic Days reports.

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