Arkansas Rice: Residual Herbicides and Wet Ground

©Debra L Ferguson Stock Photography

©Debra L Ferguson Stock Photography

Rain, rain, go away, come again another day!  Our wet conditions continue to bog down our rice progress so far in 2022, and with that hinder our weed control efforts as well.  

Not only have burndown applications been challenging to make sure we can still get appropriate coverage, low temperatures and dodging showers within rainfast periods has been a struggle to maximize our chemical effectiveness. In addition, because of the excess of water, we are now running into issues with applying our residual herbicides.

For the majority of our residual herbicide products, it is against the label to apply the chemical into standing water.  But outside of just label requirements, it is best practice to avoid spraying these herbicides in standing water or even fully saturated soils for 3 additional reasons: 1. Environmental stewardship, 2. Reductions in herbicide effectiveness, and 3. Increases in rice injury potential.

Most of our herbicides are water soluble, and as such, readily move with water flow.  This can lead to downstream contamination of sensitive areas when any of our standing water may try to move off our fields.  Additionally, other off-target movement potential such as volatility, may increase in these areas of saturation.

Saturated conditions will also decrease the performance of many of our residual herbicides.  Weed control may be reduced due to movement of the herbicide outside of our treated area or the dilution effect.  

As an example, a warning of this potential is even provided directly on the Prowl H2O label: “If soil is saturated at the time of application, allow the soil surface to dry before restoring the permanent flood.  Prowl H2O requires alternate wetting/drying cycles to be activated.  Weed control will be reduced if the soil surface is not allowed to dry out before restoration of the permanent flood.”

Conversely, some herbicides may have extreme enhanced activity, resulting in severe crop injury potential.  For example, from the Bolero herbicide label dealing with water-seeded rice (which with our heavy saturated conditions is partially comparable): “If rain should occur after soil preparation, Bolero 8 EC Herbicide should not be applied until the soil is dry enough to support tillage operations… Rice in areas which do not completely drain when the seeding flood is removed may be injured or killed.”

Overall, having fully saturated conditions or standing water is not a good time to be applying our residual herbicides.  Especially with current weather forecasts indicating we may be receiving even more rain in the very near future, prolonging the length of time of these saturated conditions exist.

If you have any questions, please don’t hesitate to reach out. And as always, good luck out there.

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