Control Weeds With Treated Fertilizer

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Flooded rice field

Pretreating fertilizer with a herbicide helps improve product placement while saving trips across the field, strengthening weed control.

In some cropping or pasture systems, impregnated fertilizer requires rainfall for activation. In rice, however, the fertilizer coated with a crop protection product, such as Loyant® herbicide or Novixid® herbicide, is applied into the flood.

Because the application method essentially bathes the weeds with the herbicide-coated fertilizer, minimal herbicide directly contacts the rice plant. 

Applying herbicide-treated fertilizer does not change fertilizer application timing; it instead combines fertilizer delivery with a herbicide spray. The method also helps improve weed control when part of a comprehensive weed control program.

To coat, or impregnate, fertilizer, the herbicide is applied to dry fertilizer during blending at the retail facility or fertilizer supplier.

Fertilizer that will be coated with Novixid or Loyant should be a premium-grade product with a size guide number (SGN) of at least 200, such as premium-grade granular urea or premium-grade granular ammonium sulfate. Using dusty fertilizer material is not recommended.

A fertilizer rate of 150 pounds per acre is recommended for impregnation with Loyant, with a minimum 100-pound rate allowed. For those impregnating fertilizer with Novixid, a minimum rate of 150 pounds of fertilizer per acre is required and a 200-pound rate is recommended.

Labeled herbicide rates are 16 ounces per acre for Loyant and 27.4 ounces per acre for Novixid.

Best management practices dictate using commercial blending equipment with proper nozzle arrangement to ensure even blending. The herbicide should be coated onto the fertilizer in stages for optimum distribution and a dry final product.

Once coated with herbicide, the fertilizer should be applied as soon as possible and not left out overnight before applying.

When the rice reaches the four- to five-leaf stage, or first tiller, coated fertilizer is applied into the flood. The field’s water level should be maintained for at least 10 days.

For best results, coated fertilizer should be applied to weeds that are less than 4 inches tall. Also, at least 70% of weeds present should be submerged in the flood at time of application. Weeds such as jointvetch should be completely under water to achieve the best control with impregnation.

Loyant® and Novixid® are not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Consult the label before purchase or use for full details. Always read and follow label directions.