Calibration Error Leading to Overapplication
A grower is applying a preemergence herbicide to a 30-acre field of soybeans. The label rate is 1.5 pints per acre. The grower's sprayer has a 200-gallon tank and is calibrated to deliver 15 gallons per acre. The grower fills the tank with 200 gallons of water and adds 20 pints of herbicide, intending to treat 13.3 acres. After spraying 10 acres, the tank is empty. The grower realizes the sprayer was actually delivering 20 gallons per acre due to a worn nozzle. The field has sandy soil with low organic matter, and the herbicide is known to leach. The grower notices some soybean seedlings are emerging with yellowing and stunting.
1. Calculate the actual application rate and determine if it deviates from the label. Show your work.
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The grower intended to apply 1.5 pints per acre. They mixed 20 pints in 200 gallons, planning to cover 13.3 acres (200 gal ÷ 15 gal/acre = 13.3 acres). The actual rate would be 20 pints ÷ 13.3 acres = 1.5 pints/acre if the sprayer delivered 15 gal/acre. However, the sprayer actually delivered 20 gal/acre. The actual area covered with 200 gallons is 200 gal ÷ 20 gal/acre = 10 acres. The actual application rate is 20 pints ÷ 10 acres = 2.0 pints per acre. The label rate is 1.5 pints per acre. The actual rate is 2.0 pints/acre, which is 0.5 pints/acre higher, or 33% over the label rate. This deviation is significant and exceeds the label rate. The overapplication could lead to crop injury, as evidenced by yellowing and stunting. The grower must recalibrate the sprayer and may need to report the incident if required.
2. What are the environmental and legal implications of this overapplication?
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Environmentally, the overapplication increases the risk of herbicide leaching into groundwater due to the sandy soil and low organic matter. It may also cause injury to the soybean crop (as observed) and potentially affect non-target plants. The herbicide may persist longer or contaminate surface water through runoff. Legally, applying a pesticide at a rate exceeding the label is a violation of FIFRA. The grower could face civil penalties. Additionally, the grower may not be able to sell the crop if residues exceed tolerances. The grower should document the incident, recalibrate the sprayer, and consult with the state lead agency. They may need to take remedial actions such as incorporating the herbicide or planting a cover crop. The grower should also check if the product has a label statement about overapplication and follow any instructions. Overall, the overapplication has both environmental and legal consequences.