Tank Mix Gone Wrong Before Planting
You are a private applicator preparing a 500-gallon tank to burndown a 30-acre field two weeks before planting corn. You plan to mix a residual herbicide, a glyphosate product, and a surfactant. The label for the residual product lists a maximum single rate and a seasonal maximum, requires a specific carrier volume, and warns against mixing with certain products. You have a half-full jug of residual from last season with a faded label, and a new jug of glyphosate. Your sprayer was last used for a broadleaf herbicide on turf and was rinsed but not with a tank cleaner. You need to finish before rain tomorrow.
1. Before mixing, what must you verify about the products and the sprayer, and what do you do about the faded jug?
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Product verification:
- Read the current label for each product: rate (single and seasonal), carrier volume, adjuvants, mixing order, and prohibited tank-mix partners.
- The faded jug is a stop-work item: if you cannot confirm the product identity, EPA reg. number, and label directions, you cannot legally or safely use it. Do not guess by color or memory. Use a fully labeled container or dispose of it per label/state rules.
- Confirm the glyphosate product's label allows the tank mix and check for any antagonism or mixing-order instructions.
Sprayer verification:
- A rinse is not the same as a tank cleaner/deactivation for a prior broadleaf herbicide. Residues can injure the corn.
- Use the prior product's label-recommended cleaner and procedure (often a detergent/ammonia-type cleaner, followed by rinse and flush of boom/lines/nozzles).
- Check nozzles/screens for residue and confirm output.
Judgment point: an unidentifiable product and an inadequately cleaned tank are both reasons to delay, even with rain coming.
2. How do you decide whether to spray tonight or wait, given the rain forecast?
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Decision framework:
- Label constraints first - carrier volume, rainfast interval, temperature/wind limits, and any restriction on application before planting.
- Weather - if rain falls before the product's rainfast window, efficacy is lost and you may need a retreatment, which risks exceeding seasonal maximum rates.
- Tank cleanliness - if the cleaner procedure cannot be completed and verified tonight, spraying risks crop injury that costs more than a delayed burndown.
- Product identity - the faded jug cannot be used until identified.
Conclusion logic: the cost of waiting (a few days, possibly a different burndown product) is smaller than the cost of a failed burndown plus a replant or a seasonal-max violation. Do not let the rain forecast override label compliance and tank hygiene. If you proceed, use only verified products, complete the cleaner procedure, and confirm the rainfast window against the actual forecast.
3. What records should you create for this application, and why does each matter?
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Record at minimum:
- Date, time, location/field, acreage treated.
- Product name, EPA reg. number, rate per acre, total product used - proves rate and seasonal-total compliance.
- Carrier volume and adjuvant/surfactant used.
- Applicator name/certification number and supervisor (private applicator).
- Weather: wind speed/direction, temperature, and rain timing relative to application.
- Sprayer setup: nozzles, pressure, boom height, and the tank-cleaning procedure performed.
Why each matters:
- Rate and total use records defend against seasonal-max and misapplication allegations.
- Weather records support drift and efficacy decisions.
- Cleaning records show due care and protect against carryover injury claims.
- Reg. numbers tie the record to the exact labeled product, which is what regulators check.
Exam point: records are evidence. A complete record can resolve a complaint; a missing one cannot.