The Second Burndown: Seasonal Caps, Tank Math, and a Roadside Ditch
An applicator is hired to burndown and preplant-treat 160 acres of no-till soybean ground. He plans to tank-mix a Group 2 ALS herbicide labeled at a single rate of 0.75 oz/A with a Group 4 product and 1% v/v methylated seed oil. The Group 2 label states: maximum single rate 0.75 oz/A; maximum 1.25 oz/A per crop season; minimum 14 days between applications; do not apply within 50 feet of surface water; restricted-entry interval 12 hours; do not graze or feed forage from treated areas. The sprayer holds 1,000 gallons and is calibrated at 15 GPA with a 90-foot boom. The grower already applied 0.75 oz/A of the same Group 2 product to this field 21 days ago and wants the full rate again because “the first one didn’t hold.” A roadside ditch, dry now but carrying runoff after rain, borders the field and drains to a creek.
1. How many acres does the 1,000-gallon tank cover at 15 GPA, and how much Group 2 product should go in it? Is the grower’s request legal?
Read the worked answer
Do the arithmetic first, then test it against the label - the label is the binding limit.
- Coverage: 1,000 gal ÷ 15 gal/A = 66.7 acres per tank.
- Product at 0.75 oz/A: 66.7 × 0.75 = 50 oz per tank.
But 0.75 oz/A is not legal on this field today. The seasonal maximum is 1.25 oz/A and 0.75 oz/A was already applied. A second full-rate pass would total 1.5 oz/A - 0.25 oz/A over the cap. Meeting the 14-day interval (21 days elapsed) does not cure a seasonal-total violation; interval and total are separate limits, and the more restrictive one controls.
Because the label lists a single rate rather than a range, there is no labeled reduced rate to retreat with. Cutting to 0.5 oz/A would stay under the season cap but would be an off-label rate and would stack more selection pressure on the same site of action. The defensible call: do not load this product for a second pass. Load a different, labeled mode of action effective on the escapes, or use mechanical/spot treatment.
What would change the answer: a label with a rate range and at least 0.5 oz/A of season allotment remaining would allow a reduced-rate retreatment.
2. Can he spray the field edges next to the roadside ditch? What must he decide before the boom is unfolded?
Read the worked answer
Treat the ditch as surface water until proven otherwise. The label sets a 50-foot no-apply buffer to surface water, and a ditch that conveys runoff to a creek is a direct conduit, not a dry strip of grass. The fact that it is dry today does not clear it - the label protects waters of the state, and runoff after the next rain carries residue straight to the creek.
Reasoning steps:
- Measure and flag a 50-foot unsprayed setback from the top of the ditch bank, not from the centerline.
- Shut off boom sections over the setback; verify with a foam or dye pass before spraying the rest of the field.
- Reduce off-target movement into the setback: low-drift or air-induction nozzles, a spray quality the label allows, and no spraying when wind carries toward the ditch or when a temperature inversion is likely (calm, clear evening).
- If the ditch is a jurisdictional water with an aquatic-use requirement, only an aquatic-labeled product can go near it - this one cannot.
If the applicator cannot hold the setback with the equipment he has, he does not spray that pass.
3. Five days after the application the beans have not emerged and the grower wants to turn cows onto the field. He argues the 12-hour REI has expired. How do you answer?
Read the worked answer
The REI and the grazing restriction are two different label statements, and only one has expired.
The 12-hour REI governs worker entry for hand labor and similar tasks. The label separately says do not graze or feed forage from treated areas - that restriction has no stated expiration on the label as written, so it does not lapse at 12 hours, 5 days, or at emergence. With no labeled grazing interval, the conservative and defensible position is that livestock stay off.
Additional practical reasoning:
- No stand plus a residual herbicide means the grower may replant. Check the label’s replant/plant-back interval and rotation restrictions before any reseeding decision; that interval, not the REI, governs the next crop.
- If the grower wants a specific grazing clearance, the answer comes from the label or the manufacturer in writing - not from a neighbor, a dealer, or the calendar.
- Document the conversation and the label basis for the recommendation; if the grower overrides it, the applicator’s record should show the advice given.