Fertigation / Chemigation Injection Rate

The injection-pump rate to apply a liquid fertilizer or chemical through an irrigation system.

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Example

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Checked against published worked examples from: Washington State University Extension (Peters, Neibling, Hoffmann).

Details, formula, and sources

ScopeTotal product = the per-acre rate x the acres; injecting it evenly over the irrigation SET means the pump runs at total / set time. Applying 5 gal/acre over 40 acres in a 6-hour set is 200 gal total at 33.3 gph (0.56 gpm). Set the metering pump to that, start after the system reaches pressure and the last emitter flows, then flush with clear water. For a stock solution the resulting concentration is the injection flow / system flow x the stock strength. CRITICAL: an EPA-required anti-siphon/check-valve/interlock package must protect the water source from backflow whenever a chemical is injected. A rate estimate; the product label (FIFRA), the state chemigation rules, and a drawdown calibration govern.

Formula or tabletotal_product_gal = product_rate_gal_per_acre x area_acres; injection_rate_gph = total_product_gal / set_time_hours; injection_rate_gpm = injection_rate_gph / 60.

Source and editionFertigation / chemigation injection-rate practice (EPA chemigation rules; the product label under FIFRA), by name; the label, the state chemigation regulations, and a drawdown calibration govern.

Free accessThe injection-rate arithmetic is public first-principles (total product over the set time); the per-acre rate, acres, and set time come from the recommendation and the irrigation schedule.

What governsEstimate. AHJ and licensed professional govern.

API field namesproduct_rate_gal_per_acre, area_acres, set_time_hours, total_product_gal, injection_rate_gph, injection_rate_gpm

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