Fertigation / Chemigation Injection Rate
The injection-pump rate to apply a liquid fertilizer or chemical through an irrigation system: total 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 and source
total_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.
Fertigation / 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.
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