Irrigation Set Time Calculator

How long to run a set from crop ET and application rate. Uses ETo you already have. Not an ETo engine.

Formula

ETc = ETo × Kc
hours = ETc / application rate
hours with DU = hours / DU

Example: ETo = 0.25 in, Kc = 1.1, rate = 0.2 in/h
  ETc = 0.275 in
  hours = 1.38 h
  with DU 0.80 → 1.72 h

Kc values are crop and growth-stage specific (FAO-56 Table 12).

References

1. Allen RG, et al. FAO Irrigation and Drainage Paper 56. ETc = ETo × Kc. Chapter 6 crop coefficients.
2. USDA NRCS. Irrigation Guide. Set time from net depth and application rate; DU adjustment.

Field planning aid only. Confirm rates with your agronomist, label, and local extension. Not a pesticide or fertilizer recommendation.