Irrigation Zone Runtime and Cycle-and-Soak
The controller runtime to apply a target depth.
Example
You enter
- Target depth this run (in) 0.75
- Precipitation rate (in/hr) 1.2
- Distribution uniformity (0-1) 0.75
- Max cycle before runoff (min) 10
You get
- Net runtime 37.5 min
- Gross runtime (DU adjusted) 44.1 min
- Cycles 5
- Per cycle (min) 8.824
Checked against published worked examples from: UF/IFAS Gardening Solutions.
Details, formula, and sources
ScopeNet (depth / rate x 60), gross (net x the Irrigation Association run-time multiplier 1 / (0.4 + 0.6 DU), so the dry quarter gets the target), and a cycle-and-soak split into runs short enough to beat runoff on the soil and slope. The DU comes from a catch-can audit and the soil caps the cycle length; a program aid, not a guaranteed schedule.
Formula or tablenet_min = target_in / precip_in_hr x 60; gross_min = net_min x RTM, RTM = 1 / (0.4 + 0.6 x du); cycles = ceil(gross_min / max_cycle_min); per_cycle_min = gross_min / cycles.
Source and editionFirst-principles runtime and cycle-and-soak relations with the Irrigation Association scheduling references (by name); no edition cycle.
Free accessThe runtime and cycle-and-soak relations are public irrigation-scheduling practice. The DU comes from a catch-can audit and the soil intake rate governs the cycle length.
What governsEstimate. AHJ and licensed professional govern.
API field namestarget_in, precip_in_hr, du, max_cycle_min, net_min, gross_min, cycles, per_cycle_min
- Net runtime net = target depth / precipitation rate x 60 (depth over rate)Irrigation Association scheduling references
- DU adjustment gross = net x RTM, RTM = 1 / (0.4 + 0.6 DU_LQ) (1.18 at DU 0.75); until 2026-09-26 the tile divided by DU (1.33)Irrigation Association Recommended Audit Guidelines (2009), Eq. 3-11 / Table 3-8
- Cycle-and-soak the gross time splits into cycles no longer than the soil/slope runoff limit, with soak gaps between themIrrigation Association scheduling references