Irrigation Scheduler
1Field Location
Search, click the map, or type coordinates. Elevation is auto-fetched.
📏 Elevation
🌾 Farm Area
1 ha = 10,000 m² · 1 Ropani = 508.7 m² · 1 Kattha = 338.6 m² · 1 Acre = 4,047 m²
3Soil Data
Choose how to define soil hydraulic properties. Root zone depth and depletion fraction p are pre-filled from your crop selection — update them below if needed.
🌱 Soil Input Method
Fetches clay, silt, sand, field capacity and wilting point from SoilGrids v2.0 (ISRIC, 250 m) for the selected map location.
Enter soil texture fractions and organic matter. Hydraulic properties are estimated using the Saxton & Rawls (2006) pedotransfer functions (SSSA J. 70:1569–1578).
Enter measured or literature values directly. AWC is calculated as (FC − WP) × 10 mm/m.
⚙ Soil Parameters for SWB
Research basis: FAO (Doorenbos & Pruitt 1977) shows crops extract water in a 40-30-20-10% pattern from top to bottom quarters of the root zone — roughly 70% from the upper half. Molz & Remson (1974), Hoogland et al. (1981), and FAO-56 §8 (p.163) confirm that triggering on the full depth delays irrigation beyond what the crop actually experiences. The stress coefficient (Ks) and ETc still use the full Zr as required by FAO-56.
2Crop & Season
Select crop and sowing date. Root zone depth and depletion fraction are set automatically and carried into soil properties.
🌾 Crop & Sowing Date
📊 Current Crop Status
4Schedule Settings & Irrigation Method
📅 Simulation Start & Horizon
🚰 Water Source Optional
💧 Irrigation Method & Efficiency
d_gross = d_net ÷ η
Volume = d_gross × farm area
Set 0 to skip duration
5Observed Rainfall
Enter measured daily rainfall. Future dates use zero rain (conservative).
🌧 Rainfall — Simulation start → Yesterday
Enter observed rainfall (mm/day) for each past day. Leave 0 if none or unknown. Forecasted rain is excluded from the SWB.
⚡ Today's Rainfall (mm) — Optional
If rain has occurred today before irrigation, enter the amount here.
6Review & Run
Confirm settings then run the simulation.
📋 Input Summary
📅 Daily Simulation Log
▼ ShowSWC (blue) vs FC (green dashed) and RAW threshold (red dashed). Green dots = irrigation.
Kc Curve (Days After Sowing)
Rainfall · Irrigation · ETc · ET₀ (mm/day)
⚠ Stress Sensitivity — Simulated Period
Methods & References
ET₀ — FAO-56 Penman-Monteith
Weather from Open-Meteo ERA5 + ECMWF. Reference: Allen et al. (1998). FAO Irrigation Paper No. 56.
Crop coefficients (Kc) & growth stages
Dual Kc approach (FAO-56 §7): ET = (Ks·Kcb + Ke)·ET₀. Kcb = basal transpiration coefficient (FAO-56 Table 17). Ke = soil evaporation coefficient tracking the topsoil (Ze=0.10–0.15 m) evaporation layer. Ks = water stress coefficient (FAO-56 §8 Eq.[84]) reducing transpiration when soil depletion exceeds RAW. Stage durations and Kcb from FAO-56 Annex 1 Tables 1, 12 & 17. Kc_ini is dynamically adjusted following FAO-56 Fig. 29 (p.142–143): the tabulated Kc_ini value is corrected upward or downward based on mean ET₀ during the initial stage and the observed wetting interval (days between rain ≥ 3 mm events). Frequent wetting raises Kc_ini toward 1.15; infrequent wetting lowers it toward 0.15. The user-entered Kc_ini acts as a floor — the adjustment only increases above it if wetting frequency warrants.
Effective root zone (67% rule): the irrigation trigger is based on soil water depletion in the upper 67% of the rooting depth, not the full Zr. Research basis: Doorenbos & Pruitt (FAO-24, 1977) 40-30-20-10 water uptake distribution; FAO-56 §8 p.163; Borg & Grimes (1986); Prasad (1988). Approximately 70% of actual root water uptake occurs in the upper two-thirds of the root zone, so using full Zr delays the trigger beyond what the plant actually experiences. The Ks stress coefficient and ETc calculation continue to use the full root zone depth (as required by FAO-56 Eq.[84]), while the trigger depth uses Zr_eff = 0.67 × Zr(t). The irrigation dose is sized to refill the full root zone deficit.
Soil Water Balance (AquaCrop simplified)
Soil Water Balance — Enhanced model
SWC(t) = SWC(t−1) + Pe(t) + Irr(t) − ETc_actual(t) − Drainage(t). TAW(t) = AWC × Zr(t) (dynamic). RAW(t) = p × TAW(t). Effective rainfall Pe uses USDA SCS Curve Number method (TR-55, 1986): CN derived from hydrologic soil group (from Ks; Rawls et al. 1993) and 5-day antecedent rainfall for AMC class. No ET cap on infiltration — rain above ET raises SWC correctly. Deep drainage simulated by tipping-bucket model when SWC > FC (Saxton-Rawls Ks × 24 h × drainage fraction). Yield reduction estimated from Ky response factors (FAO Water Report 33; Doorenbos & Kassam, 1979). References: Steduto et al. (2009). AquaCrop. | USDA TR-55 (1986).
Soil hydraulics — Saxton & Rawls (2006)
θ_WP, θ_FC, θ_S, Ks from sand, clay, OM. AWC = (θ_FC − θ_WP) × 1000 mm/m. Reference: Saxton & Rawls (2006). SSSA Journal 70:1569–1578.
SoilGrids v2.0
ISRIC SoilGrids REST API, 250 m, 0–30 cm. Reference: Poggio et al. (2021). SoilGrids 2.0. SOIL 7:217–240.
Effective rainfall & Rice AWD
USDA-SCS method: Pe = 0.9×P (P ≤ 25 mm) or 22.5 + 0.1×P (P > 25 mm). USDA-NRCS NEH Part 630, Ch. 10. AWD: 50 mm ponding per event. Reference: Bouman et al. (2007). Agric. Water Mgmt.
Map: © OpenStreetMap contributors · Elevation: Open-Meteo DEM · Geocoding: Nominatim/OSM