Cotton Water Requirement Calculator
Work out the seasonal and per-irrigation water requirement of cotton (FAO-56 ETc = ET₀ × Kc, peak Kc 1.18) for your field, climate, soil and irrigation method.
Keep moisture even through flowering and boll development; alternate-furrow or drip irrigation suits cotton's deep roots well. Ease off near maturity to open bolls cleanly and avoid regrowth.
Indicative planning figures based on published research averages. Local soil tests, varieties and weather change actual requirements — confirm with your agronomist or extension officer.
Disclaimer: This tool is for general informational and estimation purposes only and is not professional financial, tax, accounting or legal advice. All figures are estimates — verify with a qualified professional before making decisions. Read the full disclaimer.
Farmers and irrigation planners use the free Cotton Water Requirement Calculator to turn the FAO-56 crop coefficients for cotton into a real seasonal water volume and an irrigation interval for their own field — no agronomy tables, works offline.
About Cotton Water Requirement Calculator
Cotton draws 700–1300 mm over its long season, and flowering-to-boll-development is the period where water management makes or breaks the crop. This calculator uses the FAO-56 method — crop evapotranspiration ETc = ET₀ × Kc — with cotton's own crop coefficients (Kc 0.35 initial, 1.18 mid-season, 0.6 late) across a 180-day season. Pick your climate band (which sets reference ET₀), irrigation method (drip, sprinkler, pivot or surface — each with its own efficiency) and soil texture, and it returns the seasonal water need in cubic metres, the peak daily demand, the net depth per irrigation and how many days to wait between irrigations.
How to use Cotton Water Requirement Calculator
- 1Enter your field area and choose the climate band matching your season.
- 2Select your irrigation method and soil texture.
- 3Read the seasonal water volume, peak daily demand and irrigation interval, then follow the scheduling note.
Why use Cotton Water Requirement Calculator?
- ✓Uses cotton's real FAO-56 Kc curve, not a flat factor
- ✓Accounts for drip / sprinkler / pivot / surface efficiency
- ✓Gives seasonal volume, peak daily need and an irrigation interval
- ✓Free, instant and fully in-browser — works offline in the field
Frequently asked questions
How much water does cotton need?+
Cotton draws 700–1300 mm over its long season, and flowering-to-boll-development is the period where water management makes or breaks the crop. The exact figure depends on climate and season length; this tool sums ET₀ × Kc across the crop's 180-day growth stages for your conditions.
When does cotton need the most water?+
From flowering through boll development — the long reproductive phase. Water stress then sheds squares and young bolls; excess water late causes rank vegetative growth and delayed opening. Drip excels here.
Is drip irrigation worth it for cotton?+
Usually yes — cotton's deep roots and long season make drip's 30–40% water saving and fertigation precision very profitable, and it avoids the waterlogging that flood irrigation risks in heavy cotton soils.
What is ET₀ and Kc?+
ET₀ (reference evapotranspiration) is how fast a standard grass surface loses water in your climate. Kc (crop coefficient) scales it to a specific crop and growth stage. Crop water use ETc = ET₀ × Kc — the basis of FAO-56 irrigation scheduling.
Is this calculator free and private?+
Yes — free, no sign-up, and all calculation runs in your browser, so it works offline in the field and your data never leaves the device.
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