Leaching Requirement Calculator
Estimate the extra irrigation water (leaching fraction) needed to keep root-zone salinity in check, from irrigation-water and crop-tolerance EC.
Salty irrigation water concentrates in the root zone as the crop transpires; a fraction of each irrigation must drain past the roots to flush salts. LR = ECw ÷ (5×ECe − ECw). Higher water salinity or lower crop tolerance demands more leaching — and good drainage to remove it.
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 engineers use the free Leaching Requirement Calculator to get an accurate answer in seconds — no formulas to remember, works offline in the field.
About Leaching Requirement Calculator
Irrigating with even mildly saline water steadily concentrates salt in the root zone, because the crop takes up water but leaves most salts behind. To stop salinity building to crop-damaging levels, a fraction of every irrigation must pass below the roots, carrying salts with it — the leaching requirement. Using the FAO leaching equation, this tool estimates what fraction of extra water you must apply from your irrigation-water salinity (ECw) and the crop's salinity threshold (ECe), and the total water factor it implies.
How to use Leaching Requirement Calculator
- 1Enter your system or field values into the inputs.
- 2Read the headline result and the supporting breakdown.
- 3Apply the guidance in the note to your irrigation plan.
Why use Leaching Requirement Calculator?
- ✓Uses the standard, citable irrigation engineering formula
- ✓Clear inputs with sensible defaults
- ✓Instant result with the working shown
- ✓Free, fully in-browser and private
Frequently asked questions
What is the leaching requirement?+
It is the minimum fraction of applied irrigation water that must drain below the root zone to keep salts from accumulating to harmful levels. LR = ECw ÷ (5×ECe − ECw), where ECw is irrigation-water salinity and ECe is the crop's soil-salinity tolerance. Saltier water needs more leaching.
Why do I also need good drainage for leaching?+
Leaching only works if the salty drainage water can actually leave the root zone. On poorly-drained soils the flushed salts (and a rising water table) come straight back. Effective leaching needs adequate natural or installed subsurface drainage to carry the salt away.
Is this tool free and private?+
Yes — free, no sign-up, and all calculation runs in your browser, so it works offline and your data never leaves the device.
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