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Calcimator

Salinity Management Calculator

Calculate leaching requirement from irrigation water EC and crop salt tolerance using FAO guidelines, plus SAR and salinity hazard assessment.

Inputs

%
%

Results

Leaching requirement (%)

16.4

Total water with leaching (in)

33.8

Gross irrigation needed (in)28.2
Extra leaching water (in)5.6
Total water (acre-ft)281.6
Leaching water (acre-ft)46.3
Est. drain water EC (dS/m)7.3
Sodium Adsorption Ratio (SAR)3.2
SAR hazard (1-4)1
Salinity hazard (1-4)2
Est. TDS (ppm)768
Salt loading (tons/acre/yr)2.08
How to Use This Calculator
  1. Enter Irrigation water EC (dS/m), Crop EC threshold (dS/m), and Seasonal crop ET (in).
  2. Set Field size (acres), Sodium (meq/L), and Calcium (meq/L).
  3. Adjust Magnesium (meq/L), Target yield (%) as needed.
  4. Review Leaching requirement (%) and Total water with leaching (in).
  5. Use Gross irrigation needed (in) and Extra leaching water (in) to inform your decision.

How the result changes with Target yield (%)

Target yield (%)Leaching requirement (%)Total water with leaching (in)
733.429.2
814.529.6
906.930.3
9711.631.9

What each input means

Irrigation water EC (dS/m)
Electrical conductivity of irrigation water (1 dS/m = 1 mmho/cm).
Crop EC threshold (dS/m)
Soil ECe at which yield begins to decline. Corn=1.7, wheat=6.0, cotton=7.7, alfalfa=2.0.
Seasonal crop ET (in)
Total season evapotranspiration requirement.
Field size (acres)
Total irrigated field area.
Sodium (meq/L)
Sodium concentration in irrigation water for SAR calculation.
Calcium (meq/L)
Calcium concentration in irrigation water.
Magnesium (meq/L)
Magnesium concentration in irrigation water.
Target yield (%)
Acceptable yield level (100% = no yield loss tolerated).
System efficiency (%)
Irrigation application efficiency.

What each result means

Leaching requirement (%)
Fraction of applied water that must drain below the root zone.
Gross irrigation needed (in)
Irrigation depth needed for crop ET (before leaching).
Total water with leaching (in)
Total water to apply including leaching requirement.
Extra leaching water (in)
Additional water depth needed for leaching.
Total water (acre-ft)
Total seasonal water in acre-feet for the field.
Leaching water (acre-ft)
Extra water volume for leaching.
Est. drain water EC (dS/m)
Estimated EC of drainage water below root zone.
Sodium Adsorption Ratio (SAR)
SAR of irrigation water. <10=low, 10-18=medium, 18-26=high, >26=very high.
SAR hazard (1-4)
Sodium hazard: 1=low, 2=medium, 3=high, 4=very high.
Salinity hazard (1-4)
Water salinity hazard: 1=low, 2=medium, 3=high, 4=very high.
Est. TDS (ppm)
Estimated total dissolved solids in irrigation water.
Salt loading (tons/acre/yr)
Estimated salt deposited per acre per season.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Irrigation water EC (dS/m) = 1.2, Crop EC threshold (dS/m) = 1.7, Seasonal crop ET (in) = 24, Field size (acres) = 100 = 9 input(s) provided
  2. Calculate Leaching requirement
    Leaching requirement = min(100, leachingRequirement * 100)
    16.4 = 16.4
  3. Calculate Total water with leaching
    Total water with leaching = grossIrrigationIn / (1 - min(0.9, leachingRequirement))
    33.8 = 33.8
  4. Calculate Gross irrigation needed
    Gross irrigation needed = netCropWaterIn / (systemEfficiency / 100)
    28.2 = 28.2
  5. Calculate Extra leaching water
    Extra leaching water = totalWaterIn - grossIrrigationIn
    5.6 = 5.6

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