Agriculture Water Stress Coefficient Ks
Evaluate named FAO-style root-zone depletion stress coefficient with caller readily available fraction; assumes known accessible TAW/depletion and does not diagnose actual plant health or choose irrigation timing.
Description
A root-zone water-stress coefficient reduces modeled crop transpiration as depletion passes a supplied readily available threshold.
A root-zone water-stress coefficient reduces modeled crop transpiration as depletion passes a supplied readily available threshold. Total available water and current depletion must refer to the same accessible root zone.1, 2
Evaluate named FAO-style root-zone depletion stress coefficient with caller readily available fraction; assumes known accessible TAW/depletion and does not diagnose actual plant health or choose irrigation timing.
When to use Agriculture Water Stress Coefficient Ks
Use this tool to evaluate named FAO-style root-zone depletion stress coefficient with caller readily available fraction; assumes known accessible TAW/depletion and does not diagnose actual plant health or choose irrigation timing.
Prepare the field, crop, soil or material measurements for the intended period. Confirm units, dry/wet bases and supplied parameters; keep paired observations aligned.
How to use Agriculture Water Stress Coefficient Ks and understand its results
- Prepare the field, crop, soil or material measurements for the intended period. Confirm units, dry/wet bases and supplied parameters; keep paired observations aligned.
- Enter totalRootZoneAvailableWaterMm, currentRootZoneDepletionMm, callerReadilyAvailableDepletionFraction using the field table and calculation rules, then run the tool.
- Read readilyAvailableRootZoneWaterMm, modelCropWaterStressCoefficient. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| totalRootZoneAvailableWaterMm | Total root zone available water mm | number | Required |
| currentRootZoneDepletionMm | Current root zone depletion mm | number | Required |
| callerReadilyAvailableDepletionFraction | Caller readily available depletion fraction | number | Required |
Enter positive total available water in mm, nonnegative depletion no greater than that total and readily available fraction p in [0,1). Return readily available mm and a coefficient from zero to one. Equality at RAW returns one; complete depletion returns zero.
RAW = p TAW; Ks = 1 for depletion≤RAW, otherwise (TAW−depletion)/(TAW−RAW) Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| readilyAvailableRootZoneWaterMm | Readily available root zone water mm | number |
| modelCropWaterStressCoefficient | Model crop water stress coefficient | number |
{
"input": {
"totalRootZoneAvailableWaterMm": 100,
"currentRootZoneDepletionMm": 60,
"callerReadilyAvailableDepletionFraction": 0.5
},
"output": {
"readilyAvailableRootZoneWaterMm": 50,
"modelCropWaterStressCoefficient": 0.8
}
}Limitations and assumptions
Root accessibility, depletion and p are caller inputs. The FAO-style coefficient does not diagnose actual plant health or select irrigation timing, and evaporation and crop response details remain outside it.
Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Agriculture Soil Water Holding Capacity: Integrate measured layer field-capacity minus wilting-point water with explicit root accessibility; differs from soil porosity or gross field-capacity storage and no crop rooting depth is inferred. For a complementary task, use Agriculture Crop Evapotranspiration: Integrate reference ET×caller crop coefficients across unequal stage durations, keeping modeled daily rates; no mutable crop calendar or universal Kc lookup.
Further background: ETc under soil water stress conditions.
References
Similar or alternative tools
- Agriculture Soil Water Holding Capacity
Integrate measured layer field-capacity minus wilting-point water with explicit root accessibility; differs from soil porosity or gross field-capacity storage and no crop rooting depth is inferred.
- Agriculture Crop Evapotranspiration
Integrate reference ET×caller crop coefficients across unequal stage durations, keeping modeled daily rates; no mutable crop calendar or universal Kc lookup.