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Calcimator

Soil Moisture Deficit Calculator

Calculate soil moisture deficit and MAD-based irrigation triggers from sensor data, field capacity, and crop ET.

Inputs

%
%
%
%

Results

Plant available water capacity (in)

5.4

Soil moisture deficit (in)

2.88

Current plant available water (in)2.52
Current depletion (%)53.3
MAD trigger depth (in)2.7
Irrigation needed now? (1=Yes)1
Days until trigger0
Recommended application (in)2.88
Trigger sensor reading (%vol)22.5
Relative water content (%)46.7
How to Use This Calculator
  1. Enter Field capacity (%vol), Wilting point (%vol), and Current soil moisture (%vol).
  2. Set Root zone depth (ft), Allowable depletion (%), and Crop ET (in/day).
  3. Adjust Sensor depth (in) as needed.
  4. Review Plant available water capacity (in) and Soil moisture deficit (in).
  5. Use Current plant available water (in) and Current depletion (%) to inform your decision.

How the result changes with Field capacity (%vol)

Field capacity (%vol)Plant available water capacity (in)Soil moisture deficit (in)
140.360
243.240.72
367.565.04
4611.168.64

What each input means

Field capacity (%vol)
Volumetric water content at field capacity for your soil type.
Wilting point (%vol)
Permanent wilting point — below this, plants cannot extract water.
Current soil moisture (%vol)
Current volumetric water content from sensor reading.
Root zone depth (ft)
Effective rooting depth of the crop.
Allowable depletion (%)
Management Allowable Depletion threshold for triggering irrigation.
Crop ET (in/day)
Daily evapotranspiration rate for the crop.
Sensor depth (in)
Depth of soil moisture sensor placement.

What each result means

Plant available water capacity (in)
Total plant available water in the root zone at field capacity.
Current plant available water (in)
Current amount of plant-available water in the root zone.
Soil moisture deficit (in)
Water needed to refill soil to field capacity.
Current depletion (%)
Current depletion as percentage of total PAW.
MAD trigger depth (in)
Depletion depth that triggers irrigation.
Irrigation needed now? (1=Yes)
1 if current depletion exceeds MAD threshold, 0 otherwise.
Days until trigger
Estimated days before depletion reaches MAD at current ET.
Recommended application (in)
Application depth to refill to field capacity.
Trigger sensor reading (%vol)
Set sensor alarm at this volumetric water content.
Relative water content (%)
Current moisture as % of plant-available range (0=wilting, 100=FC).

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Field capacity (%vol) = 30, Wilting point (%vol) = 15, Current soil moisture (%vol) = 22, Root zone depth (ft) = 3 = 7 input(s) provided
  2. Calculate Plant available water capacity
    Plant available water capacity = (fc - wp) * rootDepthFt * 12
    5.4 = 5.4
  3. Calculate Soil moisture deficit
    2.88 = 2.88
  4. Calculate Current plant available water
    2.52 = 2.52
  5. Calculate Current depletion
    53.3 = 53.3

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