Variable Rate Irrigation Calculator

Calculate VRI prescription rates by management zone based on soil AWC, crop ET demand, and pivot flow capacity.

Field size (acres)

Number of VRI zones

Soil AWC (in/ft)

Effective root depth (ft)

Allowable depletion (%)

Current depletion (%)

Crop ET (in/day)

Pivot flow rate (GPM)

Application efficiency (%)

Tab to move between fields

Total AWC in root zone (in)

5.4

Gross application depth (in)

1.91

MAD trigger point (in)2.7

Current depletion (in)1.62

Days until irrigation trigger4.3

Average zone size (acres)20.8

Volume per zone (gal)1,078,174

Total field volume (gal)6,469,041

System run time (hr)134.8

VRI water savings (%)8

Water saved (gal)517,523

How to Use This Calculator

Enter Field size (acres), Number of VRI zones, and Soil AWC (in/ft).
Set Effective root depth (ft), Allowable depletion (%), and Current depletion (%).
Adjust Crop ET (in/day), Pivot flow rate (GPM) as needed.
Review Total AWC in root zone (in) and Gross application depth (in).
Use MAD trigger point (in) and Current depletion (in) to inform your decision.

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