The Potential of Variable Rate Irrigation for the Southeast

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The Potential of Variable Rate Irrigation for
the Southeast

• Kerry Harrison
• Calvin Perry
• University of Georgia

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The importance of irrigation to the Southeast
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Georgia Irrigated Area by Crop
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Georgia Irrigation Systems by Type
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Pivot Proliferation
10 mi x 7 mi aerial photograph
Seminole County, GA
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Georgia Irrigation Amount by Crop
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Irrigation is a Management Tool

• Justus von Liebig's Law of the Minimum states
  that yield is proportional to the amount of the
  most limiting factor

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What is Variable Rate Irrigation?

• The application of different volumes or rates of
  water to different segments of a field
• Rates are based on perceived or measured water
  requirements of sub-field zones

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Why implement VRI?
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Irregularly shaped fields
Tift County, GA 2001
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Overlapping pivots
Tift County, GA 2001
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Non-crop Inclusions
Tift County GA, 01
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Non-crop Inclusions
Field opposite Marine Corps Logistic Base,
Albany, GA, 2001
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Non-crop Inclusions
Tift County, GA 2001
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Non-crop Inclusions
Tift County, GA 2001
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Topographic Variability
Camilla, GA, 2001
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Soil Variability
well drained sand
heavy clay soil
poorly drained organic soil
Tift County, GA 2001
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Soil Variability
poorly drained organic soil
Tift County GA, 2001
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Pond Traversal
Tift County GA, 2001
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Watering non-cropland
Tift County, GA, 2001
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Off Site Irrigation
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Multiple Crops or Crop Stages
Turf Farm Tift County GA, 2001
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Why implement VRI?

• We cannot realize benefits from variable rate
  fertilization if we do not first properly manage
  water
• Water conservation issues are becoming more
  important in the southeast
• Current systems waste a considerable amount of
  the applied water

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Reasons for sub-optimal water application

• Irregularly shaped fields
• Overlapping pivots
• Non-crop inclusions intrusions
• Topographic variability
• Soil variability
• Pond/wetland traversal
• Multiple crops under same pivot

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Limited VRI is already practiced in the Southeast

• End gun controls cut off water at field edges
• Manual valves can be used to turn off individual
  sprinklers

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Can we do better?

• We can potentially benefit from
• irrigation scheduling
• installing more efficient sprinklers
• irrigation management (uniformity analysis)
• differential rate control
• remote control monitoring of pivots
• ?????

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Potential roadblocks for implementing VRI

• Pumps need to match changing conditions (steep
  vs. flat pump curves)
• Cost of equipment (in todays economic
  situation)
• Age of current pivot systems?
• Great diversity of current systems

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Georgia VRI Counties 31 Systems
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Thanks for your attention!
For more information contact
Kerry Harrison Extension Engineer P. O. Box
1209 Tifton, GA 31793 229-386-3442
Voice 229-386-3448 FAX
kharriso_at_.uga.edu