Logical thinking, analysis and synthesis

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PARTIAL ROOTZONE DRYING
IRRIGATION MANAGEMENT FOR POTATO CROPS Adolfo
Posadas, Guliver Rojas, Miguel Málaga, Victor
Mares and Roberto Quiroz
CIP Annual Meeting November 2008
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Outline

• Facts on water and potato crops
• Description of irrigation systems
• Description of PRD
• Theoretical basis of PRD
• The experiment treatments and procedures
• Results
• Conclusions
• Future work

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FACTS

• Potato is a water-demanding crop 0.5m3/kgdm
• Drought is common and increasing
• Water is becoming a scarce resource
• A large fraction of potato is produced under full
  or supplementary irrigation
• Optimizing the supply of irrigation water is
  required
• Increase yields
• Increase WUE

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IRRIGATION SYSTEMS

• Conventional irrigation water to full soil
  capacity and crop ET demand
• Restricted irrigation water short of soil
  capacity and/or crop ET demand
• RDI Regulated deficit irrigation
• PRD Partial rootzone drying

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PRD
First irrigation
Second irrigation
Wet zone Dry zone
Dry zone Wet zone
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THEORETICAL BASIS OF PRD

• Chemical signaling (ABA) from water stressed
  roots prompts stomatal closure
• Hydraulic signal through xylem water pressure and
  plant turgency prompts stomatal opening
• Contradictory signals reduce water vapor loss
  without preventing gas exchange

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Experiment

• Treatments
• CI1 100 water lamina in all furrows (100 water
  volume)
• CI1/2 50 water lamina in all furrows (50 water
  volume)
• PRD1 100 water lamina in alternate furrows (50
  water volume)
• PRD1/2 50 water lamina in alternate furrows
  (25 water volume)

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Conventional Irrigation
CI ¹
100
100
CI ½
50
50
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Partial Root Drying PRD1
100
0
0
100
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Partial Root Drying PRD1/2
0
50
50
0
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EXPERIMENTAL PROCEDURE

• Pre-experimental phase seven cycles of blanket
  irrigation
• Experimental phase six cycles of differentiated
  irrigation starting 60 days after planting

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RESULTS
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CONCLUSIONS

• PRD improved WUE
• Yield reduction caused by PRD not proportional to
  reduction in water used
• Tuber quality improved by PRD

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FUTURE WORK

• Field work to
• Test earlier PRD
• Test indicators for watering
• Compare early vs late varieties
• Analyze water cost scenarios
• Assess effect of PRD on soil borne pathogens and
  beneficial soil microorganisms
• Indoors work to
• Assess physiological responses (ABA, leaf
  turgency, leaf expansion, reflectance,
  photosynthesis, root growth, tuberization
  dynamics) to PRD

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