Irrigation ToolBox PowerPoint

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Irrigation Water Management Training
Irrigation Scheduling Objectives and Concepts
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Irrigation Water Management
Applying Water

• According to crop needs
• In amounts that can be held in the soil and be
  available to crops
• At rates consistent with the intake
  characteristics of the soil and the erosion
  hazard of the site
• So that water quality is maintained or improved

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Irrigation Scheduling

• A part of irrigation water management

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Three Keys to Good Irrigation

• Good Distribution Uniformity (DU)
• Good Timing
• Minimize Surface Runoff

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DU Distribution Uniformity
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DUlq Exercise

• 1.7 inches 2.0 inches
• 1.8 inches 2.1 inches
• 1.9 inches 2.2 inches
• 2.0 inches 2.3 inches
• Given the 8 measurements above, what is the DUlq
  for this irrigation?

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Try to Determine what the Consultant Knows

• A farmer has hired a consultant to schedule
  irrigations on his drip tape system.
• The consultant tells the farmer to irrigate this
  week for 80 hours.
• What does the consultant know?

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What is scheduling?

• The decision of when and how much water to apply
  to a field
• There are many methods available
• It is not always an option (but remember that not
  to decide is to decide.)

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WILLARD " They told me that you had gone totally
insane and that your methods were unsound."
KURTZ " Are my methods unsound?" WILLARD " I
don't see any method at all, sir."
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Water Balance Approach

• Water used must be replaced
• Any guesses why this is also called the checkbook
  method?

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Balance the soil water

• Know how much water the soil can store
• Know how much water the plant has used

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How much water can the soil hold?

• Know the depth of the root zone
• Know the water holding capacity of the root zone

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How much water has the crop used?

• Know the actual crop evapo-transpiration

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When Do You Irrigate?

• Know the Management Allowable Depletion (MAD)

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