Irrigation Water Management Training Irrigation Scheduling Objectives and

Irrigation Water Management Training Irrigation Scheduling Objectives and Concepts

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

Irrigation Scheduling • A part of irrigation water management

Three Keys to Good Irrigation • Good Distribution Uniformity (DU) • Good Timing* • Minimize Surface Runoff

DU Distribution Uniformity

DUlq Exercise • • 1. 7 inches 1. 8 inches 1. 9 inches 2. 0 inches 2. 1 inches 2. 2 inches 2. 3 inches • Given the 8 measurements above, what is the DUlq for this irrigation?

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?

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. )

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. "

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

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

How much water can the soil hold? • Know the depth of the root zone • Know the water holding capacity of the root zone

How much water has the crop used? • Know the actual crop evapotranspiration

When Do You Irrigate? • Know the Management Allowable Depletion (MAD)