Hydrology & Water Resources Engineering - Vol 3 | 44. Irrigation Requirement and Frequency of Irrigation by Abraham | Learn Smarter
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44. Irrigation Requirement and Frequency of Irrigation

Irrigation serves a pivotal role in enhancing agricultural productivity, particularly where rainfall is inconsistent. This chapter explores crucial elements such as Crop Water Requirement, Irrigation Requirement, effective rainfall, and irrigation frequency, emphasizing their interrelatedness and significance in efficient irrigation system design. Additionally, it discusses strategies for optimizing irrigation scheduling and improving water use efficiency, promoting sustainability in agricultural practices.

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Sections

  • 44

    Irrigation Requirement And Frequency Of Irrigation

    This section covers the critical components involved in determining irrigation requirements and their frequency, emphasizing their significance in agriculture.

  • 44.1

    Crop Water Requirement (Cwr)

    Crop Water Requirement (CWR) refers to the total amount of water essential for a crop's complete growth and development.

  • 44.1.1

    Definition

    Crop Water Requirement (CWR) is the total amount of water needed by a crop for optimal growth in a specific climate and soil condition.

  • 44.1.2

    Components

    This section introduces the crucial components that make up Crop Water Requirement, emphasizing the roles of evapotranspiration, soil evaporation, and plant transpiration.

  • 44.1.3

    Factors Affecting Cwr

    This section discusses the critical factors that affect the Crop Water Requirement (CWR), including climatic conditions, crop type, soil characteristics, and agronomic practices.

  • 44.2

    Irrigation Requirement (Ir)

    Irrigation Requirement (IR) quantifies the volume of water necessary for crops, accounting for effective rainfall and natural water sources.

  • 44.2.1

    Definition

    Irrigation Requirement refers to the total amount of water necessary for crops, accounting for effective rainfall and other water sources.

  • 44.2.2

    Equation For Ir

    The equation for Irrigation Requirement (IR) helps determine the amount of water needed for crops, factoring in effective rainfall and other natural contributions.

  • 44.2.3

    Methods To Determine Ir

    This section outlines three primary methods for determining the irrigation requirement (IR), which includes the Soil Moisture Deficit Method, Pan Evaporation Method, and the Crop Coefficient Method.

  • 44.2.4

    Gross And Net Irrigation Requirement

    This section explains the concepts of Gross Irrigation Requirement (GIR) and Net Irrigation Requirement (NIR), highlighting their definitions and relationships in irrigation systems.

  • 44.3

    Effective Rainfall (Er)

    Effective Rainfall (ER) is the portion of total precipitation available for crops, critical for irrigation planning.

  • 44.3.1

    Definition

    Effective rainfall is the portion of total precipitation that is available for crop use, crucial for planning irrigation.

  • 44.3.2

    Estimation Methods

    This section explains the different methods used for estimating effective rainfall, which is critical for determining irrigation requirements in agriculture.

  • 44.4

    Frequency Of Irrigation

    This section defines frequency of irrigation and outlines key factors affecting it.

  • 44.4.1

    Definition

    The frequency of irrigation is the interval between successive irrigations, which is influenced by various factors including crop type and climate conditions.

  • 44.4.2

    Factors Affecting Frequency

    This section outlines the various factors that influence the frequency of irrigation in agricultural practices.

  • 44.4.3

    Determination Of Frequency

    The frequency of irrigation is determined by calculating the irrigation interval based on soil moisture depletion.

  • 44.4.4

    Common Ranges Of Frequency

    The section defines the common irrigation frequency ranges for different types of crops based on their root depth.

  • 44.5

    Irrigation Scheduling

    Irrigation scheduling is crucial for optimizing water usage and improving crop yield while minimizing losses.

  • 44.5.1

    Purpose

    The purpose of irrigation scheduling is to optimize water usage, enhance crop yield, and minimize water losses.

  • 44.5.2

    Approaches

    This section discusses various approaches to irrigation scheduling to optimize agricultural productivity.

  • 44.5.3

    Iw/cpe Ratio Method

    The IW/CPE Ratio Method calculates the irrigation water applied relative to cumulative pan evaporation, helping to optimize irrigation practices based on crop needs and climatic conditions.

  • 44.6

    Water Use Efficiency (Wue)

    Water Use Efficiency (WUE) refers to the ratio of crop yield to the total water used, highlighting the importance of efficient water management in agriculture.

  • 44.6.1

    Definition

    Water Use Efficiency (WUE) is the ratio of crop yield to the total water used, highlighting the importance of optimizing water in agriculture.

  • 44.6.2

    Techniques To Improve Wue

    This section outlines various techniques to enhance Water Use Efficiency (WUE) in agricultural practices.

  • 44.7

    Duty And Delta Relationship

    The Duty and Delta Relationship describes the relationship between the amount of land irrigated by a unit discharge of water (Duty) and the total depth of water required by the crop during a base period (Delta).

  • 44.7.1

    Duty (D)

    Duty in irrigation refers to the amount of land irrigated by a unit discharge of water over a specified period.

  • 44.7.2

    Delta (Δ)

    Delta (Δ) represents the total depth of water required for a crop during its entire base period, calculated based on crop duty.

  • 44.8

    Leaching Requirement

    The leaching requirement is the additional water necessary to remove excess salts from the root zone in saline soils.

  • 44.8.1

    Definition

    Leaching Requirement is the additional water needed to remove excess salts from saline soils.

  • 44.8.2

    Leaching Requirement Formula

    The Leaching Requirement Formula calculates the additional water needed to flush excess salts from the root zone in saline soils.

  • 44.9

    Case Studies And Examples

    This section provides practical examples and case studies to illustrate the calculation and scheduling of irrigation requirements.

  • 44.9.1

    Sample Irrigation Scheduling Chart

    This section introduces a sample irrigation scheduling chart that outlines essential parameters for effective irrigation management.

Class Notes

Memorization

What we have learnt

  • Understanding Crop Water Re...
  • Irrigation Requirement (IR)...
  • Optimizing irrigation frequ...

Final Test

Revision Tests