AG843 Crop Water Relations and Irrigation
   Table of Contents
1. Unit outline and aims 
4. Unit reading list
2. Outline of lecture titles:  
Lecture titles from weeks 1-10.  
5. Comments on webpage
3. Useful websites 6. Unit Assessment
7. example: irrigation scheduling 8. Past exam papers

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     Photos courtesy of NRCS Irrigation Page

Unit outline  and aims for AG843 Crop Water Relations and Irrigation

There is an increasing use of water for the irrigation of agricultural crops, and the possibility of irrigation has greatly enhanced production and food stability in many tropical and semi-tropical countries. In this module, students will be provided with an understanding of the physical and physiological principles of water supply and utilisation by crops. These principles are used to illustrate the basis of irrigation management, and the characteristics of a variety of irrigation systems are compared.

At the end of this module you will be able to:

The module is comprised of three complementary sections that explore the relationships between soil and water, the relationship between water and crops and the characteristics of irrigation schemes. Examples of some of the topics covered include the following:
                                                            Photo courtesy of NRCS Irrigation Page

Outline of lecture titles :

    Week1      Soil water dynamics                                                                         LS
    WK2        Water uptake by plants                                                                   LS

    WK3        Reference crop evapotranspiration                                                MD

    WK4         Crop coefficients and actual evapotranspiration                           MD

    WK5         Synthesis of soil and crop water relations                                     LS

    WK6         Irrigation scheduling and sources of water for irrigation             JAF

    WK7         Irrigation Methods I: Surface and sub-surface irrigation            JAF
                     examples of surface irrigation

   WK8         CANCELLED                                                                                  JAF

  WK9         Irrigation Methods II:  Overhead Irrigation.                                  JAF
                    examples of overhead irrigation

 WK 10       Soil water conservation and module synthesis (ppt.file)                 JAF

        LS: Dr Lester Simmonds, Dept of Soil Science                     email:
        MD: Dr. Mike Dennett, Dept of Agricultural Botany             email:
        JAF: Dr John Finn, Dept of Agriculture.                                email:

Module assessment
Course-work:  30% of module
Summer Examination:  70% of module. (One of a choice of at least three questions to be answered in one hour. See top of page for link to past exam papers.)

Course-work and further details will be distributed in week 5.

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Useful websites
NEW!  Managing Drought Stress by Supplemental Irrigation
As part of a larger website looking at envrironmental stresses of plants also looks at the role of irrigation in alleviating drought stress: Managing Drought Stress by Supplemental Irrigation
There is a good overview, with several links to relevant online booklets and websites.

CROPWAT: A computer program for irrigation planning and management.
CROPWAT is a decision support system developed by the Land and Water Development Division of FAO.
See Doorenbos and Kassam (1979) and/or Doorenbos and Pruitt (1977) for basis of calculations used in CROPWAT (see References).

Revised FAO Methodology for Crop Water Requirements
In the early 1970's, FAO developed a practical procedure to estimate crop water requirements, which has become a widely accepted standard, in particular for irrigation studies. Since the publication of the methodology as FAO Irrigation and Drainage Paper No24, new concepts and advances in research made a review and revision necessary.

Special Issue of Experimental Biology on water deficits and plant growth
  - J. Exp. Bot. Vol. 51(350) Sept. 2000: Turgor, Cell Growth and Leaf Development; Root Function and Adaptatio; Synthesis and Functions of ABA; Whole Plant Integration and Agriculture Exploitation

Guidelines for Planning Irrigation and Drainage Investment Projects

Agricultural Investment to Promote Improved  Capture and use of Rainfall in Dryland Farming

USDA's Natural Resources Conservation Service provides a very impressive selection of photos of various irrigation methods.

The Irrigation Association
As the irrigation industry's organization, they "represent professionals who channel their expertise toward a common goal -efficient irrigation. Conservation, the quality & quantity of water, is our mission."
See in particular the page about their water management committee.

See a short Encarta article about irrigation.
The International Commission on Irrigation and Drainage (ICID)  is dedicated to enhancing the worldwide supply of food and fibre for all people by improving water and land management and the productivity of irrigated and drained lands through appropriate management of water, environment and application of irrigation, drainage and flood management techniques.

 Surface irrigation: furrows (left) and gated pipe (right). Photos courtesy of NRCS Irrigation Page.


Recommended reading


Kay M (1986). Surface irrigation systems and practice. 631.7-KAY (2 copies).

Barrow C (1987). Water resources in the tropics. 631.70913-BAR

Doneen LD and Westcot (1984). Irrigation practice and water management. Folio 631.6-FAO I Rev 1.

Doorenbos J and Kassam AH (1979). Yield responses to water. FAO. Folio631.6-FAO.

Doorenbos J and Pruitt WO (1977). Guidelines for predicting crop water requirements. FAO Drainage Paper 24. Folio 631.6-FAO/24 (2 copies).

Hargrove WL (1988). Cropping strategies for efficient use of water and nitrogen. 631.5-CRO (2 copies).

Hillel D (1997). Small-scale irrigation for arid zones. 631.7-HIL.

KellerJ and BliesnerRD (1990). Sprinkle and trickle irrigation. 631.7-KEL.

Penman HL (1986). Scientific aspects of irrigation schemes. Folio 631.7-SCI.

Soil water reading list

"Soil Science: Methods and applications". Author - D.L.Rowell  (See chapters on "Water in soil" and "Availability of water"  written by Dr Simmonds and closely linked to lecture material.)  Published by Longmans.

Other useful general texts on soil physics are:
Soil Physics. T.J. Marshall and J.W. Holmes. Published by Cambridge University Press.

"Fundementals of Soil Physics" and "Applications of Soil Physics". Both by D.  Hillel, published by Academic Press.

General reading

Human appropriation of renewable fresh water. 1996. Postel, Daily and Ehrlich. Science 271: 785- 788.

How many people can the Earth support? Joel E. Cohen. See especially Chapter 14 (Water: a Case Study) for a consideration of water availability as a limiting factor to human population growth.

Threats to the World’s Water. Maurits la Riviere. Scientific American, September 1989. Pp 48-55.

Additional reading
Edwards CA, Madden P, Millar R, and House G  (1991). Sustainable Agricultural Systems, Soil and Water Conservation Society, Iowa, USA

Special Issue of Experimental Biology on water deficits and plant growth


If you have any comments or wish to suggest any additions or improvements to this webpage, please email Dr John Finn at
If you find other websites relevant to this unit or individual lectures, please email  me the web address so that it can be included as a link.
Last updated January 2001.
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