Authors:

Blaine Hanson
UC Irrigation and Drainage Specialist
Stephen Grattan
UC Plant-Water Relations Specialist
Allan Fulton
Soils and Water Farm Advisor, Kern County

Salinity can be a particular problem in irrigated arid and semi-arid agricultural lands. Although a great deal of advanced research has been done on salinity, until now few publications have made this research easily available to growers and irrigators. This handbook bridges that gap. Its 34 short chapters cover the basics of salinity - what it is and how plants respond to it - and provide non-technical, practical, step-by-step guides on measuring and managing salinity in the field. Appendixes, illustrations, tables, graphs glossary, references, index.

1993, 156 pp - Publication 93-01 - $25
Last revised 03/03

Funded by the California Energy Commission and the U.S. Department of Agriculture Water Quality Initiative
If you have comments or suggestions, please email the LAWR webmaster at lawrweb@ucdavis.edu

Last updated March 2, 2007

Water Management Handbook Series
Agricultural Salinity and Drainage
Publication #93-01

Table of Contents

List of Tables

List of Figures

Preface

Introduction

Crops, Water, and Salinity

• Units of Concentration and Definitions
• Irrigation Water Composition and Salinization
• How Plants Respond to Salinity
• Electrical Conductivity
• Measuring Soil Salinity
• Crop Salt Tolerance
• Sodium and Chloride Toxicity in Crops
• Salt Accumulation in Leaves Under Sprinkler Irrigation
• Boron Toxicity and Crop Tolerance
• Combined Effects of Salinity and Boron
• Salinity-Fertility Relations

Water, Soils and Salinity

• Estimating the Sodium Adsorption Ratio
• How Water Quality Affects Infiltration
• Assessing the Suitability of Water for Irrigation
• Assessing Soil Salinity

Soil Salinity Patterns and Irrigation

• Salt Movement and Distribution in Soil
• Salt Distribution Under Micro-Irrigation
• Salt Distribution Under Furrow Irrigation
• Salt Distribution Under Sprinkler Irrigation
• Upward Flow of Saline Shallow Groundwater

Managing Salinity and Reclaiming Soil

• Crop Response to Leaching Fraction and Salt Distribution
• Maintenance Leaching
• Leaching Under Saline Shallow Water Tables
• Finding the Attainable Leaching Fraction
• Amendments for Reclaiming Sodic and Saline/Sodic Soil
• Reclaiming Boron-Affected Soils
• Irrigating With Saline Water
• Irrigation Frequency, Salinity, Evapotranspiration and Yield

Subsurface Drainage

• Improving Subsurface Drainage
• Water Table Depth Criteria for Drain Design
• Designing Relief Drainage Systems
• Reducing the Salt Load Through Drainage System Design
• Interceptor Drains
• Measuring Hydraulic Conductivity With the Auger Hole Method
• Observation Wells and Piezometers
• Reducing Drainage by Improving Irrigation

Appendices

• Appendix A: Guide to Assessing Irrigation Water
• Appendix B: Guide to Assessing Soil Salinity
• Glossary

Salinity has plagued crop production in irrigated regions of the world since the beginning of recorded history. It is particularly common in arid and semi-arid areas where evapotranspiration — evaporation of water from soil combined with transpiration of water from plants — exceeds annual precipitation, and where irrigation is therefore necessary to meet crop water needs.

Much of the irrigated land in California’s Imperial and San Joaquin Valleys is either already affected or threatened by salinization. Soil salinity becomes a problem when the concentrations of soluble salts in the root zone are at levels high enough to impede optimum plant growth. Most soil salinization in the Imperial and San Joaquin Valleys results from the presence of shallow saline water tables, but salinization can also be caused by saline irrigation water coupled with poor irrigation management. Salinity problems also exist in other areas of the state. Irrigated agriculture in coastal environments are becoming increasingly threatened by salinity in the ground water.

Since 1954, when the U.S. Department of Agriculture published its landmark text, Diagnosis and Improvement of Saline and Alkali Soils (Agricultural Handbook No. 60), much has been learned and written about the effects of salinity on plants and soils and on how salinity can be diagnosed and managed. The most recent text on the subject, Agricultural Salinity Assessment and Management, edited by K.K. Tanji and published by the American Society of Civil Engineers in 1990, is a comprehensive and useful reference source for agricultural scientists and engineers. The United Nations Food and Agricultural Organization (FAO) publication, Irrigation and Drainage Paper 29, Water Quality for Agriculture, by R.S. Ayers and D.W. Westcot presents in-depth, detailed, and up-to-date information on salinity management for those who lack advanced academic training in the field.

This handbook, Agricultural Salinity and Drainage, has been developed to bridge the gap between the advanced technical salinity literature and practical information on salinity intended for lay audiences. As such, it brings material from salinity texts together with information gathered from our own field experience. It is meant to be an accessible, user-friendly resource for agricultural consultants and advisors, as well as for local, state, and federal agricultural and water agency management staff. The handbook consists of thirty-eight short chapters covering a broad spectrum of salinity and drainage topics, written so as to be easily understood by anyone with a general agricultural background. Appendices A and B — presented as shorthand guides to assessing soil salinity and to determining the suitability of a given water for irrigation — also function as guides to the handbook itself. It should be noted that in order to make the handbook easy to use, the authors have generalized in some cases and have simplified technical concepts wherever further qualification would have extended beyond the scope of the publication.

Please direct any comments or questions about the material contained herein to Blaine Hanson (email: brhanson@ucdavis.edu) or Stephen Grattan (email: srgrattan@ucdavis.edu), Department of Land, Air and Water Resources, University of California, Davis, CA 95616-8628; telephone number: (530) 752-1130; fax number: (530) 752-1552.