Table Of ContentINTERPRETING
SOIL TEST RESULTS
WHAT DO ALL THE NUMBERS MEAN?
THIRD EDITION
pH 4.70
SAR 8
Ca2+
Na+
15%
cmol(+)/kg
PAM HAZELTON
ppm
PBC
AND BRIAN MURPHY
INTERPRETING
SOIL TEST RESULTS
WHAT DO ALL THE NUMBERS MEAN?
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INTERPRETING
SOIL TEST RESULTS
WHAT DO ALL THE NUMBERS MEAN?
THIRD EDITION
SAR 8
pH 4.70
Ca2+ Na+
15%
cmol(+)/kg
PBC
ppm
PAM HAZELTON AND BRIAN MURPHY
© Pamela Hazelton and NSW Offi ce of Environment and Heritage 2016
All rights reserved. Except under the conditions described in the Australian Copyright Act 1968 and
subsequent amendments, no part of this publication may be reproduced, stored in a retrieval system or
transmitted in any form or by any means, electronic, mechanical, photocopying, recording, duplicating
or otherwise, without the prior permission of the copyright owner. Contact CSIRO Publishing for all
permission requests.
National Library of Australia Cataloguing-in-Publication entry
Hazelton, P. A. (Pamela Anne), author.
Interpreting soil test results : what do all the numbers mean? / Pam Hazelton and Brian Murphy.
Th ird edition.
9781486303960 (paperback)
9781486303977 (epdf)
9781486303984 (epub)
Includes bibliographical references and index.
Soils – Analysis.
Soils – Testing.
Murphy, B. W. (Brian William), author.
631.42
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Foreword
At the University of Adelaide (and I imagine it is the same at all Australian universities) we
get regular requests from students and others (mainly advisers and consultants in soil
management) for advice on how to interpret soils data. Typically we get inquiries about
soil-test results from fertiliser companies, engineering reports on clay reactivity, heavy-
metal concentrations in municipal waste products, bore and dam water analyses, soil water
contents and hydraulic conductivities. The units accompanying such data invariably
appear as a dog’s breakfast of the Systeme International mixed with colloquial names
dating back to the early 20th century (e.g. bags, bushels, quintals, milliequivalents, etc).
Naturally, people ask whether a good Australian textbook exists ‘to guide us through the
minefield of numbers we face out there’. Well, here it is – a friendly book containing
exemplar tables and units with plenty of explanatory text to guide you through the
quagmire of colloquial terms in soil science that we need to extricate ourselves from. The
omnibus reference-text falls between a classical methods manual and a book of results
with typical generalisations to be drawn from them. It gives users of soil data some yard-
sticks against which the significance or importance of the numbers they obtain in standard
soil tests can be assessed. For many users of Australian soils data this book will come as a
lifeline, and we will certainly add it to the reading lists for our students.
Drs Cameron Grant and Jock Churchman
Australian Society of Soil Science Inc. Publications Committee
v
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Contents
Foreword v
About the Authors ix
Preface xi
Acknowledgments xii
Introduction xiii
1 Soil sampling issues: aspects of design and implementation
of soil investigations 1
1.1 The fundamental problem of sampling to test soils 1
1.2 Purposes of soil sampling 2
1.3 Specialised sampling methodologies for soils 4
1.4 Statistical requirements for sampling 4
1.5 Sampling for soil mapping 4
1.6 Assessment of soil health, soil quality, soil condition or soil capability 8
1.7 Investigations for landscape design and development: some guidelines 8
2 Soil physical properties 11
2.1 Particle size distribution 11
2.2 Water-holding properties of soils 14
2.3 Hydraulic conductivity (K) 21
2.4 Bulk density and air porosity 26
2.5 Soil strength 32
2.6 Aggregate stability 34
2.7 Visual assessment of soil structure 38
2.8 Water repellence 39
3 Soil properties and soil behaviour for engineering 41
3.1 Unified soil classification system (USCS) 41
3.2 General levels of interpretation for plastic limit, liquid limit and plasticity index 47
3.3 Earthworks 48
3.4 Expansive soils 56
3.5 Engineering interpretation of soil strength 58
3.6 Soil factors that can affect the resistance of concrete and steel pipes to corrosion 60
4 Soil erodibility and erosion hazard 63
4.1 Erosion types 63
4.2 Erosion hazard 63
4.3 Soil erodibility for water erosion 65
4.4 Soil erodibility for wind erosion 70
vii
viii Interpreting Soil Test Results
5 Soil chemical properties 73
5.1 Soil acidity 73
5.2 Cation exchange capacity and exchangeable cations 80
5.3 Nitrogen (N) in soil 84
5.4 Phosphorus (P) in soil 87
5.5 Potassium (K) in soil 91
5.6 Sulfur 92
5.7 Nutrients in plants 92
5.8 Trace elements and micronutrients 93
5.9 Nutrients removed in farm products 93
5.10 Salinity 95
5.11 Soil sodicity 106
5.12 Fertilisers and soil ameliorants 114
5.13 General fertility rating of soils in NSW 118
5.14 Acid sulfate soils 119
6 Organic matter content of soils 125
6.1 Soil organic matter 125
6.2 Estimating carbon densities for greenhouse sinks 128
7 Application of wastewater and waste materials 131
7.1 Water quality properties relevant to soils: effluent, runoff and groundwater quality 131
7.2 Quality of wastewater for irrigation 136
7.3 Site selection for the irrigation and disposal of wastewater 139
7.4 Application of biosolids to agricultural soils 141
8 Soil contamination: some considerations 145
8.1 Introduction 145
8.2 General assessment of soil contamination and determination of critical levels 145
8.3 Concentrations of heavy metals in soils 148
8.4 Heavy metals and trace elements as nutrients 153
8.5 Key references in relation to soil contamination 153
9 Units and conversions 155
9.1 SI units 155
9.2 Other units and conversions 156
10 General and technical suggested references 161
References 163
Appendix 1 183
Index 185
About the Authors
Dr Pam Hazelton has worked as a soil scientist for over 35 years. She graduated in Science
from the University of Sydney, then gained a Diploma of Education from the University of
New England and a PhD from the University of NSW for her research on the morphology
and genesis of scald soils in arid regions. She is an experienced pedologist, having produced
many of the Western Division Land System maps and soil landscape maps in the south-
eastern areas of New South Wales. In recent years her interests have been in urban and
coastal soils with an emphasis on environmental engineering. She lectures in the Faculty
of Engineering and IT in the School of Civil and Environmental Engineering in the Uni-
versity of Technology Sydney and is a visiting lecturer at the Grand Ecole EPF School of
Engineers, Sceaux, France.
Dr Brian Murphy has worked as a soil scientist for over 30 years with a strong focus on
applied soil science. He graduated in Agricultural Science from the University of Sydney in
1973, and obtained his Masters in 1986 and his PhD in 1999 for his work on soil structure
in cropping systems. As a practising soil scientist Dr Murphy has had a strong focus on the
application of soil science to urban land use, agriculture, carbon sequestration, hydrology
and salinity. He is an experienced pedologist (having produced several soil maps) and an
experienced researcher with numerous published scientific papers, and provides day-to-
day advice on the management of soils for a range of natural resource issues. He has also
been an editor of a successful, widely used textbook on the characterisation and manage-
ment of soils.
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