Soil Sampling and Methods of Analysis
SUSANTA KUMAR PAL M.Sc (Ag), Ph.D Professor, Agricultural Chemistry and Soil Science Bidhan Chandra Krishi Viswavidyalaya Mohanpur-741252, Nadia, West Bengal, India
2013
Published by Sumit Pal Jain for
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ISBN : 978-93-81450-57-4 All rights reserved, 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 or otherwise without the prior written permission of the publisher / Author. This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author/editor(s)/contributors and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The author/editor(s)/contributors and publisher have attempted to trace and acknowledge the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission and acknowledgements to publish in this form have not been given. If any copyright material has not been acknowledged please write and let us know so we may rectify it. Laser Type Setting and Printed at : Jai Bharat Printing Press, Delhi.-110032
Dedicated to my departed Parents & elder brother
FOREWORD
Soil Science is an important and basic science in agriculture which deals with different domains of soil research namely, soil formation, genesis and classification, soil physics, soil chemistry, soil fertility and plant nutrition, soil biology, etc. Characterization as well as our understanding of soils requires that they are precisely analysed and described. While the physical properties of soils determine their adaptability to cultivation, chemical properties tells about their chemical environment and nutrient status to the crop production - the most important use of soils on this densely populated planet. Determination of different soil physical and chemical properties in the field or in the laboratory following suitable analytical methods is first step towards appropriate soil managements and scientific recommendations for increasing crop production. The present book entitled “Soil Sampling and Methods of Analysis� is certainly a good attempt taken by Dr. Susanta Kumar Pal, Professor of Agricultural Chemistry and Soil Science and is really appreciable. I have gone through the entire manuscript and found that the author has taken keen interest in writing this book consisting of 19 chapters. This analytical book on soil science has been written involving basic chemistry and explaining the text with incorporation of some pictures and figures which are unique feature of the book. The author has paid equal emphasis on writing each chapter, of which the chapter 18 and 19 are an important inclusion to the existing analytical books related to soil science. vii
Foreword / viii
The author has also put some questions at the end of each chapter relating analytical determination of soil parameters which will definitely be useful to the students, researchers and teachers of agriculture in general and soil science in particular. I am confident that this well written and compiled analytical book will be useful for post graduate students and researchers, and also important addition to university library.
Dilip Kumar Das Professor and Former Head Department of Agricultural Chemistry and Soil Science Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia, West Bengal, India
PREFACE
This book is a compilation of some user friendly well accepted analytical methods for characterising soil physical and chemical properties. Primarily the book is meant to cater the need of students of agricultural universities and is expected to be helpful to the teachers and researchers of this related field. The text presented in the book is subdivided into 19 chapters and 15 appendices. Each method is discussed here under four subheads viz., principle, equipments and materials, procedure and calculation. The methods have been explained in a simpler language. Steps of calculation have been made easy understandable as far as practicable. Each chapter is ended with some relevant questions and their answers on that topic. Basic principle of different chemical analyses and working principle of the instruments used in soil analysis laboratories has been discussed in a very lucid manner. Inspite of the best efforts, the text may still contain some discrepancies. Any suggestion from the readers for improvement of the book in future will be highly appreciated. The author gratefully acknowledges the every source from where the technical matters are drawn. Kalyani Dated: 9th August, 2012
S.K.Pal ix
CONTENTS
Foreword.................................................................................................... vii Preface ......................................................................................................
ix
1.
Collection and Processing of Soil Samples...............................
1
1.1
Sources of Error in Soil Chemical Analysis .....................
1
1.2
Composite Soil Sample .......................................................
1
1.3
Soil Sampling Tools ............................................................
2
1.4
Collection of Soil Sample ....................................................
4
Questions and Hints ............................................................... 10 2.
Soil Texture and Textural Class .................................................. 11 2.1
Particle Size Distribution Analysis ...................................
11
2.2
Determination of Soil Textural Class ................................
21
Questions and Hints ............................................................... 24 3.
Density and Porosity of Soil .......................................................
27
3.1.
Determination of Bulk Density of Soil .............................
27
3.2.
Determination of Particle Density of Soil ........................
29
3.3
Determination of Porosity of Soil by Indirect Method ... 31 Questions and Hints ............................................................... 32 xi
Contents / xii
4.
Soil Aggregate Analysis ............................................................... 35 4.1
Wet Sieving Method of Soil Aggregate Analysis ............
35
4.2
Dry Sieving Method of Soil Aggregate Analysis.............
39
Questions and Hints ............................................................... 40 5.
Soil Moisture ..................................................................................
43
5.1
Determination of Soil Moisture .........................................
43
5.2
Soil Moisture Constants ......................................................
46
5.3
Determination of Soil Moisture Potential ........................
54
Questions and Hints ............................................................... 61 6.
Flow of Water in Soil ..................................................................... 63 6.1
Determination of Hydraulic Conductivity of Saturated Soil: Laboratory Methods .................................................... 63
6.2
Determination of Unsaturated Hydraulic Conductivity by using Campbell Equation ..............................................
69
6.3
Determination of Diffusivity and Sorptivity of Soil .......
71
6.4
Determination of Infiltration Rate of a Soil by Ring Infiltrometer ..........................................................................
75
Questions and Hints ............................................................... 76 7.
Soil Consistency ............................................................................. 79 7.1
Determination of Liquid Limit or Upper Plastic Limit ..
79
7.2
Determination of Plastic Limit or Lower Plastic Limit...
81
7.3
Determination of Sticky Limit ........................................... 82 Questions and Hints ............................................................... 83
8.
Basics of Quantitative Chemical Analysis .................................. 85 8.1
Law of Mass Action .............................................................
85
8.2
Activity and Activity Coefficient ....................................... 86
8.3
The Hydrogen Ion Exponent or pH ..................................
87
8.4
Volumetric (Titrimetric) Analysis .....................................
88
Questions and Hints ............................................................... 110 9.
Instrument and its Principle of Functioning ........................... 115 9.1
Balance and Weighing ......................................................... 115
9.2
pH Meter ............................................................................... 119
Contents / xiii
9.3
Conductivity Bridge ............................................................ 125
9.4
Colorimeter and Absorption Spectrophotometer ........... 128
9.5
Flame Spectroscopy ............................................................. 133
9.6
Inductively Coupled Plasma –Atomic Emission Spectroscopy (ICP-AES) ...................................................... 143 Questions and Hints ............................................................... 147
10. Soil Reaction ................................................................................... 149 10.1 Determination of Soil pH..................................................... 149 10.2 Determination of Lime Potential of Soil ........................... 152 10.3 Forms of Soil Acidity ........................................................... 153 10.4 Lime Requirement .............................................................. 160 Questions and Hints ............................................................... 167 11. Electrical Conductivity and Water Soluble Salt ...................... 169 11.1 Determination of Electrical Conductivity of Soil Solution .......................................................................... 169 11.2 Water Soluble Salts .............................................................. 172 Questions and Hints ............................................................... 185 12. Soil Organic Matter ....................................................................... 189 12.1 Direct Method of Soil Organic Matter Determination.... 190 12.2 Indirect Method of Soil Organic Matter Determination .. 190 Questions and Hints ............................................................... 202 13. Ion Exchange Capacity and Exchangeable Bases .................... 207 13.1 Exchange Capacity ............................................................... 207 13.2 Determination of Exchangeable Bases ............................... 213 Questions and Hints ............................................................... 214 14. Nitrogen in Soil .............................................................................. 215 14.1 Determination of Total Nitrogen in Soil (Modified Kjeldahl Method) ................................................................. 215 14.2 Determination of Mineralizable (Available) Nitrogen in Soil ..................................................................... 218 14.3 Determination of Exchangeable Ammonium Nitrogen in Soil .................................................................... 221 14.4 Determination of Nitrate Nitrogen in Soil ......................... 223
Contents / xiv
14.5 Determination of Organic Forms of Nitrogen in Soil (Stevenson, 1996) .................................................................. 224 14.6 Determination of Soil Microbial Biomass Nitrogen ......... 228 Questions and Hints ............................................................... 229 15. Phosphorus in Soil ........................................................................ 231 15.1 Determination of Available Soil P ..................................... 231 15.2 Determination of Total Soil P .............................................. 239 15.3 Determination of Different Fractions of Inorganic Soil P ...................................................................................... 241 15.4 Determination of Organic P in Soil ..................................... 244 15.5 Determination of Phosphate Fixing Capacity of Soil .... 246 15.6 Measurement of Microbial Biomass Phosphorus in Soil (Brookes et al. 1982) ............................................................... 248 Questions and Hints ............................................................... 250 16. Potassium in Soil ........................................................................... 253 16.1 Forms of Soil K .................................................................... 253 16.2 Determination of K Fixation Capacity of Soil (Jackson, 1973) ....................................................................... 261 16.3 Determination of Quantity/ Intensity Relationship of K in Soil (Hesse, 1971) ......................................................... 262 Questions and Hints ............................................................... 267 17. Sulphur in Soil ............................................................................... 269 17.1 Determination of Available S in Soil (Ensminger, 1954) .. 269 17.2 Forms of Sulphur in Soil ....................................................... 272 17.3 Measurement of Microbial Sulphur in Soil (Saggar et al. 1981) ................................................................ 278 Questions and Hints ............................................................... 279 18. Micronutrients in Soil .................................................................. 281 18.1 Determination of Available Micronutrient Cations (Zn, Cu, Fe and Mn) in Soil .................................................. 281 18.2 Fractionation of Micronutrient Cations in Soil (Shuman, 1985) ...................................................................... 284 18.3 Determination of Boron in Soil .......................................... 286
Contents / xv
18.4 Determination of Available Molybdenum in Soil........... 289 Questions and Hints ............................................................... 291 19. Some Soil Polluting Heavy Metals ............................................ 295 19.1 Plant Available Fraction of Nickel, Cadmium, Lead and Chromium ..................................................................... 295 19.2 Determination of Arsenic in Soil ........................................ 296 Questions and Hints .............................................................. 299 References ................................................................................................. 301 Appendices ............................................................................................... 305
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