Methods in agricultural chemical analysis: a practical handbook

289 Pages·2002·1.371 MB·English

by  N T Faithfull

METHODS IN AGRICULTURAL CHEMICAL
ANALYSIS
A Practical Handbook
To Alwyn, Antonia and Bethan
M
ETHODS IN
A C
GRICULTURAL HEMICAL
A
NALYSIS
A Practical Handbook
N.T. Faithfull
Institute of Rural Studies
University of Wales
Aberystwyth
UK
CABI Publishing
CABI Publishing is a division of CAB International
CABI Publishing CABI Publishing
CAB International 10 E 40th Street
Wallingford Suite 3203
Oxon OX10 8DE New York, NY 10016
UK USA
Tel: [phone] Tel: [phone]
Fax: [phone] Fax: [phone]
E-mail: [email protected] E-mail: [email protected]
Web site: www.cabi-publishing.org
©CAB International 2002. All rights reserved. No part of this publication may
be reproduced in any form or by any means, electronically, mechanically, by
photocopying, recording or otherwise, without the prior permission of the copy-
right owners.
A catalogue record for this book is available from the British Library, London,
UK.
Library of Congress Cataloging-in-Publication Data
Faithfull, N.T. (Nigel T.)
Methods in agricultural chemical analysis: a practical handbook / N.T. Faithfull.
p. cm.
Includes bibliographical references (p. 206).
ISBN 0–85199–608–6
1. Soils--Analysis--Handbooks, manuals, etc. 2. Plants--Analysis--Hand-books,
manuals, etc. 3. Chemistry, Analytic--Handbooks, manuals, etc. I. Title.
S593 .F19 2002
630’.2’43--dc21
2002005768
ISBN 0 85199 608 6
Typeset by Wyvern 21 Ltd, Bristol
Printed and bound in the UK by Biddles Ltd, Guildford and King’s Lynn
Contents
Preface xii
About the Author xv
Disclaimer xvi
Acknowledgements xvii
Abbreviations and Acronyms xx
Chapter 1 Experimental Planning 1
Experimental Design 1
Plot size 2
Equipment Considerations 2
Autoanalysis 2
Samplers 4
Peristaltic pumps 4
Chemistry module 5
Heating bath and dialyser 5
Colorimeter and spectrophotometer 6
Chart-recorders 6
Chart reader 7
Flow injection 8
Batch Size 8
Sampling Protocol 9
Soils 9
Composts 10
Feeds 10
v
vi Contents
Plant components 15
Microbiological analysis 16
Biological substances 16
Fertilizers 16
Chapter 2 Sample Preparation 17
Pre-treatment of Samples and Sample Contamination 17
Trace Element Analysis 17
Sub-sampling 18
Drying Techniques 19
Air-drying 19
Oven-drying 19
Vacuum oven 19
Freeze-drying 20
Desiccation 22
Milling, Grinding and Homogenization 22
Freezer mill 23
Homogenization 23
Storage of milled samples 24
Chapter 3 Weighing and Dispensing
Weighing Errors 26
Corrections of weighings in vacuo 26
Incorrect calibration of the balance 26
Static charge 27
Convection currents 27
Absorption of moisture by the sample 27
Absorption of moisture by the sample container 27
Dispensing Errors 28
Bottle top dispensers 28
Syringe pipettes 29
Chapter 4 Acid-digestion, Ashing and Extraction Procedures 30
Acid-digestion and Washing 30
Acid-digestion of soils 30
Total soil nitrogen 31
Acid-digestion of plant materials 32
Digestion systems 32
Distillation systems 32
Microwave acid-digestion 34
Dry ashing 35
Extraction Procedures – Plant-based Materials 36
Oils, fats and waxes 37
Fibre, lignin, cellulose, nitrogen-free extract and starch 38
In vitro digestibility 42
Nitrate and water-soluble carbohydrate 48
Water content in silage 50
Contents vii
Extraction Procedures – Soils 50
pH extractants 51
Phosphate extractants 52
Potassium extractants 54
Trace element extractants 54
Chapter 5 Analysis of Soil and Compost 57
Soil Analytical Procedures 57
Method 5.1. Determination of extractable boron 57
Method 5.2. Cation exchange capacity, exchangeable bases and
base saturation 59
Method 5.3. Determination of effective cation exchange
capacity (ECEC) 66
Method 5.4. Determination of fulvic and humic acids 68
Discussion 5.5. Determination of available nitrogen 71
Method 5.5a. Determination of nitrate by selective ion electrode 71
Discussion 5.5b. Determination of total mineralized nitrogen 72
Method 5.5b.i. Determination of extractable ammonium-N 73
Method 5.5b.ii. Determination of extractable nitrate-N 74
Discussion 5.6. Determination of organic plus ammonium nitrogen 74
Method 5.6a. Determination of soil nitrogen by autoanalysis 75
Method 5.6a.i. Reduction of nitrate before digestion and
colorimetric analysis 75
Method 5.6b. Determination of organic plus ammonium-N by
digestion and distillation 76
Discussion 5.7. Determination of soil organic matter 78
Method 5.7a. Determination of soil organic matter by loss on
ignition 78
Method 5.7b. Determination of easily oxidizable organic C by
Tinsley’s wet combustion 79
Discussion 5.8. Determination of pH and lime requirement 81
Method 5.8a. Measurement of pH 82
Method 5.8b. Determination of lime requirement 82
Method 5.8c. Determination of pH in soils with soluble salts 83
Discussion 5.9. Determination of extractable phosphorus 84
Method 5.9a. Determination of extractable phosphorus (manual
method) 84
Method 5.9b. Determination of extractable phosphorus
(automated method) 86
Method 5.9c. Determination of resin extractable phosphorus
(automated method) 87
Method 5.10. Determination of extractable magnesium, potassium
and sodium 89
Method 5.11. Determination of extractable trace elements 91
Discussion 5.12. Determination of extractable sulphur 93
Method 5.12a. Determination of extractable sulphur (manual
method) 94
viii Contents
Method 5.12b. Determination of extractable sulphur (automated
method) 96
The Analysis of Composts
Method 5.13. Determination of CEC in composts 101
Method 5.14. Determination of Ca, K, Mg and P in composts 103
Method 5.15. Determination of heavy metals in compost 104
Chapter 6 The Analysis of Fertilizers 106
Fertilizer Analytical Procedures 107
Discussion 6.1. Determination of total nitrogen in presence of
nitrate and organic N 107
Method 6.1a. Determination of total nitrogen in presence of
nitrate and organic N, with final determination by distillation 108
Method 6.1b. Determination of total nitrogen in presence of
nitrate and organic N, with final determination by autoanalysis 109
Discussion 6.2. Determination of phosphorus in fertilizers 110
Method 6.2a. Determination of water-soluble phosphorus
(extraction) 114
Method 6.2a.i. Determination of water-soluble phosphorus
(autoanalysis) 114
Method 6.2a.ii. Determination of water-soluble phosphorus
(manual method) 116
Method 6.2b. Determination of 2% citric acid-soluble phosphorus
– method for basic slags (Thomas phosphate) 117
Method 6.2c. Determination of total phosphorus in the acid
digest from Method 6.1b. with final determination by autoanalysis 118
Discussion 6.3 Determination of potassium in fertilizers 119
Method 6.3a. Determination of water-soluble potassium 120
Method 6.3b. Determination of ammonium oxalate-soluble
potassium 120
Method 6.3c. Determination of potassium in the acid digest from
Methods 6.1a. or 6.1b 121
Liming Materials 121
Method 6.4. Determination of the moisture and neutralizing
value of liming materials 122
Method 6.5. Determination of fineness of grinding (150 µm/100
mesh fraction) 123
Chapter 7 The Analysis of Animal Feed and Plant Materials 124
Discussion 7.1. Determination of acid detergent fibre, cellulose
and lignin 125
Method 7.1a. Determination of acid detergent fibre 125
Method 7.1b. Determination of lignin 126
Method 7.1c. Determination of cellulose and ash 127
Method 7.2. Determination of crude fibre 128
Method 7.3. Determination of modified acid detergent fibre (MAD
fibre) 130
Contents ix
Method 7.4. Determination of neutral cellulase plus gamanase
digestibility (NCGD) of feeding stuffs 131
Method 7.5. Determination of neutral detergent fibre (NDF) or plant
cell-wall constituents 133
Method 7.6. Determination of nitrate in plant material by
autoanalysis 135
Discussion 7.7. Determination of total nitrogen (crude protein) in
plant material and feeding stuffs 137
Method 7.7a. Determination of total nitrogen (crude protein) in
plant material by autoanalysis 138
Discussion 7.8. Determination of oil in feeding stuffs by extraction
with petroleum spirit 141
Method 7.8a. Determination of oil in feeding stuffs by extraction
with petroleum spirit 142
Method 7.8b. Determination of oil in rapeseed 142
Method 7.9. Determination of pepsin–cellulase digestibility of plant
material 143
Discussion 7.10. Determination of total phosphorus in plant
material and feeding stuffs 144
Method 7.10a. Determination of total phosphorus in plant material
by autoanalysis 145
Discussion 7.11. Determination of total potassium in plant material
and feeding stuffs 146
Method 7.11a. Preparation of plant sample solution by dry
combustion 147
Method 7.11b. Determination of potassium in plant material by
flame photometry (dry ashing extract) 148
Method 7.11c. Determination of potassium in plant material by
flame photometry (Kjeldahl acid digest) 148
Discussion 7.12. Determination of starch by acid
hydrolysis 149
Method 7.12a. Determination of starch in potatoes by hydrolysis
and autoanalysis 149
Discussion 7.13. Determination of trace elements in
plants and feeds 150
Method 7.13a. Determination of trace elements in plants and feeds 151
Method 7.14. Determination of water soluble carbohydrate by
autoanalysis 151
Chapter 8 The Analysis of Silage 154
Method 8.1. Determination of ammonium-N in silage 154
Method 8.2. Determination of moisture in silage 156
Method 8.3. Determination of pH in silage 159
Discussion 8.4. Determination of volatile fatty acids (VFAs)
in silage 159
Method 8.4. Extraction method for obtaining silage juice for
analysis for VFAs 164