The effects of compaction and residue management on soil properties ...

The effects of compaction and residue management on soil properties and growth of Eucalyptus grandis at two sites in KwaZulu-Natal, South Africa. by

Diana Nicolle Rietz

Submitted in fulfillment of the academic requirements for the degree of Doctor of Philosophy in the Discipline of Soil Science School of Environmental Sciences College of Agriculture, Engineering and Science University of KwaZulu-Natal Pietermaritzburg

March 2010

As the candidate’s supervisor I have/have not approved this thesis for submission.

Signed: __________________ Name: Prof J.C. Hughes Date: 31 March 2010

As the candidate’s co-supervisor I have/have not approved this thesis for submission.

Signed: __________________ Name: Dr C.W. Smith

Date: 31 March 2010

Abstract Concerns have been raised over the long-term site productivity (LTSP) of short rotation plantation forests, such as those of Eucalyptus, in South Africa. This is because diminished productivity of long rotation plantations overseas has been found to be generally due to decreases in soil porosity and organic matter. Since soil porosity and organic matter in plantations are mainly affected by soil compaction by harvesting machinery and residue management, the more frequent harvesting of short rotation plantations are of particular concern. Therefore the effects of soil compaction and residue management on soil properties at two sites, one a low organic carbon, sandy soil (Rattray), the other a high organic carbon, clay soil (Shafton) were investigated. The potential of early E. grandis productivity as an indicator of changes in soil properties at these sites was also evaluated.

Three different levels of compaction (low, moderate and high) were applied to the sites by three methods of timber extraction, i.e. manual, logger and forwarder loaded by a logger, respectively. Three types of residue management, i.e. broadcast, windrow and residue removal were also applied. A factorial treatment design was used to ensure a resource-efficient study that allowed separation of main and interaction effects.

Various soil physical and chemical properties were measured at intervals from before treatment implementation, until approximately 44, and 38 months after treatment implementation at Rattray and Shafton, respectively. Trees were planted at a commercial espacement at both trials, and their growth monitored over the same time period. In addition, to accelerate early growth, negate silvicultural variation, and determine changes in stand productivity with treatments, a portion of the treatment plots were planted at a very high density and harvested when these trees reached canopy closure at about six months of age.

Moderate and high compaction treatments at both sites resulted in significant increases in penetrometer soil strength, and often in bulk density. Increasing residue retention decreased the compaction effects of machinery and, generally,

ii

increased the total quantity of nutrients contained in residues and soil. Changes in soil bulk density and organic matter as a result of the treatments in turn affected soil water characteristics, generally decreasing plant available water capacity with increasing compaction intensity and residue removal. Tree growth measurements showed that at both sites, tree productivity was negatively affected at some point by increasing compaction. In contrast, residue management only significantly affected tree growth at Shafton, initially increasing and later decreasing growth with residue removal. These variations in tree growth over time in response to treatments are most likely a result of changes in tree characteristics that occurred with age. In addition, trees did not always reflect changes in soil properties that may affect LTSP, most likely because these soil properties had not yet reached levels that would affect tree growth.

It was therefore concluded that early tree growth is not always a good indicator of changes in LTSP, and that soil properties are a more reliable indicator. Plantation management practices that lead to soil compaction and residue removals will negatively impact LTSP in South Africa. However, variable responses of the two soils indicate that soils vary in their sensitivity to compaction and residue management. This therefore needs to be quantified across a range of major soil types in the South African forestry industry.

iii

Preface

The experimental work described in this thesis was carried out in the School of Environmental Sciences, University of Kwa-Zulu Natal, Pietermaritzburg, from January 2004 to March 2010, under the supervision of Professor Jeffrey C. Hughes and Dr Colin W. Smith.

These studies represent original work by the author and have not otherwise been submitted in any form for any degree or diploma to any tertiary institution. Where use has been made of the work of others it is duly acknowledged in the text.

iv

DECLARATION - PLAGIARISM

I, Diana Nicolle Rietz declare that

1.

The research reported in this thesis, except where otherwise indicated, is my original research.

2.

This thesis has not been submitted for any degree or examination at any other university.

3.

This thesis does not contain other persons’ data, pictures, graphs or other information, unless specifically acknowledged as being sourced from other persons.

4.

This thesis does not contain other persons' writing, unless specifically acknowledged as being sourced from other researchers. Where other written sources have been quoted, then: a. Their words have been re-written but the general information attributed to them has been referenced b. Where their exact words have been used, then their writing has been placed in italics and inside quotation marks, and referenced.

5.

This thesis does not contain text, graphics or tables copied and pasted from the Internet, unless specifically acknowledged, and the source being detailed in the thesis and in the References sections.

Signed: …………………………………………………………

v

Acknowledgements So many people and organisations were involved in the completion of this thesis. However, some stand out, whose contribution must be acknowledged. First and foremost, I would like to thank the director of the Institute for Commercial Forestry Research, Prof Colin Dyer, for giving me the means to perform this study. It would not have been possible otherwise. My supervisor Prof Jeff Hughes, supported me with his vast knowledge, saint-like patience and dry humour, gave me good advice and direction, all the while giving me room to work in my own way. My co-supervisor, Dr Colin Smith has encouraged me, helped me to learn in leaps and bounds, and has done his utmost to turn me into a scientist who can not only do the science, but can communicate it to others. All three examiners were extremely thorough and added considerable value to this thesis. SAPPI Forests (Pty) Ltd and Mondi Ltd for permission to use their land and for supplying the means to implement the trials. The field work for this study was extensive, physically demanding and often in adverse weather conditions. However, several people made the experience as pleasant as possible, and I have many good memories, and count them all my friends. They are Messers Gregory Fuller, Denis Oscroft, Michael Buthelezi, Musa Mkhwanazi, the late Bheki Ndawonde and Ms Chané Nel. After the field work, came the laboratory portion of the study, and Mr Tad Dorasamy and the late Mr Essack Abib of the University of KwaZulu-Natal created the space for me to work, and assisted me in many areas. I will always be grateful to Mrs Mary Galbraith and Mr Michael Buthelezi, who performed many of the routine analyses. Thanks also go to Mr Michael Chetty who compiled the results and provided laboratory support. Dr Principle Ndlovu and Dr Keith Little helped with the statistical analyses, thereby increasing the value of the data. The tedious tasks of proof reading, formatting and printing this thesis were kindly carried out by Ms Patricia Stannard, Ms Chloe Boshoff, and Mrs Sally Upfold. Many friends have done more for me than I can ever repay or express, but in particular, Mr Gert van den Berg, Ms Patricia Stannard, Mr Sean Best, Dr Louis Titshall, Ms Cathy Ford, Dr Carol Rolando, Dr Keith Little and Ms Justine Tempest. My parents, Jennifer Rietz, Kenneth Winch and Peter Rietz, have taught me more than I will ever be able to consciously fathom. Lastly, my dear animals, Kayla, Your Man, Zeta, Cara and Axe brought sanity and happiness to me, even in the darkest days of this thesis, and of my life. vi

Table of Contents

Abstract………………….………………………………………………………… Preface…………………………………………………………………... Declaration………………….…………………………………….......…………. Acknowledgements……………………………….………….………………. List of Tables………………….………………………………………………… List of Figures………………….……………………………………………….. List of Plates………………….…………………………………………………. List of Appendices………………….…………………………………………. Glossary of Terms………………….…………………………………………. List of Symbols and Abbreviations…………………….……………….

Page ii iv v vi xiv xviii xxii xxiii xxvi xxix

Chapter 1: Introduction……………….………..……………………..………. Aim and outline of the study……..………………………………………..

1 3

Chapter 2: Concepts of Sustainability……….…..……………………….

5

2.1 Introduction……………….…………………………....…………………….. 2.2 Criteria for LTSP studies of forest plantations…..…………….…..….. 2.3 LTSP of South African Eucalyptus plantations………………………... 2.4 Measurement of management effects on LTSP………………….…….. 2.4.1 Soil measures …………….…………………………...…..…………. 2.4.2 Plantation measures …..………….………………………………….. 2.4.2.1 Theoretical determination of productivity…………………… 2.4.2.2 Physical determination of productivity……………………….

5 7 10 11 12 17 18 18

Chapter 3: Materials and Methods……………….…………………...……

23

3.1 Description of sites, trial layout and treatment implementation……. 3.1.1 Description of trial sites………..….……………………….....……… 3.1.2 Site history………….……………………………...……………..…… 3.1.2.1 Rattray………….…………...………………….....…………… 3.1.2.2 Shafton………….……………...………………....…………… 3.1.3 Trial layout………….……...……………………...…………..….…… 3.1.4 Treatment implementation……..…….…………………………....… 3.1.5 Pre-planting operations……...…….…………………………….…… 3.1.6 Genetic material………..….………………………….....…………… 3.1.7 Planting………….…………..………………...…………………….… 3.2 Site measurements………….……...……………………...……………..… 3.2.1 Soil sampling………….………..…………………....…………..…… 3.2.2 Soil bulk density………….……..……………….……...……….…… 3.2.2.1 Troxler………….……………………………...…………..……

23 23 26 26 27 28 30 34 34 35 37 38 39 39

1.1

vii

3.2.2.2 Undisturbed soil cores…………………………….….….…… 3.2.3 Penetrometer soil strength………………...………….……..….…… 3.2.4 Soil water………….…………………………......………….………… 3.2.5 Residue sampling…..……….…………………………...….……..… 3.2.6 Tree measurements ..………………………………………………… 3.2.6.1 Sub-plot tree measurement and harvesting……………….. 3.2.6.2 Tree thinning and main plot tree measurements…...……... 3.3 Laboratory procedures and calculations………...………….……..…… 3.3.1 Soil sample processing and analysis…………...…………..….…… 3.3.1.1 Particle size analysis………………………………...…..…… 3.3.1.2 Soil water retention (undisturbed soil cores) ……………… 3.3.1.3 Calculation of Troxler bulk density…………………………... 3.3.1.4 Bulk density (undisturbed soil cores) ……………......…..… a) Maximum bulk density and compression index and compaction sensitivity index……………………….… b) Relative bulk density………….…………………….… 3.3.1.5 pH, total nitrogen, extractable phosphorus (Bray-2) and exchangeable cations……..…………………….….………… a) Calculation of soil nutrient quantities………...….….. 3.3.1.6 Organic matter and carbon………….……………..…….….. a) Walkley-Black method……………………………..…. b) Loss on ignition method………….……...…………… 3.3.1.7 Least limiting water range (LLWR) ………...………..……… 3.3.2 Residue sample processing and analysis………………………….. 3.3.2.1 Carbon and nitrogen………….…………………..……….…. 3.3.2.2 Sample preparation ………….………………...…………..… 3.3.2.3 Phosphorus, potassium and sodium…………….………..… 3.3.2.4 Calcium, magnesium, copper, iron, zinc and manganese.. a) Calculation of residue nutrient quantities……….….. 3.3.3 Tree component processing and analysis…………………….……. 3.3.3.1 Aboveground components …………………...………...…… 3.3.3.2 Belowground components……………………...…...….……. 3.3.4 Biomass index, basal area and stemwood volume calculations…. 3.4 Statistical analyses………….………………….…………...……………….

Page 40 41 42 42 43 43 44 45 45 45 45 46 47 47 48 48 49 49 50 50 50 50 51 51 51 51 52 52 52 53 54 54

Chapter 4: Effect of Compaction Treatments and Residue Management on Soil Bulk Density and Strength…….

56

4.1. Introduction………………………………………………………………....... 4.1.1. Effect of compaction, machinery movement and residue management on soil physical properties…..……………..………... 4.1.2. Soil bulk density and strength…………………...………...………… 4.1.3. Persistence of soil compaction…………………...……….....……… 4.1.4. Chapter rationale and objectives………………….......................... 4.2. Materials and methods…………………...…………………….................. 4.2.1. Troxler bulk density – statistical analysis…...……………….……… 4.2.2. Penetrometer soil strength – statistical analysis…...………………

56 58 60 62 63 63 63 64

viii

4.3. Results and discussion…………………...………………….................... 4.3.1. Maximum bulk density and compression index……………………. 4.3.2. Treatment effects on bulk density………………...……………….... 4.3.2.1. Rattray…………………...……...……………...……………… 4.3.2.2. Shafton…………………...……………………...…………….. 4.3.3. Penetrometer soil strength……………...……...…………………..... 4.3.3.1. Rattray…………………...…...………………...……………… a) Residual compaction………………………….…….... b) Effect of compaction treatments on PSS…………… c) Variation in PSS as a result of compaction treatments……………………...…………………........ d) Residue management effects………………….…..... 4.3.3.2. Shafton…………………...…………………...………………... a) Residual compaction………………………….…….... b) Effect of compaction treatments on PSS…………… c) Variation in PSS as a result of compaction treatments……………………...…………………........ d) Residue management effects………………….…..... 4.4. Conclusions………………...…………………...…………………..............

Page 66 66 66 66 68 70 70 70 71 73 73 76 76 77 79 80 83

Chapter 5: Changes in Residues, Soil Organic Carbon and Nutrients over Time…………………….…...………………….. 5.1. Introduction……………...…………………………………...………………. 5.1.1. Management effects on soil organic matter and nutrients……..…. 5.1.2. Residue management……………...……………………………...…. 5.1.2.1. Eucalypt harvest residue……………...…………………...… a) Residue biomass (organic input) ………………...…. b) Factors affecting residue decomposition…………… c) Residue nutrient concentrations and contents…….. 5.1.2.2. Effect of residue management on soil pH and nutrient availability…………………………………………………...…. 5.1.3. Effect of compaction on soil organic matter and nutrient dynamics…………….…...………………………………...………….. 5.1.4. Chapter rationale and objectives…..…………......………………… 5.2. Materials and methods……………...…………………………………...…. 5.3. Results and discussion……………...………...………………………...… 5.3.1. Quantity of residues………………....……………………………….. 5.3.1.1. Rattray……………...………...………………………...……… 5.3.1.2. Shafton……………...…………………………………...…….. 5.3.2. Changes in soil organic carbon……...…..……...…...……………… 5.3.2.1. Rattray……………...…………...…………...………………… 5.3.2.2. Shafton…………………………...………...……..…………… 5.3.3. Changes in soil pH and site nutrient pools……...……..…...……… 5.3.3.1. Rattray…………………………………...…...………..………. 5.3.3.2. Shafton……………...……………………………….………… 5.4. Conclusions……………...………………………………...………..……….

85 85 86 87 87 87 88 88 90 90 92 92 93 93 93 94 95 95 97 98 98 103 108

ix

Page

Chapter 6: Effect of Compaction Treatments and Residue Management on Soil Water and Aeration…………...….. 6.1. Introduction………...…………………………………...….………………… 6.1.1. Soil water availability and aeration…………...…..……….………… 6.1.1.1. Total porosity and pore-size distribution.…………...……… 6.1.1.2. Effect of soil bulk density and organic carbon on water retention………...…………………….…………….…………. 6.1.2. Least limiting water range…………...……………………………….. 6.1.3. Soil bulk density and organic carbon effects in forestry soils......... 6.1.4. Soil water supply………...…………………………………...……..… 6.1.5. Chapter rationale and objectives………...………………………….. 6.2. Materials and methods…..…...…………..……...………………...………. 6.2.1. Statistical analysis of the effect of soil bulk density and organic carbon on soil water retention and availability (undisturbed soil cores)…………………………………………………………..……….. 6.2.2. Effect of soil bulk density and organic carbon on least-limiting water range (undisturbed soil cores)………...………………….…... 6.2.3. Treatment effects on soil water availability and least-limiting water range (undisturbed soil cores)………...…………..………….. 6.2.3.1. Compaction treatments……..…...………….……………….. 6.2.4. Statistical analysis of treatment effects on soil water content (thetaprobe)……………………………………………………………. 6.3. Results and discussion……….………………...………………………….. 6.3.1. Effect of bulk density and organic carbon on soil water (undisturbed soil cores)……………………………………...……...... 6.3.1.1. Rattray………...……………………………………..………... a) Water retention………...………………….…..…….... b) Porosity and pore-size distribution……..….....…….. c) Water availability………...…………………..….……. d) Least limiting water range………...…………..…….. 6.3.1.2. Shafton………...……………………...……………………….. a) Water retention………...………………….…..…….... b) Porosity and pore-size distribution……..….....…….. c) Water availability………...…………………..….……. d) Least limiting water range………...…………..…….. 6.3.2. Treatment effects on soil water availability and least-limiting water range (undisturbed soil cores)..………...……………………. 6.3.2.1. Compaction treatments………...…………………………….. a) Rattray………...………………...……………………... Bulk density………...……..………………………. Organic carbon……….....………………………... Bulk density and organic carbon…..……...……. b) Shafton………...………………………..…………….. 6.3.2.2. Residue management………...………………...……………. a) Rattray………...………………………...………...…… b) Shafton………...…………………………..……...…...

111 111 111 112 113 114 116 117 117 118

118 119 119 120 120 121 121 121 121 124 125 128 129 129 132 133 136 138 138 138 138 140 141 143 143 143 143

x

Compaction treatment x residue management interaction.. a) Rattray………......………………………………...…… b) Shafton………...…………………………………...….. 6.3.3. Soil water content (thetaprobe)………...………...…………………. 6.3.3.1. Rattray………...………………..………………...…………… 6.3.3.2. Shafton………...………………..………………...…………... 6.4. Conclusions………...…………………………..……...………………….…

Page 145 145 147 147 147 149 150

Chapter 7: Tree Survival and Productivity……......……………...….…

152

7.1. Introduction……...………………...…………………...………………...….. 7.1.1. Productivity……...………………...…………………...……………… 7.1.2. Factors affecting productivity……...…………………...……………. 7.1.2.1. Measurements of foliage and fine roots………...………….. a) Specific leaf area……...………………......………….. b) Leaf area index……...………………...…...…………. c) Foliar nutrients……...………………...……...……….. d) Root:shoot ratio……...………………...……………… 7.1.2.2. Ontogeny……...………………...………………...……...…… 7.1.3. Compaction effects on survival and productivity……...………..…. 7.1.3.1. Effect of compaction on survival and aboveground productivity……...……………………………………...……… 7.1.3.2. Effect of compaction on belowground productivity………… 7.1.3.3. Effect of compaction on SLA, LAI, foliar nutrients and root:shoot ratio in eucalypts……...……….…………………. 7.1.4. Residue management effects on growth, productivity and survival……...………………...………………...….……………...….. 7.1.4.1. Effect of residue management on survival and aboveground productivity…………………….....…………… 7.1.4.2. Effect of residue management on belowground productivity……...………………...………………….....…….. 7.1.4.3. Effect of residue management on SLA, LAI, foliar nutrients and root:shoot ratio in eucalypts……...……..……...………. 7.1.5. Compaction x residue management effects on survival and productivity……...………………......………………...…….………… 7.1.6. Chapter rationale and objectives…………...……………………….. 7.2. Materials and methods……...………………...………………...…………. 7.2.1. Herbicide application effects on trees at Shafton……........………. 7.2.2. Statistical analysis of effects of soil properties on tree growth and productivity…………………………………………………………….. 7.3. Results and discussion……...………………......………………....……… 7.3.1. Productivity and allometry……...……..…………...…………….….. 7.3.1.1. Effect of biomass index on total and component productivity……...………………...………………....………... 7.3.1.2. Allometric relationships………...………………...…….……..

152 152 152 154 154 154 154 156 156 157

6.3.2.3.

157 159 161 162 162 163 164 165 165 166 166 167 167 167 167 169

xi

Page 7.3.1.3.

Effect of SLA, LAI, foliar nutrients and root:shoot ratio on productivity……...………………………………………….….. a) SLA……...…………………….….………...……..…… b) LAI……...………………...……………………..……… c) Foliar nutrient concentrations………...……….…….. d) Root:shoot ratio……...…………...……...……..…….. 7.3.1.4. Effect of treatments on SLA, LAI, foliar nutrients and root:shoot ratio……………………………………....…….….. a) SLA and LAI ……………………………...……...….... b) Foliar nutrient concentrations………..………………. c) Root:shoot ratio……...…………………..……………. 7.3.2. Survival……...………………...………………...………...………...… 7.3.2.1. Rattray……...………………...………………...……………… a) Sub-plot trees……...………….……...……………….. b) Main plot trees……...………….……...………………. 7.3.2.2. Shafton.………………...………………................................. a) Sub-plot trees……...………….……...………………. b) Main plot trees……...………….……...……………… 7.3.3. Growth…...…………...…………......…………...…………...……….. 7.3.3.1. Rattray…...…………...……...……...…………...…………..... a) Effect of compaction treatments and residue management on tree growth in sub-plots….……….. b) Effect of compaction treatments and residue management on tree growth in main plots…………. c) Effect of compaction treatments and residue management on overall tree growth......……………. d) Effect of compaction treatments and residue management on basal area and volume of trees in main-plots………………………………………………. 7.3.3.2. Shafton…...…………...…………......…………...…………… a) Effect of compaction treatments and residue management on tree growth in sub-plots….……….. b) Effect of compaction treatments and residue management on tree growth in main plots…………. c) Effect of compaction treatments and residue management on overall tree growth......……………. d) Effect of compaction treatments and residue management on basal area and volume of trees in main-plots………………………………………………. 7.3.4. Comparison between sub-plot and main plot tree survival and growth……….....………...………...………...………...……………... 7.4. Conclusions………...…...……...………...………...………...………..........

Chapter 8: General Discussion and Conclusions……….................. 8.1

Effect of compaction treatments and residue management on soil properties…………………………………...………...………...………........

171 171 171 172 174 174 174 174 176 179 179 179 179 180 180 181 182 182 182 186 188

188 189 189 192 194

195 196 198

200

200

xii

8.1.1 8.1.2 8.1.3

Compaction treatments…………...………...………...……….......... Residue management……...…...………...………...………...……... Interaction between compaction treatments and residue management………...………...…………...………...………............. 8.1.4 Conclusions………...……...…...………...………...………...………. 8.2 Eucalyptus productivity as an indicator of changes in soil properties………...………...……………………….……...………...………. 8.3 Implications of the study and future work…………...………...……….. 8.3.1 Compaction treatments…………...………...………...……….......... 8.3.2 Residue management……...…...………...………...………...……... 8.3.3 Use of densely planted sub plots and tree productivity…………… 8.3.4 Future work…………………………………………………………….. 8.3.4.1 Future of the trials at Rattray and Shafton………………….. 8.3.4.2 Further LTSP Research……………………………………….

Page 200 202 203 204 205 207 207 208 209 210 210 210

References………...………...…………..………...………....………...…………..

212

Appendices………...………...………...…………………………………………...

243

xiii

List of Tables Table 3.1: Site and climatic information for the two study sites……………. Table 3.2: Geological, topographical and soil information for the two study sites…………………………………..………………………………..………. Table 3.3: Selected soil properties at Rattray. Average (n = 8) values are given with standard deviations in parentheses..………………………….. Table 3.4: Selected soil properties at Shafton. Average (n = 8) values are given with standard deviations in parentheses……………………….…… Table 3.5: Soil organic carbon content (as determined by Walkley-Black) at Rattray and Shafton. Average (n = 27) values are given, with standard deviations in parentheses………………………………..……….. Table 3.6: Combination of treatments used for the trials…………………… Table 3.7: Details of planting operations at Rattray and Shafton………….. Table 3.8: Time after treatment implementation (months) at which soil and residue samples were taken at Rattray and Shafton………………... Table 4.1: Maximum bulk density (MBD; Mg m-3), compression index (CIndex) and compaction sensitivity index (CSI) for soils at the two trials using the models of Smith (1995)...………..……………………………….. Table 4.2: Range of relative bulk density values (i.e. ratio between soil core bulk density and MBD) at two soil depths under the compaction treatments at Rattray………………………………..……………………….. Table 4.3: Range of relative bulk density values (i.e. ratio between soil core bulk density and MBD) at two soil depths under the compaction treatments at Shafton………………………………..……………………….. Table 4.4: Mean relative PSS1 of CM and CH treatments relative to the CL treatment with different residue management at Rattray to a soil depth of 0.3 m………………………………..………………………………..……... Table 4.5: Level of significance (p) of compaction treatments (i.e. CM and CH) and residue management effects on relative (to the CL treatment) PSS1 values with soil depth at Rattray. Two-way ANOVA’s were performed; blocking factor- soil depth…………………………………….... Table 4.6: Mean relative PSS1 of CM and CH treatments relative to the CL treatment under different residue management at Shafton to a soil depth of 0.25 m………………………………..……………………………… Table 4.7: Level of significance of (CM and CH) compaction treatments and residue management effects on relative (to the CL treatment) PSS1 values with soil depth at Shafton. Two-way ANOVA’s were performed; blocking factor- soil depth………………………………..………………….

Page 24 24 25 25

26 28 35 38

66

68

69

75

75

81

82

Table 5.1: Nutrient contents (kg ha-1) of broadcast E. grandis harvest residues after felling (time)…………………..………………………………. 89 Table 5.2: Nutrients held in broadcast or windrowed residues as a percentage of that held in the soil (0 – 0.6 m)a at TP at Rattray………… 102 Table 5.3: Nutrients held in broadcast and windrow residues as a percentage of that held in the soil (0 – 0.6 m)a at TP at Shafton………... 106

xiv

Page Table 5.4: Significant results of residue management and compaction treatment effects on mean macronutrient values (kg ha-1) of soil depth layersa and total nutrients (residues + soil 0 - 0.6m) at Shafton at harvesting of sub-plot trees (TH) and final soil measurement (TF). Treatments with different letters are significantly different (p