'A STUDY OF THE SUITABILITY OF CALLOW FOR RECLAMATION' BY LILLIAN MARY STUART HARRISON A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY OF THE UNIVERSITY OF LONDON. DEPARTMENT OF MINERAL RESOURCES ENGINEERING IMPERIAL COLLEGE OF SCIENCE AND TECHNOLOGY UNIVERSITY OF LONDON ' OCTOBER I9#f ABSTRACT The purpose of this project was to investigate the suitability of callow (calcareous clay overburden arising from the excavation of Oxford Clay) as a growing medium in reclamation schemes. Its abundance and relative "cheapness" means that it is an ideal top-soil replacement material, if it could be proved to be of benefit to reclamation schemes, Samples of the callow were analysed in the laboratory for nutrient status, pH, water-relationships, cation exchange capacities and other soil-related variables. A series of sites was established so that natural succession on callow could be studied, to investigate whether natural colonisation may provide clues as to the suitability of certain species for reclamation. Field and greenhouse trials were carried out on the callow, to investigate the best types of agricultural uses and fertiliser regimes for use with callow as a growing medium, A variety of grasses, legumes, herbs, shrubs and trees colonise the callow when it is left to natural succession. Natural succession, analysed by ordination techniques could not be related to any of the measured soil-related variables. The callow was found to be deficient in nitrates and phosphates. Growth trial results confirmed these findings. A variety of grass seed mixes with or without legumes can be established on the callow, once nutrient deficiencies are corrected. Crops, such as winter wheat, barley and oil seed rape failed in all trials. Problems with drainage caused set-backs to the field trials section of the project. If treated and cultivated at the correct time of year, callow can be considered to be a suitable growing material for standard agricultural grass seed mixes, once nutrient levels are increased. It is not advised that crops be grown on callow as a pioneer cover. 3 CONTENTS Title Page 1 Abstract 2 Table of Contents 3 List of Figures 5 List of Plates - 8 List of Tables 9 CHAPTER 1. Objectives. H CHAPTER 2. Introduction. ^5 2.1. The Importance of Bedfordshire in Brickmaking. 13 2.2. Geology of the Marston Vale. 16 2.3. Oxford Clay Mineralogy. 20 2.4. Soils of the Marston Vale. 20 2.5. Agriculture. 24 2.6. Climate. 26 2.7. Evapotranspiration. 32 2.8. Environmental Problems of the Brickfields. 34 CHAPTER 3. Background to Natural Colonisation. 51 3.1. Natural Vegetation. 51 3.2. Natural Colonisation of Other Clay Substrates. 52 3.3» Flora of the Oxford Clay. 55 3.4. Flora of the Clay Pits. 56 3.5. The Contribution of Derelict Clay Pits 57 Towards The Conservation of Rare Plants in the U.K. 3.6. Reclamation of Other Clay Overburdens. 59 3»7. Reclamation of the Brick Pits to Agriculture/ Forestry. 66 3.8. Restoration to Recreational After-Uses. 70 3 .9. Other Uses for the Bedfordshire Clay Pits. 71 CHAPTER 4. Field Work Sites. 72 4.1. Quest Pit. 72 4.2. Rookery Pit• 72 4.3. L-Field. 76 4.4. Coronation Pit. 79 4.5. Jubilee Pit, Buckinghamshire. 82 4.6. Bletchley Site II, Buckinghamshire. 85 Upper Dean Clay Pit. 4.7. 85 4.8. Ickwell Clay Pit. 87 Box End, Kempston Clay Pit. 4.9. 87 4.10 Brook Farm Clay Pit. 87 CHAPTER 5* Callow Analysis. 91 5.1. Sampling Techniques. 91 5.2. Moisture Content of the Fresh Samples. 97 5.3« pH Measurements in Distilled Water. 100 5*4. pH Measurements in Calcium Chloride. 100 5«5* Cation Exchange Capacities. 103 5.6. Loss-On-Ignition. 109 CONTENTS (Continued) CHAPTER 5 (continued) 5#7* Conductivity. 113 5.8. Salt Content. 116 5.9* Sodium Levels. 118 5.10. Magnesium Levels. 121 5.11. Potassium; 124 5.12. Calcium. 126 5.13* Phosphorus. 127 5.14. Total Nitrogen. 132 5.15. Field Capacity. 138 5.16. Maximum Water Capacity. 140 5.17. Bulk Density. 144 5.18. Soil Profile Development on Callow. 147 5*19* Discussion. 152 CHAPTER 6. Natural Vegetation Analysis. I65 6.1. Objectives of the Vegetational Survey. 165 6.2. Sites Used in the Vegetational ctudy. 166 6.3* Background to Vegetation Survey Methods. 168 ;>.4. Introduction to Ordination. 169 6 .5 . Methods of Random Sampling. 178 6 .6. Results from Random VegetationSampling. 180 6.7. Transects. * 207 6 .8. Species-Diversity Indices. 214 6 .9. Differences Between the Two Different Aspects at Bletchley Site I • 6.10. Discussion. CHAPTER 7. Field Trials. 229 7.1. Introduction. 229 7*2. Sites. 229 7.3* Selection of Species 230 7.4. The Rabbit Problem. 247 7.5* Experimental Design. 247 7*6. Results. 253 7.7» Discussion. 267 CHAPTER 8. Greenhouse Trials. 279 8.1. Introduction. 279 8.2. Work Previously Carried out on the Callow. 279 8 .3 . Summer 1982 Trials. 288 8.4. The Second Set of Greenhouse Trials. 298 8.5 . The Third Set of Greenhouse Trials. 305 8.6. Discussion. 306 CHAPTER 9» Conclusions and Recommendations 308 References. 313 Acknowledgments • 324 Appendix I• 325 Appendix II. 333 5 LIST OF FIGURES C H A P T E R 1 . Page 1.1. Location of the Marston Vale in Bedfordshire, 12 CHAPTER 2. 2.1. Solid Geology of Bedfordshire. 17 2.2* Surface Geology of Bedfordshire. 18 2.3• Present Outcrop of the Oxford Clay and Jurassic 19 Rocks in Southern England. 2.4. a) Average Maximum and Minimum Temperatures at Stewart by, May 1978 - December 1980. 27 b) Average Maximum and Minimum Temperatures at Stewartby, January I98I - October 1983. 28 2.5. a) Monthly Rainfall at Stewartby, Bedfordshire 29 1970 - 1976. b) Monthly Rainfall at Stewartby, Bedfordshire 30 1977 - October I983. 2.6. Average Annual Rainfall in Bedfordshire. 31 2.7« Annual Average Wind Speed and Direction Rose at 33 Cardington. 2.8. Average Annual SO^ Concentrations. 39 2.9* Average Annual fluoride Concentrations. 40 CHAPTER 3. CHAPTER 4. 4.1. Location of Survey Sites in and Around Stewartby. 73 4.2. Process of Waste Disposal in Rookery Pit. 77 4.3. Location of Some of the Survey Sites in Relation to the Oxford d a y Deposits in Bedfordshire. 78 4.4. Location of the Two Bletchley Sites. 83 4.5. Location of Jubilee Pit. 84 4.6. Cross Section through Brook Farm d a y Pit. 89 CHAPTER 5. 5.1. Non-random Soil-Sampling Technique following a Zig-Zag Course.' 92 5.2. Soil Corer. 94 5.3* Moisture Content of Fresh Samples: December 1982. 98 5.4. Moisture Content of Fresh Samples: March 1983. 99 5.5- Distilled Water pH Measurements. 101 5.6. Calcium Chloride pH Measurements. 102 5*7« The Structure of the d a y Lattice Sub-Units. 103 5.8. The Attraction of Cations to a Colloidal Surface. 105 5«9» The Addition of a Potassium Based Fertiliser to a 106 Soil Colloid System. 5.10. The Riel ease of Potassium into Solution. 1 0 6 LIST OF FIGURES (Continued) P a g e 5.11. Cation Exchange Capacities of the Callow. 1 1 0 5.12. Loss on Ignition of the Callow. 112 5.13 • Specific Conductivity of the Callow. 115 - 5.14. Meq. salts per litre of Saturated Callow. 117 5.15. Sodium Content of the Callow. 1 2 0 5*16. Magnesium Content of the Callow. 123 5.17* Potassium Content of the Callow. 125 5*18. Calcium Content of the Callow. 128 5*19. Pump and Manifold for Kjeldahl Digestion 136 Apparatus • 5*20. Total Nitrogen Content of the Callow. 139 5.21. Soil Moisture Diagram. 141 5*22. Water Relations of the Callow: October I983. Percentage Moisture. 142 5.23. Water Relations of the Callow: October 1983 143 Percentage Field Capacity. 5.2*+. Water Relations of the Callow: October I983 145 Pore Space. 5.25. Relationship Between Moist Bulk Density and 14 6 Packing Density. 5*26. Water Relations of the Callow: October I983 148 Bulk Density. 5*27• The Relationship Between Bulk Density and Pore Space. 5.28. The Four Phosphate Reservoirs Which Supply Phosphate to Water in the.Soil as it is 1 6 2 Removed by Plants. CHAPTER 6. 6.1. Continuum Concept of Vegetation. 170 6.2. Successional Trends in Some of the More common 186 Species. 6 .3 . Reciprocal Averaging. 1. Stand Ordination: 189 Point Quadrats. 6.4. Reciprocal Averaging. 2. Species Ordination: 190 Point Quadrats. 6 .5 . Reciprocal Averaging: 3* Stand Ordination: 202 Square Quadrats. 6 .6. Reciprocal Averaging: 4. Species Ordination: 203 Square Quadrats. 6.7 . Transect in 3 year Old Callow Mound. 210 6 .8. Transect in 6 year Old Callow Mound. 211 6.9. Transect in 10 year Old Callow Mound. 212 6.10. Transect Down 16 Year Old Callow Mound. 213 6 .1 1 . Lognormal Distribution of Relative Abundances of Diaton Species in a Sample Taken from an Undisturbed Community in Ridley Creek, Pennsylvania. 214 6.12. a) Dominance Diversity Curves: 1-45 years 217 b) Dominance Diversity Curves: 61 - 97 years. 217 6.13. Berger Parker Dominance Indices. 220 LIST OF FIGURES (Continued) P a g e CHAPTER 7. 7.1. The Disrupting Effect of a Subsoiler on the Soil 231 7.2. Vegetation Trials at Elston. 248 7.3. Callow Portion of Field Trials at Brogborough. 249 7.4. Elstow Plots - Pre-harvest Monitoring. 271 7.3 Elstow Plots - Harvest . 273 CHAPTER 8 . 8.1. Average Yields from I98O Greenhouse Trials. 28l 8.2.