CONTENTS. 



CHAPTER PAGE 



I. HISTORICAL AND INTRODUCTORY - i 



II. THE REQUIREMENTS OF PLANTS - .... 19 



III. THE CONSTITUTION OF THE SOIL- - - 52 



IV. THE CARBON AND NITROGEN CYCLES IN THE SOIL - 80 

 V. THE BIOLOGICAL CONDITIONS IN THE SOIL - - 104 



VI. THE RELATIONSHIP BETWEEN THE MICRO-ORGANIC POPULATION 



OF THE SOIL AND THE GROWTH OF PLANTS - - 117 



VII. THE SOIL IN RELATION TO PLANT GROWTH - 140 



VIII. SOIL ANALYSIS AND ITS INTERPRETATION - - 153 



APPENDIX METHODS OF SOIL ANALYSIS - 170 



A SELECTED BIBLIOGRAPHY OF PAPERS ON SOIL CONDITIONS AND 



PLANT GROWTH - - 175 



INDEX 180 



viii 



