INTRODUCTION.
The purpose of this volume is to give the broad outlines of our present knowledge of the relationships of the population of living organisms in the soil to one another and to the surface vegetation. It is shown that there is a close relationship with vegetation, the soil population being dependent almost entirely on the growing plant for energy material, while the plant is equally dependent on the activities of the soil population for removing the residues of previous generations of plants and for the continued production in the soil of simple materials, such as nitrates, which are necessary to its growth. It is also shown, however, that the soil population takes toll of the plant nutrients and that some of its members may directly injure the growing plant.
The soil population is so complex that it manifestly cannot be dealt with as a whole in any detail by any one person, and at the same time it plays so important a part in the soil economy that it must be seriously studied. Team work therefore becomes indispensable, and fortunately this has been rendered possible at Rothamsted.
Each group of organisms is here dealt with by the person primarily responsible for that particular section of the work. The plan of the book has been carefully discussed by all the authors, and the subject matter has already been presented in a course of lectures given at University College, London, under the auspices of the Botanical Board of Studies of the London University. The interest shown in these lectures leads us to hope that the subject may appeal to a wider public, and above all to some of the younger investigators in biological science. They will find it bristling with big scientific problems, and those who pursue it have the satisfaction, which increases as the years pass by, of knowing that their work is not only of interest to themselves, but of great importance in ministering to the intellectual and material needs of the whole community.
CONTENTS.
| CHAP. | PAGE | |
|---|---|---|
| I. | Development of the Idea of a Soil Population | [1] |
| Sir E. John Russell, F.R.S., Director. | ||
| II. | Occurrence of Bacteria in Soil—Activities connected with the Acquirement of Energy | [20] |
| H. G. Thornton, B.A., Head of the Department of Bacteriology. | ||
| III. | Conditions affecting Bacterial Activities in the Soil—Activities connected with theIntake of Protein Building Materials | [39] |
| H. G. Thornton, B.A., Head of the Department of Bacteriology. | ||
| IV. | Protozoa of the Soil, I. | [66] |
| D. W. Cutler, M.A., Head of the Department of Protozoology. | ||
| V. | Protozoa of the Soil, II. | [77] |
| D. W. Cutler, M.A., Head of the Department of Protozoology. | ||
| VI. | Soil Algæ | [99] |
| B. Muriel Bristol, D.Sc., Algologist. | ||
| VII. | Soil Fungi—The Occurrence of Fungi in the Soil | [118] |
| W. B. Brierley, D.Sc., Head of the Department of Mycology. | ||
| VIII. | Soil Fungi—The Life of Fungi in the Soil | [131] |
| W. B. Brierley, D.Sc., Head of the Department of Mycology. | ||
| IX. | The Invertebrate Fauna of the Soil (other than Protozoa) | [147] |
| A. D. Imms, D.Sc., Head of the Department of Entomology. | ||
| X. | The Chemical Activities of the Soil Population and their Relation to the GrowingPlant | [164] |
| Sir E. John Russell, F.R.S., Director. | ||
| Index | [181] |
CHAPTER I.
THE DEVELOPMENT OF THE IDEA OF A SOIL POPULATION.
From the earliest times agriculturists have been familiar with the idea that decomposition of vegetable and animal matter takes place in the soil, and that the process is intimately connected with soil fertility.
By the middle of the nineteenth century three different ways were known in which the decomposition occurred. One had been since early times specially associated with soil fertility, in that it gave rise to humus, the black sticky substance in farmyard manure or in soil—which was supposed up to 1840 to be the special food of plants. No good account of the process or of the conditions in which it occurred is, however, given by the older writers.
A second resulted in the formation of nitrates. This process became known as nitrification: it was described by Georgius Agricola (1494-1555) in his book “De Re Metallica,” and it was of great importance in the seventeenth and eighteenth centuries, because it was used for the manufacture of gunpowder in the great wars of that period. The conditions for the making of successful nitre beds were so thoroughly investigated that little fresh knowledge was added to that of 1770[A] until quite recently. This process, however, was not usually associated with soil fertility, although both Glauber (1656) and Mayow (1674) had insisted on the connection.