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SOILLESS GARDENING by W. F. GERICKE PUTNAM LONDON 42 Great Russell Street, W. C. I. THIS BOOK IS DEDICATED TO MY W1FK WHOSE UNFALTERING FAITH IN THE ULTIMATE REALIZATION OF CROP PRO DUCTION WITHOUT SOIL WAS A GREAT HELP IN ESTABLISHING HYDROPONICS. HYDROPONICS was really the second name to be applied to the science of soilless gardening. The first was aquicul ture, chosen because of its analogy to agriculture. Later it was found that this word had already been used in another connection and so could not be employed again. Hydro ponics was then selected because of its parallel relationship with geoponics, the Greek word meaning earth working, or, literally, agriculture. Hydroponics can now be carried on without restriction by anyone who desires to do so. But scientific research on the sub ject must be safeguarded, the public must be protected from exploitation, and business interests must assume the responsi bility for the development of the science. My own wishes are that research and educational institutions shall profit from the growth of hydroponics, that I shall be free to conduct research and teach the new subject, without being responsible for busi ness development except in an advisory capacity where this is needed. Those private individuals who gave of their private funds to test the validity of new ideas, and who provided the laboratory of practice wherein the dross of impracticability was removed from the hydroponic theory, have earned the utmost considera tion. They deserve the right to be consulted before any publi cation is made of results obtained in their plants. It is a pleasure to acknowledge here the cooperation and aid given the development of hydroponics by theestablishment of plants by Vetterle and Reinelt, Frank L. Lyons and E. W. Brundin, the California Packing Corporation, George O. Brehm, Martha Jane Dawson, Carl Gericke, Max B. Miller, Donald French, Pan American Airways, Inc., and E. O. Freund. vii viii Preface I am indebted to the Parafline Companies, Inc., for providing the asphalt-paper basins to California Redwood Association for the wooden basins to Pacific Portland Cement for the con crete basins. These were donated to me for experimental pur poses, and each material was the first of its kind used for soilless crop production. Nurseries provided planting stock. I am indebted to Vet terle and Reinelt, George C. Rocding, John Armstrong, and Jan de Graaf for their encouragement to hydroponics with lib eral donations of materials. The good wishes of a host of scientists who have followed the development since its first announcement in 1929 have been a great inspiration, and among these I especially wish to mention Dr. B. E. Livingston. W. F. GKRICKE. CHAPTER PAGE PREFACE vii 1. INTRODUCTION i Social implications . . 5 The cycle of conservation 6 Water culture 7 Molecules and ions 9 Knops formula 10 Plant physiology 10 Hydroponics 14 Development of hydroponic technique 17 2. APPARATUS 20 Hydroponic basins 20 Depth of the basin 21 Area of the basins 23 Search for suitable materials 23 The use of concrete 25 Sheet metal 26 Wooden basins 28 Other basin materials 29 Basins to hold plants for display 29 Seedbeds 30 Construction of seedbeds 31 Seedbed dimensions 33 Hints on construction 33 Water capacity 35 Faults of wet seedbeds 36 Dry seedbeds 37 Choice of seedbed materials 37 Nutritive action of the seedbed 38 Use of soil beds 39 Decayof seedbeds 39 3. NUTRIENT SOLUTIONS 43 Sources of plant food 43 Sources of chemicals 43 ix x Contents I H AFTER PAGE 3. NUTRIENT SOLUTIONS Cont. Cost of chemicals 46 Distribution of complete mixtures 46 The nutrient solution 47 Testing for nitrogen and phosphorus 51 The basic formula 52 Three-salt combinations 55 Preparing the mixture 56 Distributing plant food 58 Reactions 60 The pH scale Go Satisfactory range of pH . 61 Determining the pH 62 Buffer action of carbonates 63 4...