CONTENTS 



PAGE 



INTRODUCTION ... ... . . . 1 



BASIC BESSEMER SLAG . . . .. . 2 



BASIC OPEN HEARTH SLAG 4 



ROCK OR MINERAL PHOSPHATES 8 



REVIEW OF PREVIOUS EXPERIMENTS .... 10 



REVIEW OF POT EXPERIMENTS WITH INSOLUBLE PHOSPHATES 10 



REVIEW OF FIELD EXPERIMENTS WITH ROCK PHOSPHATES . 11 



THE ESSEX EXPERIMENTS . . . . . ' . .18 



CHARACTER OF THE SOIL 18 



RAINFALL .20 



DETAILS OF EXPERIMENTS 21 



FIELD EXPERIMENTS ON BOULDER CLAY SOILS ... 22 



DISCUSSION OF THE RESULTS ON THE BOULDER CLAY SOILS 29 



FIELD EXPERIMENTS ON LONDON CLAY SOILS ... 30 



DISCUSSION OF THE RESULTS ON THE LONDON CLAY SOILS 42 



FIELD EXPERIMENTS ON CHALK SOILS .... 43 



CONCLUSIONS DRAWN FROM THE FIELD EXPERIMENTS . . 45 



THE APPLICABILITY OF THE RESULTS . . ... . 48 



AN INVESTIGATION INTO THE REASON WHY BASIC 



PHOSPHATES HAVE CAUSED INCREASED YIELDS . 49 



THE EFFECT OF PHOSPHATES ON THE BOTANICAL COMPOSI- 

 TION OF THE HERBAGE 49 



DISCUSSION OF THE RESULTS OF THE BOTANICAL ANALYSIS 59 



EFFECT OF PHOSPHATES ON THE MOISTURE CONTENT AND 



TEMPERATURE OF THE SOIL 63 



THE EFFECT OF PHOSPHATES ON THE TEXTURE OF THE SOIL 73 



