CONTENTS 

 PART I 



CHAPTER I 



The NoRifAL Son. and its Requirements . 3 



CHAPTER II 

 Sick Soils not Influenced by Parasites . 23 



CHAPTER III 



Soil Sickness Due to the Presence of Para- 

 sites Harmful to Plants . . -41 



CHAPTER IV 

 Methods of Treating Sick Soils ... 53 



PART II 



CHAPTER V 

 The Healthy Host and its Requirements . 63 



CHAPTER VI 



Causes of Diseases in Crops . . .71 



A. Diseases of a Mechanical Nature 



B. Diseases Due to Physiological Causes 

 c. Diseases of Unknown Origin 



