CONTENTS 



PART I. THE NEED FOR FERTILIZERS. 



SECTION I. PLANT GROWTH WITHOUT 

 FERTILIZERS. 



PAGE 



The necessity of air for plant vigour ....... I 



The water needed by plants . 3 



The soil conditions suited to the growth of plants 5 



References ............ 8 



SECTION II. THE INCREASE OF CROPS 

 BY THE USE OF FERTILIZERS. 



Crop stimulation with nitrogen 9 



Root growth with phosphorus . . . . . . . .12 



Leaf development with potassium 19 



References ............ 21 



PART II. THE SOURCES OF FERTILIZERS. 



SECTION I. MINERAL DEPOSITS OF 

 FERTILIZERS. 



Nitrates of soda and potash .... .... 22 



Rock phosphates ........... 27 



Potash mines ........... 40 



Limestone formations . . . . ... . . . 43 



Gypsum 45 



References 46 



SECTION II. FUEL BY-PRODUCTS. 



Ammonia ............ 48 



Gas lime ............ 54 



Soot 57 



References 59 



