xiv CONTENTS 



PAGES 



Nitrogen 173 



Rothamsted Rotation 174 



Nitrogen Obtained from Atmosphere by Legumes 175 



Distribution of Nitrogen in Legumes 176 



Legumes Feed on Nitrates 177 



Nitrification in Soil 178 



How Maintain Soil Nitrogen 180 



CHAPTER XVII 



Cellulose Fermentation 



What is Cellulose? 182 



Cellulose in Soil , 183 



Early Observations 184 



Discovery of the Organisms 185 



Products 186 



Function 187 



CHAPTER XVIII 



Influence of Soil Alkali on Bacteria 



Kinds of Alkali 191 



Kind and Number of Microorganisms in Alkali Soil 191 



Stimulation of Bacteria by Alkali 192 



Toxicity of Alkali Salts 194 



Variation in Toxicity 195 



Antagonism 195 



iHov^ to Overcome Poisonous Action 197 



Neutralizing Salt 197 



Removing tkt Salt 198 



v^/JrlriJL J. JiK. .A.1A. 



Influence of Heat and Poisons on Soil Bacteria 



Heat 200 



Antiseptics 202 



How Account for These Conditions 203 



Metallic Poisons 206 



Ammoniiiers 206 



Nitrification 207 



Nitrogen Fixation 207 



How does the Arsenic Act? 208 



