CONTENTS XXV11 



Chapter XXV 



TRANSFORMATION OF MINERALS IN THE SOIL 



Nature of mineral transformation by microorganisms. Decomposition of 

 rocks and rock constituents by microorganisms. Nature of phosphorus 

 compounds in the soil. Decomposition of organic phosphorus compounds 

 by microorganisms. Transformation of insoluble tri-calcium phosphates 

 into soluble forms by microorganisms. Transformation of insoluble phos- 

 phates by inorganic and organic acids formed by microorganisms. Trans- 

 formation of potassium in the soil by microorganisms. Transformation of 

 calcium in the soil. Transformation of magnesium in the soil. Transfor- 

 mation of manganese in the soil. Transformation of zinc. Transformation 

 of iron. Transformation of aluminum in the soil. Role of minerals in 

 bacterial metabolism 644 



Chapter XXVI 



TRANSFORMATION OF ORGANIC MATTER IN THE SOIL 



Nature of soil organic matter. Decomposition of organic matter added 

 to the soil. Transformation of the various constituents of the organic 

 matter added to the soil. Evolution of carbon dioxide as an index of 

 decomposition of organic matter in the soil. Formation of ammonia 

 (and nitrate) as an index of decomposition of organic matter in the soil. 

 Formation of "humus" as an index of decomposition of organic matter 

 in the soil. Nature of soil "humus." Chemistry and classification of 

 humus compounds. Soil organic matter and the activities of microorgan- 

 isms. Carbon-nitrogen ratio in the soil 669 



Chapter XXVII 



MICROBIOLOGICAL ANALYSIS OF SOIL AS AN INDEX OF SOIL FERTILITY 



Soil fertility and microbiological activities. Methods for determining the 

 microbiological condition of the soil. Numbers of microorganisms in the 

 soil. Nitrifying capacity of the soil. Evolution of carbon dioxide. 

 Cellulose decomposing capacity of the soil. Nitrogen fixing and mannite 

 decomposing capacity of the soil. The catalytic action of the soil. Oxi- 

 dizing and reducing power of the soil 708 



Chapter XXVIII 



SOIL MICROBIOLOGICAL EQUILIBRIUM; INFLUENCE OF AIR DRYING AND PARTIAL 

 STERILIZATION UPON THE ACTIVITIES OF MICROORGANISMS IN THE SOIL 



Microbiological equilibrium in the soil. Influence of air drying of soil upon 

 the microbiological equilibrium. Influence of caustic lime upon soil 

 processes. Partial sterilization of soil. The use of heat as an agent of 

 partial sterilization. Influence of volatile antiseptics upon bacterial ac- 

 tivities in the soil. Protozoan theory. Agricere and bacteriotoxin theory. 

 Destruction of selective groups of organisms. Interrelationships of micro- 

 organisms in the soil 738 



