INDEX 



Absorption of nutrients l)y plants, 17 

 Abundance of bacteria in soil, 56-58 

 Acetic acid, 164 



Acids, interaction of, with minerals, 

 156-157, 160-161 

 organic, formed by bacteria, 80-81, 

 86-87 

 formed })y fungi, 80 

 formed in cellulose decomposi- 

 tion, 86-87 

 production of, by microbes, 249 

 Acrostalagmus, 32 

 Actinomyces, 35-37, 65, 66, 67 

 decomposing cellulose, 82, 87 

 Actinomyces scabies, influence of re- 

 action on, 221, 231-232 

 Activities of microbes, 42, 48-50 

 Alfalfa, nitrogen assimilation during 



decomposition of, 95-96 

 Algae, as corrosive agents, 157 



blue-green, fixation of nitrogen 



by, 106 

 green, relationship to nitrogen 



fixation, 111 

 in soil, 26, 37-38, 70-71 

 symbiosis with bacteria, 248 

 Amino acids, decomposition of, 127- 

 128, 164 

 nature of, 126-127 

 Ammonia, fate of, in soil, 128, 135 

 formation of, by microbes, 127-135 

 from amino acids, 127-128 

 from animal manure, 130, 140 

 from nitrate, 147, 150 

 from proteins, 131 

 influence of partial sterilization 



on, 225-227 

 influence of carbohydrates on, 

 132-133 



Ammonia, formation of, influence of 

 environmental conditions on, 

 134 

 influence of nitrogen content of 

 organic matter on, 96, 99, 132- 

 135, 146 

 influence of, on nitrification, 140- 



141 

 microbes concerned in formation of, 



131, 134 

 oxidation of, 136-145 

 Ammonification, 131-134 



as an index of soU fertility, 234-235 

 Amoebae, 38 

 Anaerobic bacteria, 31 

 Anaerobic decomposition of organic 



matter, 155 

 Animal products, kinds of, added to 



soil, 76 

 Animal substances, classification of, 

 76-77 

 composition of, 76-79 

 Animals, dependence of, on plants, 

 244 

 relation of microbes to, 45 

 Arid soils, 7 

 Artificial manure, 216 

 Ash of plants, 78, 79 

 Aspergillus, 30, 33 

 Atmosphere, nitrogen in, 247 

 Autotrophic bacteria, 26, 137, 156 

 Auximones, 195 



Availability of elements, microbial 

 methods of determination, 

 237-240 

 Azotohacter, 106-113 



action of, on minerals, 165 

 use of, for determining phosphorus 

 avaUabihty, 238-239 

 Azotohacter chroococcum, 24 



251 



