Contents xV 



CHAPTER XXIV 



Pages 



GREEN-MANURING : 237-264 



Green-manures and humus in the soil Leguminous 

 green-manures and nitrogen in the soil Green- 

 manures on sandy soils The cowpea, soybean, sand 

 vetch, crimson clover and velvet bean Green-manures 

 on loams and clay soils Leguminous green-manures and 

 the succeeding crops. 



CHAPTER XXV 



FALLOWING 265-274 



Fallow crops Fallow and cropped soils Moisture and 

 fallows Aeration and fallows Fallowing and plant- 

 food Bare fallows and nitrogen in the soil. 



CHAPTER XXVI 



SOIL BACTERIA IN RELATION TO MINERALS IN THE SOIL . . 275-302 

 Soil bacteria in relation to lime and magnesia The 

 causes of the migration of lime and magnesia The 

 liming of soils The losses of lime The importance of 

 lime Bacterial activities and lime. Soil bacteria in re- 

 lation to phosphates and other compounds of phosphorus 

 Bacterial activities and phosphorus Bacterial activi- 

 ties and phosphate fertilizers Ground bone The effect 

 of using sulfuric acid Thomas slag Other sources of 

 phosphoric acid. Activities of soil bacteria in relation to 

 potash Potash and the weathering process Lime as an 

 indirect source of potash Humus in relation to soil- 

 potash Organic acids and the decomposition of rock 

 fragments Potash salts and bacteria. Bacteria in rela- 

 tion to sulfur Sulfuretted hydrogen Sulfate of lime 

 The work of bacteria Sulfur and bacterial development. 

 Bacteria in relation to iron Iron rust and bacteria The 

 importance of iron bacteria Iron in the soil and decay 

 bacteria Influence of iron on bacteria. 



