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 MrN«HALS 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 josses 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. 



