XVI 



TABLE OF CONTENTS 



Treatment of Soils with Volatile Antiseptics and Heat. 



Effects of carbon bisulfide and heat on properties of 

 soils, 385 Hypotheses to account for effects of carbon 

 bisulfide and of heat, 386 Koch's theory, 387 Hiltner 

 and Stormer's theory, 388 Russell and Hutchinson's 

 theory, 389 Greig-Smith's theory, 390. 



CHAPTER XXII 



THE SOIL AIR 475-488 



Factors that Determine Volume. 



Texture, 391 Structure, 392 Organic matter, 393 

 Moisture content, 394. 

 Composition of Soil Air. 



Analyses of soil air, 395 Sources of carbon dioxide 

 in soil air, 396 Production of carbon dioxide as affect- 

 ing composition, 397. 

 Functions of Soil Air. 



Oxygen, 398 Carbon dioxide, 399. 

 Movement of Soil Air. 



Diffusion of gases, 400 Movement of water, 401 

 Changes in atmospheric pressure, 402 Changes of tem- 

 perature in atmosphere or in soil, 403 Suction produced 

 by wind, 404. 



Methods for Modifying the Volume and Movement of 

 Soil Air. 



Tillage, 405 Manures, 406 Underdrainage, 407 

 Irrigation, 408 Cropping, 409. 



CHAPTER XXIII 

 COMMERCIAL FERTILIZERS 489-533 



Early ideas of the function of manures, 410 Devel- 

 opment of the idea of the nutrient function of manures, 

 411 Classes of manures, 412 Commercial fertilizers, 

 413 Fertilizer constituents, 414. 

 Fertilizers Used for their Nitrogen. 



Forms in which nitrogen exists in soils, 415 Forms 

 in which nitrogen is absorbed by plants, 416 Use of 

 nitrates by plants, 417 Ammonia as a plant food, 418 



