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 



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. 



• 



475-488 



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 



