TABLE OF CONTENTS xiii 



CHAPTER XVI 



PAGES 



The Absorptive Properties of Soils .... 349-374 

 Substitution of bases, 251 — Time required for absorp- 

 tion, 252 — Insolubility of certain absorbed substances, 

 253 — Influence of size of particle, 254 — Causes of ab- 

 sorption, 255 — Zeolites, 256 — Chabazite, 257 — Pres- 

 ence of zeolites questioned, 258 — Absorption of phos- 

 phoric acid, 251) — Formation of insoluble phosphates, 

 260 — Absorption, 261 — Absorption by colloids, 262 — 

 Absorptive properties of colloidal matter, 263 — Selective 

 absorption, 264 — Absorptive power of colloidal silicates, 

 265 — Absorption by colloids versus absorption by zeo- 

 lites, 266 — Absorption by organic matter, 267 — Ab- 

 sorption of water vapor and of gases by soils, 268 — 

 Absorption of ammonia, 269 — Absorption of carbon 

 dioxide, 270 — Absorption of nitrogen and oxygen, 271 



— Relation of temperature to gas absorption, 272 — 

 Relation of absorptive capacity to productiveness, 273 



— Absorption as related to drainage, 274 — Substances 

 usually carried in drainage water, 275 — Drainage rec- 

 ords at Rothamsted, 276 — Drainage records at Brom- 

 berg, 277 — Losses of nitrogen and calcium, 278 — 

 Composition of surface water, 279. 



CHAPTER XVII 



Acid or Sour Soils 376-390 



Nature of soil acidity, 280 — Positive acidity, 281 — 

 Negative acidity, 282 — Production of sour soils, 283 — 

 Removal of bases by drainage as a cause for acidity, 284 



— Removal of bases by plants, 285 — Effect of green 

 manures on acidity, 286 — Effect of fertilizers on soil 

 acidity, 287 — Acidity in relation to climate and to for- 

 mation of soil, 288 — Weeds that nourish on sour soils, 

 289 — Crops adapted to sour soils, 290 — Crops that are 

 injured by acid soils, 291 — Qualitative tests for acidity, 

 292 — Litmus paper test, 293 — Ammonia test, 294 — 

 Zinc sulfide test, 295 — Litmus paper and potassium 

 nitrate, 296 — Acid test for carbonates, 297 — Plants as 



