XIV 



TABLE OF CONTENTS 



indicators of acidity, 298 — Quantitative determinations 

 of acidity, 299 — Potassium nitrate method, 300 — Lime- 

 water method, 301 — Resume, 302. 



CHAPTER XVIII 



Alkali Soils ......... 



Composition of alkali salts, 303 — White and black 

 • alkali, 304 — Effect of alkali on crops, 305 — Effect on 

 different plants, 306 — Other conditions that influence 

 the action of alkali, 307 — Accumulation of alkali, 308 — 

 Irrigation and alkali, 309 — Handling of alkali lands, 310 

 — Eradication of alkali, 311 — Leaching with under- 

 drainage, 312 — Correction with gypsum, 313 — Scraping, 

 314 — Flushing, 315 — Control of alkali, 316 — Cropping 

 with tolerant plants, 317 — Alkali spots, 318. 



391-403 



CHAPTER XIX 



Absorption of Nutritive Salts by Agricultural Plants 



How plants absorb nutrients, 319 — Relation between 



root-hairs and soil particles, 320 — Liebig and Sachs on 



solvent action of plant-roots, 321 — - Czapek's experiment, 



322 — Secretion of an oxidizing enzyme by plant-roots, 



323 — Importance of carbon dioxide as a solvent, 324 — 

 Insufficiency of carbon dioxide, 325 — The present status 

 of the question, 326 — Possible root action on colloidal 

 complexes, 327 — Why crops vary in their absorptive 

 powers, 328 — Extent of absorbing systems, 329 — Ab- 

 sorptive activity, 330 — The absorptive power of cereals, 

 331 — The feeding of grass crops, 332 — Leguminous 

 crops, 333 — Root crops, 331 — Vegetables, 335 — Fruits, 

 336 — Mineral substances absorbed by plants, 337 — Re- 

 lation of plant growth to concentration of nutrient solu- 

 tion, 338 — Quantities of plant food materials removed 

 by crops, 339 — Quantities of plant food materials con- 

 tained in soils, 340 — Possible exhaustion of mineral 

 nutrients, 341. 



404-420 



