XIV TABLE OF CONTENTS 



PAGES 



indicators of acidity, 208 Quantitative determinations 

 of acidity, 299 Potassium nitrate method, 300 Lime- 

 water method, 301 Resume', 302. 



CHAPTER XVIII 



ALKALI SOILS 391-403 



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. 



CHAPTER XIX 



ABSORPTION OF NUTRITIVE SALTS BY AGRICULTURAL PLANTS 404-420 



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, 334 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. 



