xii CONTENTS. 



322. Chemical Analysis, 323. Water-Soluble and Acid-Soluble Por- 

 tions most Important, 324. We cannot Imitate Plant-root Action, 324 

 Cultural Experience the Final Test, 324. Analysis of Cultivated Soils, 

 325. Methods of Analysis, 325. The Solvent Action of Water upon 

 Soils, 327. Extraction of Soils with Pure Water, 327. Continuous 

 Solubility of Soil Ingredients. Tables, 328. King's Results. Table, 

 329. Composition and Analysis of Janesville Loam, 331. Solubility of 

 Soil Phosphates in Water, 332. Practical Conclusions from Water 

 Extraction, 332. Ascertainment of the Immediate Plant-food Require- 

 ments of Cultivated Soils by Physiological Tests, 333.- Plot Tests ; 

 their uncertainties. Diagram, 334. Crop Analysis as a Test of Soil 

 Character, 337. Chemical Tests of immediately Available Plant Food ; 

 Dyer's Method, 338. 



CHAPTER XIX. 



ANALYSIS OF VIRGIN SOILS BY EXTRACTION WITH STRONG ACIDS AND ITS 

 INTERPRETATION, 340. Loughridge's Investigation on Strength of Acid 

 and Time of Digestion, 340. Writer's Method, 342. Virgin Soils with 

 High Plant-food Percentages are always Productive. Table, 343. Dis- 

 cussion of Table, 343. Low Plant-food Percentages not always Indica- 

 tion of Sterility, 346. What are "Adequate" Percentages of Potash, 

 Lime, Phosphoric Acid and Nitrogen, 347. Soil-Dilution Experiments, 

 347. Table of Compositions, 350. Figures of Plants and their Root- 

 Development, 351. Limitation of Root Action, 351. Lowest Limits of 

 Plant-food Percentages and Productiveness Found in Virgin Soils, 353. 

 Limits of Adequacy of the Several Plant-food Percentages in Virgin 

 Soils, 353. Lime a Dominant Factor in Interpretation, 353. Potash, 

 354. Phosphoric Acid, 355. Action of Lime and Ferric Oxid, 355. 

 Table of Hawaiian Ferruginous Soils, 356. Unavailability of Ferric 

 Phosphate, 3,56. Nitrogen, 357. Nitrification of the Organic Matter 

 of the Soil, 358. Analysis of Soil from the Ten-Acre Tract at Chino, 

 Cal., 358. Experiments and Results; Matiere Noire the Only Guide, 

 360. What are Adequate Nitrogen Percentages in the Humus ? 360. 

 Table of Humus and Nitrogen-Content of California!! and Hawaiian 

 Soils, 361. Confirmatory Experiment. Figure, 362. Data for Nitrogen- 

 Adequacy. Table, 363. Influence of Lime upon Soil Fertility, 365. 

 " A Lime Country is a Rich Country," 365. Effects of High Lime-Con- 

 tent in Soils, 365. Table of Soils showing Low Phosphoric Acid with 

 High and Low Lime-Content, 366. What are Adequate Lime-percent- 

 ages? Differ for Light and Heavy Soils, 367. Table Showing Need of 

 High Lime Percentages in Heavy Clay Soils, 368. European Standards 

 for Land Estimates, 369. Maercker's Table, 369. 



CHAPTER XX. 



SOILS OF THE ARID AND HUMID REGIONS, 371. Composition of Good 



Medium Soils ; Table, 371. Criteria of Lands of the Two Regions, 371. 



-Tables of Soil-Composition in Both Regions, 372. Soils of the Humid 



Region governed by Time, 374. Soils of the Arid Region Governed 



