652 



INDEX 



Plant food, essential, 12 



in crops, 75, 154, 602 



in culture experiments, 236, 343 



in sea weed, 524 



lost from manure, 200, 546, 547 

 from plants, 549 

 from soils, 411, 413, 418, 556 

 Plant food, recovered in live-stock farm- 

 ing, 199 



retained by animals, 201 



sources and cost, commercially, 157, 517 



value, 154 



water-soluble, 141 



Plot experiments for testing soils, 569, 570 

 Potassium, 42 



Potassium chlorid and sulfate, 531 

 Potassium determination, 631 

 Potassium, from sea water, 531 



in fertilizers, 157, 517 



in plant and animal products, 154, 602 

 Potassium salts of Germany, 529 

 Potato experiments, 384, 447, 511 

 Potatoes, composition, 154, 604 



statistics, 605, 618 

 Prairie soils, 78, 82, 132, 138 

 Prefixes in chemical names, 19 

 Proportions, law of constant, 8 

 Protective agents, 536 

 Protein and proteids, 37 



Quartz, 49 



Radicle, denned, 17 



Rain, composition, 309 



Rainfall and drainage records, 309, 377, 

 413, 491, 557, 580, 582 



Rainfall averages for the United States, 

 582 



Rainfall in dry farming sections, 580, 582 



Ramsay, on composition of air, 13 



Ramsay and Cameron, on transmutation 

 of elements, n 



Rate of growth, 32 



Residual soils, 54, 126, 146, 149 



Residues of crops used in soil improve- 

 ment, 199 



Rhode Island field experiments, 266 



Rice, composition, 603 

 statistics, 619 



Rock weathering, 49 



Roman agriculture, 590 



Root crops, compositidn, 417, 604 

 in Canadian experiments, 511 

 in Rothamsted experiments, 398 



Roots and tops of legumes, composition, 

 218 



Root tubercles, composition, 215 

 size, 213 



Rotation crops grown in experiments: 



Agdell field, Rothamsted, 345 



Illinois, 453 



Louisiana, 495 



Minnesota, 499 



Ohio, 245, 256, 441 



Pennsylvania, 421 



Rotation crops, plant food required, 75 

 Rotation of crops and soil fertility, 318. 



339, 362, 389, 435, 443 

 Rotation systems, 226, 231 

 Russia, agricultural conditions, 332 



soils, 66 

 Rye, composition, 603 



statistics, 617 



Sachs, on availability of plant food, 109 

 Salt, common, 535 



defined, 20 

 Salt deposits, 53, 529 

 Sand soils, 80, 98, 100, 138, 468, 498 

 Science, defined, i 

 Scotland, soils, 63, 642 

 Seed factor in crop production, 575 

 Semiarid section, rainfall records, 331, 580, 



582 

 S6nebier's discovery of carbon fixation, 



307 



Shale, 50 



Shutt, on loss of organic matter and nitro- 

 gen, 200, 559 



Silicates in earth's crust, 47, 48 

 Silicon, 44, 46 

 Slag phosphate, 192 

 Snow, composition, 310 

 Soaps, 36 

 Sodium, 44 

 Sodium in fertilizer experiments, 364, 380, 



402, 508 

 Soil analysis, methods, 626 



classification, 54, 116 



composition, 58, 138 



depletion, 556 



by natural agencies, 61 

 Soil fertility theories, 300, 362, 366, 385 



formation, 54 



materials, 55 



provinces of the United States, 116 



samples, method of collecting, 626 



series, 116, 132 



stimulants, 45, 158, 533 



structure, 116 



surveys, 57, 77, 114, 5^7, 555 



texture, 116 



types, 55 

 Soils of Africa, 66, 67 



Canada, 103 



central states, 77, 138 



