760 



INDEX 



Organic matter, effect on nitrification, 

 449. 



effect on phosphates, 520. 



effects on soil, 150. 



effect on soil bacteria, 435. 



efficiency of fertilizer, 569. 



estimation of, 141. 



losses in digesting food, 597. 



maintenance in soil, 151. 



relation to air in soil, 476. 



soil content, 126. 



soils of U. S. content, 146. 



source of carbon dioxide, 479. 



specific heat relations, 297. 

 Organic nitrogen, plant food, 497. 

 Organisms in soil, 421. 



effect of heat on, 289. 



effect of drainage on, 632. 



macro- in soil, 421. 



micro- in soil, 424. 

 Orthoclase mineral, 9. 



solubility of, 338. 



weathering of, 22. 

 Osmotic activity of plant roots, 412. 

 Outlets to the drains, 656. 

 Oxbows, 40. 



Oxidation and soil fertility, 137. 

 Oxidation as weathering agent, 19. 

 Oxidation of sulfur in soil, 525. 

 Oxygen, 4, 6. 



Oxygen, absorption of, 367. 

 Oxygen, effect on soil bacteria, 433. 

 Oxygen in soil, air functions, 480. 

 Oxygen in soil, relation to carbon dioxide, 

 479. 



Packers and crushers, 678. 

 Packer, sub-surface, 679. 

 Partial solution of soil, 329, 331. 

 Particles, in soil, chemical composition, 

 101. 



in soil, mineral composition, 99, 



in soil, physical character, 98. 



of soil, classification, 95. 



of soil, number, 118. 



surface exposed in soil by, 120. 

 Peas, materials used as food, 496. 

 Peat, defined, 36. 

 Peat, nitrogen compounds in, 133. 

 Peat, specific gravity of, 113. 

 PenidUium glaucum in soil, 427. 

 Percolation of water, 233. 



effect of pressure on, 233. 



effect of texture and structure on, 

 235. 



effect on air movement, 483. 



Percolation of water, losses from, 265. 



losses from, control, 267. 



objection to, in irrigation, 704. 



Rothamsted figures on, 266. 

 Peridotite, 8. 



Permutite, absorption by, 357. 

 Peruvian guano, 508. 

 Phillipsite, solubility, 339. 

 Phosphate, acid, to reinforce manure, 610. 



bone, early manufacture, 492. 



calcium, root action on, 406. 



effect of bacteria on, 439, 437. 



fertilizers, 511. 



fertilizers, relative availability, 516. 



insoluble, 358. 



of iron and aluminum, 337. 



row rock, to reinforce manure, 610. 



relation to carbon dioxide, 482, 



reverted, 515. 

 Phosponc acid, absorption of, 352, 357. 

 Phosphorite as fertilizer, 512. 

 Phosphorus m soil, 4, 6. 



effect on toxic material, 137. 



effects on plant growth, 549. 



in soil separates, 101. 

 Physical agencies of weathering, 14. 



absorption, 359. 



changes due to heat, 291. 



character of soil separates, 98. 



effect of organic matter, 150. 

 Piedmont soils, 34. 

 Plagioclase, 9. 



Plane table for soil survey, 727. 

 Planker, as soil pulverizer, 680. 

 Plant food, elements of, in soil, 3. 

 Plant food, deficiencies and manurial 

 needs, 334. 



distribution in liquid and solid ma- 

 nure, 586. 



elements, abundance of, 5. 



elements, essential, 417. 



elements, sources of, 4. 



appearing in manure, 597. 



in soil minerals, 101. 



in plants, 418. 



limiting elements, 4. 



proportion of feed in manure, 581. 



relation to bacteria, 428. 



relation to dilution, 332. 



shown by analysis, 330. 



supplied in sewage, 711. 

 Plant growth, effects of nitrogen, 547. 



factors for, 3, 



functions of water, 243. 



and the soil solution, 347, 



and strength of soil solution, 417. 



