INDEX 



761 



Plant nutrients, absorption of, 404. 

 Plant roots in soil, 424. 

 Plant roots, solvent action, 405. 

 Plants, absorptive power, 412. 



acid in juices, 379. 



available water for, 261. 



composition of, 128. 



effept of alkali on, 394. 



effect on availability of phosphorus, 

 518. 



effect on granulation, 192. 



indicating an acid soil, 382. 



requirements for growth, 3. 



soil-forming agents, 18. 



soil shelters, 287. 



succession on soil, 1. 



utilize simple and complex material, 



water requirements of, 244. 

 Plasticity, causes of, 172, 

 Plasticity, defined, 170. 

 Plow attachments, 671. 



effect on granulation, 195. 



hillside, 670. 



as tillage implement, 666. 



subsoil, 672. 



sale of, 670. 

 Plowing, correct position of furrow, 668. 



depth, 669. 



fall, relation to dry-farming, 713- 



under manure, 608. 

 Poncelet's formula, 652. 

 Pore space in spherical particles, 109. 



in soil, 115. 



in soil, calculation, 116. 

 Porosity and diffusion of gases, 483. 

 Positive acidity, 375. 

 Potassium in soils, 4, 6. 



absorption of, 358. 



chloride, 523. 



effects on plant growth, 551. 



effect on toxic material, 137. 



fertilizers, 522. 



nitrate test for acidity, 388, 389. 



soil separates content, 101, 



solubility, 339. 



sulfate, 523. 

 Poultry manure, composition, 582, 588. 

 Pressure, atmospheric, affects soil air, 



484. 

 Properties of soil separates, 98, 99, 101. 

 Protein decay, 447. . 

 Proteins in soil, 127. 

 Protozoa, relation to soil productive- 

 ness, 471. 

 Province, the, in soil classification, 723. 



Puddled soil, 110. 



Pulverizing action of plow, 195, 665. 

 Putrefaction and decay, 443. 

 Putrefaction, products of, 445. 



Quartz, mineral, 9. 

 Quartz, specific heat, 299. 

 Quartz, in soil separates, 99. 

 Quartzite, 6. 

 Quicklime, 539. 



Quicksand, management in drainage, 

 660. 



Radiation, effect of moisture, 305. 



Radiation from soil, 302. 



Rainfall, distribution in world, 683, 686. 



effect on soil ventilation, 483. 



relation to irrigation, 682. 

 Raw rock phosphate, 512. 

 Reclamation service of the United 



States, 688, 690. 

 Reconnoissance soil surveys, 737. 

 Reduction of nitrates, 455. 

 Reinforcement of manure, 609. 

 Residual effects of manure, 614. 

 Residual soils, colors, 33. 



characters of, 32. 



composition of, QQ. 



defined, 31. 



distribution of, 34. 



origin of, 31. 

 Resinous material in soil, 275. 

 Reverted phosphate, 515. 

 Ridge tillage versus level, 287. 

 Riparian rights, modified under irriga- 

 tion, 691. 

 Ripening and moisture, 253. 

 Rodents in soil, 421. 

 Rock flour, 68. 

 Rock rot, 68. 

 Rock-forming minerals, 8. 

 Rock, definition of, 7. 

 Rocks, acid, 7. 



basic, 7. 



classification of, 6. 



coefficients of expansion, 17. 



decay agencies of, 14. 



law of decay, 24. 



soil-forming, 6. 



solubility in sodium carbonate, 26. 



weathering of, 13. 

 Rolling and moisture control, 284. 

 Roller as soil pulverizer, 679. 

 Root crops, feeding power, 415. 

 Root-hairs and food absorption, 404. 

 Root-hairs, relation to soil particles, 405, 



