292 SOIL PHYSICS AND MANAGEMENT 



However, for immediately correcting the effect of the alkali 

 applications of from 75 to 200 pounds of potassium salts may be 

 used when they can be obtained at reasonable prices (Fig. 194). 

 Coarse stable manure is as efficient as potassium salts, and even 

 straw or green manure turned under has a very beneficial effect. 



QUESTIONS 



1. What conditions give rise to alkali soils? 



2. On what kind of lands as to topography is alkali most abundant? 



3. What is the source of the alkali salts? 



4. What is the composition of black alkali? 



5. What salts constitute the white alkali ? 



6. Note effects of black alkali upon the soil and organic matter. 



7. How many pounds of alkali in the surface foot of soil in each column 



in the table of page 282 ? 



8. How does irrigation cause a rise of alkali? 



9. What are "alkali marshes"? 



10. What is the first effect of alkali on plants ? 



11. What is the nature of the effect of alkali upon trees? 



12. Is the effect of alkali the same on all plants? 



13. What effect does alkali have on germination ? 



14. Why are shallow rooted crops more affected by alkali ? 



15. What methods are adopted for preventing evaporation? 



16. What means are taken to start crops whose young plants are very 



sensitive to alkali ? 



17. How is black alkali neutralized? 



18. What objections to removal of alkali by scraping? 



19. Why cannot alkali be washed off of land? 



20. How may the Australian salt bush be used to remove alkali ? Does 



this plant have any value? 



21. Describe the reclamation of the Utah tract. 



22. What percentage of the water applied was carried off by drainage? 



23. Why is a hardpan detrimental in removing alkali ? 



24. What is the effect of flooding on tilth? How may the condition be 



corrected ? 



25. What is the importance of reclamation of alkali lands from an economic 



standpoint? 



26. Why do alkali soils occur in humid regions? How does the alkali differ 



from that of arid regions? 



27. What is the substance that does the injury? 



28. How is corn affected by magnesium carbonate? 



29. What are the remedies to be used? 



REFERENCES 



1 Hilgard, E. W., Soils, 1906, pp. 442-43. 



'Hilgard, E. W., Report of California Station, 1894-95. 



* Op. Cit., p. 449. 

 4 Op. Cit., p. 467. 



"Dorsey, C. W., Bulletin 35, Bureau of Plant Industry, U. S. D. A., Alkali 

 Soils of the United States, 1906, pp. 174-194. 



Op. Cit., p. 157. 



