308 SOIL PHYSICS AND MANAGEMENT 



14. How does the specific heat of humus compare with other substances 



found in soils? 



15. What is the effect of evaporation on temperature of soils ? 



16. Explain the effect of moisture on specific heat of soils. 



17. Give the figures in regard to the effects of windbreaks. 



18. How many heat units would be required to raise the temperature of a 



cubic foot of soil five degrees if it weighs 80 pounds, water-free, and 

 contained 20 per cent of water? Specific heat of soil, 0.21. 



19. Give conclusion of experiments of Bouyoucos in table on page 302 with 



colored sands. 



20. Try the experiment with seeds planted in different colored soils. 



21. What effect did colo r have on different seeds? Why did melons show 



lower germination ? 



22. What influence does color have on very wet soils? 



23. Explain effect of latitude on temperature of soils. 



24. Explain action of atmosphere in absorption of heat. 



25. What is the effect of slope on temperature? 



26. What part does conductivity play in temperature? 



27. Which will warm up quicker in spring, a cultivated soil or a compact 



soil? Why? 



28. Why is dry, loose chalk a poorer conductor of heat than quartz powder? 



29. Why is fine sand a poorer conductor than coarse sand? 



30. Why is wet soil a better conductor than dry? 



31. For truck crops do we need good or poor conductors? 



REFERENCES 



'Georgeson, Agricultural Science I. p. 251. 



2 Stellwaag, Wollny, Forsch. der Agricultur Physik, Vol. 5, p. 210. 



8 Bouyoucos, George J., Technical Bulletin 17, Michigan Station, 1913. An 



Investigation of Soil Temperature and Some of the Most Important 



Factors Influencing It, p. 30. 

 <Uloth, Flora, 1871, p. 185. 



"Haberlandt, F. Landw. Versuchs-Stationen. xvii, p. 104. 

 "Hall. A. D., The Soil, 1912, p. 123. 

 7 Duffi A. Wilmer, A Textbook of Physics, 1912, p. 232. 



8 Bouyoucos, G. J., (see above), p. 12. 



9 Patten, H. E. Bulletin 59, Bureau of Soils, U. S. D. A., Heat Transference in 



Soils. 1909, p. 34. 



10 Patten, H. E., (see above) , p. 27. 

 "Unpublished Data, University of Illinois. 

 "Bouyoucos, G. J., (see above), p. 31. 



u Pott. H. E., Landw. Versuchs-Stationen, xx, p. 288. 

 "Bouyoucos, G. J., (see above), p. 19. 



