THE PROPERTIES OF SOILS 69 



QUESTIONS AND PROBLEMS 



1. What are the different senses in which the terms heavy soil and 

 light soil are used? 



2. What are the kinds of soils most commonly found in your locality? 

 What crops are best adapted to each of these kinds of soil ? 



3. What procedure should be followed to bring a hard, cold soil into 

 good tilth ? 



4. Why will farm crops not grow in saturated soil? In periods of 

 wet weather corn leaves sometimes turn yellow; what is the explanation 

 of this fact? 



5. W T hat is the water table of a soil? 



6. Why will a fine soil retain more film water than a coarse soil ? Why 

 is a sandy soil in regions of limited rainfall classed as a wet soil ? 



7. What is the relation between frequent surface cultivation and con- 

 servation of soil moisture? and rise of capillary water? and evaporation 

 from the surface? 



8. Name the factors which determine the soil's temperature, and ex- 

 plain what you understand to be the influence of each of these factors. 

 How may the farmer use this knowledge? 



9. In what ways may the farmer encourage the development of helpful 

 soil organisms? 



10. One farmer plowed his field of clay soil immediately after a long 

 period of rainy weather ; another prepared a clay field for fall wheat, plow- 

 ing it near the close of a summer's drought. Give reasons for or against 

 these two practices. 



EXERCISES 



1. Microscopic study of soil particles. Place on a glass plate a 

 mass of soil the size of a pinhead ; add two drops of water and rub 

 with a glass rod until the fine soil pellets are broken down ; place 

 a small amount of the muddy water on a slide and examine under 

 a high-power microscope. Notice particles of different minerals as 

 shown by differences in color. Notice also masses of organic matter. 



2. Mechanical sorting of soils. 1 Select several types of soil, in- 

 cluding gravelly soil, sandy loam, peaty loam, and clay. Weigh out 

 the same quantity of each (10 or 15 grams). Using glass tubes of the 



1 Centrifugal Method of Mechanical Soil Analysis, Bulletin 24, Bureau of 

 Soils, United States Department of Agriculture. 



