IMPORTANCE OF SOIL 



207 



Pieper and Beauchamp, Everyday Problems in Science, Unit 

 2 



Powers, Neuner, and Bruner, This Changing World, Chap. 

 15 ; Man's Control of His Embroilment, Chap. 4. 



Skilling, Tours through the World of Science, Tours 1, 2 



Van Buskirk and Smith, The Science of Everyday Life, 

 Chap. 7 



Watkins and Bedell, General Science for Today, Unit 3 



Webb and Beauchamp, Science by Observation and Experi- 

 ment, Unit 7 (part) 



Wood and Carpenter, Our Environment: Its Relation to 

 Us, Topic 4; Our Environment: How We Use and Con- 

 trol It, Topic 13 



Special references 



Loomis, Field Book of Common Rocks and Minerals 



Hawksworth, Strange Adventures of a Pebble 



Fabre, This Earth of Ours 



Small, The Boys' Book of the Earth 



Washburne, The Story of the Earth 



Fall, Science for Beginners 



Grew, The Romance of Modern Geology 



Reed, The Earth for Sam 



WHAT YOU SHOULD AIM TO ACQUIRE FROM 

 THIS STUDY 



1. Understand thoroughly the work of the various 

 agencies of erosion. 



2. Know the importance and means of protecting fer- 

 tile places from being eroded. 



3. Develop a scientific attitude toward the preserva- 

 tion of certain forest lands as a means of preventing 

 floods and excess erosion. 



TEST OF MASTERY OF THE TOPIC 



In your notebook complete the statements, answer the 

 questions, and comply with the instructions. 



1. Running water causes 



2. Plants change into soil by growing in of the 



rock. 



3. Water erodes rock in two ways: by 



_ it. 



it and by 



4. When water falls to the earth from the clouds what 

 three things may happen to it? 



5. When water freezes it and helps to rocks. 



6. Heating causes rocks to 

 them to _ 



while cooling causes 



Select the word or group of words which most satis- 

 factorily completes each of the following statements. 



7. The wearing away of rocks or soil is called 

 conservation irrigation cultivation erosion 

 sedimentation 



8. Water is an agent of erosion when it 



evaporates boils contracts freezes condenses 



9. The most common cause of erosion in desert regions is 

 wind sun plants dryness extreme temperature 



10. Glaciers consist largely of 



rocks vegetation ice sediments streams 



11. Soil is protected from erosion by 



irrigation vegetation reclamation animals 

 wind 



TOPIC 3. THE IMPORTANCE OF SOIL 



SUGGESTED PROBLEMS AND QUESTIONS 



1. How are soils formed ? 



2. What are the different kinds of soil? 



3. Upon what factors does crop raising depend? 



4. How are waste lands sometimes reclaimed by 

 irrigation and drainage? 



5. How is soil fertility maintained? 



SUGGESTIONS AND HELPS FOR STUDY 



1. Carefully read and study the problems listed 

 above. 



2. Proceed to the study of the problems, securing 

 material from your textbooks and other reference 

 works. 



3. Much of your knowledge of this topic will have 

 to be obtained from books. However, a number of 

 texts listed for reference in this topic suggest some 

 interesting experiments for certain phases of the 

 work. Do as many of these as you can. 



4. If you are living in or near a rural community 

 you may be able to find materials for many of the 



problems by personal observation and investigation. 

 5. Study the definitions of the following words. 



legume a plant such as the pea or bean, bearing pods. 

 nodules thickened knots or lumps on roots of le- 

 gumes. 

 hittmis decayed vegetable matter. 



EXPERIMENTS OR DEMONSTRATIONS WHICH WILL 

 HELP ANSWER THE PROBLEM QUESTION'S 1 



Experiment 129. What are the different kinds of soil? 

 Collect samples of soil from different places (field, hill- 

 side, pasture, woods, etc.). Keep the samples tightly closed 

 in a tin can or jar until you are ready to examine them. 

 After you have examined them carefully, make a table in 

 your notebook and record facts about the samples. In the 

 table, use these headings : source of soil, coarse or fine, 

 color, dry or moist, amount of humus. 



Experiment 130. What enables water to rise in soils? 



Obtain some capillary (hair-like) tubes of different diam- 

 eters. Arrange them in a dish from the largest to the small- 

 est diameter as shown in Figure 334. Pour water, colored 

 with ink, into the dish until the water level is above the 



1 See workbook, p. 75. 



