AGEICULTUEE FOR SOUTHERN SCHOOLS. 11 



easier to work? In what other ways does organic matter increase 

 the productiveness of soils ? 

 Lesson 9. — Germ Life in the Soil. 



1. Nature of bacteria. 



2. Relation to organic matter. 



3. Relation to nitrogen. 



4. Conditions essential to growth. 



Illustrative material : Charts showing forms of bacteria and nitrogen 

 cycle. 



Lesson 10. — Classification of Soils. 



1. Basis of classification. 



2. Characteristics of soil ingredients. 



3. Humid and arid soils. 



4. Soil surveys of United States Department of Agriculture. 

 Illustrative material : Soil-survey maps. 



Special reference: Soil surveys of Bureau of Soils, United States De- 

 partment of Agriculture. (Secure survey of county or area in w^hich 

 school is located.) 



Exercise 8. — Collection of Local Soil Types. 



Purpose: To gain practice in taking soil samples and to secure 

 material for further study. 



DireetioThs: If a soil survey has been made of the region in which 

 the school is located, the map which accompanies the report should 

 be used to determine the principal soil types of the district. If no 

 survey has been made, soils should be collected which represent gen- 

 eral types as the clay, sand, loam, and leaf mold suggested for Ex- 

 ercise 9. Students should be impressed with jfche necessity for great 

 care in taking samples which may be sent away for analysis. 



In taking samples of soil at any great depth a soil auger is neces- 

 sary. Suitable augers may be purchased, or one may be made by 

 welding a |-inch gas pipe with a cross bar to a l|-inch wood auger. 

 One yard of oilcloth will make four square pieces suitable to receive 

 the samples as they are removed from the borings. 



Borings are made by holding the auger in a vertical position, bear- 

 ing down upon it and turning until the point has penetrated the 

 ground to a depth of 2 or 3 inches. In pulling the auger out a sec- 

 tion of soil comes out in much the same condition as it existed when 

 in place. The process of boring a few inches out at a time is repeated 

 until the desired depth of 3 feet, 6 feet, or more is reached. 



To ascertain the character of and variations in the material from 

 the surface downward it is necessary to bore only a few inches at a 

 time, not to exceed 6 inches in even the lighter soils, for the reason 

 that important changes of color and other characteristics are other- 

 wise likely to be overlooked. It is very essential that all variations 

 in color, texture, and structure, and the occurrence of other proper- 

 ties within the 3-foot or 6-foot section, as the case may be, should be 



