330 AGRICULTURE 



5. Rotate the crops so as to defeat or check the de- 

 velopment of insect pests and plant diseases. Lack of 

 this has been the chief cause of the rapid advance of the 

 Mexican boll weevil in cotton territory. 



6. Rotate the crops so as to make use of all tillable 

 land every season. 



7. Rotate the crops so as to secure an even distribu- 

 tion of labor for both man and beast during the entire year. 



8. In southern territory rotate crops so as to pro- 

 vide for winter forage for live stock and cover crops to 

 prevent leaching and erosion. 



TOPICS FOR INVESTIGATION 



1. What commercial fertilizers are used in your re- 

 gion? In what form' is the fertilizer applied? What is 

 the quantity used per acre? The cost? To what extent 

 is green manuring employed ? What crops are chiefly used ? 

 What is meant by a "5-8-7" commercial fertilizer? 



2. To make the litmus-paper test for acid in soils, take 

 a small piece of blue litmus paper and place it between 

 pieces of thoroughly dampened soil, pressing the soil close 

 and leaving it in contact with the paper for five minutes. 

 If the paper turns red, the soil is acid and needs lime. 

 Secure samples of soil taken at a depth of six inches from 

 several different parts of your farm, including both upland 

 and lowland areas, and make the litmus-paper test. 



3. Draw a diagram of your home farm showing the 

 different fields. Now work out several different crop rota- 

 tions based on your principal crop, and taking into account 

 the necessity for growing some legume for improving the 

 soil. Compare with the rotations suggested by other mem- 

 bers of the class. 



