TILLING SOIL 375 



soil. (3) To aerate the soil and thus sweeten and 

 warm it. (4) To destroy weeds and form a soil mulch 

 which will prevent rapid evaporation from the surface. 



Practical Exercises 

 1. Field Studies of Tillage 



Go to a field where plowing or cultivation is being 

 done. Make notes of your observations as follows: 



Free Bulletins, IT. S. Dept. of Agriculture 

 No. 306. Some Soil Problems for Practical Farmers. 



Problems 



1. How many square feet in one square yard? In 

 one acre ? 



2. If soil is cultivated to the depth of four inches, 

 how many cubic feet of cultivated soil per acre? How 

 many, if cultivated to the depth of six inches? If cul- 

 tivated to the depth of eight inches? 



3. How much more plant food is made available with 

 cultivation to the depth of eight inches than with a four- 

 inch depth of cultivation ? 



4. How many times as much available plant food 

 in soil cultivated to the depth of six inches as in soil 

 cultivated only four inches deep? 



5. If a man and team can plow one and a half acres 

 six inches deep, or two acres four inches deep in a day, 

 how much more does it cost per acre to plow land six 



