SOIL 37 



3. Find the number of pounds of nitrogen, potash 

 and phosphoric acid in the cultivated soil per acre for 

 each of the four kinds of soil. 



4. If the soil is cultivated to the depth of eight 

 inches, how many pounds of each of the three fer- 

 tilizing substances per acre in each of the soils given in 

 the table? 



5. How many pounds of nitrogen, potash and 

 phosphoric acid are used, annually, per acre, by a crop 

 of 20 bu. of wheat ? In how many years will one-half 

 of all the nitrogen in clay be used up by this crop 

 feeding to the depth of eight inches ? 



6. How will this affect future crops? 



7. Work the same problem for the other soils. 



8. Use a 50 bushel corn crop per acre and work 

 problem 7. Also a 60 bu. oat crop. A 120 bu. potato 

 crop. 



9. Pupils will furnish data for similar problems. 



