244 FARM ARITHMETIC. 



a pound, phosphoric acid 5 cents a pound, and potash 5 

 cents a pound? 



4. A certain soil contains 4,800 pounds of nitrogen, 

 6,700 pounds of phosphoric acid, and 16,400 pounds of 

 potash in the first 8 inches. How many crops of wheat 

 would the nitrogen in this soil supply, supposing that none 

 of the nitrogen is withdrawn in any other crop or is lost, 

 and no additional nitrogen is added to the soil? How 

 many years would the phosphoric acid hold out? How 

 many the potash? 



5. If the wheat straw, two tons an acre, is annually 

 restored to this land, how many years will it take to en- 

 tirely exhaust the soil of these three elements of plant 

 food? 



6. This farmer does not permit his land to run down. 

 He uses a wheat f-ertilizer on his wheat consisting of 1,200 

 pounds of dissolved bone, 500 pounds of sulphate of am- 

 monia, and 300 pounds of muriate of potash. He uses 

 250 pounds of this mixture an .acre. State the percent- 

 ages of nitrogen, phosphoric acid, and potash in this mix- 

 ture. 



7. If 300 pounds of this mixture were used on each 

 acre, how many pounds of potential plant food would be 

 added to the soil ? 



8. When 22 bushels of wheat and one ton of straw 

 are removed how many pounds of plant food will be 

 drawn out of the soil ? 



9. How many pounds of the fertilizer mixture men- 

 tioned in Problem 6 will be required to equal the draft 

 of the wheat crop mentioned in Problem 8? 



10. The farmer decides to try a new fertilizer he finds 

 advertised. This fertilizer analysis is known as an 8-3-3, 



