8 



FARM ARITHMETIC. 



16. Determine number of pounds of plant food an 

 average crop of cotton removes from the soil when the 

 yield of cotton lint is 165 pounds and cottonseed 330 

 pounds an acre. 



17. Determine number of pounds of plant food the 

 average oat crop removes from the soil when yield is 28.6 

 bushels and 2,400 pounds straw an acre. 



Important truth. These problems show how the soil 

 is depleted when various crops, including cottonseed, 

 corn stover and straw, are sold or otherwise not returned 

 to the land. 



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BEEF MILK BUTTER WHEAT 



Dairy Farming Helps the Land. 

 In the sketch are shown the amounts of nitrogen, phosphorus and potassium 

 removed from the land when 1,000 pounds each of beef, milk, butter and wheat 

 are sold. 



18. How many bushels of w^heat an acre has been 



grown when 36 pounds of nitrogen are removed by the 



grain from the soil? 



Solution: Wheat grain is 2..39^f nitrogen; therefore 2.3% of 

 the nuinber of pounds of wheat per acre must equal 36, i. e. : 



2.3% = 36 



1% = 15 



100% = 1.500 Pounds an acre, or 



1500 ^ 60 = 25 Bushels an acre. 



This amounts to dividing 36 by 2.3 and multiplying the re- 

 sult by 100, which is the same as dividing 36 by .023. 



19. In problem 18, suppose the 36 pounds to be the 



