42 VEGETABLE GARDENING 



The materials to be used are: 



Nitrate of soda 15.5% nitrogen 



Dried blood 10. % nitrogen 



Tankage, 7. % nitrogen and 8. % phosphoric acid 



Acid phosphate 14. % phosphoric acid 



H. G. sulphate of potash.. .50. % potash 



The nitrogen is to come in equal quantities from each 

 of the three materials containing that element, in round 

 numbers, 23 pounds from each. 



As 100 pounds of nitrate of soda contain 15.5 pounds 

 of nitrogen, in order to find out how many pounds of 

 nitrate of soda will be required to furnish 23 pounds (one- 

 third of the 70 pounds required) we solve the proportion : 



15.5 : 23 :: 100 : X = 150 pounds, in round numbers 



The fish is also to be used in quantity sufficient to 

 furnish 23 pounds of nitrogen, and as 100 pounds of fish 

 contain 10 pounds: 



10 :23 :: 100 :X = 230 pounds 



Tankage to furnish the other pounds of nitrogen is 

 needed. As 100 pounds of tankage contain 7 pounds 

 of nitrogen: 



7 : 23 :: 100 : X = 330 pounds 



The 330 pounds of tankage supply 27 pounds of phos- 

 phoric acid. We need 160 pounds in all and must there- 

 fore use acid phosphate to furnish 133 pounds. As 100 

 pounds of acid phosphate contain 14 pounds of phos- 

 phoric acid : 



14 : 133 :: 100 : X = 950 pounds 



As 100 pounds of high-grade sulphate of potash contain 

 50 pounds of potash, and we need 200 pounds: 



50 : 200 :: 100 : X = 400 pounds 



