172 CHEMISTRY OF FARM PRACTICE 



tilizer when a portion is used under the crop and the remainder 

 as a side application or topdressing. 



PROBLEM: Suppose that 500 pounds of a 3-8-3 mix- 

 ture is applied to corn land before the crop is planted, 200 

 pounds of 7-5-5 mixture is applied at the time of the second 

 cultivation of the crop, and that 100 pounds of nitrate of 

 soda is applied when the plants are about 4 feet tall, what 

 percentages and what composition will the entire fertilization 

 give? 



This is a different application of the principles given 

 under (1); however, the same type will serve as an illus- 

 tration. The calculation shows that the entire application is 

 800 pounds of fertilizer analyzing nitrogen equivalent to 

 5.88 per cent of ammonia, 6.25 per cent phosphoric acid, 

 and 3.13 per cent of water-soluble potash. 



(6) To convert fertilizers from one formula to another. 



PROBLEM : Convert a 4-8-4 fertilizer to a 3-9-2 formula, 

 using dried ground fish, 10 per cent ammonia and 6 per 

 cent available phosphoric acid, and 16 per cent acid phos- 

 phate. Calculate the number of pounds of each of these 

 materials and of filler. An inspection of the two formulas 

 shows that the greatest difference is in the potash content 

 of the two formulas, hence the potash content of the 4-8-4 

 fertilizer will limit the number of pounds that can be used. 

 A ton of 4-8-4 fertilizer contains 80 pounds of potash, while 

 a ton of 3-9-2 fertilizer contains only 40 pounds of potash, 

 therefore 1000 pounds of the 4-8-4 fertilizer can be used. 

 This leaves 20 pounds of nitrogen and 100 pounds of phos- 

 phoric acid to be furnished by dried ground fish and acid 

 phosphate. The nitrogen is the smallest amount and should 

 be supplied first because the dried ground fish also furnishes 

 some phosphorus, which must be deducted from the balance 

 to be furnished before the amount of acid phosphate is cal- 

 culated. Twenty pounds of nitrogen is furnished by 200 

 pounds of dried ground fish analyzing nitrogen equivalent 

 to 10 per cent of ammonia, 6 per cent or 12 pounds of phos- 



