TlIK BULT.TCTIN. 



33 



Continued. 



4 and 11 and 5= and 14^ respectively. It has been assumed that there is a uniform increase or decrease in the 

 between checks. 



and stover. In one year in Field C twice the normal qnantity of 

 nitrogen gave the best returns, the yield of corn being 48.5 bushels, 

 and the profit $14.51 over cost of fertilizer on basis of corn alone 

 and $20.15 on basis of corn and stover. As ari average for the • 

 seven years 18 pounds of nitrogen per acre (twice the normal 

 quantity) gave the largest profits, though 27 pounds of nitrogen 

 gave slightly the largest yield of corn. 



These results emphasize the importance of nitrogen for the pro- 

 duction of corn on this soil when applied in connection with the 

 proper amount of phosphoric acid and some potash. 



The fertilizer application which gave best results in these tests 

 (Is'a P K) cost $5.44 per acre and yielded a profit of $11.50 over 

 cost of fertilizer, on basis of corn alone, or $16.70 on basis of corn 

 and stover. The average yield of corn during the seven years from 

 this fertilization was 39.8 bushels of corn per acre; the yield with- 

 out fertilizer was 15.6 bushels per acre, or an annual average in- 

 crease of 24.2 bushels per acre due to fertilizer. Without fer- 

 tilizer the land lost rapidly in productiveness, while with the larger 

 quantities of nitrogen (18 and *27 pounds per acre) there were 

 larger yields in after years than in the first year, the average for 

 the entire seven years being larger than for the first year. 



9 



