The Bulletin 89 



phoric acid and potash constant, is given in the second section of Table 

 IX. In these experiments, on one plat the nitrogen was reduced to 

 one-half the normal quantity, making the application 4i/o pounds of 

 nitrogen per acre, or 2.4 per cent in the amount of fertilizer mixture 

 used; and on two of the plats it was increased by two and three times 

 the normal quantity (9 pounds per acre), making the application 18 

 and 27 pounds per acre respectively, or on the four plats 41/0, 9, 18 and 

 27 pounds of nitrogen per acre. 



The average results for two years in Field A showed the largest 

 yields and profit to have come from the application containing three 

 times the normal quantity of nitrogen, or 27 pounds nitrogen per acre, 

 the average yield of corn being 41.8 bushels per acre, and the profit 

 $14.88 over cost of fertilizer, on basis of corn alone, or $21.90 on basis 

 of corn and stover. For four years in Field B the largest profit was 

 secured from the application containing twice the normal quantity of 

 nitrogen per acre, or 18 pounds of nitrogen, the average yield being 

 38.4 bushels corn per acre, and the profit $13.04 over cost of the fertil- 

 lizer on basis of corn alone or $20.05 on basis of corn and stover. In 

 one year in Field C twice the normal quantity of nitrogen gave the best 

 returns, the yield of corn being 48.5 bushels, and the profit $17.36 over 

 cost of the fertilizer on basis of corn alone and $24.41 on basis of corn 

 and stover. As an 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 increase in yield of corn. 



These results emphasize the importance of nitrogen for the produc- 

 tion 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 

 (N'o P K) cost $5.44 per acre and yielded a profit of $13.92 over cost 

 of fertilizer, on basis of corn alone, or $20.42 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 M'ithout fertilizer was 15.6 

 bushels per acre, or an annual average increase of 24.2 bushels per acre 

 due to fertilizer. Without fertilizer the land lost rapidly in productive- 

 ness, 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. 



E-jfect of Van/ing Quantities of Phosphoric Acid. — The results under 

 this title in Table IX show the effect on yields of com and stover of 

 varying quantities of phosphoric acid, the nitrogen and potash re- 

 maining the same. On one plat one-half the nonnal quantity of phos- 

 phoric acid was applied or an amount represented by 65.5 pounds of 

 16 per cent acid phosphate and equivalent to 31/2 per cent phosphoric 

 acid in the fertilizer mixture. On two plats were applied two and 

 three times the normal quantities of phosphoric acid represented by 

 263 and 394 pounds of 16 per cent acid phosphnte respectively, or 42 

 and 63 pounds of phosphoric acid per acre. The results in all the 

 fields show increased yields and profits for all the quantities of phos- 

 phoric acid, but the largest yields, increases and profits in all the fields 

 were from the plats receiving the normal quantity of phosphoric acid 



