The Bulletin 



87 



three fields, the average annual increase for two years in Field A being 

 21 bushels; for four years in Field B 15.2 bushels of corn per acre; and 

 for one year in Field C 12.5 bushels, or an avei'age for the seven years 

 in the three fields of 16.5 bushels, worth $11.92 over cost of fertilizer 

 on basis of corn alone, or $17 on basis of corn and stover. From this 

 it is seen that potash added to phosphoric acid has increased the yield 

 of corn 10.3 bushels more than phosphoric acid alone, at a profit of 

 $8.01 over cost of fertilizer, showing that potash was effective in corn 

 production on this soil when used in connection with phosphoric acid, 

 but valueless when used alone. 



Nitrogen, Phosphoric Acid and Potash, IST P K (Plats 8, 10^, and 6). 

 When all three of the fertilizer materials Avere used together to make a 



Fig. XII. Corn in 1911 on Field B at the Iredell Farm. Complete fertilizer on left. 

 Yield of grain was 127 times as great on Plat 15 (NPK) as on Plat 14 (O). 



complete fertilizer, increased yields were obtained on all three plats 

 in the three fields, the average annual increase for two years in Field 

 A being 21.9 bushels; for four years in Field B 17.8 bushels of corn 

 per acre ; and for one year in Field C 18.7 bushels, or an annual average 

 increase for the seven years in the three fields of 19.1 bushels, worth 

 $11.92 over cost of fertilizer on basis of corn alone, or $17.27 on basis 

 of corn and stover. 



When compared with each other these results show that nitrogen 

 added to phosphoric acid, potash added to phosyjhoric acid, and nitrogen 

 and potash added to phosphoric acid have yielded practically the same 

 profits, though nitrogen and phosphoric acid have produced largest 

 average increased yields over unfertilized plats (18.8 bushels per acre), 

 than phosphoric acid and potash (36.5 bushels per acre), and nitrogen, 

 phosphoric acid and potash were larger than either of the other two 



