The Bulletin 69 



433.5 pounds of seed cotton, worth $16.63 for the fertilizer application 

 containing one-half normal (5 pounds of nitrogen per acre) quantity of 

 nitrogen; 524.6 pounds, worth $19.57 for the fertilizer containing nor- 

 mal (10 pounds nitrogen per acre) quantity per acre; 589.4 pounds, 

 worth $20.17 for the fertilizer with twice normal (20 pounds nitrogen 

 per acre) quantity nitrogen; and 616.8 pounds, worth $19.10 for the 

 mixture containing three times normal (30 pounds nitrogen per acre) 

 quantity of nitrogen with nomial amounts of phosphoric acid and 

 potash. 



These results indicate that nitrogen is not the most important or con- 

 trolling constituent for the production of cotton on this soil and that 

 the most profitable quantity of nitrogen to use per acre lies between 10 

 and 20 pounds per acre. 



Effect of Varying Quantities of Phosphoric Acid. — This part of the 

 experiment was planned to show the effect on the yields of seed cotton 

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

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

 phoric acid was applied, or an amount represented by 87.5 pounds of 

 16 per cent acid phosphate and equivalent to 6.5 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 350 and 

 525 pounds of 16 per cent acid phosphate respectively, or 56 and 84 

 pounds of phosphoric acid per acre. The yields show good profits for 

 all of the fertilizer mixtures. In Field A the largest yield and greatest 

 profit per acre was secured on an average from the plat receiving three 

 times normal (525 pounds of 16 per cent acid phosphate carrying 84 

 pounds of phosphoric acid) phosphoric acid, while in Field B the plat 

 to which a twice normal (350 pounds of 16 per cent acid phosphate 

 carrying 56 pounds of phosphoric acid) application of phosphoric acid 

 with normal amounts of nitrogen and potash gave a slightly increased 

 yield and profit over the plat receiving three times normal (N P3 K) 

 phosphoric acid. HoAvever, as an average of all the tests on both fields 

 there was a slightly greater profit over cost of fertilizer in favor of the 

 heavy CN P3 K) application. 



The results on both of the fields, as well as the averages, show that 

 the normal application (175 pounds of 3 6 per cent acid phosphate car- 

 rying 28 pounds of phosphoric acid per acre) is not sufficient phosphoric 

 acid in this soil for most profitable returns per acre with cotton. 



By increasing the phosphoric acid application, with normal quanti- 

 ties of nitrogen and potash present, from 14 pounds to 28 pounds per 

 acre each pound of phosphoric acid added yielded a profit of about 16 

 cents for each pound of the increase increasing from 28 pounds to 56 

 •pounds per acre each gave a profit of 23.5 cents per pound increase 

 while increasing from 56 to 84 pounds of phosphoric acid per acre only 

 gave an increase of a little less than 5.7 cents per pound for each pound 

 of the 28 pounds of increase in phosphoric acid. 



Effect of Varying Quantities of Potash. — This portion of the experi- 

 ments was arranged to show the effect on the yield of seed cotton of 

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

 ing constant. On one plat only one-half the normal quantity of potash 

 was applied, or 1.8 per cent in the fertilizer mixture, or 5 pounds of 



