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The Bulletin 



used. In Fields A and C tlie greatest increase in yield and profit per 

 acre resulted from the li P K application; and in Field B the largest 

 increase and. profit was from the N P3 K application. 



The results on all of the fields as well as the averages, show that one- 

 half the normal quantity of phosphoric acid is not sufficient for best 

 returns. The largest average increased yield of seed cotton was from 

 the heavy application of acid phosphate (525 pounds per acre) along 

 with the normal quantities of potash and nitrogen, though the largest 

 profit when cost of fertilizer is considered, was from the normal 



Fig. X. Cotton in 1906 on Plat 21 (NPK) of Field A at the Iredell Farm. Contrast with 

 growth shown in Fig. IX, where no phosphoric acid was applied. Produced almost 

 eight times as great a yield of seed cotton as the NK application. 



fertilizer application containing 200 pounds of acid phosphate. The 

 experiments are being continued according to the same plan on these 

 several fields, and the results from year to year will no doubt throw 

 additional light on this as well as other phases of the problem of the 

 best and most profitable fertilization for cotton. 



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

 periments is designed to study the effect on the yield of seed cotton of 

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

 maining 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 potash per acre, while on two other plats two and three times 

 the normal quantities were given, or 20 and 30 pounds of actual potash 

 per acre respectively. On basis of the normal fertilizer mixture this 

 would represent 5.7 and 7.5 per cent of potash in the mixture. 



The results are quite uniform in all three of the fields, indicating 

 that 1.8 per cent in the mixture, or 5 pounds of potash per acre, is not 



