The Bulletin 83 



sufficient for the most profitable yield of cotton on this soil, when used 

 in counection with the regular quantities of nitrogen and phosphoric 

 acid employed in the mixtures. The largest average increase in yield of 

 cotton, as well as the greatest profit, was obtained from the plats receiv- 

 ing the normal quantity of potash, which was 3.3 per cent in the mix- 

 ture, or 10 pounds to the acre. This quantity is supplied by 50 pounds 

 of 20 per cent manure salt. 



Effect of Varying Quantities of Fertilizer. — The results of the ex- 

 periments show the effect of increasing and decreasing the normal 

 (N P K equals 400 pounds of a fertilizer mixture containing 7 per cent 



Fig. XI. Relative residual effects of applications of phoiphoiic acid and nitroseii on rye 

 sown in 1911 in cotton after the first picking on Field B of the Iredell Farm. 



phosphoric acid, 21/4 per cent potash and S^A per cent nitrogen) fer- 

 tilizer application on the yields. The applications were at the rate of 

 200 pounds per acre (1/2 I^ P K) ; 400 pounds per acre, N P K; 600 

 pounds per acre (iVo JST P K) ; 800 pounds per acre (2 JST P K) ; 

 1,000 pounds per acre (2V2 N P K). The results on the several fields 

 and the averages of the three fields are quite uniform in showing in- 

 creased yields and increased profits for the several increases in the 

 amounts of fertilizer, the quantity of fertilizer per acre varying from 

 200 to 1,000 ])ounds. The largest yield, as well as the greatest profit, 

 were obtained from the 1,000-pound application. It is possible that 

 the limit of the most profitable fertilization for cotton on this soil has 

 not been reached, and that more than 1,000 pounds per acre would 

 give remunerative returns. Additional experiments have been put out 

 to test this, the quantity running up to 1,800 pounds per acre. 



In addition to larger profits from heavy fertilization of the right 

 •kind, the land is in all probability improving in productiveness and 

 value. Results on these plats and fields in after years will be most 

 valuable in throAving light on this most important phase of the proper 

 fertilization for immediate returns and for the permanent improve- 

 ment of the soil. This latter phase of farm practice is not given the 

 thought and consideration it should receive by most farmers. 



