578 



Journal of Agricultural Research 



Vol. V. No. 13 



Table II. — Average yield of cotton on fields A, B, and C, with seven years' fertilization 

 at the Iredell Substation 



Average yield of seed cotton per acre. 



Field A 



(1903,1904. 



1906, and 



1909)- 



Field C 

 (1908). 



Average 

 increase 

 per acre 

 due to 

 fertilizer. 



Nitrogen 



Phosphoric acid 



Potash 



Nitrogen and phosphoric acid 



Nitrogen and potash 



Phosphoric acid and potash 



Nitrogen, phosphoric acid, and potash . 



Lime 



Lime, nitrogen, phosphoric acid, and 

 potash 



Pounds. 



210. 6 

 6 



3 

 5 



655- 

 301 



897. 

 348. 



855 



923 



97 



728. 



Pounds. 

 505-0 

 860.0 



435-0 



620. O 

 400. o 



725.0 



I, 070. o 



430.0 

 945-0 



441.8 

 85-4 



520. 1 

 96-5 



608.0 



717.7 



27.0 



573-5 



A glance at Table II will show that phosphoric acid is the limiting 

 or controlling element of plant growth for this soil. An average increase 

 for the seven years' treatment of 441 .8 pounds is obtained with phosphoric 

 acid alone, while there was an increase of only 85.4 pounds with potash 

 and no increase at all with nitrogen. Nitrogen added to phosphoric 

 acid produced but a slight increase over the latter constituent alone, 

 while potash added to phosphoric acid produced a somewhat better yield. 



Table III shows an 8-year average with cotton at the Experiment 

 Station Farm at Raleigh with typical Cecil sandy loam. 



Table III. — Average yield of cotton on fertilized fields A and B at the North Carolina 

 Experiment Station Farm, Raleigh 



Average yield of seed cotton 

 per acre. 



Field A (1902, 

 1903, 1904. 1906, 



Field B (1905. 



1907, and 



1909). 



Average 

 increase per 

 acre due to 



fertilizer. 



Nitrogen and phosphoric acid 



Nitrogen and potash 



Phosphoric acid and potash 



Nitrogen, phosphoric acid, and potash 



Lime 



Nitrogen, phosphoric acid, potash, and lime. . 



Pounds. 

 I, 154- 5 

 994- 6 

 I, 126. o 



I, 130. 8 



619.5 



1,007. 2 



Pounds. 

 768.2 

 437-7 

 895-3 



925-7 



320. I 



975-3 



Pounds. 



415- I 

 169.9 

 464.4 



524.6 



31-9 



572-7 



