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. 
Average 
increase 
per acre 
due to 
fertilizer. 
Treatment. 
Field A 
(1903,1904, 
1906, and 
1909). 
Field B 
(1905 and 
1907). 
Field C 
(1908). 
Pounds. 
Pounds . 
Pounds. 
Pounds. 
Nitrogen. 
210. 6 
377*5 
505-0 
-II. 7 
Phosphoric acid. 
655-6 
897-5 
860. O 
441*8 
Potash. 
301.3 
537-5 
435 *o 
85-4 
Nitrogen and phosphoric acid. 
897-5 
727 - 5 
620. 0 
520. I 
Nitrogen and potash. 
348.8 
406.3 
400. 0 
96- 5 
Phosphoric acid and potash. 
855-0 
959-8 
725*0 
608. O 
Nitrogen, phosphoric acid, and potash. . 
923.8 
I, 002. 3 
1, 070. 0 
717. 7 
Time. 
97 - 5 
l6o. O 
430.0 
27. O 
Time, nitrogen, phosphoric acid, and 
potash. 
728. 8 
637 - 5 
945 *o 
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 Earin 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. 
Average 
increase p^p 
acre due to 
fertilizer. 
Treatment. 
Field A (1902, 
1903,1904,1906, 
and 1908). 
Field B (1905, 
1907, and 
1909). 
Nitrogen and phosphoric acid. 
Pounds. 
h 154 . 5 
Pounds. 
768. 2 
Pounds. 
415 * I 
Nitrogen and potash. 
994-6 
437*7 
169.9 
Phosphoric acid and potash. 
I, 126. O 
895-3 
464.4 
Nitrogen, phosphoric acid, and potash_... 
1,130. 8 
925-7 
524-6 
Time. 
619.5 
32a 1 
31-9 
Nitrogen, phosphoric acid, potash, and lime.. 
r, 007. 2 
975-3 
572- 7 
