12 MISC. PUB. 528, U. S. DEPT. OF AGRICULTURE 
COMMERCIAL FERTILIZERS 
Since there is a direct relation between the plankton content of pond 
water and its fish productivity, an increase in plankton will lead to an 
increase in fish (table 2) (20). The application of commercial fer- 
tilizer to pond water increases the amount of plankton and when suf- 
ficient fertilizer is applied to double the plankton content the amount 
of fish supported by the pond is about doubled. 
FicurE 3.—The large bluegill came from a fertilized pond in which this species 
averaged 4 ounces in weight. The small one came from an unfertilized pond 
in which the fish averaged a weight of 1.1 ounces. Both ponds were stocked at 
the HEME of 1,500 bluegill per surface acre of water (after Ala. Agr. Expt. Sta. 
Bul. 254). 
TABLE 2.—Plankton and fish production of fertilized ponds in Alabama, 
September 9 to May 1 (20) 
Production of— 
Pond No. Fertilizer 
Plankton | Fish per 
per liter acre 
Milligra Pounds 
ese ee eee Paes ee None! <c2 5. S352 ab ie eG Se eee 4.8 90 
Di eape 2S er eee Superphcsphates 22 ss22 3 ee ee ee eee eS 3.5 134 
Ate Sen Speer a Beste Superphosphate-NaNi@ 35s ee eee 6.5 156 
Alun Wes eee hae DV Se Superphosphate--(NiE}):s 0. ee LT 174 
eet Se oe Ss eee Superphosphate+-NaN 03+KCl_--_-__.-_-_-_-__.-____--_- 8.0 251 
Gee eS eee Superphosphate+NaN O3+KCl1+CaC 03 _____-___________- 24.4 330 
[OEE Si Se LIN IN(O gee a a em Oe ee es 4.5 79 - 
1 Developed excessive acidity. 
