16 
such as cottonseed and soybean meals, (3) hay and plant compost, and 
(4) offal, such as sewage, garbage, and tankage. Materials of the 
first three classes are the main ones used in this country. To obtain 
results within a growing season, organic fertilizers should contain con- 
siderable soluble material or should decay and go into solution with- 
out too great lapse of time. For this reason, such materials as bone- 
meal are unsatisfactory since they not only are insoluble but also decay 
very slowly. 
Farm manure is a mixture of animal excrement and straw or other 
bedding materials. Its quality as fertilizer varies greatly with the 
animal ; source, the amount of bedding material, the manner in which 
it has been collected and stored, and its age (table 3). The percentage 
of nitrogen, phosphoric acid, and potash in manure is approximately 
0.5-0.25-0.5, which means that its content of fertilizer materials is 
low in comparison with that of commercial fertilizer. At this ratio, 
1 ton of manure is equivalent to 100 pounds of 10-5—10 mixed fertilizer 
(10). For plankton production it is distinctly low in content of phos- 
phoric acid and for this reason superphosphate often must be added 
when manure is used as a pond fertilizer. Manure from chickens is © 
much higher in content of nitrogen and phosphoric acid than is that 
from other farm animals (table 3). In all manures, 50 percent or 
more of the fertilizer materials are in soluble form and do not require 
decay to become available for plant growth. 
MISC. PUB. 528, U. S. DEPT. OF AGRICULTURE 
TABLE 3.—Percentages of fertilizing elements in various organic materials 
(SZ. LO, Hb) 
ie Phos: = “ “G ee = 
P . itro- | phoric | Potas : : itro- | phoric | Potasn 
Organic material zen EG (K30) Organic material gen acid | (K20) 
(P20s) (P20s5) 
Percent; Percent| Percent Percent| Percent| Percent 
Florsemanuretes sess 0. 50 0. 30 0.24 || Sewage sludge (acti- 
Cow manures. 132 Sil . 16 Valed) senwe. ae oneaee .0 S20 0.2 
Sheep manure-_-_-_-------- . 65 . 46 . 23 || Sewage sludge (Imhoff) __ QN5 1.0 Sil 
Hog manunrete ee esses . 60 .46 34-45) Al faliasha yee eres 2n3 Ali .9 
Chicken manure_____--_-_- 1.00 . 80 .40 || Bluegrass hay_____-_____- 1.5 5 1.5 
Cottonseed meal]_________ 7.0 2.5 2.0 TiN ObMyAN a yee eee .8 2 5G 
There is considerable question as to the desirability of rotting 
manure before it is used either on land or in ponds. In pond fertili- 
zation, fresh manure may be superior to rotted manure because in the 
process of rotting it will have lost much of its nitrogen. A reduc- 
tion of nitrogen appears to stimulate the growth of ‘unwanted fila- 
mentous aleae and is therefore undesirable. During the process of 
decay of large quantities of manure or other organic fertilizer, the 
supply of oxygen dissolved in the water may be depleted and the 
fish may suffocate. The danger of thus removing oxygen is much 
greater in warm, quiet water than i in cold, rough water in which de- 
composition is retarded and wave action adds oxygen to the water 
from the air. 
The seed meals, such as those of cottonseeds and soybeans, are com- 
monly used in hatchery pond fertilization. These are produced by 
pulverizing the cake that remains after the extraction of oil from 
the seeds, The fertilizer formula of cottonseed meal is about 7—2.5-2; 
