the botton. via seston sedimentation and settling of plant mattero Meehean 

 (1933) stated that crustaceans and chJ.ronomids may utilize proteins and 

 carbohydrates directly, or through the action of bacteria and protozoa. 

 Not only may organisms grow and multiply at the expense of organic m.atter, 

 but saprophytic activity of bacteria and molds releases soluble organic and 

 inorganic materials. Bacterial activity depends on t he carbon-to-nitro- 

 gen (CsN) ratio of the parent substance, according to Meehean (^-935). It 

 is low when ratios fall below lOsl and good when 20 ;1 or higher. The im- 

 portance of carbohydrates and C:N ratios in nitrt>gen fixation has been 

 indicated by Neess (19ij9) ■ Lawson (1937) and others have pointed out the 

 relation of productivity to the presence of organic matter and have indicatec; 

 the need for it in humus -deficient waters. 



The Fertilization Process 



Two approaches can be made to artificial enrichment. The first^ nu- 

 tr-ient addition;, is the common and accepted practicej it is what the word 

 "fertilization" ordinarily implies. The second liberation of nutrients 

 present, is a direct approach only in theoryj it operates as a secondary 

 effect in the former method, and has been given little substantial consider- 

 ation as a separate process. 



The primary concern of nutrient addition is the nature of fertilizing 

 substances. These are readily classified into two groups: orf,anic and 

 inorganic fertilizers. The composition of several fertilizers, reported in 

 the reviewed literature, is presented in table 1, Prince and Bear (19ii3) 

 listed the nitrogen, phosphate, and potash content of various organic 

 materials that are used or could be used as fertilizers. Complete current 

 analyses of many fertilizers appear in State agriculturel publications deal- 

 ing mth such matters. 



Organic fertilizers contain a large percentage of organic carbon in 

 addition to many minerals. These supply most of the elements necessary 

 for metabolic activity and are usable for overall enrichment of waters or 

 as a source of carbon in an organic-deficient environment. Organic fer- 

 tilizers may be in the form of manures, composts, commercial meal residues, 

 or many other organic byproducts, Neess (19U9) explained the advantages 

 of meal fertilizers in terms of their high C;N ratios. Smith and Swingle 

 (19U3) found that organic fertilizers tend to crowd ponds with excessive 

 plant ^^rowthsj especially filamentous green algae (Swingle, 19U7) . 

 Wiesner (1937) suggested the use of composted aquatic plants as an inex- 

 pensive, readily available fertilizer. Swingle and Smith (19^0) recom- 

 mended barnyard manure to clear muddy waters, Hora (1950) stated that 

 the carbon in manures reta ns nitrogen for a longer period than inor- 

 ganic fertilizers and ensures a sufficiency of carbon dioxide and nitro- 

 gen. 



Inorganic fertilizers lack organic carbon and are available as single 

 compounds (e, g., ammonium sulfate; sodium nitrate, potassium chloride), 



12 



