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U. S. BUREAU OF FISHERIES 



ascribes this to the fact that the concentration of potassium had ex- 

 ceeded the upper limit that plants can stand. Most experiments 

 grave better results with complete fertilization — that is, when all three 

 elements, potassium, phosphorus, and nitrogen were added — than 

 with any partial fertilization. Fisher (1924), however, maintains 

 that nothing can be gained from the addition of either nitrogen or 

 potassium, and that phosphorus alone should be added. Walter 

 (1925) claims that in old ponds phosphorus alone is the most suitable 

 fertilizer. There can be no question but that the fertilizer require- 

 ments will diifer in different localities, depending in large measure 

 on the chemical nature of the pond soil and of the water. 



In the work at Fairport, several fertilizer mixtures have been 

 tried. In 1926 a 3 to 1 mixture of sheep manure and bone meal was 

 used. The results obtained were not at all encouraging. One reason 

 for this may be that the phosphorus in the bone meal is very insoluble. 



FiGUKK o. — I'artial view of the D series of ponds at the Fairport station 



Beginning with 1927, superphosphate has been- used in place of the 

 bone meal. A 3 to 1 mixture of sheep manure and superphosphate 

 gave very good results during 1927 and 1928. In 1929 the propor- 

 tions of sheep manure and superphosphate were varied in the direc- 

 tion of more phosphate. It is our opinion, at present, that a 1 to 1 

 mixture of sheep manure and superphosphate is preferable to a 3 to 1 

 mixture. 



In 1928 and 1929 soybean meal was tried as a pond fertilizer in a 

 few ponds. That this material has possibilities is shown by the 

 results obtained in E 3 during 1929. This pond with an area of 

 0.128 acre produced 1,457 bass fingerlings, averaging 2i/^ inches (6.21 

 centimeters) in length, and 15 selects averaging by^ inches (13.9 centi- 

 meters). The pond was fertilized with soybean meal. That soybean 

 meal may be expected to increase fish production is also evidenced by 

 a series of experiments carried on in the C pond during 1928, which 

 were planned to determine the effect of different fertilizers on plank- 



