INSPECTION OF COMMERCIAL FERTILIZERS 



59 



gram applications per pot, with the result that no appreciable increase in either 

 yield of crop or recovery of nitrogen was noted. The present experiment differed 

 from that of 1928 only in the use of 16% superphosphate to supply all of the phos- 

 phoric acid, whereas equal amounts of superphosphate and basic slag phosphate 

 were used in 1928. The basic slag phosphate was eliminated because it is known 

 to carry some manganese. 



The following table shows average yields and nitrogen recovered per pot.The 

 pots receiving dried red blood with the regular basic fertilizer are included in the 

 table as a basis for comparison. 



(a) AU the phosphoric acid from 16% superphosphate. 



(b) Phosphoric acid half from 16% superphosphate and half from basic slag. 



No significant increase either in yield of dry matter or in nitrogen recovered is 

 noted where manganese carbonate was used, with superphosphate to supply the 

 whole ration of phosphoric acid. 



A rather slight increase is noted both in dry matter yield and in nitrogen re- 

 covered where manganese sulfate was used in varying amounts up to 7.8 grams per 

 pot. This latter amount, the maximum ration of manganese, appears to have 

 caused a depression in assimilation of nitrogen, accompanied by a slight decline in 

 dry matter yield. 



The minimum amount of manganese sulfate used (2.6 grams per pot) is equiva- 

 lent to the use of about 370 pounds of commercial manganese sulfate per acre. 



