54 



CONTROL SERIES No. 54 



centage of seed hull, naturally gave the lowest nitrogen availability as its decom- 

 jiosition in the soil would be somewhat slower. 



Rubberseed Meal. The first experiment on this material indicates that its 

 nitrogen availability is quite satisfactory, comparing favorably with both Cot- 

 tonseed Meal and Rapeseed Meal. 



Smirow Tankage. The product under experiment this year showed a some- 

 what lower availability of total nitrogen and a higher availability of water insol- 

 uble nitrogen than did the sample secured in 1929. Both experiments, however, 

 showed the j'roduct to contain nitrogen of fair quality. 



Supernite Tankage. This season's results confirm the availability shown 

 by other samples of the product in 192S and 1929, and indicate that the nitrogen 

 is of very satisfactory quality. 



Whale Guano. Results this season, as in the past two years, indicate that 

 the nitrogen furnished by this product is of very satisfactory quality. 



The Effect of Manganese Sulfate on Yield of Dry Matter and Recovery 



of Nitrogen. 



The study of the effect of compounds of manganese on yield of crop and assimi- 

 lation of nitrogen, which was begun in 192S, has been continued this season. The 

 use of carbonate of manganese was discontinued, as two previous experiments 

 gave negative results. In this experiment all of the pots received the same basic 

 ration of nitrogen, phosphoric acid and potash that was used in the main experi- 

 ment, the nitrogen being supplied from Dried Red Blood. The following table 

 gives average yields of dry matter and nitrogen recovered with the various 

 treatments. 



Conclusion. No increase either in dry matter yield or in nitrogen recovery 

 was noted with any of the treatments with the manganese salt. 



VEGETATION POT EXPERIMENT WITH PHOSPHATES. 



This is a report of results of a vegetation pot experiment to determine the 

 availability or crop-producing value of certain phosphatic materials largely used 

 as sources of phosphoric acid, both in mixed fertilizers and as fertihzer simples. 

 Some of the phosphates employed in this experiment are comparatively new, 

 others have been produced by jjrocesses more or less modified from the original. 

 While some of the materials have been iised by the trade, with apparently satis- 

 factory results, yet there is a lack of recorded data as to the actual crop-producing 

 value of the phosphoric acid which the products carry. 



