67 



across each section: Rye, wlioat, oats, crimson clover, 

 l)ur clover, narrow leal" vetch, hairy vetch, and rape. 

 On December 24, 1917, specimen plants from the plots 

 fertilized with dried blood and with calcium cyanamid 

 were dug with a hand trowel, placed in covered jars, 

 and taken to tlie laljoratory to be photographed. The 

 plants were taken up and handled as nearly alike as 

 possible. The condition of the root and top is clearly 

 sliown in Plates X, XI and XII. The roots of all plants 

 fertilized with dried blood were unhealthy, poorly de- 

 veloped, and appeared to be practically dead. The ab- 

 sence of root hairs is showai by the dearth of soil ad- 

 hering to the roots. The few roots produced by bur 

 clover were all dead at the time the plants were photo- 

 graphed. Rape, crimson and bur clover had been so 

 severely injured that scarcely enough plants could be 

 found for photographic purposes; while wheat, rye, 

 oats, and the vetches were still living, but making no 

 growth. 



An examination of the plants in the plot to which 

 cotton seed meal w^as applied showed that there was 

 some injury to plant roots in this plot, Init not nearly 

 so much injury as was found on the plot fertilized with 

 dried blood. 



Water soluble manganese has been recovered from 

 the plots fertilized wath cotton seed meal or dried 

 blood, but none lias been found in the plots treated with 

 calcium cyanamid. x\pparently calcium cyanamid has a 

 sufficient basic tendency to prevent the development of 

 soluble manganese in this soil. The fact that the lime 

 recfuirement of the plots fertilized with dried blood and 

 with calcium cyanamid is 2568 and 856 pounds per acre, 

 respectively, supports this view. 



Discussion 



It is believed that the work here presented offers fur- 

 ther explanation of the cause of infertility of acid soils. 

 Regarded in a broad way, it may be stated that the re- 

 sults emphasize the importance of sufficient active 

 bases in the soil to prevent the solution of such com- 

 pounds as manganese and possible aluminum, iron, 

 etc. This view is substantiated by the fact that soil ex- 

 tracts which are toxic, apparently, because of the pres- 

 ence of soluble manganese, may be made non-toxic by 

 the addition of either calcium, sodium, or potassium 

 hydroxide. Such toxic extracts may be greatly im- 

 proved by the precipitation of only a part of the soluble 



