VANILLIN AS A ROIL CONSTITUENT 329 



the effect of the vanillin on cowpeas, figure 3 on garden peas, and 

 figure 4 on string beans. The photographs show that even at 

 this early stage of growth each of the crops is retarded by vanillin. 

 When the crops were harvested the vines and pods from each 

 plot were piled separately, and photographed together with the 

 yield from one of its check plots. It is also shown here in the 

 case of each crop that the vanillin treated plots yielded much 

 less than the untreated soil. These photographs are shown in 

 figure 5. 



PRESENCE OF VANILLIN AND ITS EFFECT IN THE SOIL SIX 

 MONTHS AFTER APPLICATION 



The question of the length of time the vanillin would persist 

 in the Arlington soil and have an influence on its crop-producing 

 power has also been investigated by a chemical study in the 

 laboratory and by pot tests. Samples of soil for these purposes 

 were obtained from the plots the last of November, six months 

 after the substance was applied, and after it had matured a crop. 

 The soils were examined for vanillin by the method already de- 

 scribed by Shorey. 7 The method, in brief, consists of making 

 an alkaline extract of the soil. The extract is acidified and fil- 

 tered and then shaken out with ether. The aldehyde is re- 

 moved from the ether by sodium bisulphide solution, acidified, 

 and the liberated aldehyde again taken up in ether. The ether 

 extract obtained by this process will contain aldehydes if present 

 in the soil. Vanillin was found to be present in each of the soils 

 from the plots to which the substance had been applied six months 

 previously. 



Pot tests were made in the soil from these plots, in order to 

 determine if the vanillin still had an effect on growth. In these 

 experiments, which were conducted by growing wheat, cowpeas, 

 garden peas, and beans in small paraffined wire pots, it was 

 found that each of the vanillin-treated pots produced poorer 

 wheat than soil from the check plots. Wheat was reduced in 

 growth 26% in the soil from the vanillin plot which grew cowpeas 



7 Jour. Agr. Research, 1: 357, 1914. 



