FIELD TEST WITH A TOXIC SOIL CONSTITUENT: VANILLIN. }) 
the field the preceding season; that is, cowpeas on the cowpea soil 
from the check plot and from the vanillin plot, string beans on the 
string bean soil from both check and treated plots, garden peas on 
the garden pea soil from both check and treated plots. Two pots 
were used in each case and two plants in each pot. The plants grew 
from December 11 to January 6. The vegetative growth made in 
this experiment is given in Table VI. 
Table VI. — Growth of cowpeas in pots of soil from cowpea field plot; garden peas in 
soil from garden pea field plot; string beans in soil from string bean field plot; collected 
sir months after treatment with vanillin. 
> 
Green weight of plants 
upon — 
Relative 
Plot. 
Soil from 
plots un- 
treated. 
Soil from 
vanillin 
plots. 
growth, 
checks 100. 
Grams. 
4.30 
5.60 
7.80 
Grams. 
3.05 
4.00 
7.35 
71 
71 
String hp.ans pint, 
94 
The figures in the table show that vanillin was still harmful to the 
respective crops six months after the application of vanillin, and after 
it had produced the same crop in the field. These experiments show 
that vanillin persists in this heavy silty clay loam soil and affects its 
fertility for a considerable length of time. 
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