FIELD TEST WITH A TOXIC SOIL CONSTITUENT: VANILLIN. 9 



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 

 six months after treatment with vanillin. 



Plot. 



Green weight of plants 

 upon — 



Soil from 

 plots un- 

 treated. 



Soil from 

 vanillin 

 plots. 



Relative 



growth, 



check--=100. 



Cowpeas plot 



Garden peas plot 

 String beans plot 



Grams. 

 4.30 

 5.60 

 7.80 



Grams. 

 3.05 

 4.00 

 7.35 



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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