26 



BULLETIN 108, U. S. DEPARTMENT OF AGRICULTURE. 



in the field the preceding season, that is, cowpeas were grown on the 

 cowpea soil from the check plot and from the salicylic aldehyde plot, 

 string beans on the string bean soil from both the check and treated 

 plot, and garden peas on the garden pea soil from both check and 

 treated plot. Two pots were used in each case and two plants were 

 grown in each pot. The plants grew from December 11 to January 

 6. The vegetative growth made in this experiment is given in 

 Table XV. 



Table XV. — Growth of cowpeas in soil from the covjpea field plots, string beans in soil 

 from the string bean field plots, and garden peas in the soil from garden pea field plots. 

 Collected six months after treatment iviih salicylic aldehyde. 



Crop grown in pots in greenhouse and previously in the field. 



Soil from 

 check plots. 



Cowpeas 



String beans. 

 Garden peas 



Grams. 

 4.30 



5.60 



Soil from 



salicylic 



aldehyde 



plots. 



Grams. 

 3.80 

 7.20 

 4.30 



Relative 



growth, 



check=100. 



The table shows that the salicylic aldehyde treated soil was still 

 harmful to the respective crops in samples collected six months after 

 the application of the salicylic aldehyde, the test plants growing about 

 five months after the harvesting of the same crop in the field. It is 

 also interesting to note that the relative order of toxicity shown 

 toward the different crops is the same in these smaller vegetative 

 experiments in the paraffined wire pots as in the case where the crops 

 were harvested in the field. This would also seem to indicate that 

 the observed order of toxicity toward these plants, namely, garden 

 peas, cowpeas, string beans, may be more than accidental. 



SUMMARY. 



Compounds of an aldehyde nature exist in many soils. Such soils 

 are usually unproductive. When separated from the soils, the alde- 

 hyde material is toxic to plants in pure water and in nutrient 

 solutions. 



One of these soil aldehydes is identified as salicylic aldehyde. 

 This compound in very small amounts is harmful to plants in distilled 

 water and in nutrient solutions. It is harmful to plants grown in 

 pots of soil. It greatly decreases the yield of crops grown in the 

 field. It persists in the field soils for months. 



There is some evidence which suggests that lime and phosphate 

 ameliorate the effects of salicylic aldehyde. Its chemical nature sug- 

 gests that increased oxidation in soils under field conditions probably 

 prevents its formation or accumulation. 



o 



WASHINGTON : GOVERNMENT PRINTING OFFICE : 1914 



