115 



their addition lo llic soil al the lime of planting llie 

 previous crop, A study of the combined yields obtain- 

 ed shows that the smallest total yield was obtained 

 from the untreated pot; on this basis of comparison, 

 the presence of pyrogallol, vanillin and coumarin in- 

 tluenced the crop yields but little. It does not appear 

 from this work that either vanillin or coumarin is 

 injurious to crops unless applied in very large quan- 

 tities just ])efore the crop is planted. Further, it does 

 not appear that pyrogallol has any beneficial effect 

 on the yields obtained under the conditions of these 

 •experiments. 



The results obtained from the use of the nitrogenous 

 compounds, pyridine and quinoline, are in strict accord 

 with those obtained the first year. Instead of being 

 harmful, as they are in water cultures, these substances 

 have proved to be beneficial; and the benefit is roughly 

 proportional to the amounts of the materials applied. 

 The crop of oats obtained from the pots which had 

 received 9 cc of these compounds was about four 

 times as great as that from the untreated pot. When 

 potassium and phosphorus were added to the pyridine 

 and quinoline treated pots, the yields were roughly ten 

 times as great as that of the check, and from six to 

 eight times as great as that from the pot receiving 

 potassium and phosphorus only. There is no evidence 

 from this experiment that there is any cumulative in- 

 jury resulting from the addition of such compounds 

 to the soil in which plants are grown; as a matter of 

 fact, there api)ears to be slightly less injury from the 

 second dose of vanillin and coumarin than there was 

 from the first dose. 



Are fertilizers valuable because they carry plant 

 food, or are they effective because they serve as an 

 antidote or to decompose toxic com})ounds? Is there 

 a plentiful supply of available phosphorus and potas- 

 sium in soils at all times? A little light is shed on 

 these questions by the data in the above table. For 

 example, compare the untreated pot yields with those 

 with the pot treated with kainit and phosphate; by 

 this comparison, phosphorus and potassium are not 

 much needed. But if a comparison is made between 

 the pot with nitrate and with complete fertilized pot, 

 it will be seen that the effect of the phosphorus and 

 .potassium has been very great. By this method of 



