116 



comparison, two values of qiiile different magnitude 

 may be obtained for the phosphate-potassium combi- 

 nation. In the same way, two very different values 

 may be obtained for the nitrate of soda. The differ- 

 ence between the total yield of the untreated pot and 

 the nitrate pot is 120 grams; but the difference between 

 the phosphate-kainit pot and the complete fertilized 

 pot is 478 grams. Apparently this soil is inadequately 

 supplied with either nitrogen or the mineral nutrients, 

 if large crop yields are to be considered. On the other 

 hand, if these fertilizers owe their effectiveness to 

 their action on toxic compounds existing in the soil. 

 then it takes a complete fertilizer to get the desired 

 results on this soil. 



The deficiency of mineral elements may be shown 

 by another set of comparisons. Nitrate of soda alone 

 is much more effective than either pyridine or quino- 

 line alone, whtm used for oats; but when the mineral 

 elements are added to pyridine and quinoline, while 

 the nitrate is re])eated, then for the second crop the 

 residues from these two nitrogenous toxins become 

 more effective than nitrate, in promoting the growth of 

 a crop of corn foHowing the oats. In other words, one 

 application of ])yridine and quinoline, along with the 

 mineraLs, is more effective tlian is two applications of 

 nitrate of soda. 



In the light of these comparisons, and in the light of 

 the fact that neither lime, carbon bhick, nor pyrogallol 

 increased tlie |)ro(hicliveness of tliis soil, the conclusion 

 seems justitied that lliis poor soil is unproductive, not 

 so much because of the presence in it of toxic com- 

 pounds, but because of ;in cicliud deficiency of avail- 

 (tblr pliiut foods. 



(^.omi)arisons similar to those above may l)e made 

 from most of the data presented in the other tables in 

 this publication. 



