430 SCHREINER— TOXIC SOIL SUBSTAXXES. [April i8, 



bulletin on the field experiments over a period of five years on such 

 an acid soil. A second period in which the soil will be limed to 

 produce neutrality is now begun and it will be interesting to learn 

 how the manganese will behave under this new condition. 



That even the ordinary chemicals used in fertilizers, potash, phos- 

 phates, or nitrates can afifect the harmful action of organic sub- 

 stances has already been incidentally alluded to in the preceding 

 paragraphs. Our researches have shown that the harmful soil con- 

 stituents, vanillin and dihydroxystearic acid have their poisonous 

 effects greatly diminished or even entirely overcome by the addition 

 of sodium nitrate, whereas their harmful characteristics remain un- 

 impaired by the addition of phosphates or potash fertilizers. Ni- 

 trate is an oxidizing substance and we have shown root oxidation 

 to be increased greatly by its use, whereas both vanillin and dihy- 

 droxystearic acid decrease root oxidation and are themselves capable 

 of being oxidized. The efifect of nitrate and these two substances 

 are therefore opposed to each other and thus neutralize each other, 

 or, what is more probable, neutralize their effects. The substance, 

 quinone, on the other hand has its poisonous action reduced by potash 

 salts, not by nitrate nor phosphate. Quinone is an active oxidizing 

 substance, while potash reduces root oxidation thus again showing 

 that these two substances antagonize each other in their effects. 

 The substance cumarin we have found to be very toxic to plants. 

 This toxicity is not diminished by nitrate nor by potash, as was the 

 case respectively with the preceding substances, but its action was 

 most remarkably overcome by the addition of phosphate and it 

 seemed to make no difference in what form the phosphate was used, 

 whether it was as a calcium salt or as a sodium salt, or as the mono- 

 basic, dibasic, or tribasic salt. 



I have mentioned these illustrations of specific fertilizer action 

 to show the possibilities of the future in adapting fertilizer treatment 

 to meet the specific needs of the soil based upon a perfectly rational 

 basis of soil treatment to meet the requirements of specific crops or 

 the requirements of plants suffering from unhealthy, insanitary soil 

 conditions, which involve the presence of biochemical transforma- 

 tions resulting in. compounds detrimental to the best plant devel- 

 opment. 



