1912J SCHREINER 6* SKINNER— FERTILIZER SALTS 47 



This shifting of the region of greatest growth was accompanied 

 by a corresponding change in the absorption of plant nutrients, 

 although this is not as marked as the green weight. All of these 

 facts are in harmony with the conclusion drawn from the data 

 already given, that phosphate fertilizers were antagonistic to 

 cumarin, that potash fertilizers were antagonistic to quinone, and 

 that nitrate fertilizers were antagonistic to vanillin and to dihy- 

 droxystearic acid. 



In regard to the exact mechanism of the chemical or physio- 

 logical character of the interactions between these toxic substances 

 and the fertilizer salts, nothing definite can be said. Attention, 

 however, should be called in this connection to the fact that the 

 reducing poisons vanillin and dihydroxystearic acid are antago- 

 nized by those fertilizer combinations which stimulate oxidation, 

 and that the oxidizing poison quinone is antagonized by the fer- 

 tilizer combinations checking oxidation, thus indicating that there 

 is some correlation between these functions. A discussion of the 

 interaction of cumarin and phosphate fertilizers would be mere 

 speculation in the present state of our knowledge. 



Attention must also be called again to the fact that the obser- 

 vations here recorded for phosphate, nitrate, and potash were 

 obtained with the salts, calcium acid phosphate, sodium nitrate, 

 and potassium sulphate, and that the observed results, therefore, 

 may be caused by these substances as a whole, that is, as com- 

 binations rather than individual elements. For deciding this 

 question, further investigation is necessary, involving experiments 

 with other salts and combinations. 



These actions of the different fertilizer combinations or differ- 

 ent fertilizer requirements, as they may be styled, show a certain 

 parallelism with field observations on soils and their fertilizer 

 requirements, and one is tempted to ask to what extent may the 

 different fertilizer requirements of different soils or of the same soil 



same 



That 



mful bodies occur in soils has been am 



are influenced directly or indirectly by fertilizer salts is also clear 

 from this and other researches. That the constitution of the 

 organic matter varies from soil to soil and in the same soil under 



