1913-] SCHREINER— TOXIC SOIL SUBSTANCES. 429 



quantity of nitrogen for the use of the plant. The biochemistry of 

 these life forms in the soil, the multitudinous changes which they 

 work have remained unstudied, only those facts were determined 

 which influence the amount of the so-called plant food, ignoring even 

 much material that is more truly plant food than the mineral sub- 

 stances and inorganic nitrogen compounds studied. In all lines of 

 human activity the sanitary surroundings, the proper medical treat- 

 ment and the proper nutrition of animals and of man, are receiving 

 attention and the proper sanitary condition of the plant's home, the 

 soil, will also receive more and more attention to prevent its har- 

 boring the germs of devastating plant diseases, and such decompo- 

 sitions or biochemical changes as produce substances inimical to the 

 health of the plant, killing it or weakening it, so that it falls a ready 

 prey to pathological organisms. In this campaign for a sanitary 

 home for the plant, the above factors of better cultivation, better 

 drainage, judicious liming, crop adaptation or crop rotation, and the 

 use of fertilizers, will play an important part and as we learn more 

 of the functions of the latter, their use will become more general 

 and more specific so that we will be able to tell which will be the 

 best suited for any particular soil condition or soil trouble, and in 

 the future these will no doubt be modified and even augmented with 

 other chemicals to meet special requirements. Some such special 

 fertilizers are already on the market and more will follow, the only 

 danger is that the advertising art will outstrip the science, which 

 should be the basis for such changes. 



The use of copper preparations in special orange fertilizers, or 

 the use of manganese or other catalytic substances to promote oxida- 

 tion in soils are illustrations of such use. The oxidation by man- 

 ganese has received special attention in our laboratories and in the 

 field and the conclusion seems warranted that such catalytic sub- 

 stances depend upon the form in which they are introduced or pres- 

 ent in the soil and the form of the organic matter in the soil, which 

 with the manganese forms activating combinations. In the field 

 work its action is still uncertain so far as increased oxidation or 

 increased crop growth is concerned. On poor soils, with acid tend- 

 encies, the results are doubtful, as will be shown by a forthcoming 



