426 SCHREIXER— TOXIC SOIL SUBSTANCES. [April i8, 



h\poxanthine, products of animal fluids and nuclein degradation; 

 and nucleic acid itself. These compounds increase plant growth and 

 the results obtained would seem to show that the plant can use these 

 compounds directly in building up the plant proteins and nucleins 

 without further decomposition to ammonia and production of ni- 

 trites and nitrates. 



Nor should I pass over the physiologically doubtful or inert soil 

 substances without suggesting that these have a potentiality for good 

 or bad, depending upon future changes brought about by oxidation, 

 reduction, or other biochemical action resulting in the production of 

 beneficial or harmful compounds. Nor should I fail to mention that 

 many of these physiologically inert substances, as, for instance, the 

 water insoluble resins, have a marked physical effect on the soil, 

 often coating the soil grains and shielding the soil minerals as well 

 as other organic substances from the solvent action of the soil 

 waters, thus effectively interfering with an otherwise normal soil. 



In speaking of the elimination and neutralization of toxic soil 

 substances we must not lose sight of the fact now fairly well demon- 

 strated by biochemical and biological researches that in every soil 

 there is a balance of beneficial and harmful factors, soil fertility or 

 infertility being the resultant of the two groups. As one or the 

 other group of factors gains the ascendency, the fertility is raised 

 or lowered, as the case may be. This balance is influenced by cul- 

 tural treatment, such as draining, plowing, or otherwise working the 

 soil, by the application of fertilizers, by liming, by the growth of 

 plants, by crop rotation, etc. All of these factors affect the biology 

 of the soil, the soil bacteria, the molds, and other microorganisms 

 and through them the entire biochemical process in soils. Although 

 the number of toxic soil constituents may be very large and probably 

 but imperfectly represented by those we have thus far been able to 

 isolate, it appears nevertheless significant that they are substances 

 which have resulted from partial oxidation, but in their present form 

 have reducing properties, and under favorable conditions are subject 

 to further oxidation. They may be said to have resulted under im- 

 perfect conditions of oxidation or aeration whether this be the direct 

 result of poor drainage, of soil acidity, or lack of lime, or poor cul- 



