622 EXPEKIMENT STATION EECORD. 



come. The toxic solutions were markedly improved by treatments similar to 

 those which benefit the extracts of unproductive soils. Treatment with absorb- 

 ing agents or biief boiling was beneficial. The toxic solutions were greatly im- 

 proved after one set of wheat plants had been grown in them. TTndoubtedly 

 there was some toxic material directly absorbed by the first set of plants, but 

 the amount was entirely too small to account for the diminished toxicity of the 

 solutions when the second set of plants was grown. The vanillin solution, for 

 example, was so reduced in toxicity that a solution originally containing 5(M) 

 parts per million was no more toxic to the second set of plants than a solution 

 of 50 parts per million was to the first. It has been found that an equal num- 

 ber of wheat plants can remove in a similar length of time not more than 30 to 

 50 parts per million of nitrates from solution and there is no reason to believe 

 that toxic substances should be removed at a much more rapid rate. The oxi- 

 dizing powers of the roots therefore appear to be able to act upon the toxic 

 organic materials in such a way that their toxic properties are lost. The large 

 amount of root surface which most plants possess makes this oxidizing power 

 an important one in relation to soil conditions and especially in relation to the 

 destruction of toxic conditions through crop rotation. 



" In the experiments described it was shown that while the plants alone and 

 fertilizer -substances alone were able to accomplish a partial destruction of the 

 toxic substances the combined action of plants and substances ordinarily em- 

 ployed as fertilizers caused a much greater destruction of toxic material and 

 consequent improvement in growth." . . . 



" It has been demonstrated by the studies described in this bulletin that sub- 

 stances commonly used as fertilizers in agi'icultural practice have in addition 

 to their function as plant nutrients a well-defined power to overcame and actu- 

 ally destroy toxic bodies. Substances like nitrate of soda and lime, acting in 

 cooperation with the activities of the plant roots, -are able to destroy or render 

 harmless various organic substances which previously had a toxic effect on the 

 plants." 



It is stated that previous investigations of the Bureau had shown that 

 "toxic soil extracts may be greatly improved by the addition of fertilizer sub- 

 stances, but up to the present the method by which amelioration was l)rought 

 al>()ut had not been demonstrated. It had been distinctly shown, however, that 

 amelioration was not due to the addition of plant nutrients, since equal, if not 

 greater, improvement resulted from treatments which added nothing in the 

 nature of plant nutrients. The present investigations become of value, there- 

 fore, in showing that fertilizer substances have a power to act destructively 

 upon deleterious organic compounds, especially when associated with the activi- 

 ties of growing plants." 



On humus acids, A. J. Van Schermbeck (Jour. Prakt. Chem., n. scr., 15 

 (1907), No. 10-11, pp. 511-525; ahs. in Chem. Zcntbl., 1901, II, No. 8, p. 62-',).— 

 A report of previous studies by P. Malkomesius and R. Albert is critically 

 reviewed. The author considers the term humus acids as used by these investi- 

 gators as having no significance and doubt is cast upon the results of their 

 work on the subject. Attention is called especially to the complex character of 

 the humus extract obtained by repeated extraction with boiling alcohol accord- 

 ing to the Fresenius method. It is believed that the precipitated substances 

 obtained by such methods are simply absorption complexes formed when colloids 

 and resinous matter are precipitated l)y an electrolyte. The results of tests of 

 various niethods of determining the acidity of a moor soil are reported, from 

 which the conclusion is drawn that for judging of the danger of injury to roots 

 of plants extraction in water with pressure of the residue is the best method; 



