THE INFLUENCE OF ARSENIC UPON THE BIOLOG- 



ICAL TRANSFORMATION OF 



NITROGEN IN SOILS 



J. E. GREAVES 



(Utah Experiment Station, Logan) 



Arsenic occurs in many virgin soils and is repeatedly added to 

 others in insecticides, in commercial fertilizers, or in the flue dust 

 from various smelters. Some investigators hold that arsenic may 

 accumulate in soil in quantities sufficient to injure Vegetation grown 

 upon such soil, and that the plants may in turn poison animals which 

 feed upon them. The work described in this paper was undertaken 

 to see if the lower plants, the ammonifiers and nitrifiers, of the soil 

 are injured by arsenic, for they are readily experimented with and 

 yield results in much shorter time than higher plants. Such results 

 may also indicate the way in which a study of the higher plants 

 should be pursued, for it is probable that substances which influence 

 the soil organisms may also influence higher plants, differing only in 

 degree ; but results of this kind must be accepted only as indicative, 

 not as absolute proof, of what may occur with higher plants, for 

 as pointed out by Guthrie and Helms, ^ all plants are not equally 

 :sensitive to poisons. 



I. INFLUENCE OF ARSENIC UPON AMMONIFICATION 

 Method of experimentation. The work was carried on with a 

 typical bench soil, a sandy loam, fairly high in calcium and iron 

 content, and supplied with an abundance of all the essential ele- 

 ments of plant food with the exception of nitrogen which was low, 

 a characteristic of arid soils. The soil was air dried, sieved and 

 stored in a large box, so that all determinations could be made on the 

 same soil. 



Determination of the ammonifying powers was made by Lip- 



1 Guthrie and Helms : Agr. Gas. New South Wales, 1903, xiv, p. 114. 



2 



