JOM£ OF AGKlCELTim RESEARCH 



Vol. XVIII Washington, D. C, Oct. 15, 1919 No. 2 



RATE OF ABSORPTION OF SOIL CONSTITUENTS AT 

 SUCCESSIVE STAGES OF PLANT GROWTH 



By John S. Burd ' 

 Professor of Agricultural Chemistry, College of Agriculture of the University of 



California 



Data derived from the periodic cuttings of a crop of barley in 191 6 

 were used in a previous paper (i)^ to develop certain general relations 

 between the amounts of soil constituents acquired by the plant at various 

 stages of growth and those present in the water extracts of soils. It is 

 evident that the value of conclusions drawn from such data is somewhat 

 limited if based upon results obtained from a single soil. On the other 

 hand, the detailed and laborious studies necessary in such inquiries may 

 not be indefinitely repeated; and further work of this kind was not 

 originally contemplated. In the course of the work referred to, however, 

 certain aberrations in the data appeared to indicate errors or to lead to 

 conclusions of such an extraordinary character as to demand additional 

 experimental verification, so a further study was carried out the following 

 season, 191 7. The principal object of this paper is to present the result 

 then obtained. Since, however, these justify the data from the earlier 

 work and corroborate certain important conclusions logically deducible 

 therefrom, but not hitherto published, the complete results of the 

 periodic harvests from both studies will be considered. 



CONDITIONS OF THE EXPERIMENTS 



The details of the experiments were formulated primarily to insure: 

 That the individual plants in each experiment should have access 

 to an equal volume of soil. 



That there should be no opportunity for loss of soil constituents 

 by drainage or leaching, or gain from the constituents of rain or irriga- 

 tion water. 



That there should be no opportunity for removal of plant con- 

 stituents by the washing off of effloresced or soluble constituents by rain. 



' Thanks are extended to Messrs. A. W. Christie and J. C. Martin for performing the analyses reported 

 herein and for assistance in the computations, etc., and to Prof. G. R. Stewart for supervision of the cultural 

 arrangements and harvesting of the plants. 



2 Reference is made by number (italic) to "Literature cited," p. 72. 



Journal of Agricultural Research, Vol. XVIII, No. 9 



Washington, D. C. Oct. 15, 1919 



sm Key No. Calif.-ai 



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