UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



AGRICULTURAL SCIENCES 



Vol. 1, No. 3, pp. 39-49 December 14, 1912 



THE EFFECTS OF CALCIUM AND 

 MAGNESIUM CAEBONATES ON SOME BIO- 

 LOGICAL TEANSFORMATIONS OF 

 NITROGEN IN SOILS 



LIBRARY 

 NEW YORK 

 BOTANICAL 



QARDBN. 



BY 



W. P. KELLEY 



HISTORICAL INTRODUCTION 



Loew^ and his co-workers found, some years ago, that the 

 growth of a number of plants may be markedly influenced by 

 variations in the ratio of calcium to magnesium, both in solution 

 and soil cultures. Osterhout- also showed that a more or less 

 definite relation between other elements in culture solutions is 

 necessary for maximum growth. These and other researches have 

 drawn attention to certain long neglected phases of plant physi- 

 ology and strengthen the view that in addition to the mere 

 jjresence of the necessary elements, plants also demand a physio- 

 logically balanced relation between the elements in solution if 

 maximum growth is to be produced. By means of artificial cul- 

 ture solutions principles of great importance are being worked 

 out, but in generalizing from culture solutions to natural soils, 

 many difficulties arise. The great complexity of the factors in- 

 volved and the difficulties inherent in the question necessitate 

 the greatest care in making broad generalizations regarding soils. 



iLoew and May, Bur. Plant Ind. U. S. D. A., Bui. No. 1; Aso, Bui. 

 Col. Agr. Tokyo, vol. 4, pp. 361-370; vol. 5, p. 49.5; vol. 6, p. 97; Loew and 

 Aso, vol. 7, pp. 395-407. 



2Bot. Gaz. 42, 127-134; 44, 2.59-272; 48, 98-104. 



