INFLUENCE OF CALCIUM AND MAGNESIUM COMPOUNDS 

 ON PLANT GROWTH 1 



By F. A. Wyatt, 3 

 Assistant in Soil Fertility, Agricultural Experiment Station of the University of Illinois 



INTRODUCTION 



Some investigators seem to question the advisibility of using mag- 

 nesium-bearing minerals in agricultural practices, since they deem mag- 

 nesium detrimental to optimum plant growth. Magnesium in some forms 

 is detrimental to plant growth. However, the natural carbonates, such 

 as limestones and dolomites, are not detrimental but in reality beneficial 

 to plant growth when applied in amounts sufficient to neutralize soil 

 acidity. Plants were found to grow and mature normally in pure dolo- 

 mite and limestone. 



In scientific circles considerable attention has been paid to the theory 

 that calcium and magnesium must occur in a definite ratio for the opti- 

 mum production of crops. Loew claims to have proposed this theory in 

 1892 (15) 3 , and much work has been conducted along this line, especially 

 during the last decade. From the data presented in the following pages 

 it will be seen that the ratio, within wide limits, had no effects. 



The presence of sufficient quantities of calcium and magnesium in all 

 soils is essential for the profitable production of crops. Various forms 

 and quantities of these two elements may largely control the yields and 

 composition of the harvests. 



It is a well-known fact that plants will tolerate larger amounts of an 

 essential element than they require. The quantity of calcium and mag- 

 nesium taken up by plants is dependent upon the amount available and 

 upon the kind of plants. The silicates of calcium and magnesium are 

 relatively insoluble, while the chlorids are very soluble. Dolomite is 

 denser and less soluble than limestone but more soluble than magnesite. 

 Synthetic compounds of magnesium are more soluble, however, than 

 similar compounds of calcium. 



Alfalfa, when grown in sand and soil cultures with varying amounts of 

 calcium and magnesium minerals, such as dolomite and magnesite, also 

 with prepared compounds of these two elements, such as the chlorids, 

 sulphates, and carbonates, was found to contain varying amounts of 



1 This paper was submitted in partial fulfillment of the requirements for the degree of Doctor of Philos- 

 ophy in Agronomy in the Graduate School of The University of Illinois in 1915. 



2 It is with pleasure that I acknowledge my indebtedness to Prof. C G. Hopkins, Dr. A. L. Whiting, 

 arid Prof. J. H. Pettit for suggestions and helpful criticisms. 



3 Bibliographic citations in parentheses refer to " Literature cited," p. 616-619. 



Journal oi Agricultural Research, Vol. VI, No. 16 



Dept. of Agriculture, Washington, D. C July 17, 1916 



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(589) 



