JOTOEOFAGRIQlLTIlRALltESEMCH 



Vol. XVIII Washington, D. C, November i, 191 9 No. 3 



NATURAL CARBONATES OF CALCIUM AND MAGNESIUM 

 IN RELATION TO THE CHEMICAL COMPOSITION, BAC- 

 TERIAL CONTENTS, AND CROP-PRODUCING POWER 

 OF TWO VERY ACID SOILS 



By S. D. Conner, Associate Chemist in Soils and Crops, and H. A. NoYES,^ Research 

 Associate in Horticultural Chemistry and Bacteriology, Purdue University Agricultural 

 Experiment Station 



INTRODUCTION 



Agricultural limestones so frequently contain large quantities of mag- 

 nesium that the question of the relative values of calcium and magnesium 

 carbonates as neutralizers of soil acidity is of great practical impor- 

 tance. Many instances where magnesium has had detrimental effects 

 on plant growth have been reported, as have also other instances where 

 magnesium limestones have produced greater crop growth than did pure 

 calcium limestones. The literature on the subject is very extensive 

 and has been fully reviewed by others (j, 4, 5, 6)? 



The present paper reports results of pot and laboratory tests on two 



very acid soils of distinctly different types. The data were all obtained 



from experiments conducted under controlled moisture conditions with 



natural carbonates of high purity. The calcite used analyzed 56 per 



cent calcium oxid and o.i per cent magnesium oxid. The dolomite 



contained 30.4 per cent calcium oxid and 20.5 per cent magnesium oxid. 



The magnesite contained 0.12 per cent calcium oxid and 46.2 per cent 



magnesium oxid. No basic or artificial carbonates were used in the 



experiments reported. 



SOILS USED 



The analyses of the soils used, an acid silty clay very low in organic 

 matter content and an acid black peaty sand high in organic matter 

 content, are given in Table I. 



The two soils are shown to be of quite different composition. The 

 variation between the nitrogen and humus determinations is large. 

 Both the Hopkins ^ potassium-nitrate and the Jones * calcium-acetate 



* Resigned Nov. i, 1918. 



' Reference is made by number (italic) to " Literature cited," p. 125. 



* Wiley, H. W., ed. officiai, and provisionai, methods op analysis, association of official 



AGRICULTURAL CHEMISTS. AS COMPILED BY THE COMMITTEE ON REVISION OF METHODS. U. S. Dcpt. 



Agr. Bur. Chem. Bui. 107 (rev.), 272 p., ij fij;., 1908. Reprinted 1912. 



* Jones, C. H. method for determining the lime requirement op .soils. In Jour. Assoc. Off. Agr. 

 Chem., v. i, no. i, p. 43-44. 1915- 



Journal of Agricultural Research, Vol. XVIII, No. 3 



Washington, D. C. Nov. i, 1919 



sk (119) Key No. Ind.-6 



