496 



Journal of Agricultural Research 



Vol. XII, No. 8 



INFLUENCE OF CALCIUM CARBONATE, MAGNESIUM CARBONATE, AND 

 LIMESTONE ON BACILLUS RADICICOLA (ALFALFa) IN STERILE SOIL 



Colby silt loam. — This experiment was planned to measure the effect 

 of calcium carbonate, magnesium carbonate, and limestone on the 

 reproduction of Bacillus radicicola in sterilized Colby silt loam soil. 

 The alfalfa strain, which is supposed to be sensitive to acidity, was selected 

 for this work. The soil was treated with i per cent of mannit, and the 

 magnesium carbonate was added. Two-hundred-gm. portions of the 

 treated soil were placed in 500-c.c. Erlenmeyer flasks. The flasks were 

 then plugged and sterilized according to the method used in the pre- 

 ceding experiments. Inoculations were made by introducing a i-c.c. 

 suspension of the organisms. 



From the data presented in Table XVIII it will be seen that calcium 

 and magnesium carbonates increased greatly the number of alfalfa 

 organisms in this soil. The magnesium carbonate after one week did 

 not increase the number of these organisms to any greater extent than 

 did calcium carbonate. The smaller amounts were surprisingly efifective, 

 though the increase was not as great as that obtained with larger 

 amounts. Limestone increased the number of these organisms to a 

 very slight extent. 



TablB XVIII. — Influence of calcium carbonate, magnesium carbonate, and limestone 

 on Bacillus radicicola {alfalfa) in sterile Colby silt loam treated with mannit 



INFLUENCE OF CALCIUM AND MAGNESIUM CARBONATES ON BACILLUS 

 RADICICOLA (lupine) IN STERILIZED SOIL 



Colby silt loam. — Since the alfalfa strain of Bacillus radicicola was 

 greatly benefited by the carbonates of magnesium and calcium, it seemed 

 desirable to see what effect a similar treatment would have on the lupine 

 strain of B. radicicola, which is frequently termed an acid-resistant 

 organism. Limestone was eliminated in this experiment; otherwise the 

 procedure for this test was similar to that in the preceding experiment. 

 The results of this test are tabulated in Table XIX. 



