Feb. 35, 1918 Influence of Carbonates on Soil Bacteria 



479 



INFLUENCE OF CALCIUM CARBONATE, CALCIUM CHLORID, MAGNESIUM 

 CARBONATE, MAGNESIUM CHLORID, DIBASIC MAGNESIUM PHOSPHATE, 

 AND MONOCALCIUM PHOSPHATE ON THE BACTERIA IN SOIL 



Colby silt loam. — Since the increase in number of bacteria in soil 

 treated with magnesium carbonate seemed far too great to be accounted 

 for by the correction of the soil acidity alone, an experiment was made 

 to study the efifect of a neutral salt of magnesium, and a magnesium 

 phosphate, on the number of bacteria in Colby silt loam soil. Two 

 points were considered in planning this test : First, the action of the mag- 

 nesium and calcium ions on the bacteria; and second, the possibility 

 of the combining of the calcium or magnesium, especially the latter, with 

 the phosphate of the soil, thus liberating the phosphate in a more avail- 

 able form. 



It was reported by Truog (56) that magnesium phosphate favors the 

 phosphorus assimilation by plants more than any other phosphate. If 

 this be true, then the bacteria (lower plant life) should be favored by a 

 phosphate when in this form. Therefore the question arises, Does the 

 magnesium carbonate when added to soil react with the phosphates to 

 form magnesium phosphate? 



In order to make these tests, magnesium carbonate, magnesium chlo- 

 rid, dibasic magnesium phosphate, also calcium carbonate, calcium chlo- 

 rid, and monocalcium phosphate were added to the soil alone and in 

 various mixtures. 



TabIvE VI. — Influence of calcium carbonate, calcium chlorid, magnesium carbonate, 

 magnesium chlorid, dibasic tnagnesium phosphate, and m.onocalcium phosphate on the 

 bacteria of Colby silt loam 



Treatment. 



Number of bacteria in i gm . of dry soil. 



After I 

 week. 



Rela- 

 tive. 



Rela- 

 tive. 



None 



0.1 per cent magnesitun chlo- 

 rid 



0.1 per cent calcium chlorid. . . 



Full calcium carbonate 



Full magnesium carbonate . . . 



0.1 per cent dibasic magne- 

 sium phosphate 



0.1 per cent monocalcium 

 phosphate 



0.1 per cent dibasic magne- 

 sium phosphate-f-fuU cal- 

 cium carbonate 



0.1 per cent monocalcium 

 phosphate-Ffull calcium 

 carbonate 



0.1 per cent dibasic magne- 

 sium phosphate-l-full mag- 

 nesium carbonate 



O.I per cent monocalcium 

 phosphate + full magne- 

 sium carbonate 



28,000,000 



16,000,000 



18, 200,000 

 S9, 100, oco 

 165,000,000 



30, 500, 000 



38,000,000 



74, 100, 000 

 38,000,000 

 191,000,000 

 223,000,000 



57 



65 



31S 



590 



264 

 I3S 

 6S2 

 800 



I4S 



86 



314 



481 



a 13 



as8 

 700 

 639 



The effect of magnesium phosphate on the number of bacteria was com- 

 pared with that of magnesium carbonate, calcium phosphate, and cal- 

 cium carbonate. If the action of the magnesium and calcium carbonates 

 27811°— 18 2 



