Feb. as. 1918 Influence of Carbonates on Soil Bacteria 491 



From the data presented in Table XIII it appears that there was no 

 decided gain in total nitrogen in the Plainfield sand, and only a small gain 

 in Colby silt loam. It is difficult to explain why no gain, and in some 

 cases a loss, of nitrogen was found. The loss may have been due to a 

 disturbance in the balance of the flora of these soils. Since the mannit 

 which was added to the soil, and the neutralization of some of the soil 

 acids by the basic substances caused a great increase in the number of 

 bacteria, it is possible that a part of the nitrate nitrogen was set free as 

 elemental nitrogen. However, a gain in total nitrogen is shown in the 

 Colby silt loam soil due to the carbonate and limestone treatment. 



INFLUENCE OF CALCIUM CARBONATE, MAGNESIUM CARBONATE, AND 

 LIMESTONE ON ORGANISMS IN PURE CULTURE 



An effort was made to determine the influence of calcium carbonate, 

 magnesium carbonate, and limestone on pure cultures of bacteria in steril- 

 ized soil. In order to simplify the vv^ork, only Colby soil was employed. 



It was obser\^ed that when this soil is heated for a long period at a 

 high temperature, there is a reduction in soil acidity. Other investi- 

 gators have reported similar results in acid soils. Conner (10) showed a 

 decrease in acidity when soil was heated to complete dryness. He sug- 

 gested that possibly the acid silicates were hydrolyzed with the formation 

 of a base. On heating soil to 140° C. for one hour. Sharp and Hoagland 

 (55) noted a decrease in acidity. On the other hand, Schreiner and 

 Lathrop (54) increased the acidity in an acid-reacting soil by heating the 

 soil for three hours at 30 pounds' pressure, which in all probability 

 changed the organic matter to such an extent as to increase the acidity. 

 The work of Kelley and McGeorge (jo) and Darbishire and Russell (//) 

 showed a change in the soil consituents on heating, especially in the solid 

 inorganic constituents, which were made more soluble. 



In order to overcome as much as possible this reduction in acidity, 

 various methods of sterilization were tried. Both dry and moist soils 

 were sterilized in Erlenmeyer flasks, which were heated in steam under a 

 pressure of 15 pounds for three hours. On testing this heated soil for 

 its degree of acidity by the Truog zinc-sulphid test, the dry soil showed 

 practically no change in its acid content, while the moist soil, one-half 

 and full water-saturated, showed a considerable decrease. The very wet 

 soil after sterilization contained less acid than that which received one 

 half as much water. From the evidence it seems safe to conclude that 

 the silicates of this soil are partially hydrolyzed with the formation of 

 bases. 



Further tests were conducted with dry soil. It was dried for 24 

 hours at about 45° C. and placed in flasks; these were then plugged and 

 sterihzed for three hours at 15 pounds' pressure. After sterilization, the 

 soil received water sufficient to bring it to half saturation. This was 

 done to determine if hydrolysis took place by adding water after the soil 



