Feb. 25, 1918 Influence of Carbonates on Soil Bacteria 467 



later decreased the nitrate content, and it was assumed that a loss of 

 nitrate nitrogen occurred because of the increase in the total number of 

 microorganisms. 



Allen and Bonazzi (j) showed that the addition of ground limestone 

 to a noncalcareous soil brought about a more rapid nitrification. Kelley 

 {28) studied the effects of calcium and magnesium carbonates on ammoni- 

 fication and nitrification in a California soil high in basic substances. 

 His results showed that calcium carbonate benefited ammonification 

 slightly and nitrification to a great extent, while magnesium carbonate 

 was toxic to both processes. This investigator failed to show any def- 

 inite ratio of calcium and magnesium which favored the nitrifying and 

 ammonifying power of this soil. With Hawaiian soils, high in lime and 

 magnesium oxid, Kelley (29) obtained similar results. Dolomitic and 

 calcareous limestones gave results similar to those obtained with calcium 

 carbonate. 



Kellerman and Robinson (27) obtained nitrification of ammonium 

 sulphate in a soil with a high magnesium content. When calcium car- 

 bonate was added, an increase in nitrification was noted; with magnesium 

 carbonate a decrease, except when the latter substance was added to the 

 soil in very small amounts. Owen (52) reported that magnesium car- 

 bonate favored nitrification more than calcium carbonate. 



White (6j) and Voorhees and Lipman {58) treated soil with pure lime 

 and with a lime containing magnesium. Better nitrification and in most 

 cases better ammonification was obtained from the magnesium than 

 from the nonmagnesium limed soil. Soil treated with magnesium car- 

 bonate and inoculated into a liquid medium was shown by Lipman and 

 Brown {41) to retard nitrification. 



It was shown by Ehrenberg (12), Lemmermann, Aso, Fischer, and Fres- 

 enius {37), and Wheeler, Sargent, and Hartwell {60), that when lime or 

 calcium carbonate was applied to soil, the decomposition of organic 

 matter was accelerated. 



NITROGEN FIXATION 



Fischer {15, 16) demonstrated the fact that both lime and magnesium 

 oxid increased the reproduction of Bacillus azoiobacter in soil. The oxid 

 of magnesium seemed to give better results than lime. 



So much is Bacillus azotohacter influenced by lime that Christensen and 

 Larsen (9) suggested the use of this organism to measure the reaction of 

 soil. In a later publication Christensen (8) showed that the growth of 

 this organism in solution took place only when inoculated with a basic 

 soil. In their work with Danish soils, Weis and Bornebusch (^g) confirmed 

 Christensen's results. Loew (45) showed that lime added to a soil in- 

 creased the growth of the film of B. azotohacter formed in liquid cultures. 

 Results similar to Loew's were obtained by Cauda (6) when calcium car- 

 bonate was used. 



