1912] Kelley : Biological Transformations of Nitrogen in Soils 40 



DISCUSSION 



The experimental data presented above show that under the 

 conditions employed and in the soils studied, calcium carbonate 

 stimulated the ammonificatiou of dried blood to a limited extent 

 but exercised a more noteworthy stimulating effect on nitrifica- 

 tion. With magnesium carbonate a pronounced toxic effect was 

 produced. In the ammonificatiou of dried blood there was sus- 

 tained a loss of about one-third as compared with the experiments 

 without the use of carbonates, w^hile in the nitrification experi- 

 ments magnesium carbonate completely inhibited nitrate forma- 

 tion. It is also noteworthy that no evidence of antagonism be- 

 tween calcium and magnesium carbonates was observed. It is 

 not intended, however, to generalize from these results. It does 

 not follow that similar results would be obtained from any soil. 

 In fact, data already obtained from other soils show that the 

 phenomena observed in the two soils above discussed are not of 

 universal occurrence under similar conditions. 



A further study of the lime-magnesia ratio in reference to 

 nitrogen transformations in soils is now under way with the 

 use of several types of Hawaiian soils and interesting results have 

 already been obtained. A more complete interpretation of the 

 results obtained is reserved for a subsequent publication after a 

 wider range of observations have been made. Before a satis- 

 factory understanding of the lime-magnesia question in regard 

 to field crops is presented it is imperative that we have more 

 specific knowledge concerning the effects produced on the various 

 organisms of soils, now generally admitted to be of fundamental 

 importance in plant growth, and it is especially important that 

 the effects produced on the organisms affecting nitrogen trans- 

 formations be more fully understood. It is hoped that this work 

 may stimulate other investigations along this line. 



The author wishes to extend his thanks to Dr. C. B. Lipman, 

 in whose laboratory this work was carried out, for many valuable 

 suggestions offered from time to time and the great interest 

 shown. 



