ABSTRACTS 559 



plays an important part. For example, in acid soils organic nitrogen 

 nitrifies much more rapidly than nitrogen from ammonium sulphate; 

 the reverse is true in non-acid soils. 



In soil treated with calcium carbonate there is an enormous multi- 

 plication of the nitrate bacteria. At first, one or two weeks after treat- 

 ing, calcium carbonate stimulates nitrate formation, later the reverse 

 is true. In the presence of organic nitrogenous substances as casein 

 and gelatin, calcium carbonate did not permanently increase the accumu- 

 lation of nitrates. 



All soils stored under conditions that prevent leaching showed a gain 

 in nitrate nitrogen. 



Considering the data given, as a whole, it seems that under laboratory 

 conditions the beneficial effect of CaCOa on plant growth must be ac- 

 counted for by some processes other than the direct effect on nitrifica- 

 tion as this effect of CaCOs on nitrification takes place before higher 

 plants begin to draw heavily on the nitrogen of nitrates. Moreover, 

 the period of rapid accumulation from liming may result in a loss of ni- 

 trogen from leaching of the nitrates. These questions can be deter- 

 mined only by field tests. — Z. N. 



The Influence of Some Common Humus-Forming Materials of Narrow 



and of Wide Niti-og en-Carbon Ratio on Bacterial Activities. P. E. 



Brown and F. E. Allison. (Soil Science, 1916, 1, 49-75.) 



Ammonification, nitrification and azofication were found to be in- 

 creased to a considerable extent by application of the common humus- 

 forming materials (dry) in maximum amounts for farm conditions; 

 horse-, cow- and rotted manures, oat straw, timothy-, cowpea- and 

 clover hays and corn stover. In general the manures favored and the 

 legume hays depressed ammonification. Increases in ammonification 

 were independent of the N-C ratio of the materials added, and were 

 probably dependent on the chemical composition of the substances. 

 If the humus-forming materials especially the manures, had been ap- 

 plied undried as under field conditions, ammonification would have 

 been accentuated. 



In contrast, nitrification was increased by leguminous green manures, 

 and retarded somewhat by animal manures. These increases were ap- 

 parently independent of the N-C ratio in the substances. 



Azofication was favored by manure, straw stover and non-leguminous 

 hays, and leguminous hays in order, the N-C ratio of these materials 

 being of little or no significance as indicated by their effects on 

 azofication. 



Indications were, however, that non-legumes and straws might in- 

 crease azofication on soils to a large enough extent to make their use 

 more profitable than that of legumes which add nitrogen to the soil, but 

 are somewhat more expensive to use. 



The substances with wide N-C ratio decreased the crop yield while 

 those of narrow ratios gave increases. The N-C ratio was found to be 

 of more importance in determining the effect on the second crop of oats 

 than on the first crop. 



