10 University of California Publications in Agricultural Sciences [Vol. 1 



scribed have exhibited. ]\Ioreover, it would seem that the salt- 

 content in the lower layers of this soil, which increases as we 

 go down, has very seriously checked the development of these 

 organisms there and was probably assisted by the unfavorable 

 physical condition mentioned. In soil No. 10, while the salt- 

 content is only meager, we have a rather coarse, sandy soil with 

 hardly any humus, which is therefore for that reason an unfavor- 

 able medium for the development of bacteria, to say nothing of 

 the lack of moisture there and the great heat which these desert 

 soils must absorb from the sun. We therefore have a very much 

 smaller ammonifying power in the upper layers of the soil than 

 exists even in soil No. 9, from Imperial, and then a very rapid 

 decrease to almost no ammonifying power in the lower layers. 



By a general survey of all of these data, it would certainly 

 seem that we are justified in drawing the conclusion that am- 

 monification and the ammonifying flora of soils are vigorous for 

 several feet down in the arid region and are limited in their 

 activities only by the presence of large amounts of salt or a 

 lack of humus and moisture. Since, however, California soils, 

 taken by and large, are deep, we have reason, from the facts 

 above given, to suJ)pose that tbe ammonifying power in most 

 of these soils, which are not in any way ' ' abnormal, ' ' is vigorous 

 at great depths. 



NITRIFYING POWERS OF SOIL COLUMNS 



By very many and perhaps by most plants, nitrate is the 

 form of nitrogen taken up. It is therefore of importance not 

 only to study ammonia formation in soils, but nitrate formation 

 as well. In these investigations we have studied qualitatively 

 and quantitatively the production of nitrites and nitrates in 

 ammonium sulfate solution by soils from the different depths 

 in everv case. Here also, as in the ammonification work. 5 grams 

 of soil were used to inoculate 50 c.c. of culture solution. The 

 residts obtained in this work are set forth in a qualitative man- 

 ner, as to nitrate formation merely, in table II, since it is 

 sufficient for the purpose of this preliminary paper to know to 

 what depths in the soil nitrates are produced. Later publica- 

 tions, giving the more complete data of these investigations, will 



