University of California Fublications in Agricultural Sciences [Vol. 1 



humus and moisture, or in the presence of alkali salts, the activi- 

 ties of ammonifying organisms are seriously handicapped. 



To discuss these more in detail we find, for example, in soil 

 No. 1, derived from the mesa soil at Arlington Heights. River- 

 side, a strong ammonification, varying but little from the first 

 foot down to the seventh, below which depth we find a sudden 

 marked decrease in ammonia production, for the reason, doubt- 

 less, that from the sixth foot down to the twelfth we find a 

 layer of hardpan which, owing to its poor aeration and poor 

 water conditions, is unfit for the development of a vigorous bac- 

 terial flora. In other words, we find in this soil-column, through 

 the ammonifying power of the various depths of soil, an expres- 

 sion of the vigor and numbers of bacteria present in these soil 

 layers and also of the amounts of soluble nitrogen which can 

 there be expected to be made available through the agency of 

 soil organisms. 



In soil No. 2, however, which represents a good, deep alluvial 

 soil, we find a very vigorous ammonification from the first seven 

 feet, and only slightly reduced ammonia production in the eighth 

 and ninth feet, after which we find a large reduction of about 

 50 per cent in ammonia production for the other three feet. 

 We have here, therefore, good vigorous ammonia production down 



