4 Vniversity of California Publications in Agricultural Sciences [Vol. 1 



before iising. In this way by the use of a plumber's torch at 

 every depth as we descend from the surface of the soil down 

 to the twelve-foot depth, we obtain, by starting at sterile sur- 

 faces, a sample of soil representing as nearly as possible the true 

 condition which obtains at very depth. The samples are marked 

 properly, taken to the laboratory, and examined for their am- 

 monifying, nitrifying and nitrogen-fixing powers by means of 

 a modified Remy method, the solutions employed for the work 

 being prepared in accordance with the formulae used by J. G. 

 Lipman.^ Every 50 c.e. portion of the medium in a 250 c.c. 

 Erlenmeyer flask is inoculated with 5 grams of soil. 



DESCRIPTION OF SOILS EMPLOYED IN THESE 



EXPERIMENTS 



The descriptions given below represent the soils which were 

 employed for bacteriological examinations and sampled for the 

 purpose as above described. The numbers employed below are 

 used throughout all the following tables so as to make unneces- 

 sary any further descriptions. 



Soil No. 1. Red clay loam mesa soil, from Riverside, California, on 

 which good orange trees were growing at time of sampling. The soil is 

 well supplied with potash, but rather poor in phosphoric acid and very 

 poor in humus and nitrogen. It is underlaid by hardpan at six feet from 

 the surface, which continues on down to the twelve-foot depth. With the 

 careful cultivation which is given it, along ^vith proper fertilization and 



tillage, the soil produces profitable crops of oranges and lemons. 



Soil Xo. 2. Silty alluvial loam, from Davis, California. The samj^les 

 used were obtained from between some fig trees at the University Farm. 

 This soil is practically uniform in color from the first foot to the twelfth 

 and only becomes slightly different in texture below the fifth foot, becoming 

 gradually coarser and sandier as we descend to the lower layers. It is 

 well supplied with potash, phosphoric acid, and lime and has, for a soil of 

 the arid region, a normal content of humus. 



Soil No. 3. Sandy alluvial loam, from Davis, California. Samples were 

 taken from a wheat field at the University Farm, only to a depth of ten 

 feet. This soil is well supplied with phosphoric acid, potash and lime, 

 but rather poor in humus and nitrogen. The sand is of a coarse nature 

 and becomes rapidly coarser, descending from the first foot down to the 

 twelfth, where it is found as very coarse sand. 



1 Bulletin 180. N. J. Agr. Expt. Station. 



