424 EXPERIMENT STATION RECORD. 



the sit;nitifaiu'e of intestiiuil bacteria other than /{. coli. "A new chapter has 

 been hitroduced on the bacteriology of sewage and sewage effluents, in recogni- 

 tion of the growing importance of this branch of the subject." 



SOILS— FERTILIZERS. 



The production of active nitrogen in the soil, (J. S. Fraps (Texas Stu. Bui. 

 106, pp. -f/Sl, figs. 5). — This bulletin reports the results of laboi*atory studies of 

 the rate of animonification and nitrification in different kinds of Texas soils 

 under varying conditions of basicity, acidity, fertilization, and moisture, as well as 

 of pot experiments to determine the relation of the rate of production of active 

 nitrogen to plant growth. The sum of ammonia and nitrates is considered 

 active nitrogen. 



The method of procedure in the laboratory studies was in general as follows : 



" Five hundred gm. of air-dry soil, which had been sifted through a 3 mm. 

 sieve, was mixed with 20 gm. of fresh garden earth, an amount of nitrogenous 

 substance containing 0.3 gm. nitrogen, and water equal to one-third of the satu- 

 ration capacity of the soil. The nitrogenous substance and the garden earth 

 were first mixed together, then these were incorporated w^ith the dry soil, the 

 water added, and the whole mixed thoroughly until the mass was uniform. 



"The mixture was then placed in 500 cc. precipitating jars, shaking it down 

 by tapping gently against a wooden block. A test tube, with a small perforation 

 in the end, was inserted to a depth of about 1 in., and the jar, with its con- 

 tents, was weighed and placed iu a water bath kept as nearly as possible 

 at 35° C. . . . 



" Every Monday, Wednesday, and Friday each jar was placed on a coarse 

 balance and water added slowly through the test tube until its original weight 

 was restored. This method of supplying the water retains the surface of the 

 soil in an open, porous condition. 



"After 4 weeks the contents of the jar were mixed thoroughly. One hundred 

 gm. were placed in a funnel on a perforated porcelain disc, and washed with 

 water until the volume of the filtrate was about 100 cc. Nitrates were then 

 determined in the filtrate by the Tiemann-Schulze method and calculated to 

 the original, air-dry weight of the mixture. 



" For the ammonia determination, an amount equal to 200 gm. of the dry 

 soil was placed in a flask with dilute hydrochloric acid (1:25) in quantity 

 sufficient to make 500 cc. with the water already present in the sample. The 

 mixture of soil and acid was shaken thoroughly, filtered after standing over 

 night, and 250 cc. of the filtrate distilled with magnesia. The ammonia was 

 caught in standard acid and the solution titrated back with ammonia. Correc- 

 tion was made for the ammonia in the reagents. Both nitric and ammonical 

 nitrogen were corrected from the quantity present in the original soil. . . . 



" The saturation capacity of the soil was estimated as follows : Fifty gm. 

 soil are placed in a I5 in. carbon filter on a perforated porcelain plate, weighed, 

 and water added until the soil is saturated. After the soil has drained 15 min- 

 utes, protected from evaporation, the apparatus is weighed again. The gain 

 in weight is the saturation capacity, and is expressed in percentage of the 

 original soil." 



Basicity of the soils was determined by three methods as follows : 



"(1) Ten gm. of soil were digested with 100 cc. fifth-normal nitric acid for 

 12 hours, and 10 cc. of the filtrate was titrated with caustic soda and phenol- 

 phthalein. Since salts of iron and aluminum are acid to this indicator and the 

 corresponding hydroxids are precipitated during the titration, this method does 



