SOILS FERTILIZERS. 21 



bonate and carbonic acid in water, the authors conclude that soils treated with 

 water, calcium carbonate, and carbonic acid in such proportions as they exist in 

 nature act differently than is generally assumed. 



The influence of snow cover on soil temperature, (i. Friesenhof {Met. 

 Ztschr., 2(1 (1U09), Xo. G, pp. 273-275). — The need and importance of systematic 

 studies of this subject are pointed out and the conditions which must be taljen 

 into consideration in making such studies are explained. 



Results of recent investigations in soil bacteriology and their value for 

 agricultural practice, J. Simon ( Mitt. Okonom. Gesell. ,Sachsen, 1908-9, pp. 

 1-27, figs. 2). — This article discusses the importance from an agricultural stand- 

 point of the activities of micro-organisms in the soil in the light of recent prog- 

 ress in this field of Investigation, and indicates the practical means that may be 

 used to promote the beneficial activities. 



The influence of depth of cultivation upon soil bacteria and their activi- 

 ties, W. E. King and C. J. T. Doryland {Kansa.-i /Sf«. Bui. 161, pp. 211~2.'j2, 

 pf/s. 3, dgms. 2). — This is an account of preliminary experiments on the influence 

 on the bacterial content of stirring (plowing) silt loam and fine sandy loam to 

 different depths (2 to 12 in.). 



The following volumetric method was used in these studies: 



" One cc. of soil was placed in a sterile test-tube to which was added 19 cc. 

 of sterile distilled water. This was shalven for Vi minutes, and from each tube, 

 by means of a sterile platinum loop, which was constructed and graduated to 

 hold 1 cu. mm. of water, approximately 1 cu. mm. of the soil suspension was 

 transferred into 10 cc. of sterile liquefied agar. The inoculated medium was 

 then poured into a sterile Petri dish." 



A special form of small steel soil sampler and a sample case used in the work, 

 as well as the method of taking the samples, are described. 



" The soil samitler is made of steel and consists of a steel tube 7 cm. long 

 with an inside diameter of f in. and an outside diameter of I'g in. The plunger, 

 with a plunger-rod h hi- in diameter, is connected with the cylinder through a 

 I in. hole, and is clamped and held at the desired place by a set screw. The 

 plunger-head is just a working fit inside the cylinder. The plunger-rod is 

 graduated so that the plunger-head allows 1, 2, 3 or 4 cc. of soil to be taken, as 

 desired." - 



The following conclusions are suggested l)y the results: 



" Deep plowing (8 to 10 in.) tends to increase the number of soil bacteria in 

 both sandy and silt soils. 



" Deep plowing tends to increase bacterial activity. More ammonia is pro- 

 duced. 



" Deep plowing tends to decrease deuitrification or the reduction of nitrates 

 and the liberation of free nitrogen. 



" The volumetric method of quantitative bacteriological soil analysis has the 

 following possible advantages over the gravimetric method: (a) It is more 

 simple and convenient; (h) there is less danger of contamination; (r) the re- 

 sults are placed on a more accurate basis for comparison. The volumetric 

 method can be used to advantage when comparative results are desired. 



" Increased soil temperature increases bacterial activity. 



"An excess of moisture in soil reduces the number of bacteria and is detri- 

 mental to bacterial activity. 



" The maximum number of bacteria is found within the fifth and sixth inches. 

 Either side of this zone the numbers of bacteria decrease. 



" Due to certain conditions, different siiecies of bacteria are present in soil, 

 at different times in predominating numbers. 



