24 EXPERIMENT STATION RECORD. 



"More than half the entire county is covered with the common prairie soil 

 known as brown silt loam, and about one-third consists of two upland timber 

 types, the yellow silt loam (hilly) and the yellow-gray silt loam (undulating), 

 the former occupying almost one-fifth of the entire county. . . . 



" The most significant fact revealed by the investigation of the Knox Coimty 

 soils is the low phosphorus content of the common brown silt loam prairie." 



Soil investigations, [L. T. Sharp] {Nevada Stci. Rpt. 1913, pp. 24-38).— 

 The first part of this paper discusses the soils of Nevada relative to fertility 

 and crop production, and the second part reports the status of scientific investi- 

 gations looking to soil improvement. 



Chemical analyses of representative soil types show them to be " intrinsically 

 rich in mineral plant food and naturally deficient in nitrogen." Alkali was 

 present in various amounts in almost all the soils examined. 



A series of experiments on the biological fixation of nitrogen did not war- 

 rant definite conclusions, but, " the evidence at hand ... on the whole is 

 rather favorable to the explanation of the accumulation of nitrates in Colo- 

 rado soils ... by Headden and Sackett" (E. S. R., 29, p. 621; 30, p. 818). 



Studies of bacteria in soils as affected by irrigation showed that the water 

 content most suitable for ammonification was not the optimum condition for 

 nitrification. Ammonification was most rapid with 25 per cent water content, 

 and was not markedly affected by differences of 3 per cent in water. On the 

 other hand, 19 per cent of water was most advantageous for nitrification, and 

 the rate of nitrification decreased over 50 per cent as the water content 

 increased to 25 per cent. " It is probable that 18 to 20 per cent of water is 

 the most suitable water content for this soil, . . . for the bacterial processes 

 taking place in it." 



Studies of colloids as protective substances for bacteria, particularly in the 

 presence of alkalis, showed that aluminum hydroxid rendered sodium chlorid 

 and sodium sulphate in solution at certain concentrations less toxic. Alumi- 

 num hydroxid and colloidal starch were more or less toxic to pure cultures of 

 ammonifying organisms and slightly depressed ammonification with mixed cul- 

 tures. Aluminum hydroxid stimulated nitrification to some extent. 



Heat movement in pseudo-isotropic soil, A. v. Andebk6 (Met. Ztschr., 30 

 {1913), No. 12, pp. 580-589). — ^A mathematical exposition of heat movement in 

 soils is given. This is based on the assumptions that a homogeneous pervious 

 soil stratum, which would be isotropic but for the effect of meteorological fac- 

 tors and ground water variations, may be considered pseudo-isotropic, and that 

 the sum of the factors, including amplitude, phase, and variations in heat ca- 

 pacity and conductivity, which influence heat movements in pseudo-isotropic 

 soils, may be expressed by Fourier's law and modifications thereof. 



An erosion study, G. N. Coffey {Jour. Amer. Soc. Agron., 5 {1914), ^o. ^, 

 pp. 230-232). — ^A method described for measuring the amount of material 

 removed in suspension and solution from the surface of a given area consists 

 of surrounding a small plat on all sides except the upper one with a split 

 glazed tile surface drain so that surface wash from the plat is carried into 

 this drain and thence through a pipe to a steel tank. For determining the 

 plant food carried away in the drainage water two lines of tile are placed 30 

 in. deep surrounding the plat, the inner line being for the purpose of collecting 

 subsoil drainage from the plat and the outer line for removing surrounding sub- 

 soil water. 



Lysimeter investigations, 1913, G. Richtee {Mitt. Kaiser Wilhelms Inst. 

 Landw. Bromherg, 6 {1914), ^'O. 3, pp. 212-224) .—This is a brief account of a 

 continuation of work by Kriiger previously noted (E. S. R., 29, p. 125). It 



