SOILS ^FERTILIZERS. 711 



to destruction of disease germs than to its action on the cnemical properties or 

 bacteriological activities of the soil. 



Colloid materials in clay and adsorption phenomena, P. Rohland (Landw. 

 Jahrb., 39 (1910), No. 3, pp. 369-372; abs. in Chem. Zentbl.. 1910, II, No. 7, p. 

 ■'i91). — The author reviews conclusions from his previous work regarding the 

 importance and functions of colloids in the soil, and especially their bearing 

 upon plasticity, permeability, and absorptive propei'ties of soils. He does not 

 accept Ehrenberg's explanation (E. S. R., 24, p. 131) of the fact that certain 

 kinds of ions are absorbed while others are not, and he does not believe 

 that this depends in any way upon the ease or difQculty of solution of the salts. 

 He finds that with the exception of neutral calcium carbonate all calcium salts 

 are more readily soluble than calcium sulphate, of which the ion SO4 is not 

 absorbed but diffused. 



The amount of water and plant food removed from soils by drainage, M. 

 Gerlach {IUus. Landw. Zig., 30 {1910), No. 95, pp. 879-881, figs. 2).— This 

 article briefly summarizes x'esults of studies with lysimeters and on field 

 drainage systems. 



Examination of drainage water from fields of 5 farms showed 215 gm. of 

 lime per cubic meter of drainage water, 6.3 gm. of potash, and 11.8 gm. of 

 nitrogen, of which 10.9 gm. was in the forms of nitrous and nitric acids and 

 0.9 gm. in the form of organic nitrogen. No ammonia or phosphoric acid was 

 found in the drainage water. 



Observations on a farm drainage system during the spring of 1909 showed 

 1,161.6 cubic meters of drainage water per hectare, containing 6.8 kg. of total 

 nitrogen, 5.9 kg. of nitric nitrogen, 7.6 kg. of potash, and 18.7 kg. of lime. While 

 these amounts are small as compared with the total amounts present in the soil, 

 they represent a relatively large proportion of the readily available plant food 

 and would constitute in the course of years a considerable drain upon the soil 

 fertility. 



These results, as well as those of experiments with the lysimeters, show that 

 phosphoric acid is firmly fixed in the soil and is subject to little or no loss in 

 the drainage. The largest loss is in the case of lime. Potash is also removed 

 in the drainage to a considerable extent. The loss of nitrogen is smaller than 

 that of either lime or potash, and mostly in the form of nitric nitrogen. 



Examinations of a number of soils show that the surface soil is as a rule 

 richer in nitrogen and phosphoric acid than the subsoil. On the other hand, 

 the subsoils usually contain more lime and potash than the surface soil. 



Denudation and erosion in the southern Appalachian region and the 

 Monongahela basin, L. C. Glenn ( U. S, Geol. Survey Prof. Paper No. 72, 

 pp. 137, pis. 21, fig. 1; Press BuJ. Ii'iG, folio). — This paper records observations 

 in parts of Pennsylvania, Virginia, West Virginia, North Carolina, South Caro- 

 lina, Georgia, Tennessee, and Alabama on " hillside and mountain side wash 

 and wear, soil removal by gullying and soil burial by overwash, stream clogging 

 and stream overflow, the filling of mill ponds and the wrecking of dams and 

 bridges, and numerous other evils that are attributed by many observers, in 

 large part, to reckless deforestation and injudicious attempts to cultivate slopes 

 that are not adapted to agriculture. . . . 



" In the course of the study it was noted that steep slopes formed of certain 

 rocks could be safely cultivated, but that others, no steeper, composed of other, 

 different rocks were cultivated with disastrous results. . . . 



" Much of the area is not properly agricultural laud and should not be cleared 

 and forced into agricultural use, because that forcing means quick destruction 

 both of the area itself and of the lower-lying areas on the same stream- 

 ways. . . . The agricultural problem involves the selection of the areas best 



