854 EXPERIMENT STATION RECORD. 



The large spaces occurring in tilled soils retard tbe capillary rise of 

 water, but, on the other hand, increase the velocity with which water 

 penetrates downward from the surface, often to a remarkable degree. 

 If crumbly soils are pressed together (rolled), the upward movement 

 of water is increased in proportion to the increase in density, but the 

 percolation of atmospheric water is retarded. The presence of stones 

 diminishes the capillary rise of water in the soil in proportion to the 

 quantity of stones present, and the same is true of the percolation of 

 water. 



In soils which are made up of layers of different physical constitu- 

 tion the passage of water from one h.yer to another, either upward or 

 downward, is hindered more and stopped sooner the wider the dif- 

 ference between adjacent layers in the fineness of their particles or in 

 their other physical properties. Water rises or sinks from a coarse- 

 grained to a line-grained layer much more readily than the reverse. 



The capillary movement of water in a soil occurs only when consid- 

 erable water is present. It ceases when the soil contains 30 to 50 per 

 cent (according to the fineness of the particles) of the quantity of water 

 required for saturation, and instead there is a very much slower move- 

 ment of water from the surface of one particle to that of another. If 

 the water envelopes are diminished beyond a certain limit the move- 

 ment of water ceases altogether. 



Cajiillary rise and percolation of water in the soil declines as the 

 water content of the soil diminishes, because the so-called surface ten- 

 sion of the liquid increases at the same time.^ 



The to ater -holding capacity of the soil. — The quantities of water in 

 soils are best expressed in percentages of the volume of the soil occu- 

 pied by water. The old method of expressing the water in ijercent- 

 ages by weight is misleading on account of the variations in the 

 specific gravity of soils.^ 



After movement ceases water is retained in the soil by surface 

 attraction and also by the affinity of the colloid substances ibr water. 

 Other things being equal, the quantity of water stored u}) by the soil 

 is greater the finer the soil particles and the greater the quantity of 

 colloid material present. 



'Meister, Programm des Jahresberichtes 1857-'58 der k. landwirthschaftliclien 

 Centralscbule Weihenstephan. W. Scliumacher, Physik des 15odeus, 1894, p. 91. 

 F. Haberlandt, WisseiiHcbaftlich-praktische Untersuchnngeu auf deiii Gebiete des 

 Pflanzenbaues, 1, 1875, p. 9. A. Scbleh, Ueber die Bedeutnng des Wasscrs iu den 

 Pflanzen und die Regnliriiug desselben in uuserer Culturbuden, Inaugural-Disserta- 

 tion, Leipzig, 1876. A. von Liebeuberg, Ueber das Verhalteu des Wassers im Boden, 

 Inaugural-Dissertation, Halle, 1873. H. von Klenze, Landw. Jalirb., 1877, p. 83. 

 A.Mayer, Lebrbuch der Agriculturcbemie, II. W. Edler, Die capillare Leitungdes 

 Wassers in den durch den Scliinie'scben Scbliimmapparat abgescbiedenen bydrau- 

 liscben Werthen, Inaugural-Dissertation, Gottiugen, 1882. .-V. Mayer, Forsch. Geb. 

 agr. Pbys., 14, p. 254. E. Wolluy, Ibid., 7, p. 2G'J, and 8, p. 206. 



»A. Mayer, Landvr. Jabrb., 1874, p. 753. 



