578 STATE BOARD OF AGRICULTURE. 



That part of the water added to the soil may become inactive or avail- 

 able and thus be removed from the field of action as far as the freezing- 

 point lowering is concerned seems to be proved beyond any doubt. Some 

 of the evidences that may be brought forward which tend to confirm this 

 fact are as follows: (1) The lowering of the freezing point of the agri- 

 cultural soils at the minimum water content decreases with successive 

 freezings as will be shown subsequently. This decrease is taken to mean 

 .liat the process of freezing produces a change in the physical condition 

 of the soil, and thereby releases some of the inactive water. This re- 

 leased and free water goes to dilute the original soil water and thereby 

 decreases the depression of the soil solution. 



(2) As has been shown in a former paper (9) when to a soil like clay, 

 for instance, is added a certain amount of water and this wet soil is 

 placed to freeze in an expansion apparatus like the dilatometer, only 

 part of the water added freezes, as measured by the amount of expan- 

 sion; the remainder of the water added apparently is prevented by the 

 soil from freezing. This phenomenon has been observed also by Foote 

 and Blair (10) in hydroges such as aluminum, silica, iron, etc. 



(3) Cameron and Gallagher (11), and Keen (12) in conducting ex- 

 periments to obtain information concerning the laws governing the 

 evaporation of water from soils, found that the amount of water evap- 

 orated per unit of time was practically the same from a high moisture 

 content down to a certain point and then it began to decrease quite 

 rapidly. From the point where the rate of decrease commenced and 

 downward, the soil water sliowed a lower vapor pressure than the free 

 water. This diminution in the rate of evaporation and the reduction in 

 the vapor pressure are taken by us to indicate that the soil water was 

 not free but existed in an inactive or unavailable form. 



(4) The investigations of Briggs and Shantz (13), and those of a 

 great number of other investigators on the wilting coefficient of soils, 

 show that plants begin to wilt and die when the percentage of water in 

 the soil is still considerable. Some investigators have attributed this 

 phenomenon to the extremely slow movement of water in the soil at that 

 low water content and consequently to the failure of the plants to obtain 

 water at a sufficient rate to replenish that lost through evaporation and 

 thus avoid wilting. We are inclined to attribute the wilting of plants 

 partly also to their inability to absorb or extract the water which is held 

 by the soil in an inactive or available form, at a sufficient rate. 



(5) Jones (14) and his associates, working upon the lowering of the 

 freezing point of various hydrates, found that these substances yielded 

 far greater depression of the freezing point than should be expected. 

 Jones attempted to explain these abnormal results by assuming that 

 these hydrates take up water, forming complex compounds with it, and 

 thus remove it from the field of action as far as the freezing point lower- 

 ing is concerned. 



Many other evidences could be cited which go to indicate that part of 

 the water contained by the soils exists in an inactive or unavoidable form 

 but the foregoing may be considered sufficient. 



m Jour. AgT. Res., v. 8, No. 6, 1917. 



(10) Jour. Am. Chem. Soc, V. 38, No. 3, 1916. 



(11) Bui. No. 50, Bu. Soils, U. S. Dept. Agr., 1908. 

 (12^ Jour. Agr. Sci., 6, 1914. 



(13) Bui. No. 230, Bur. Plant Tnd.. U. S. Dept. Agr., 1912. 



(14) Jones H., Blemeptg of Physical Chemistry, p. 238, 1910. 



