The Movements of Soil Water. 59 



multiplied vegetatively in the test, it might reveal a possible 

 complex character of the material in bud sports, but other di- 

 vergencies might be well ascribed to local effects. On the other 

 hand, if introduced in the form of seeds, the possible complex 

 character of the material would soon become apparent, especially 

 if the generations were followed properly. In the actual manage- 

 ment of the cultures, it is found profitable to re-introduce forms 

 from the original or control lot in order to follow the first 

 stages of their adjustment repeatedly. 



STUDIES IN SOIL PHYSICS, II. 



The Movements of Soil Water. * 



E. E. FREE. 



From a theoretical point of view it is not possible to say 

 that any one of the main soil constituents is more important 

 than any other, since all are necessary to a proper functioning. 

 Practically, however, there can be no two opinions as to the 

 supreme importance of the soil water. Nine times out of ten it 

 is the supply of this constituent which limits crop production. 

 Usually the other constituents are sufficiently, if not maximally, 

 favorable, and poor water supply and infertility go hand in hand. 

 Controlled water usually means controlled fertility. The soil 

 water must occupy, then, a very prominent place in the theories 

 of the soil physicist, and the study of its nature and movements 

 must ever be a most important and absorbing branch of his 

 activity. Nor is the importance of the soil water intrinsic only. 

 It is the medium of the soil solution and only through it are the 

 necessary food elements carried from soil to plant. From soil 

 chemist, as from soil physicist, the soil water is receiving ever 

 increased attention and especially so in the Hght of the most mod- 

 ern theories of the dynamics of plant food. { 



Nearly everv discussion of soil water has been based upon a 

 classification which was made very early in the study of the sub- 

 ject. The soil water is divided into hygroscopic, capillary and 



♦Published by permission of the Secretary of Agriculture. 



JSee, Cameron.— Jour. Phys. Chem.. 14; 320-372, 393-4S1 (1910). 



