160 



THE PRINCIPLES OF SOIL MANAGEMENT 



Table XXV 



water. Various salts in solution as fertilizers or otherwise, 

 tend to overcome this weakness, and therefore to in- 

 crease the moisture capacity. 



Increase in temperature decreases the surface ten- 

 sion, until near the boiling point it is almost nil. Briggs 

 reports that at 0C. the tension of pure water is 75.6 

 dynes per square centimeter, and at 25C. it is 72.1. 

 At the lower temperature more water is held in the 

 soil, and this is one reason why soils appear more moist 

 in cool seasons. (See also page 183.) 



78. Gravitational water. By reference to the ori- 

 ginal illustration (page 141), it will be noted that the 

 gravitational water was defined as that portion in excess 



