CHAPTER III 

 SOIL WATER AND SOIL AIR 



WATER IN THE SOIL 



Why water is needed. The importance of water for 

 plant use has already been intimated in Chapter I. It is not 

 only directly useful in the various ways noted in that chapter, 

 but it has indirect benefits upon plant life almost as great. 



Water is a great solvent. That is, it has the power of 

 changing substances from a solid condition to one known as 

 a solution. A lump of sugar placed in a glass of water soon 

 disappears as a solid. The sugar is held invisibly in some 

 way by the water, for we know that water in which sugar is 

 dissolved tastes sweet and when evaporated leaves a solid 

 residue of sugar. This property of water acting as a 

 solvent enables it to dissolve certain solid substances of 

 the soil so that they may pass in solution into the plant, 

 the only possible way for them to enter. The same property 

 enables the water to carry dissolved material from place to 

 place in the soil, as from the depths to the surface when the 

 water moves upward. 



Water also brings about changes in the position of the 

 soil particles with reference to one another, making the soil 

 in some instances granular, and in others more compact. 

 This fact will be kept in mind as a further consideration of 

 the action of water in the soil since it is an important one in 

 connection with soil management. 



