WHAT WATER DOES IN SOILS 



55 



Blasting hard subsoils or "hardpan." In some places 

 there is a good deal of "hardpan." This is a kind of rock 

 formed in the soil in sheets, at 

 from three to six feet depth. 

 Where trees are to be planted, 

 it is sometimes blown to pieces 

 by a charge of giant powder 

 exploded at that depth before 

 the tree hole is dug. The tree 

 roots can then go down to their 

 proper depths. The same can 

 be done when there is close, 

 hard clay subsoil at a few feet 

 down. Digging the tree holes 

 into such clay does no good. 

 The holes are soon filled with 

 water by rains, and the trees are 

 likely to die, even if the holes 

 have been filled, with good soil. 



PLANT 



)D IN SOIL WATER 



FIG. 29. Testing the soil by 

 means of a " soil probe." This 

 tells how far irrigation water 

 has penetrated, and it also tells 

 whether there is hardpan. 



Water dissolves most things. 

 When we boil down any 

 natural water till its moisture has evaporated, we al- 

 ways find that something solid remains behind. This 

 is best shown when the water is boiled in a bright silver 

 spoon, in which a little white film or crust may then be 

 seen. In a tea kettle that has been used for some time 

 we find more or less of a stone-like crust that has gradu- 

 ally been left by the water. Sometimes, as in alkali or 

 mineral waters, a residue is left which has a salt taste. 



