THE RELATION OF SOILS TO IRRIGATION. 27 



the same effedl both in plant life and in the soil — for 

 all nature was torn off the same bolt. If the soil is 

 very wet for two or three weeks and is well filled with 

 vegetable matter, although the plant is overgrown, it 

 becomes sick just as much as a horse with colic. But 

 keep the soil so the air can penetrate it and neutralize 

 these acids, and the more of this vegetable matter the 

 better and heavier the plant will fruit. One strong 

 point in favor of irrigation is that it neutralizes these 

 acids and brings them more surely under the control 

 of the scientific cultivator, so that they riiay be more 

 fully utilized in the structural growth of the plant. 



Color and Texture. — The color of soil depends 

 exclusively on its composition, humus forming nearly 

 a black soil, while sand gives a light yellow, and iron 

 oxide produces a red color. The darker soils, other 

 things being equal, have the highest absorptive power 

 toward solar heat. This is shown when muck is 

 applied to the surface of snow in the spring. We 

 have often found in the rich valleys of the Rocky 

 Mountain region a dark, chocolate loam interspersed 

 here and there by deposits of a lighter and more chalky 

 nature, all being, however, extremely rich in gypsum 

 and salts that are valuable in the produ(5lion of fruits, 

 cereals, and vegetables. Investigation shows that one 

 acre foot in depth of a fairly good agricultural soil 

 contains four thousand pounds of phosphoric acid, 

 eight thousand pounds of potash, sixteen thousand 

 pounds of nitrogen and lime, magnesia, soda, chlorine, 

 sulphur, and silica — all of which are more fully ren- 

 dered available in maturing plant life when irrigation 

 is brought into prac5tice upon them. 



