THE IMPROVEMENT OF SOILS. 4Q 



but cannot be substituted for ditching in wet, swampy 

 lands. 



105. The advantages of drainage are numerous, 

 of which may be mentioned the following: 



(i.) It makes the soil warmer. The evaporation 

 of water from any surface is cooling. The heat of 

 the sun falling on a wet soil is taken up in convert- 

 ing the water into vapor, and does not reach the roots 

 of the plant. 



(2.) It keeps the plant food from becoming too 

 much diluted, and leaves it in a concentrated form 

 for absorption by the plant. 



(3.) It gives free access of air to the roots of 

 plants. Water not only keeps out the air, but 

 drowns or destroys the soil roots. 



(4.) It aids in bringing about a proper decompo- 

 sition of organic matter, and preventing the forma- 

 tion of organic acids that are hurtful. Swampy lands 

 which are generally sour and unproductive for valu- 

 able crops are rendered productive by draining. 



106. Deep plowing and sub-soiling not only as- 

 sist in draining the soil, but also render it better able 

 to stand a drought. The surplus water of heavy rains 

 can sink down without washing, while the capillary 

 action of a thoroughly pulverized soil draws mois- 

 ture from a greater depth in time of drought, and the 

 roots penetrate more easily beyond the influence of 

 the sun's rays and find abundant food, while air can 

 also reach a lower depth more readily and exercise 

 its disintegrating effect. 



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