IMPROVEMENT OF THE SOIL. 



45 



CHAPTER III. 



THE IMPROVEMENT OF THE SOIL. 



A soil may be improved in texture, in depth, and by the 

 addition of such constituents necessary for the growth of 

 plants as may be wanting. 



The texture of a clayey -soil can be rendered more per- 

 vious by thorough draining, deep trenching, and by the 

 application of sand, ashes, lime and unfermented manure. 

 Any clayey, retentive subsoil will be greatly benefited by 

 good underdrains. A wet soil is always cold, as water 

 has a much greater capacity for heat than has earth. 

 The same quantity of heat that will warm the earth four 

 degrees will warm water but one. Water, also, is a bad 

 conductor of heat downwards. Boiling water can be 

 gently poured over cold water without heating the latter, 

 except a very little at the surface. Now, if the soil in 

 spring be saturated with water colder than the summer 

 rains, unless it be removed by drainage, the rains cannot 

 descend to carry warmth into the ground; neither will the 

 wet soil conduct the atmospheric heat downwards with 

 much rapidity. But draw off the cold water by proper 

 drains, and the warmer water can percolate through and 

 raise the temperature of the soil. As the warmer water 

 settles, the porous space it occupies will admit warm air. 

 (Thompson.) Drainage, also, by admitting the atmosphere, 

 renders the soil much more friable. Soils w r ell drained 

 have likewise been found to suffer far less from summer 

 droughts than before. Underdrains should be not less 

 than three feet below the surface, and four feet is much 

 to be preferred. 



Trenching renders the upper stratum of soil more light 



