48 ON INCREASING THE GROWTH 



deeper portions, as well as an intermingling of the 

 different kinds of soil. The latter circumstance not 

 only places a more efficacious substratum of earth at 

 the disposal of plants, but likewise insures a more 

 equable distribution of its moisture. By carrying off 

 its superabundant water ^ or draining' ^ the soil is not 

 merely rendered more dry, friable, and warm, but 

 also more energetic and sound ; — more energetic, 

 because air now penetrates, instead of water, into its 

 interstices, producing a more active weathering and 

 decay ; — sounder, because the access of air prevents 

 the further generation of acids, which are notoriously 

 disadvantageous to plants grown upon the land. By 

 coating with marl or lime, the free acids already pres- 

 ent in the soil are most rapidly neutralized, and the 

 activity of the ground in decomposing and dissolv- 

 ing its organic and inorganic components is mate- 

 rially promoted. At the same time an exces- 

 sive binding of the soil is corrected; an improve- 

 ment which might also be attained, were it not in 

 the majority of cases too expensive, by burning 

 earths of this description. A judicious interchange 

 or rotation of crops may also essentially improve the 

 physical constitution of a soil, inasmuch as leafy 

 plants (for instance, peas, clover, etc.) shade the 

 ground, and keep it moist during a whole summer, 

 whilst deeply-rooting plants (for instance, rape, etc.) 

 make it loose and mellow. Finally, irrigation may 

 in like manner contribute to the improvement of the 

 character of the soil. 



