SOIL AND ITS PREPARATION. 13 



of sticky clay will absorb a slight amount of moisture, 

 but when it is reduced to a powdered condition, its ab- 

 sorbing power will be very much increased. One hundred 

 grains of fine clay left for twelve hours in contact with 

 a solution of caustic potash, the latter not filtered through 

 it, absorbed one thousand and fifty grains of potash. 



Soils have the power of separating ammonia, and other 

 bases from their solutions, and of separating alkaline 

 bases from the acids with which they were combined. 



Soils possessing the greatest amount of capillary poros- 

 ity, most friable and mellow, or, in other words, such as 

 are in the best agricultural condition, will condense the 

 greatest amount of fertilizing material; and the more 

 they are pulverized, the better will they resist the leach- 

 ing action of water. Soil in an improper physical con- 

 dition may hold fertilizing materials in sufficient quanti- 

 ties for a full crop. It will, however, yield only a small 

 percentage to the vegetation upon it, until it is made 

 friable, and so becomes conducive to growth. Carbonic 

 acid is one of the chief agents in this process; and in 

 order that this acid may be formed, the carbonaceous 

 matter in the soil must be brought in direct contact with 

 the atmosphere. As long as the soil is in a compact con- 

 dition, or is saturated with water, carbonic acid is not 

 formed. During the recent severe drouths it has been 

 observed that crops growing on deeply-plowed land have 

 suffered the least, for the reason that the greater the 

 mass of fine soil, the greater must have been the amount 

 of moisture absorbed. Heat is evolved during the de- 

 composition of vegetable matter; and the darker the, soil 

 is from decomposing vegetable matter, the warmer will it 

 become. The warmth of light-colored sands is attribut- 

 able to their conductive power. Half the crop depends 

 sometimes upon the previous preparation of the land. 

 Owing to the absence of a covering of snow and of suc- 

 cessive freezings and thawings, fall plowing, so useful at 



