228 SCIENTIFIC AGRICULTURE. 



insignificant, would, by experiment, be found to alter entirely 

 their relative agricultural value. 



By referring to tables of the analysis of plants, and then 

 analyzing the soil, we can see at once what plant the soil is 

 adapted to produce. A soil containing all the organic and 

 inorganic elements of a particular plant, may be supposed 

 capable of producing the plant: but a soil deficient in one or 

 more of these elements cannot be expected to yield a crop. 

 A soil containing very little silica could not yield grass, but 

 might still contain enough for a crop of turnips. . 



An exact analysis of the quality of a soil, with the quantity 

 of each element, requires the skill of a practical chemist, and 

 the apparatus of a laboratory: but the most important qualities 

 of a soil may be determined by a few plain and simple experi- 

 ments, which are easily made by any one, whether acquainted 

 with chemistry or not 



The soil is made up, as before said, of various proportions of 

 animal, vegetable, mineral, earthy and gaseous matters. As a 

 general rule, the earthy part of the soil is estimated at from 

 90 to 96 per cent The salts of these earthy matters are in 

 small quantities. The amount of vegetable matter varies 

 greatly in different soils: in some, as in peat and muck soils, it 

 constitutes from one half to three fourths of their entire 

 weight ; while in sand and clay soils, it amounts to only from 

 one to five per cent The principal bulk of all soils, (except 

 peat, humus and muck soils,) is sand, clay and lime ; and on 

 the proportions of these, their peculiar properties, both chemi- 

 cal and physical, depend. The fertility of a soil is not depen- 

 dent upon any one of these, but upon the proportions and 

 state of mechanical division of all the other necessary elements. 

 The mixture of sand and lime with the other elements, (except 

 the alumina,) is usually entirely mechanical: in the various 

 kinds of clay, the silex and alumina are often chemically com- 

 bined, constituting a silicate of alumina. 



