12 THE AMERICAN FARMER. 



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vegetable or animal substances which they may contain in a greater or less proportion), hence 



their mechanical texture, as well as their mineral composition, depends upon their origin. 



According to texture, soils are commonly termed rocky, stony, gravelly, sandy, silt, 

 marl, and calcareous, loam, clay, etc. Though rocks and stones cannot properly be termed a 

 portion of the soil, yet when mingled with the finer soil or found to any great extent upon 

 the surface, these terms are commonly applied to distinguish such soils from others of different 

 characteristics. 



Although rocks and stones have long been, and are at present, the great pest to the New 

 England farmer, yet they are not entirely useless, as they frequently benefit crops by the 

 warmth, protection from winds, and the moisture they afford, as well as by the gradual 

 decomposition of those which contain lime, potash, and other fertilizing elements which con 

 tribute to the support of the soil, these elements being furnished by the decomposition of 

 the rocks through the action of the atmosphere, the crumbling of them by the agency of 

 frost, or by the dissolving of their mineral properties by water pure water itself being a 

 strong solvent, while water containing carbonic acid, such as rain-water (which always con 

 tains it), will dissolve limestone, chalk, and even the hardest marble in time, though the 

 latter, of course, much more slowly than the former. 



Some soils are peculiarly fine in texture, being almost entirely free from stones, gravel, 

 or sand, such as that of certain of the Western prairies, while others possess but little mineral 

 element, being composed mostly of vegetable matter, such as peat swamps, and salt marshes. 



Prof. S. ~W. Johnson, Director of the Connecticut Agricultural Experiment Station, who 

 is one of the best authorities on this subject, says, that the fertility of the soil depends, 

 chemically, first, upon the presence in it of all the ash elements and of nitrates in proper 

 quantity, and, second, on their occurrence there in such states of combination as to give a 

 constant and regulated supply ; that numerous experiments have demonstrated that a soil 

 destitute of either phosphoric acid, sulphuric acid, potash, lime, magnesia, or oxide of iron, is 

 absolutely barren on account of such deficiency ; and that it is equally certain that a soil 

 which contains the usual amount of potash, but only in the form of feldspar, or of phosphoric 

 acid, but only as apatite, or of magnesia, but only as serpentine, is infertile, because these 

 substances do not yield their elements to the solvent agencies of the soil or plant rapidly 

 enough to serve as plant food. 



Also of silica, which was formerly supposed to be a necessary element of the soil in order 

 to sustain a healthy and prolific vegetation, that recent investigations appear to show, that 

 though it is present in many plants, it is an accidental ingredient and in no manner essential 

 to their growth or perfection; and alumina, though an abundant element of soils, is always 

 absent from agricultural plants; that soda likewise appears to be unessential to most of the 

 vegetative processes, for although it is perhaps never entirely absent from cultivated plants, 

 it often occurs in them in extremely minute quantity, so that the soda which is indispensable 

 to the blood and milk of animals must be obtained, in part at least, directly from mineral 

 sources. 



Hellriegel s experiments show that 55 pounds of potash, 55 of phosphoric acid, 17 of 

 magnesia, 17 of soda, 23 of lime, 11 of sulphuric acid, 8 of chlorine, and 54 of nitrogen (in 

 the form of nitrates), are sufficient in soluble condition, in 1,000,000 pounds of soil, in order 

 to establish there a fertility equal to the production of 33 bushels of barley grain and 2,000 

 pounds of straw per acre. Good soil, however, may contain a larger proportion of available 

 plant-food than this. The weight of an average loamy soil is estimated to be about 4,000,000 

 pounds per acre for each foot of depth. 



It is estimated by good authority, that a crop of grain of thirty -three bushels removes 

 from the soil but 140 pounds of ash elements; that is, forty pounds in the seed and one 

 hundred pounds in the straw. 



