THE SOUTHERN PLANTER, 23eoote& to Hgrfcuiturr, horticulture, ana tue ^ouseholfc &trts. Agriculture is the nursing mother of the I Tillage and Pasturage are the two breasts Arts. — Xenophon. o f the State. — Sully. FRANK: G. RUFFIN, Editor. P. D. BERNARD, Proprietor. Vol. XIH. RICHMOND, MARCH, 1853. No. 3. For the Southern Planter. SCIENTIFIC AGRICULTURE. BY PROFESSOR GILHAM. NUMBER IV. (Continaed from page 6, Vol. XIII.) Having shown in previous numbers that the organic elements of plants are carbon, oxygen, hydrogen and nitrogen; that carbonic acid, water and ammonia are the principal sources of supply of these substances to plants; that the inorganic bodies found in plants are po- tassa, soda, lime, magnesia, oxyde of iron, oxyde of manganese, silica, chlorine, sulphuric and phosphoric acids; that although the quan- tities of these bodies required by vegetation are comparatively small, they still are as ne- cessary as the more abundant organic bodies; and that the soil is the only source of supply of the inorganic food of plants; it remains lor us to consider the origin, composition and pro- perties of soils. GENERAL ORIGIN OF SOILS. Soils have their origin in the disintegration, or wearing down of the rocks which compose the crust of the earth. In mountainous and very hilly countries the rocks are protruded above the surface of the soil, and in maay places scarce any thing is to be seen except the naked rocks, while in more level regions they are found embedded far below the earth's surface. Wherever found, however, they are more or less exposed to atmospheric influences. These influences appear at first sight to have but little effect, as numberless instances are within the experience of almost every one, in which rocks have been exposed for many years, ■jt even centuries, without undergoing any ap- parent change; but if we consider for a mo- ioent that soils have been forming for thou- gands of years, we can readily understand that if the atmosphere has any influence upon the rocks, a portion, at least, must eventually be reduced to that fine state of division known as soil. The action of atmospheric agents in the disintegration of rocks and formation of soils Vot. XIII.-3. is both chemical and mechanical. The car- bonic acid of the air, although so small in quantity, exerts a powerful influence; first, by its slowly attacking certain minerals and rocks, by which existing combinations are destroyed, and new ones produced, whereby the rocks are either reduced to some form of soil, or left in such a state as to yield without difficulty to the other agencies which are constantly in operation in the air for the same purpose; and secondly, by its property of being absorbed by water, a property which, it will be remem- bered, adds materially to the solvent power of that fluid. The oxygen of the air, too, attacks certain rocks, particularly those which contain the protoxyde of iron and the sulphuret of iron. In the first case the protoxyde passes to the state of peroxyde of iron, (iron rust,) by the absorp- tion of oxygen, and in the second case the sulphur and iron both become oxydised, the sulphur passes to the state of sulphuric acid, the iron to protoxyde of iron, and these uniting with each other form sulphate of iron (copperas.) Water acts by its, solvent powers upon those constituents of the rocks which are in the smallest degree soluble in that fluid, and in this, as was stated above, it is greatly assisted by the carbonic acid which it holds in solution. Again, water, by entering the poresof the rocks, softens them, and makes them yield much more readily than they would otherwise do; and when frozen, by the great power exerted in its expansion, it destroys their cohesion entirely, so that when the ice melts, the rock falls to pieces, and sometimes to fine powder. Water also acts by its transporting power, carrying the finer particles to great distances sometimes, and by the force of attrition, causing the gra- dual wearing away of the larger ones. In mountainous regions all the finer parts of the soil as it is formed are removed from the tops and sides of the mountains, and carried into the valleys below. In cases where streams which have their rise in such regions, overflow their banks in time of freshets, the solid matter held in suspension is deposited over large areas in the form of mud, forming the soils of river bottoms, or what are called "bottom lands." The rocks wnich compose the earth's crust contain very little organic matter, and many of them none at all, hence when soils are first formed they necessarily contain but a small proportion of it. Nature, as we have seen in 66 THE SOUTHERN PLANTER, a former number, has so constituted plants that they derive most of their organic food from the air, while some depend upon that source alone for their supply. Now, in the first formation of a soil'those plants only which are capable of living at the expense of the air will take root. The growth is at first very limited; the first plants die, and falling to the earth, mingle with the soil; decay sets in, but before it is completed another growth is ma- tured, dies and rots. Thus a small quantity of organic matter is taken from the air and added to the soil; this process continues, each generation of plants making a small addition to the organic matter already collected, until, finally, the soil assumes a rich dark color, and will support a luxuriant vegetation. Plants have another very important influ- ence in preparing the soil for successful culti- vation. Their roots, particularly the roots of trees, penetrate sometimes to the distance of many feet below the surface ; by so doing, they are more firmly fixed in the ground, are more free from drought, and they meet with supplies of inorganic matter which they could not ob- tain in sufficient quantity from the surface soil. The sap, holding inorganic matter in solution, rises to the leaves, where it is spread out to the action of the atmosphere, by which it is evaporated, and more or less of its inorganic matter deposited. This process continues until the pores of the leaves becoming choked up, as it were, the leaves cease to perform their proper functions, change color, die and finally fall to the ground. These in their decay leave large quantities of organic matter, which be- comes incorporated with the soil, while all the inorganic matter which they contained, and which, as we have stated, was drawn from various depths below the surface, now becomes part of the surface soil, and, having once been in the circulation of plants, the substances which compose it, are better fitted for the wants of succeeding races. It is by this annual lop- dressing of leaves that the soil is brought, in many instances, to the condition of great fer- tility; and so beneficial is it that the very lightest soils will, for a few years after the re- moval of the natural growth, produce abundant crops. COMPOSITION OF SOILS. From what has been said in relation to the origin of soils it is manifest that they must differ very materially, both mechanically and chemically, and that a knowledge of the geolo- gy of a district of country is essential to a true appreciation of the qualities of its soils. Be- fore speaking, however, of differences resulting from differences in the rocks, we will devote a short time to the consideration of the various substances to be found in soils. From the statements made in our last num- ber it follows that every soil which is fertile without the aid of manure of any kind, must contain all the substances to be found in the ashes of cultivated plants, and in quantities sufficient to yield constant supplies to growing crops. These substances have already been enume- rated; all truly fertile soils are found to con- tain them all, together with alumina