The Brinkley argus., 1916-01-14
|. Origin and Function of Soil.


 Soil is composed of finely divided | rock particles, called inorganic mat ter, and finely divided decaying vege- table matter. It occurs in two layers which are known as soil and sub-soil. l The soil or surface layer contains more decaying animal and vegetable matter, and for that reason is darker and coarser in texture.
 In the course of time the finer parti- cles have washed down into the sub soil and have caused the layer to be- come tighter and heavier. The sur face soil furnishes the physical sup port for plants and the major portion of their plant food supply. The sub soil provides storage place for mois ture and furnishes some food for those plants which are able to send their roots into it.
 Soils have their origin from rocks. Geology tells us that the surface of the earth was once molten mass which solidified to form rock. Gradual ly the rock was broken to pieces by various chemical and physical agen cies. With alternate heating and cool traction caused Assures to develop. Water getting into Assures and freez- ing caused further division. Water running over rocks ground them down. Wind carried the covering from rocks and exposed them anew. The gases of the atmosphere produced chemical changes which led to the breaking down of rock.
 After rocks were broken down to form soil, the development of plant | growth led to the introduction of or. | ganic matter. The leaves of plants | fell to the soil and became part of | it. Upon the death of the plant the l roots and stem of the plant became a | part of the soil The decay of plants | enriched the soil by hastening the | chemical processes as well as by re. | turning plant food which could be used over again. As the forests de veloped and year after year the leaves, twigs and dead trunks were returned to the soil, the surface layer l became darker and looser and more | porous than that underneath.
 Geological Classification.
 l All soil does not now occupy its original position. This fact gives rise to two general classes, first the seden- tary or those soils which have not been moved far from their point of | origin, and second the transported soils which have been formed by ac. l emulation through the effects of wind. ice, water, or gravity. The re- | sidual forms the most important class of sedentary soils in Arkansas. This | is the main type in the western and | northwestern parts of the state. The | residual soils having been formed | practically in their present position 1 are old soils, without strata, and pre-
 senting a heterogeneous mass of ma
 terial They have been subjected tc
 teaching for long periods, and large
 part of the soluble materials have
 been washed out.
 All our river bottoms are made LII
 of alluvial or water transported soils
 A large portion of southern and south
 eastern Arkansas is made up of ma
 rine soil. or what is commonly knowr
 as coastal plains land. The sediment! which are continually being carried
 away by rivers are sooner or later de
 posted in the sea.
 Soil Particles.
 Soil particles vary in size iron
 coarse gravel to the very finest par
 ticles of clay. Between these ar
 coarse, fine and very fine sand part cles and what is known as silt. On
 can easily recognize the coarse an' fine grained soils by rubbing a yer small amount between the fingers The finer a soil is the more silt an clay it contains, the more sticky it when wet. When a soil contains i moderate amount of each of the seN
 eral grades of sand, silt and clay f usuallv works easily and is called
 loam. When it contains more sand is called a sandy loam, or more clay ? a clay loam. If it contains a larg . amount of clay it Is called clay soi
 The condition of the soil affechn the ease with which it may be worlse
 is called tilth. By good tilth"
 meant friableness. By 'pocr tilth"
 meant a cloddy or compact conditicl Tilth depends largely upon the amour
 of humus or vegetabls matter so
 contains and upon the water conter T of the soil at the time of workin'