The Brinkley argus., 1916-01-21
1. Origin and Function of Soil.

 take the course-J. H. Miller. Direc- tor Cooperative Extension Work.
 1. 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. The soil or surface layer contains more decaying animal and vegetable matter, and for that reason is darker and coarser in texture.
 Tn 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 a storage place for mois ture and furnishes some food for those plants which are able to send their roots into 1t.
 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. ing the resultant expansion and con. 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 oi the atmosphere produced chemica changes which led to the breaking down of rock.
 After rocks were broken down tt form soil, the development of plan growth led to the introduction of or ganic matter. The leaves of plant fell to the soil and became part o 1t. Upon the death of the plant tn roots and stem of the plant became { part of the soil The decay of plant l enriched the soil by hastening tn | chemical processes as well as by re turning plant food which could b | used over again. As the forests de veloped and year after year tn leaves, twigs and dead trunks wer returned to the soil, the surface lave became darker and looser and nor porous than that underneath.
 Geological Classification. All soil does not now occupy It original position. This fact gives ris to two general classes, first the seden tary or those soils which have no been moved far from their point o origin, and second the transporte soils which have been formed by a< emulation through the effects c wind, ice, water, or gravity. The rt sidual forms the most important clas of sedentary soils in Arkansas. Thi is the main type in the western an northwestern parts of the state. Tn residual soils having been forme practically in their present positio are old soils, without strata. and pr senting . heterogeneous mass of mi terial. They have been subjected teaching for long periods. and lare part of the soluble materials hay !, been washed out. ....,s.s. .,.
 All our river bottoms are made'u
 of alluvial or water transported soil A large portion of southern and soutl , eastern Arkansas is made up of m rine soil, or what is commonly know as coastal plains land. Tho sedimen' which are continually being carrie away by rivers are sooner or later a posted in the sea.
 Soil Particles.
 Soil particles vary in size fro
 coarse gravel to the very finest pa
 ticles of clay. Between these a
 coarse, fine and very fine sand par
 cles and what is known as silt O.
 can easily recognize the coarse ar f,ne grained soils by rubbing vel small amount between the finger
 The finer a soil is the more silt al
 clay it contains, the more sticky 1t
 when wet When soil contains 5 moderate amount of each of the SC 2 eral grades of sand, silt and clay
 usually works easily and Is called , loam When it contains more sand s is called a sandy loam, or more cla V q clay loam If it contains larl |. amount of clay it Is called clay SO The condition of the soil affectii ] the ease with which 1t may be work 0 is called tilth. By good tilth"
 meant friableness. By poor tilth" meant a cloddy or compact conditic Tilth depends largely upon the amou y of humus or vegetable matter a & contains and upon the water conte
 oS the soil at the time oS work1r l