The Spectator., 1915-11-05
1. Origin and Function of Soil.

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.
 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 a 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
 
 various chemical and physical agen- cies. With alternate heating and oool- ing the resultant expansion and con- traction caused Assures to develop Water getting into Assures and frees 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 a part of 1t, Upon the death of the plant the 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, twiss and dead trunks were returned to the soil. the surface layer became darker and looser and more porous than that underneath.
 Geological Glass ific atlon.
 All soil does not now occupy it's 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- 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 are old soils, without strata. and pre- senting a heterogeneous mass of ma terial. They have been subjected to teaching for long periods, and large part of the soluble materials have been washed out
 All our river bottoms are made uD 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 known as coastal plains hand The sediments which are continually being carried away by rivers are sooner or later de- posted in the sea.
 Soil Particles.
 Soil particles vary in size from coarse gravel to the very finest par ticles of clay. Between these are coarse. fine and very fine sand parti. cles and what is known as silt One can easily recognize the coarse and fine grained soils by rubbing very small amount between the fingers The finer soil is the more silt and clay it contains. the more sticky it is when wet When a soil contains A moderate amount of each of the sey- eral grades of sand, silt and clay 1t usually works easily and is called a loam. When it contains more sand 1t is called sandy loam. or more clay. clay loam. If 1t contains a large amount of clay it is called a clay soil.
 The condition of the soil affecting the ease with which 1t may be worked ts called filth. By good tilth" is