312 MISCELLANEOUS FARM SUBJECTS 



From 75 to 90 per cent of the original rock formation is not infre- 

 quently removed by leaching in the making of residual soils. 



The best natural soils are those of which the materials have 

 been derived from different strata, which have been minutely divided 

 by air and water and are intimately blended together; and in im- 

 proving soils artificially the farmer can not do better than imitate 

 the processes of nature. The materials for the purpose are seldom 

 far distant; coarse sand is often found immediately on chalk, and 

 beds of sand and gravel are common below clay. The labor of im- 

 proving the texture or construction of the soil is repaid by a great 

 permanent advantage; less manure is required, and its fertility in- 

 sured. The capital laid out in this way secures forever the produc- 

 tiveness and consequently the value of the land. 



As a result of the many processes at work we have two general 

 classes of soil. One results from the gradual -disintegration and 

 decay of rocks. Such soils, because they have not been moved from 

 where first formed, are called sedentary soils. The famous lime- 

 stone soil of Kentucky is of this class. The other class has been 

 moved more or less, and is called transplanted soil. Water, wind 

 and ice have been the chief means of transportation. 



If a soil is examined closely it will be found to contain organic 

 matter (fragments of plants), some of which can still be recog- 

 nized readily as of vegetable origin, while most of it has decom- 

 posed to such an extent that it has lost its vegetable structure and 

 original chemical composition. 



Most soils have two natural divisions as to depth; the top-soil 

 and the subsoil. The top-soil varies in depth with the soil types, 

 usually being from six inches to twenty inches deep. It is frequently 

 a little coarser in physical composition than the subsoil, because 

 the finer particles are carried away by running water, and as the 

 water percolates downward through the soil, these finer particles 

 have a tendency to move down with it, and some finer material is 

 carried down into the subsoil. The color of the top-soil varies with 

 the type, but depends largely upon the amount of organic matter, 

 or iron, or both. The organic is the more common and gives to soils 

 a black or brown color. Iron compounds usually give a reddish 

 color very much like iron rust. The top-soil is divided into the sur- 

 face soil and the sub-surface soil. The surface soil extends as deep 

 as the ground is plowed. This is the soil the farmer knows most 

 about. This is the part that requires the most careful management, 

 as it is the most important part of the soil in development of plant 

 food, in germination of seeds, and in growth of crops, since it is 

 largely concerned in absorption and retention of moisture, aeration, 

 and temperature. It is commonly the darker part of the soil, be- 

 cause of its larger organic matter content. 



The subsurface soil lies between the surface soil and the sub- 

 soil, or between the plow line and the subsoil line, where the change 

 of physical composition, texture, or color indicates the beginning 

 of the subsoil. In physical composition it differs but little from the 

 surface soil except that it contains somewhat less organic matter; 



