THE CLARKSVILLE SILT LOAM. 7 



also limits the water holding capacity of the soil, and the amount 

 of moisture stored in the surface soil above it is easily evaporated 

 during the earlier stages of crop growth, leaving a scarcity during 

 midsummer and during the ripening period of the grain. Wherever 

 this condition exists the yield of corn, in particular, is decidedly 

 decreased. Wheat is not affected adversely to so great a degree, 

 and as the crop is removed during the early summer, its yields are 

 not usually decreased by this condition to such an extent as are 

 the yields of corn. Great care is, therefore, necessary in, the plowing 

 of this type to perform the operation at a time when moisture con- 

 ditions are favorable in both the surface soil and in the subsoil. 



All of the areas of the Clarksville silt loam which are known to 

 exist in the United States occur between latitude 34 and latitude 39 

 north. Thus the range of climatic surroundings is determined more 

 by altitude than by latitude. In the lower lying areas in western 

 Tennessee and Kentucky and in the lower portion of the Ozark 

 Uplift, the length of season is adequate for the production of practi- 

 cally all the farm crops. In the higher lying portions along the 

 border of the Cumberland Plateau, and immediately adjoining the 

 Ozarks proper the growing season would not be adequate for the 

 production of tobacco and other special crops. Similarly, cotton is 

 little grown upon this soil type, except at its lower altitudes and in 

 the regions of its most southern development in the northern counties 

 of Alabama. Both the, ranges of altitude and the latitude within 

 which the type occurs, added to its textural and structural condi- 

 tions, limit its use to the production of the staple general farming 

 crops. 



IMPROVEMENT IN SOIL EFFICIENCY. 



There are two principal modifications which constitute" the most 

 essential changes to be effected with respect to the Clarksville silt 

 loam for the purpose of increasing its efficiency in crop production. 

 The first of these is the incorporation of a sufficient amount of organic 

 matter to make a complete soil and to render the soft silty compact 

 surface loam more open and friable. Throughout the entire region 

 where the soil type occurs very little live stock is kept, so that the 

 use of the stable manures is not at present possible upon any large 

 scale. These manures, however, should be carefully saved and used 

 upon the ground to be planted to any hoed crop. In order to supple- 

 ment the use of stable manures, green crops, particularly cowpeas, 

 should be raised in the regular rotation. The pea vines ,and peas 

 may be harvested and used as a forage crop, while the stubble and 

 roots are plowed in to add organic matter to the soil. It is not 

 infrequently necessary to apply lime to the Clarksvillo silt loam in 

 order to secure an adequate stand of cowpeas or other leguminous 



