8 SOILS OF THE EASTERN UNITED STATES. 



plant. To some extent the medium red clover is used for grass 

 seeding upon the Clarksville silt loam, and except where this crop is 

 subject to fungous diseases its more extended use is to be recom- 

 mended. In all cases the Clarksville silt loam should be limed before 

 being seeded to clover. 



Another fundamental difficulty with the Clarksville silt loam, 

 already mentioned, is the lack of adequate drainage, particularly in 

 the subsoil. Wherever the general valuation of land of this character 

 through the demand for it for general or special farming purposes 

 has attained to $40 or $50 an acre, it is desirable that the question 

 of tile underdrainage should be carefully considered. This is espe- 

 cially true where the bands of chert do not occur in the subsoil over 

 sufficient areas to assist in loosening and draining that portion of the 

 type. The adequate tile drainage of the fields will normally cost 

 from $12 to $20 an acre, and this should constitute a part of the 

 permanent investment in the land and its improvements. It is only, 

 therefore, where the Clarksville silt loam may be used for the pro- 

 duction of special crops like the heavy export tobacco or where the 

 increased yield of corn, wheat, and the grasses may be proved to be 

 sufficient to justify an expenditure of this magnitude that tile drain- 

 age is to be recommended. In the more remote areas where land is 

 abundant, it is probable that many years must elapse before tile 

 drainage will be justified by the increases in land values. 



The necessity for the use of lime upon this soil in order to secure 

 a satisfactory growth of cowpeas or clover has already been mentioned. 



LIMITATIONS UPON SPECIAL CROPS. 



The rather heavy character of the surface soil, the dense subsoil, 

 and the considerable altitude at which the Clarksville silt loam 

 normally is found limit its use for the production of special crops 

 with the exception of tobacco in western Tennessee and Kentucky, 

 and of apples in the Arkansas-Missouri region. Special crops have 

 not been found to be profitable over the greater portion of the type. 

 Within recent years, however, certain localities have begun the devel- 

 opment of cantaloupe growing and strawberry production, and rea- 

 sonable success has been attained with both of these crops. Other- 

 wise the inherent characteristics of the soil and its location and 

 natural drainage render it a type better suited to the production of 

 general farm crops than of specialties. 



A considerable portion of the Clarksville silt loam thus far encoun- 

 tered by the soil survey has been located upon the higher plateaus 

 surrounding the basin region of Tennessee and the bluegrass region 

 of Kentucky. It occupies what is known as the Highland Rim in 

 Tennessee and extends eastward to higher and higher altitudes until 

 it merges with the Cumberland Plateau. Throughout this region 



