166 RESOURCES OF TENNESSEE. 



well distributed throughout the year. The average date of the last killing 

 frost in the spring varies according to the locality, from April 8 to April 

 20. In a similar manner the average date of the first killing frost in the 

 fall, varies from October 8 to October 26. 



The surface varies from gently undulating to hilly, but in general lies 

 well for cultivated crops. The soils may be roughly divided into two 

 large groups, one on the outer part of the rim, consisting of those derived 

 from the decomposition of limestone; and the other on the inner part, 

 derived from siliceous or "freestone" formations. 



Limestone soils. Over large areas the limestone soils are readily dis- 

 tinguished by their dark-brown color, where recently cleared and im- 

 proved, and by their red or "mulatto" color where cultivated and worn. 

 In physical character, crop adaptability and color, this type is very similar 

 to the high-grade limestone soils of East Tennessee. Alfalfa has done 

 especially well on it. Other areas of limestone soils consist of grayish and 

 brownish loams, which are often gravelly, and which have red subsoils. 

 Some of the brown-colored soils are naturally rich, and are adapted to a 

 great variety of crops, including tobacco. The gray soils are inferior to 

 the others, and may be even classed with the "barrens" type, but are excel- 

 lent tobacco soils. 



I 







FIG. 4. View in Robertson County, northeast of Adams. 



All these soils are of good depth and the drainage is adequate. Up to 

 the present time grain farming has predominated. Tobacco has been an 



