4 SOILS OF THE EASTERN UNITED STATES. 



below the general level of the crystalline rocks which frequently 

 border it upon either side. The surface of these Triassic basins is fre- 

 quently roughened by ledges of trap rock which have broken through 

 the sandstones and shales and constitute stony elevations above the 

 general level occupied by the Penn loam. Within the areas of the 

 type itself there are considerable variations in level, since many of 

 the large streams have cut across the type, while smaller tributary 

 streams flow through it. The absolute elevation of the type above 

 sea level ranges from 100 to 400 feet in north-central New Jersey 

 and from 200 feet to 800 feet in the more southern areas of its 

 development. 



Natural drainage has been well established over the surface of 

 the greater portion of the Penn loam. The rolling topography, the 

 presence of numerous stream channels, and the loamy texture of the 

 soil tend to favor drainage conditions. There are few or no swamp 

 areas within the limits of the type. The presence of the stiff, plastic, 

 deeper subsoil frequently renders the internal drainage somewhat 

 defective over the more level areas. 



It is only upon the steeper slopes within the areas of the Penn 

 loam that erosion becomes a serious problem. 



LIMITATIONS IN USE. 



The Penn loam is limited by its textural characteristics to the 

 production of the general farming crops of the climatic region within 

 which it occurs. Within the general run of the type there are some- 

 times slightly sandy areas which are utilized for the production of 

 vegetables and small fruits, but in general the type is much better 

 suited to the production of corn, wheat, oats, rye, and grass, and to the 

 heavy export tobacco than to any other crops. Tree fruits have been 

 set to a limited extent upon some of the well-drained areas princi- 

 pally to furnish a home supply rather than on the scale of commercial 

 orcharding. 



IMPROVEMENT IN SOIL EFFICIENCY. 



While the surface drainage features of the Penn loam are usually 

 adequate, the presence of the heavy subsoil has given rise to the till- 

 age of the type in broad beds which are thrown up by the plow, 

 with water furrows at intervals of 40 to 80 feet. This practice has 

 frequently been sufficient to complete the drainage of the Penn loam 

 for the purposes of general farming. The installation of tile under- 

 drains upon many of the more level tracts would aid materially in 

 the complete drainage of the subsoil. 



In very few instances would drainage be required over the entire 

 area of the farm, and in many instances the natural drainage could 

 be supplemented by a few lines of tile laid through the low-lying or 



