12 SOILS OF THE EASTERN UNITED STATES. 



in plowing it, either with lightweight work stock or lightweight tools. 

 Within later years the introduction of disk machinery has greatly 

 facilitated both the plowing and subsequent tillage of this type. 

 The disk machinery is not so liable to become clogged by the stiff, 

 waxy clay as the old mold-board form of plow or cultivator. 



SUMMAEY. 



The Houston black clay is one of the most important of the upland 

 soils in the western Gulf States. It occupies the "black waxy" 

 prairie region of southern Oklahoma and central and southwestern 

 Texas. Small areas are also found in Alabama. 



The surface of the Houston black clay is prevalently broadly rolling 

 to undulating, with no very steep slopes and with limited areas of 

 absolutely level land lying between the ridges or undulations. The 

 surface drainage is usually good, only the more level areas suffering 

 in this respect. 



Erosion is not a serious problem except along the margins of 

 streams which cut across the formation from which it is derived, and 

 along then' principal tributaries. Such areas occupy only a small 

 percentage of the total extent of the type. 



The Houston black clay, because of its physical characteristics 

 and its surface configuration, together with its climatic location, is 

 best suited to the production of the great staple crops of the Gulf 

 region. Special crops are not grown to any extent upon the type. 

 It is probably the best and most productive of the extensive Upland 

 cotton soils of the Southern States. Throughout large areas the 

 average yield of cotton upon this type is reported at one-half to three 

 quarters of a bale per acre, and in many individual instances it ex- 

 ceeds 1 bale per acre. 



The Houston black clay is also an excellent corn soil, although a 

 smaller acreage is devoted to this crop than to cotton. The yields 

 range from 25 to 50 bushels per acre, with a general average of about 

 40 bushels. 



Winter wheat is grown to a limited extent in the more northern 

 regions occupied by this soil, and winter oats throughout the area 

 where it occurs. 



More recently alfalfa has been grown upon the Houston black clay, 

 and the better drained areas of the type are well suited to this crop. 

 It yields from 3 to 4 tons per acre under favorable conditions. 



Johnson grass has been cut for hay over restricted areas of this 

 soil, the yields ranging from 2 to 4 tons per acre. 



Under conditions of less rainfall, sorghum, millet, kafir, milo 

 maize, and other semiarid-land crops are grown to advantage. Wild 

 grass is cut in the extreme western portions of the area, giving 



