CROPPING SYSTEMS FOR THE BLACK LANDS OF TEXAS. 5 



as alfalfa. This fact suggests at once a rotation of alfalfa, grain 

 crops, and cotton, so arranged as to alternate susceptible crops with 

 those which appear to be immune. 



This work has also shown the need of a greater variety of legumes 

 which may be used under root-rot conditions. For this reason an 

 extensive test of varieties is being made in cooperation with farmers 

 in the black-land region. 



DESCRIPTION OF THE BLACK-LAND REGION. 



The black-land region comprises two parallel belts and numerous 

 isolated areas of level to rolhng prairie, aggregating between 13,000,000 



Fig. 2.— Location of the black lands, showing the average annual distribution of rainfall in the Southwest 

 (based upon records of the United States A\'cathor Bureau covering the period from 1871 to 1908, inclu- 

 sive). 



and 14,000,000 acres. The main black-land belt extends from the 

 southern part of Oklahoma in a southwesterly direction across Texas. 

 (Fig, 2.) Tt is about 550 miles long and varies in width from about 

 65 miles in northern Texas to about 25 miles in southwestern Texas. 

 West of the main belt lies the Fort Worth i)rairie, an irregularly 

 sluiped, narrow belt extending from Red River to the vicinity of 

 Round Rock, Tex. It is about 240 miles long and varies from 5 to 

 25 miles in width. The two belts are separated from Red River to 

 the vicinity of Waco, Tex., by a narrow strip of sandy timbered 

 country knowii as the east, or lower, cross timbers. Southwest of 

 Waco the two areas He contiguous and dovetail into each other. 



[Cir. 841 



