12 BULLETIN 1244, t\ s. DEPARTMENT OF AGRICULTURE. 



of darkness indicates the proportion of humus in the soil. This, in 

 turn, is dependent upon the grass covering, which bears a direct 

 relation to the precipitation. 



The relative depths of the zone of lime accumulations is also 

 dependent largely upon the moisture supply. In the extreme east- 

 ern part of the region, where there is considerable moisture, the zone 

 of lime accumulation is not well marked or else occurs at considerable 

 depths. As the precipitation decreases to the westward the lime 

 zone is found gradually nearer the surface. 



The successive belts shown on the map are merely differentiations 

 in the uniform or gradual change of these features in the soil, and 

 the boundary lines are necessarily more or less arbitrary. 



The black belt occupies the eastern part of the region and includes 

 three groups: The Barnes, the Marshall, and the Grundy and Car- 

 rington. These soils are well supplied, with humus, and the zone of 

 lime accumulation occurs at 2 to 4 feet. The heavier textures pre- 

 dominate. This belt has not been included in the present discussion, 

 as moisture conditions are such as to insure fairly satisfactory yields 

 in most seasons. 



The very dark brown belt lies just west of the black belt, and the 

 soils have somewhat less humus. The zone of lime accumulation 

 is found at about 2 feet. Here, also, the heavier textures predomi- 

 nate. This belt is indicated on the map as the Williams group. 



The dark-brown group includes soils very similar in texture to 

 the preceding group, but they are a shade lighter in color 

 and the zone of lime accumulation is a little less than 2 feet from the 

 surface. The Morton and Rosebud groups are included hi this belt. 



The soils of the brown belt, which are represented on the map by 

 the Choteau group, are mostly confined to Montana, the largest 

 areas lying in the eastern half of the State. These soils are lighter in 

 color than any of the preceding groups and probably a little less 

 productive. The zone of lime acciimulation occurs at a depth of 

 about 16 inches. 



The light-brown soil belt — the Rudyard group — occupies an area 

 north of Great Falls, Mont. These soils have less humus than any 

 other of the soil belts in this region and. are therefore lighter in color. 

 The zone of lime accumulation is also nearer the surface, at an aver- 

 age depth of about 12 inches. Because of the low moisture supply 

 these soils can hardly be considered agricultural, though exceptional 

 fanners may be able to make a living under favorable conditions. 



AGRICULTURAL RESOURCES. 



As the first step in presenting a broad outline of the agricultural 

 resources of the northern Great Plains, it may be stated that the 

 total area involved is approximately 1.52,280,000 acres. In 1919 

 there were 26,838,000 acres of improved land in farms of which 

 approximately 17,107,000 acres, or about 65 per cent, were in har- 

 vested crops, including native hay. Cereals are the chief crops ^f 

 i he region as a whole; but forage crops, especially native hay, con- 

 tribute very largely to its agricultural resources, as they make stock 

 raising possible. It is not so difficult to visualize the value of the 

 grain resources, since grain is exportable to markets where it has a 

 definite cash value. It is more diHicull to evaluate the forage 



