4 BULLETIN 1039, U. S. DEPARTMENT OF AGRICULTURE. 
On newly irrigated land small grains or flax usually are sown 
for a cash crop, and on old irrigated land a considerable acreage of 
these crops is grown in rotations following a cultivated crop or as a 
nurse crop for alfalfa. 
SOIL. 
The soil of the Belle Fourche Experiment Farm and of the sur- 
rounding section is a heavy, stiff clay, or gumbo, classified by the 
Bureau of Soils as Pierre clay. 4 This soil occupies about one-third 
of the area of western South Dakota. 
It contains about 35 per cent of clay, 43 per cent of silt, 13 per cent 
of very fine sand, and only a small quantity of humus. The soil 
is of residual origin and contains considerable quantities of calcium, 
magnesium, and sodium salts. Alkali is a problem only in seeped 
areas. 
The soil when wet is exceedingly sticky and is almost impervious to 
water. 5 Upon drying, it checks rapidly, later forming large cracks 
which permit the entrance of water. The soil can not be plowed 
when wet and is difficult to plow when dry, but disking and harrow- 
ing are comparatively easy if done at the proper time. Land plowed 
in the fall when dry becomes quite mellow in the spring from the 
alternate contraction and expansion caused by temperature changes 
during the winter. The soil contains ample quantities of plant food 
and with sufficient rainfall is capable of producing large yields of 
grain. 
NATIVE VEGETATION. 6 
The native vegetation of the locality consists largely of western 
wheat-grass (Agropyron smithii, A. occidentale) and buffalo grass 
(BulbiJis dactyloides) . Grama grass (Bouteloua oligostachya) and 
needle grass (Stipa comata) are frequently found. Buffalo grass 
usually occupies the higher and lighter soils, especially where Pierre 
clay is the soil type. Western wheat-grass is confined mostly to the 
lower slopes and bottoms. On bottom lands subject to overflow this 
grass produces considerable hay of excellent quality. 
Weeds, such as sunflower {Tlelianthus petiolaris) , gum weed (Grin- 
delia squarrosa), goosefoot {Atriplex volutans), and wild parsley 
(Peucedanum foeniculaceum) , are plentiful. They are particularly 
abundant following extremely dry seasons, when the grass may be so 
injured that weeds are practically the only vegetation. Poverty weed 
(Ira axillaris) is of considerable economic importance because of the 
4 Strahorn, A. T., and Mann, C. W. Soil survey of the Belle Fourche area, South 
Dakota. In U. S. Dept. Agr., Bur. Soils Field Oper., 9th Rpt., 1907, p. 888. 1909. 
5 Mathews, O. R. Water penetration in the gumbo soils of the Belle Fourche Reclama- 
tion Project. U. S. Dept. Agr. Bui. 447, 12 p., 4 fig. 1916. 
c Adapted from U. S. Dept. Agr. Bui. 297, p. 3. 1915. 
