SOIL. Qg 
is notably the case along the Arkansas, Smoky Hill, and Platte rivers. 
Cottonwood stands are generally open. Each tree has but little 
modifying contact with its neighbors. On the minor streams, which 
have the heavier soil, other species predominate and cottonwood and 
willow are less abundant. Growth is more dense in such situations, 
and an approach is made occasionally to true forest conditions. 
The greater proportion of the uplands in western Kansas and 
Nebraska is covered by deposits of very fine sand (0.1 to 0.05 mm.) and 
sut (0.05 to 0.005 mm.), known geologically as “ plains marl” and 
“loess.” The plains marl occurs principally in western Kansas and 
eastern Colorado, and is often very deep. The loess is found in 
eastern Nebraska, extending westward to Colorado, along the southern 
line of the State, and to some extent in Kansas in the northern tier of 
counties. The depth is variable, but is estimated to average 100 feet, 
while in places, notably south of the Platte River, in Dawson and 
Lincoln counties, loess bluffs 200 feet or more in height are common. 
The soil formed from these deposits consists chiefly of very fine sand 
and silt, the latter usually forming more than 50 per cent of the soil 
material. The clay content is small, usually not exceeding 15 per 
cent. The soils derived from the plains marl and loess are very much 
alike. ‘The former, ’iowever, usually contains a larger percentage of 
very fine sand. Calcareous matter is usually present, most often in 
the form of nodules.“ It is an easily worked soil, very fertile—the 
valuable agricultural lands of eastern Nebraska being an example 
and has a great capacity for moisture. The fact that cottonwoods 
and willows are found growing naturally on loess bluffs far above the 
water level is a good indication of its moisture-holding power. 
In both States are numerous areas of loose sand, blown and worn 
into low hills. The main sand-hill region hes in Nebraska, north of 
the Platte River, and covers an area of about 25,000 square miles. 
The largest of the minor,sand-hill areas forms a narrow belt, prac- 
tically continuous, along the entire south side of the Arkansas River 
Valley, in western Kansas. <A sand-hill area of considerable size 1s 
on the south side of the Cimarron River, in southwestern Kansas. 
Similar sand-hill areas occur south of the Platte River at various 
points. 
The sand hills are generally covered with grass and shrubby vege- 
tation, and retain moisture well. They take up water as readily 
as a sponge, and there is ttle surface run-off, no matter how heavy 
the downpour. The three Loup rivers, which rise in the sand hills 
of Nebraska, are among the finest streams in the West, and are 
@ Mechanical analyses of the plains marl and the loess are given in Bulletin 5 
of the Bureau of Soils, pp. 12-14, and in Field Operations of the Bureau of 
Soils, 1903, pp. 934-953. | — 
31149—No. 66—05 m——2 
