40 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1918, 



hrown, heavy silt loam to silty clay loam. The surface soil is uni- 

 formly mellow and friable, and the subsoil is seldom more than 

 semiplastic. In some places in the river bottoms and generally in the 

 small stream bottoms the brown to yellowish-brown color in the subsoil 

 is replaced by dark brown to black, which in the lower subsoil may be 

 mottled slightly with bluish gray, rusty brown, and brown. Dark- 

 bro^^^l concretionary material may be present. In a few places, 

 particularly about If miles northwest of Port Louisa, a small area 

 has been covered with a sandy wash from a stream whose channel 

 has become choked. In a few very small spots the subsoil is seen 

 to have a distinctly reddish cast. 



This type occurs in the first bottoms of the Mississippi and Iowa 

 Rivers in areas of varying shape and size. With the exception of a 

 small area which is Wabash silty clay loam, it is the only type mapped 

 in the small stream bottoms. Here it has a more silty soil and con- 

 tains many areas of silt loam. 



The type is naturally well drained, except for overflows where it is 

 not protected by levees. It is said that a few places in the Iowa 

 River bottoms did not overflow even before the construction of levees 

 or when the levees were broken, but they lie so little above the 

 remamder of the type that no separation has been attempted. 



The Wabash loam is one of the most extensive and important of 

 the bottom-land types. In some of the larger creek bottoms it is cul- 

 tivated, as overflows generally do not occur during the growing season. 

 The rest of the type in the small stream bottoms is left in pasture. 

 In the river bottoms the type is practically all in cultivation. Corn 

 is the chief crop, the type being preeminently adapted to its produc- 

 tion. Other main crops are oats, wheat, and hay. Corn yields 

 35 to 75 bushels per acre, averaging about 45 bushels; oats 35 to 75 

 bushels, averaging 45 bushels; winter wheat 15 to 40 bushels, aver- 

 aging 25 bushels; and hay three-fourths ton to 2 tons, averaging 

 li tons. Where the type occurs in the river bottoms it supports 

 almost no stock farming. 



This type has a considerable range in value. In the small stream 

 bottoms no farm occurs wholly on it, and an allowance in the farm's 

 valuation is doubtless made for the land subject to overflow. In 

 the river bottoms, where protected from overflow, it is very produc- 

 tive and is highly valued. It sells at prices ranging from $75 to 

 $275 an acre, depending on the protection from overflow and the 

 other common factors influencing land values. 



WABASH SILTY CLAY LOAM. 



The Wabash silty clay loam is a black silty clay loam, with a 

 depth of 12 inches, underlain by a dark-brown to black silty clay 

 loam, mottled with bluish gray and yellowish brown, which at 20 



