38 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1918. 



Buckner silt loam, coUuvial pTiase. — ^The Buckner silt loam, col- 

 liivial phase, is a dark-brown silt loam, with a depth of 18 inches, 

 underlain by a dark-brown, heavy silt loam to silty clay loam, tinged 

 with brown, soon changing to a distinctly brown slightly mottled with 

 rusty bro\vn. The surface material is moderately friable. The phase 

 as mapped includes areas of considerable extent where the texture 

 of both surface soil and subsoil is a loam. 



This phase occurs on moderate colluvial slopes between the upland 

 bluffs and the terrace or first bottom. The soil has been deposited 

 in its present position by gravity and washing from the slopes. 

 Although the slopes are gentle, care is necessary in places to prevent 

 erosion and gullying by water coming from the bluffs. 



The greater part of the phase is in cultivation, being devoted to 

 the common crops. It is chiefly adapted to the production of corn, 

 the other main crops being oats and wheat. Corn yields 30 to 70 

 bushels, averaging 40 bushels, per acre; oats 30 to 70 bushels, aver- 

 aging 45 bushels; and winter wheat 10 to 40 bushels, averaging 25 

 bushels. 



While no farm consists exclusively of this phase, it is estimated to 

 be valued at $125 to S200, with an average of S140 an acre. 



For the improvement of this soil organic matter should be added 

 to the especially loamy spots. Where there is a tendency to erode 

 diversion channels should be cut or contour plowing practiced. 



WAUKESHA SILT LOAM. 



The surface soil of the Waukesha silt loam is a dark-brown, friable 

 silt loam with a depth of 12 inches, underlain by a dark-brown silty 

 clay loam which passes at 18 to 20 inches into a yellowish-brown, 

 moderatel}^ friable silty clay loam. In some places the surface soil 

 is slightly deeper. A few areas, too small to map separately, have 

 a loam surface soil and a subsoil of grayish-browTi sandy clay or 

 silty clay loam to silty clay with considerable medium to coarse 

 sand. Some of the patches having a loam surface soil have the 

 typical yellowish-brown silty clay loam subsoil. Some areas of Cal- 

 houn silt loam, too small to map separately, also are included. On 

 the Wapello Prairie west of Wapello the Waukesha silt loam and 

 the Bremer silt loam grade together in such a manner as to make 

 the location of the separating boundary very arbitrary. 



The Waukesha silt loam occurs in areas of varying size, many of 

 them quite large, on the Iowa River terraces, where it is the most 

 extensive type. It generally adjoins the Buckner loam, Bremer silt 

 loam or silty clay loam, or Lindley silt loam. The topography is 

 level, but the drainage is good. 



The Waukesha silt loam is one of the most, if not the most, valuable 

 of the terrace types. None of it was originally forested. The greater 

 part is in cultivation, the remainder being used for farmstead sites 



