SOIL SURVEY OF LOUISA COUNTY, IOWA. 31 



Drainage of the Knox fine sand is amplo or excessive. Owing to 

 the great porosity of the subsoil, crops are apt to be afTectcd by 

 droughty periods. 



The total extent of the type is small, and, as less than half of it is 

 cultivated, its agricultural importance is slight. The uncultivated 

 parts, where the surface is more or less shifted by the wind from year 

 to year, support practically no vegetation aside from sandbur and 

 are practically wortliless. A small part of the uncultivated land is 

 forested with black oak and post oak. On the cultivated areas of 

 the type, corn, rye, and truck are the principal crops. Rye is the 

 best adapted of the grain crops to such sandy land as this. For best 

 results on this type, it is suggested that it be used chiefly for rye and 

 truck crops and that winter cover crops be sown to prevent drifting 

 as far as possible. 



Probably no farm occurs wholly on this type, but its selling price 

 is estimated to range from $40 to $100 an acre. 



PUTNAM SILT LOAM. 



The surface soil of the Putnam silt loam is a dark gravish brown 

 silt loam extending to a depth of 6 inches, and underlain by a gray to 

 grayish-brown, silty layer, which is usually very dry and powdery. 

 The silty layer extends to a depth of 12 inches, and is underlain by 

 very compact, yellowish-brown silty clay loam which passes at about 

 26 inches into a gray compact silty clay loam mottled with rusty 

 brown and to a lesser extent with yellowish brown. 



The Putnam silt loam occurs in small areas between the Clinton silt 

 loam and the Grundy or Muscatine silt loams, and generally occupies 

 positions at the heads of drainage courses. Some patches of this 

 type too small to map separately are included with the Grundy and 

 Muscatine silt loams. Surface drainage is generally fair, though 

 underdrainage, owing to the impervious subsoil layer, is naturally 

 poor. 



Probably no field occurs exclusively on this type, though practically 

 all of it is in cultivation. It is handled and cropped in the same 

 manner as the Grundy or Muscatine silt loams, and is best adapted 

 to the same crops, though it produces slightly lower yields. It is 

 probable that on the average the price of land of this type is about 

 one-third less than that of the Grundy silt loam, 



LINDLEY SILT LOAM, 



The surface soil of the Lindley silt loam is a light yellowish brown 

 silt loam extending to a depth of 10 inches. The top 2 to 3 inches is 

 sometimes dark brown. The subsoil to a depth of 20 inches is a 

 brown silt loam to loam, wdth a reddish cast, underlain by a gritty 

 silty clay of the same color. Scattered throughout the 3-foot sec- 



