THE KXOX SILT LOAM. 11 



yields and the acreage planted to this crop. In Indiana and in 

 Kentucky corn takes second rank in the total acreage of the Knox 

 silt loam devoted to crop production, and the average yield of corn 

 is about 33 bushels per acre, although in some instances from 35 to 

 38 Bushels are secured through better tillage methods and the better 

 natural drainage of the type. In Iowa and Wisconsin, although the 

 corn yield is high, averaging 38 to 40 bushels per acre, the acreage 

 devoted to this crop is secondary, being exceeded by either oats or 

 grass or by both. In general, there is a wide variation in the yield 

 of corn per acre, not only between the different areas where the soil 

 type has been encountered, but also between different fields even in 

 the same area. It is apparent from the investigations of the type 

 that this difference in yield depends principally upon the amount of 

 organic matter which is present in the surface soil. Those areas 

 of the Knox silt loam which show the darker brown or the deeper 

 gray color, as evidence of large amounts of organic matter in good 

 condition, are always marked by the highest yields of corn, whereas 

 the ashy gray or nearly white areas of surface soil show low yields 

 when planted to corn, or else the crop makes absolute failure upon 

 such tracts. The factor of the depth of surface soil, coupled with 

 that of efficiency in the tillage of the soil, also exerts a strong in- 

 fluence upon the yields of corn. Where the surface soil has a depth 

 of 12 or 14 inches, and where it is maintained in good tilth by fre- 

 quent shallow cultivation, good yields are frequently secured even 

 on those portions of the type which are somewhat deficient in 

 organic matter. It is also apparent from the statistics of corn yield 

 in the various areas where the Knox silt loam has been encountered 

 that the warmer climate of the more southern latitudes and the 

 smaller rainfall of the more western regions both exert an unfavor- 

 able influence upon the maturing of adequate yields of corn. 



It may be broadly stated with regard to the Knox silt loam that, 

 although efficient methods of management of the soil will result in 

 the production of fairly satisfactory yields of corn, still the type 

 as a whole may be considered as of only secondary importance as a 

 corn-producing soil when compared with either the Marshall silt 

 loam, the Carrington loam, or the Miami clay loam of the same 

 general region. 



In the more southern regions where the Knox silt loam is devel- 

 oped, winter wheat constitutes the crop most extensively grown. 

 In southern Indiana and in Kentucky this crop usually dominates all 

 others. It is not infrequently raised year after year upon the same 

 field with little attention to crop rotation. As a result the average 

 yields secured do not much exceed 11 bushels per acre, although in 

 these same localities those farmers who have paid better attention to 

 the management of their soils and to the rotation of crops secure 



