GROUP OF HEAVY SOILS. 
23 
surface is quite broken. Because of the uneven character of 
most of this soil the surface drainage is good. The compact 
subsoil, however, does not permit the water to move freely 
within the soil. The only difference between this soil and the 
typical Superior clay loam is the difference in topography. 
Present agricultural development .*■—Practically all of the 
merchantable timber has been removed, and very nearly all of 
the type is now cultivated. This is an excellent soil, well adapted 
to general farming and dairying, and all of the farm crops 
common to the region are successfully grown upon it. A rot - 
tiOn quite commonly practiced consists of small grain one or 
two years, followed by clover or a mixture of clover and timothy 
for one or two years, and then followed by corn. 
About the only fertilizer used is stable manure, but since the 
soil is very heavy and somewhat deficient in organic matter, a 
practice which is good, but not common, is to supplement the 
stable manure by plowing under a green manuring crop about 
once in four or five years, and for this purpose legumes are best. 
CHEMICAL COMPOSITION AND IMPROVEMENT OF SUPERIOR SILT 
LOAM AND SUPERIOR CLAY LOAM. 
These soils are similar in the texture and structure of the 
subsoil section. They differ chiefly in topography and texture 
of the surface soil, as indicated by the type names. The types 
are so closely related that methods for the improvement of one 
will apply to the others. 
The four elements with which the farmer is most concerned 
in his farming operations, and the ones which are the most apt 
to be deficient, are nitrogen, phosphorus, potassium and lime 
or calcium. He should know the part which each plays in the 
development of the plant, and what are the best methods of 
maintaining an adequate supply in the soil. 
The soil has been leaching for a large number of years, and 
has lost some of the lime carbonate which it contained. Vary¬ 
ing degrees of acidity have developed over the region. The loss 
of lime (calcium carbonate) from the soil is caused by two 
distinct factors, both of which are important. Crops require 
lime in their growth. A five-ton crop of alfalfa requires 185 
