Emil Truog 27 



CHARACTER OF SOILS DETERMINED BY FIVE FACTORS 



As is to be expected, great variations exist in the characteristics of 

 the respective horizons of soils found in various places. These varia- 

 tions are due to the extent to which the following five main factors 

 involved in soil formation have come into play. These five factors are 

 climate, native vegetation, parent rock material, topography or slope, 

 and age or maturity of the soil. The first two — climate and vegetation 

 — are active factors and have to do with dynamic forces, such as weather- 

 ing and leaching. The other three factors are of a passive nature and 

 do not represent forces or activity in themselves, but they influence 

 greatly the effects of the active factors on the product which remains 

 and, hence, the character of a soil as found and its suitability as a 

 medium for crop growth. 



From a broad or world viewpoint, climate, which not only determines 

 the rate of weathering and leaching but in turn also largely the kind 

 of vegetation which grows, has the greatest influence on the general 

 type of soils formed, particularly as regards the organic matter content 

 and the color. It determines which of the so-called zonal soils will be 

 formed, namely, podzol, chernozem, or laterite. However, within a 

 local area, such as the northern half of Wisconsin which lies within a 

 single climatic zone, parent rock material is the determining factor for 

 the texture of the soils formed. 



In a cool moist climate like that of northern Wisconsin where leach- 

 ing is severe and coniferous trees predominate, the podzols or highly 

 podzolized soils predominate. Whether of a sandy or heavier texture, 

 they are characterized by an ash gray A. 2 horizon and a brownish, yel- 

 lowish, or yellow-blue mottled B horizon, which usually has a heavier 

 texture than the A horizon. These soils, having been drastically leached, 

 are strongly acid and low in available plant nutrients, particularly 

 potassium. As media for crop growth, they are generally not satisfac- 

 tory until limed and heavily fertilized with potash. The subsoil or B 

 horizon of the heavier soils is often inadequately drained and aerated 

 for many crops. 



Compared with the northern part, the climate of the southern part 

 of Wisconsin is quite different. Here, higher temperatures have caused 



