Understanding the five soil forming factors is important because if we can understand these five factors in relation to soil development, then we can understand why soils differ, or why their productivity is different from place to place, and how different soils will affect the environment, and finally how soils may be properly used so that we can better manage our most limited resource, the soil.

Climate as a soil forming factor

Climate has two major components for soil formation. The first is the temperature. As the mean annual soil temperature increases, the weathering of the rocks and minerals in the soil will be faster. For every 10°C rise in temperature, the rate of biochemical reactions doubles. Thus, we find that soils weather faster in the southern U.S.A.. than in the northern states. Tropical soils will also weather faster because the chemical reactions will be taking place faster and the reactions will occur throughout the year. If all other environmental conditions are similar the cooler the climate the greater the quantity of organic matter in the soil.

Along with temperature is the factor of precipitation or rainfall. In general, areas with more rainfall will have greater weathering and greater leaching. However, the amount of evapotranspiration has to be accounted for. Areas that are cool and wet will have more leaching than areas that are hot and wet because more of the rainfall in a hot, wet climate evaporates back into the atmosphere before leaching can occur.

In Minnesota we can use the depth of calcium carbonate (CaCO₃) in the profile to determine the leached zone of the soil. Leaching occurs when water moves through the soil and removes the soluble constituents. The leaching zone is determined by the location of CaCO₃ in the soil profile. This is easy to locate because calcium carbonate reacts with hydrochloric acid to give off carbon dioxide or the soil bubbles when acid is applied. Soils that exhibit a leached zone are easily determined by using this chemical test. The leached zones in the picture are indicated with the red {. The calcium carbonate in the soil is the white looking material. The farther west you go in Minnesota the less the soil is leached and the closer to the surface we find CaCO₃. The thicker the leaching zone the greater the leaching and the greater the leaching index.

A leaching index can be used to assist in locating areas with differences in soil profiles due to climate. The leaching index is equal to the precipitation minus the evapotranspiration. LI=PCPT. - EVAP. 

From this map the area of the state with the greatest leaching index is the Arrowhead Region of northeast Minnesota (10 to 12 inches) and the least is in the Red River Valley of northwest Minnesota (0-2 inches).

Organism Factors

The organisms living in and on the soil respond to the climate of the area. So biotic factors and climatic factors are interrelated. Animals living in the soil can influence the soil development by their mixing activities. The mixing of the soil by organisms is called bioturbation. Humans also influence the soil with their activities of agriculture, urbanization, grazing, and forestry. Some of these changes have been negative like erosion, organic matter depletion, soil pollution, and compaction. Humans have also made soils for areas where after mining operations the landscape was destroyed. Soils have also been made when land has been reclaimed from the sea.

In Minnesota there is a direct relationship between the kind of native vegetation and the climate of the state. In eastern Minnesota the greater rainfall gave rise to a forest vegetation that was called the Big Woods in the southeast  and coniferous forest in the northeast. In central Minnesota the vegetation was prairie-border or a mixture of prairie and forest. In western Minnesota the vegetation was wet prairie (wetlands) and dry prairie. The native vegetation for the maps we have today was determined by land surveyors who recorded the vegetation on a 1 mile grid in the late 1800s. A generalized map of the native vegetation helps to understand how vegetation changes as you go westward in Minnesota. The Minnesota DNR classifies the state into three broad eco-regions as seen on this map. 

The different vegetation that developed on a soil will impart special characteristics to the soil. For forested areas like the Big Woods or coniferous forest  
the soil develops a thin surface horizon, a leached, light colored zone below the surface, and an accumulation zone that is often brown or red in color.  
 
 

"

Further west in Minnesota you reach the true "tall grass prairie Soils developing under a prairie vegetation will have a thick, black surface horizon, a result of the thick prairie roots contributing large amounts of organic matter to the surface soil, making it black.

In summary, climate affects the amount of leaching that takes place in the soil and the speed with which soil horizons develop. Vegetation affects the thickness and color of the surface horizons.

Information provided by: http://www.soils.agri.umn.edu