The last two weeks briefly described the process of soil formation and the role soils play in agriculture and our lives. Let’s start to take that information and see what that means for soils in Kansas and more specifically in our area. First, where is our state in terms of the soil forming factors?
· Parent material – Here it is influenced by several factors. About 250 millions of years ago, this area was part of an inland sea. This is evident from things we find such as limestone, shale, abundant fossils and all the sedimentary rock common here. The Flint Hills arise from this. Here the limestone parent material contained a great deal of chert (flint) which made it more resistant to chemical weather that led to the shallow soil there today on the hillsides. Much later, the Kansas Glaciation covered much of NE Kansas. That combined with the wind-blown loess (silt) that was deposited there, resulted in the deep, well-drained fertile soils of that area. Here, another major feature that influenced parent material is the Arkansas River, especially the triangle from about the Kinsley area up to Great Bend and back down through Hutchinson and Wichita. Many soils contained in that area are the result of sand deposited as the river made its bend north. The result is a varied landscape in the state with soils developed tending to have high levels of potassium and base cations like calcium and magnesium. Unfortunately this is just a thumbnail sketch.
· Climate – We have discussed climate here before for crops and it has an equally important role to play for soil formation. While most our state’s temperature regimes favor soil formation (fluctuating temperatures with four distinct seasons), our moisture regime varies widely from the SE to NW corners of the state. On average, the SE portion averages over 40 inches. The value decreases as you move westward in the state to where the Great Bend area average is around 27 inches and that number decreases to around 15 inches at the Colorado border. This combined with high evaporative demand means moisture is often limiting and that influences the rate of chemical and biological reactions and the type of native vegetation.
· Biota – Parent material and climate helped determine that for all but the SE part of the state grasslands predominated due to regular drought, rainfall patterns, and periodic fires. The climate patterns are due in large part to the Rocky Mountains and the rain shadow they produce for the western half of Kansas. The result is tall grass prairie in the east, short grass prairie in the west and where we are mixed-grass prairie. The SE corner climate resulted in forested areas. Animal life consisted of grazing animals and animals adapted to a grassland environment.
· Landscape – This varies depending on where the soil is located; flood plain, hilltop, north slope, south slope and so on.
· Time – Except where erosion has been a problem, our state’s soils have had sufficient time to mature and develop. They are much more “developed” than to the west and less “developed” than to the east.
Next week we’ll figure out what that means for our soil’s role in the environment.