Soils NOT Just Dirt Chapter 8

Defining Soil “a natural body consisting of layers (horizons) of mineral and/or organic constituents of variable thickness, which differ from parent material in their morphological, physical, chemical, and mineralogical properties and their biological characteristics” Birkeland, 1999; Joffe 1949 I need a brave student to read this slide for me. I am not too good with names but you can read them at the end there. Do you think they wrote a definition this long and weird sounding definition just to freak out high school students? No, each part is really important so lets break it down.

Why not Dirt? Soil is a living environment Has nutrients Earthworms and insects Diverse Bacteria Layers Have the words come in after you have asked what the students think: Why do you guys think soil is different from dirt? I want about 5 difference answers so everyone better be thinking of something

Soil Importance Medium for plant growth Water purifier Facilitates waste decomposition Viewing a world without soil. No plants so not sufficient amount of oxygen Ground water and aquifers are toxic and gross Nothing decomposes

Water Purification Natural filtration Chemical absorption and adsorption Living organisms Human interaction and manipulation of soils can interrupt the process of natural water purification. http://www.freedrinkingwater.com/water_quality/quality2/j-8-08-natural-purification-of-liquid-water-work.htm

ORGANIC RICH SOIL

How Soils Form There are multiple processes happening at the same time to allow soil to form. Parent Material Climate Topography Organisms Time Pedogenic regimes: Remember the part of the definition I wanted you to remember? What was it? And why do you think I am asking you now Soil Succession: Primary = 1000 years, soil is not present and in a lifeless and barren area. Secondary = some soil is already present 50-200 years Clay Factories = weathering of primary materials and formation of clay materials shows stability of soil formation Complexity = different factors that happen over a long period of time Energy = always need energy. What type of energy process might occur to produce soils?

Average Soil Sample Contains What is mineral? Solid inorganic substance of natural occurrence

Soil Horizons O – Organic: leaf litter and humus Basics O – Organic: leaf litter and humus A – Topsoil: seeds germinate and plant roots grow, made of humus and mineral B – Subsoil: clay and mineral deposits C – Regolith: slightly broken up bed rock, plant roots cannot break through Picture is called a soil profile Humus = decompose organic matter B: mineral deposits come from mineralized water that drips from the layers above C: very little organic matter

Categorizing Soil Color Density Texture Temperature Structure Moisture Porosity

Color Munsell System quantitatively measures differences in color characteristics It measures Hue: yellow, red, blue, green Value: high value= light colored, low value = dark colored Chroma: purity of color, high chroma = pure color, low chroma = less pure Yellow and red are dominate hues, blues and greens are waterlogged soils Reason for value being opposite is that we are looking at the function of the amount of light reflected Less pure is diluted by grey

Evaluating particle size Texture Evaluating particle size Gravel feels coarse Sand feels gritty Silt feels like flour Clay feels sticky and wet

Soil types

Too Much Sand Soils with lots of sand have to much space between particles. This makes it hard for them to hold water or any nutrients. Plant’s roots cannot hold well. Soils with lots of sand have to much space between particles. This makes it hard for them to hold water or any nutrients. Plant’s roots cannot hold well.

Too much Silt Soils with too much silt is very light. Commonly found in flood plains and is the components of soil that makes mud. Lots of silt makes excellent farmland, but increase erosion. This is that part of soil that blows away in sand storms Soils with too much silt is very light. Commonly found in flood plains and is the components of soil that makes mud. Lots of silt makes excellent farmland, but increase erosion. This is that part of soil that blows away in sand storms

Too Much Clay Soil with too much clay is heavy and dense. There is almost no space between the particles. Bacteria and microorganisms in the soil cannot get oxygen. Plant roots cannot push through. Soil with too much clay is heavy and dense. There is almost no space between the particles. Bacteria and microorganisms in the soil cannot get oxygen. Plant roots cannot push through.

That’s Just Right LOAM Perfect soil for plants has about equal parts sand and silt with less clay. There is large enough space between particles for air, water, and nutrients. There should be enough clay to help stick together. Perfect soil for plants has about equal parts sand and silt with less clay. There is large enough space between particles for air, water, and nutrients. There should be enough clay to help stick together. Everything is good. Plant roots can grow. Farmers and gardeners get really happy and proud of this type of soil

Structure Effected By: Chemicals Biological activity Soil use Water content Overburden Texture

Porosity Fraction of void space in the material Can contain water or air

Permeability Is the relative ease in which water and air can move through soil. Soils with low permeability do not have much drainage.

Density Less dense More Dense Someone tell me what density is Based on your previous knowledge of density “Which do you think is more dense?” Less dense More Dense

Temperature Becomes important with seed germination and crop growth Minimum temperature Optimum range of temperature Optimum temperature Maximum temperature Measured with thermometer placed 3 to 4 inches into the ground Lettuce and Spinach have the lowest minimum temperature at 35 Turnips, watermelon, okra, cucumber, and corn have the highest maximum temperature at 105 Optimal temperatures range from 65 to 95 Temperature can vary throughout the year or latitudinally

Moisture Moisture is key to controlling the exchange of water and heat energy between land surface and atmosphere

Acidity in Soils pH measures the acidity or alkalinity of soil Neural = 7.0 Acidic < 7.0 Alkaline > 7.0 Effects solubility of plant nutrients Soils normally range from 3.0-10.0 pH Most cultivated plants like slightly acidic soil pH 0-14 Before a nutrient can be used by a plant it most be dissolved in the soil solution

Soil Erosion Soil degradation is the loss of some or all of the ability of soils to support plants. One of the major causes is erosion. It can take centuries for lost topsoil to be replaced.