The Soil Profile

The 6 Soil Roles A Soil’s role includes: Serving as a foundation Emitting and absorbing gases Providing habitat Interacting with water Recycling nutrients Supporting human settlements

The 5 Factors of Formation Soil is formed by… Parent Material: the original “Mom & Pop” soil transported from elsewhere, usually by wind or water, at different speeds Climate: the amount, intensity, timing, and kind of precipitation that breaks down parts of ecosystem (i.e. rocks, trees) into soil Topography: Slope and Aspect affect the angle of the land and position toward/away from the sun that soil will be exposed to Biological: Plants, animals, microscopic organisms, and humans interact with soil in different ways Time: the amount of time it takes for the four factors (above) to interact with each other

What is a Soil Profile? A Soil Profile is a vertical cross-section of layers of soil found in a given area. Below are two examples of soil profiles.

What is a Soil Horizon? Soil horizons are the layers in a soil profile used to classify soil types. Horizons based on color, texture, roots, structure, rock fragments, and any unique characteristic worth noting. Master Soil Horizons are depicted by a capital letter in the order (from top down): O, A, E, B, C, and R

O-Horizon The “Organic Matter” Horizon Surface-layer, at depths of 0-2 feet Dark in color, soft in texture Humus - rich organic material of plant and animal origin in a stage of decomposition Leaf litter – leaves, needles, twigs, moss, lichens that are not decomposing Several O-layers can occur in some soils, consisting only of O-horizons

A-Horizon “Topsoil” or “Biomantle” Horizon Topmost layer of mineral soil, at depths of 2-10 feet Some humus present, darker in color than layers below Biomantle - most biological productive layer; earthworms, fungi, and bacteria live this layer Smallest and finest soil particles

E-Horizon The “Leaching Layer” Horizon Small layer between A & B horizons At depths of 10-15 feet Light in color, mainly sand & silt Poor mineral and clay content due to leaching – the loss of water-retaining plant nutrients to the water table Soil particles larger than in A horizon but smaller than in B horizon

B-Horizon The “Subsoil” Horizon At depths of 10-30 feet Rich in clay and minerals like Fe & Al Some organic material may reach here through leaching Plant roots can extend into this layer Red/brown in color due to oxides of Fe & clay

C-Horizon The “Regolith” Horizon At depths of 30-48 feet Made up of large rocks or lumps of partially broken bedrock Least affected by weathering and have changed the least since their origin Devoid of organic matter due to it being so far down in the soil profile

R-Horizon The “Bedrock” Horizon At depths of 48+ feet Deepest soil horizon in the soil profile No rocks or boulders, only a continuous mass of bedrock Colors are those of the original rock of the area

How to Make a Soil Profile Ingredients List Directions 3-4 copies of Master Soil Horizons Worksheet 30 sticky notes per group (7 per person) 3-4 pairs of gloves 1 large glass bowl 1 one-cup measuring cup 1 whisk 1 spatula 3.5 cups skim milk 2 packages vanilla Instant Jell-o pudding mix 1 tiny Ziploc bag Coconut w/green food coloring + raisins 1 small Ziploc bag crushed chocolate graham crackers & frosting 1 medium Ziploc bag Chocolate chip & Vanilla wafers & gummy worms 1 small Ziploc bag crushed Vanilla wafers only 1 medium Ziploc bag crushed graham crackers 1 large Ziploc bag crushed Oreo cookies 1 large Ziploc bag crushed chocolate chips In large glass bowl, whisk 3.5 cups milk with 2 pkgs. vanilla Instant Jell-o pudding mix until smooth. Let stand 5 minutes. While waiting, refer to your version of “The Soil Profile” powerpoint to review order that horizons should be. You have A, E, B, R, O, C, and vegetation as horizons. It’s up to you to order it! After 5 minutes, use spatula to scoop pudding in middle of bowl, allowing for the “dry ingredients” (the bags of various crushed up cookies) to encircle the pudding along the sides of the glass bowl. This creates a vertical cross-section of soil layers visible to you. Use sticky notes to label each horizon on outside of bowl. Fill out Master Soil Horizons Worksheet using observations of Soil Profile Dessert. Turn in worksheet to teacher. Only until you and your team members turn in their worksheet can you enjoy the delicious snack. You’re finished!