Soil Structures

A. Explain the nature and composition of soil; Soil is the outer layer of the earth Dirt is displaced Soil Composition of average soil a. 25% Air b. 25% Water c. 5% Organic Matter d. 45% Mineral Matter 4. Pore Space: Spaces between solid matter, air and water will fill pore spaces

B. Describe how soil is formed, and define terms of formation; Begins when Parent Material or Rock is weathered Weathering: process when the climate breaks rock into small pieces (4 Factors) Freeze and Thaw Rainfall Wind Water 3. River and Glacial Sediments (soil particles) Alluvial Soil: soil deposits left by rivers and oceans Glacial Soil: soil created, moved, and deposited by glaciers

4. Living Organisms a. Plants: roots break apart rocks, lichens produce acids b. Animals: earthworms, insects, bacteria and fungi

Biological Properties The Soil Ecosystem Interaction of biotic and abiotic factors in a soil environment. The process of organisms growing and decomposing.

C. List and define mineral components of soil; Mineral Matter: inorganic material, non-living Particles are labeled as Sand, Silt and Clay a.Sand: largest particle Large pore space, good aeration Well drained Not fertile, in able to hold nutrients Feels gritty b. Silt: mid sized particle Good water holding capacity Retains nutrients Feels like flour dry, velvet wet

c. Clay: Smallest particle Ability to hold water and nutrients Small pores, poor aeration and drainage Hard clumps when dry, feels sticky when wet

D. Discuss soil texture and the textural triangle; Soil Texture: determined by proportions of the three types of mineral particles a. Each Soil type has a name b. Example: 40% sand, 20% clay, 40% silt, loam soil 2. Common Soil types a. Sandy Soil: Looseness, well aerated, good for root crops b. Silty loam Soil: Very fertile, good to grow in. c. Clay Soil: Heavy, dries very hard.

3. Textural Triangle: uses percentages of particles to determine soil types. Example: 40% Sand 20% Clay 40% Silt

Practice 40% sand 22% clay and 38% silt What is the soil classified as?

Practice 90% sand 10 % clay and 25 % silt What is it?

Practice 30% sand 50 % clay and 20% silt What is it?

Soil Texturing Ribbon Method Soil Sedimentation Method See if you can make a ribbon and with which one? Which one feels grittiest? Which one feel powdery? Soil Sedimentation Method Place soil in a jar Mix soil and water Let it settle

Time for a Lab Before we begin put everything away (this could get a little dirty) Pick up lab sheets Soil Texture by Feel Answer Sheet Soil Texture Flow Chart You will need to texture each of the four samples of soil Keep your area as clean as possible

F. Define Organic Matter and common soil amendments; Organic Matter: the accumulation of decayed or partially decayed plants and animals. Common additions of Organic matter to soil: Manure, animal waste Green “Manure”, or cover crop that is plowed in Peat Moss or Compost, common for gardeners

G. Describe water relationships in the soil; Three main types of ground water. Gravitational Water: Free flowing water pulled down by gravity. Flows quickly through sand, slowly through clay Leaching: as water moves through soil it carries with it nutrients, salts and chemicals. 3. Capillary Water: held between particles, moves up and sideways through soil. As soil dries out, it pulls water up though the pore space. Plant available

4. Hygroscopic Water: water held in a thin film around the individual soil particles Not plant available

H. Describe the role of air in the soil; Air should make up 25% of the soil sample Air is in the pore space, fills with water after rain Must have a balance between air and water to maintain most plant life Too much water (lack of air), fermentation Not enough water (too much air), wilted plants

Granular: most desirable Explain soil structure; 1. Aggregates: large clusters of soil particles 2. Soil Structure: the way which aggregates are arranged (8 types of structures) Granular: most desirable Crumb: also desirable Platy Prismatic Massive Columnar Blocky Single grain

8 Types of Structure

2. Damage: Humans can destroy soil structure a 2. Damage: Humans can destroy soil structure a. Driving heavy equipment on when wet b. Working Soil when excessively wet 1) Clay particles clog pore spaces, soil compaction. 2) Poor drainage, plants cannot grow

J. Illustrate and label soil profiles; Soil Profile: a view of a cross section of soil a. Soil is arranges in layers called Horizons b. Horizon: layers of soil in the profile 1) Five major horizons, all horizons have names 2) Depth and thickness of horizon vary depending on location

Soil Horizons 2. Main Horizons a. O horizon- Litter Layer, Organic material b. A horizon- Top Soil, most fertile, up to 10 inches deep c. B horizon- Sub soil, some nutrients leached from above d. C horizon- Weathered bedrock & some leached materials e. R horizon- Bedrock, or solid rock, parent material

Erosion: the removal of soil by wind or water K. Discuss the process of soil erosion, its importance, and prevention. Erosion: the removal of soil by wind or water Loosing valuable soil that then can pollute water and air Soil Conservation Agricultural practices: Strip cropping, terraces, no till Wild land and home owners: plant roots can anchor soil in place

Erosion No till planting Terrace cropping