SOIL! SOIL: Particles of minerals, organic matter (plant and animal), water, and air; that is found on most surfaces of the land. It takes 100+ years to form 1-inch of topsoil

Soil Basics

Why do we study soils? Agriculture Engineering Construction Conservation Exploration/Mining Natural History Biodiversity

Basic Soil Facts An average soil sample is made up of minerals, water, air, and organic matter. A renewable resource- forms at rate of ~1 in in a 100 years Plant roots loosen the soil, allowing oxygen to penetrate. Plant Roots also hold soil together to prevent erosion.

Fertilizers Make plants grow faster- increase crop yields. Key Macronutrients: N,P,K Too much- causes soil acidification= stunts growth and/or kills plant. Results in crop reduction.

Soil Horizons Weathered rock mixed with organic material (humus), mineral nutrients, microorganisms, water and air form soil. Soil horizons O horizon: organic material/surface litter “HUMUS” A horizon:”topsoil” layer; most productive layer; Some HUMUS - B horizon: subsoil; minerals present here C horizon/ parent material: lower subsoil and Bedrock

Why Humus is Important? How humus improves soil conditions: Provides nutrients/fertility for plants and soil organisms Helps topsoil hold water (water-holding capacity) Improves habitats for soil organisms Improves buffering capacity, which stabilizes pH Prevents erosion Improves porosity

Soil Textures Soils have varying amounts of: Clay – finest particles of rocks and minerals Silt – fine particles of rock Sand – medium-sized particles Relative amounts of these materials determine soil texture

Chemical Properties of Soil Cation Exchange Capacity Cation: + charged mineral ions. Cation exchange capacity (CEC)- nutrient holding capacity. It’s a function of the type and amount of CLAY particles present. Clay and Organic Matter (HUMUS) have HIGH CEC Soils with HIGH CEC = HIGH PRODUCTIVITY

High CEC soil retain the fertilizer and pesticides; Leaching occurs with low CEC (sandy soils)

Three Key test to KNOW for my TEST and APES TEST PHYSICAL TESTS Soil texture by measurement- use soil triangle. Soil by texture- ribbon test. https://www.youtube.com/watch?v=2MUnGBXjtGg Color of soil CHEMICAL TESTS Nitrogen level 2.Phosphorus level 3. pH

Soil texture by measurement

Soil Triangle Provides a percent (%) composition of sediments that compose a soil Loam soil has EQUAL parts of Sand, Silt, Clay. It’s ideal for most plants.

Soil Triangle Example: 50% sand 20% clay 30% silt The percentage of sediments in the soil triangle must equal 100%

Soil Texture Determines porosity, permeability and structure of soil Porosity: space between soil particles. Depends on the soil texture. Permeability: rate at which water and air move from upper to lower soil layers. Clay has a low permeability. Structure: way in which soil particles are organized and clumped together pH: determines plants’ ability to take up nutrients from soil

Soil Lab Part II- DAY 2

Using the Soil Triangle You will record your measurements for each layer of sediment- Amt clay, silt, etc. Recall clay will be at the top, followed by silt, then sand. Calculate the %: Volume of X/ 25 x 100 Ex: silt= 15/25 x 100= 60% Repeat with clay and sand.

Soil Triangle Example: 50% sand 20% clay 30% silt The percentage of sediments in the soil triangle must equal 100%

Animated Soil Triangle

What do the test tell you about your soil? Did the ribbon test match your soil by measurement results? If not, why? Consider the texture, porosity & permeability? CEC? Recall combo of clay and humus= High CEC and High productivity Level of nutrients? What would you need to do to this soil to improve it?