Growing Plants : The Soil Profile

What is Soil Made up of?

Soil Layers Called Horizons All soil profiles do not have the same number or level of horizons. Most typical soils in North Carolina will have a minimum of the A, B and C or R horizons.

Soil Horizons

O Horizon Rich soil found where a plant cover has been in place for an extended time O Horizon is rich in organic matter in various stages of decomposition and is dark in color. It is the most fertile layer in the soil profile.

A Horizon Is the topsoil and most fertile in the absence of an O horizon. A Horizon, lies just below O Horizon, is home to earthworms and soil organisms. It is brown in color due to the organic matter in the soil.

B Horizon Is the subsoil. B Horizon is a clayey soil that has a high mineral content. B Horizon is usually brown or reddish due to the large amount of clay.

C Horizon Is parent material. C Horizon consists mainly of clumps of un- weathered rocks.

R Horizon Is bed rock. R Horizon cannot be dug by hand and very few roots can penetrate the bedrock.

Soil Structure Soil structure is how the soil particles fit together Water movement in soil vmo0FRAVgkM

Soil Structure

Sandy soils typically have a loose soil structure.

Soil Structure Silty soils have a granular soil structure.

Soil Structure Clayey soils have a blocky or platy structure.

Soil Structure Granular soil structure is the best. Plants have good root development. Water movement is at an appropriate rate – doesn’t stay to wet or too dry.

Soil Structure

Soil Texture

Soil texture is the relative proportions of sand, silt, or clay in a soil.

Soil Texture GEA

Soil Texture 1. Sand has the largest particles. Sandy soils have low moisture and nutrient holding capacity.

Soil Texture 2. Silt has medium sized particles. Silt has a good moisture and nutrient holding capacity.

Soil Texture 3. Clay has the smallest sized particles. Clayey soils have high water and nutrient holding capacity.

Soil Texture 4. Loam has almost equal parts of sand, silt and clay. This is the ideal texture for most non container outside plants.

Identifying Texture by Feel Feel test – Rub some moist soil between your fingers. Sand feels gritty. Silt feels smooth. Clays feel sticky.

Identifying Texture by Feel Ball squeeze test – Squeeze a moistened ball of soil in your hand. Coarse textures (sand or sandy loam) soils break with slight pressure. Sandy loams and silt loams stay together but change shape easily. Fine textured (clayey or clayey loam) soils resist breaking.

Identifying Texture by Feel Ribbon test – Squeeze a moistened ball of soil out between your thumb and fingers. Sandy soils won’t ribbon. Loam, silt, silty clay loam or clay loam soil ribbons less than 1 inch. Sandy clay loam, silty clay loam or clay loam ribbons 1 to 2 inches. Sandy clay, silty clay, or clay soil ribbons more than 2 inches. A soil with as little as 20 percent clay may behave as a heavy clayey soil. A soil needs 45 percent to over 60 percent sand to behave as a sandy soil.

Soil Texture by feel JCNec

Soil Texture

Soil Texture Practice 1. 50% clay, 30% silt, 20% sand _____________________________ 2. 40% clay, 10% silt, 50% sand ______________________________ 3. 12% clay, 10% silt, 78% sand ______________________________ 4. 22% clay, 60% silt, 18% sand ______________________________ 5. 30% clay, 40% silt, 30% sand ______________________________ 6. 35% clay, 42% silt, 23% sand ______________________________ 7. 30% clay, 60% silt, 10% sand ______________________________ 8. 50% clay, 45% silt, 5% sand ______________________________ 9. 40% clay, 10% silt, 50% sand ______________________________ 10. 5% clay, 15% silt, 80% sand ______________________________

What is pH? yG8 yG8 Why does soil pH matter? 9kc

Improper pH affects availability of nutrients limits plant intake Alkaline Acid Neutral Soil pH

Soil PH 1. Soil pH is a measure of the acidity or alkalinity of soils.

Soil pH 2. Soil pH ranges from (low pH) is considered an acid soil, 7 indicates a neutral soil and 8-14 (high pH) is considered an alkaline soil.

Soil pH 3. Lime will raise the pH value in soils (make the soil less acidic).

Soil pH 4. Calcium or sulfur will lower the pH value in soils (make the soil more acidic).

Soil pH 5. The ideal pH value for vegetable garden soils are 5.5 to 7.0.

Testing soil pH

Pour-thru: to measure the amount of pH in the soil.

Physical Properties of Soils 1. Permeability is the rate at which water moves through the soil. 2. Water holding capacity is the ability of a soil to hold water for plant use. 3. Porosity is the amount of air space between soil particles % of soil should be pore space which includes 25% water space and 25% air space % of soil should be soil particles which include 45% mineral matter and 5% organic matter.

Soil Sampling Q8

Soil Sampling 1. Soil sampling and testing is essential for an accurate fertilizer recommendation for growing plants. 2. Soil sampling procedures. a. Create a visual grid of the area to be planted. For gardens and landscapes, take 5-10 subsamples from the site to be evaluated. Sample before the growing season. b. Use a stainless steel soil-sampling probe. c. Take the surface sample to tillage depth or about 3-4 inches for lawns and 6-8 inches for crops.

Soil Sampling Continued… d. Mix the soil samples together. e. Remove any grass, rocks or other material besides soil. f. Avoid unusual spots in the lawn or field. Those areas need to be sent in a separate box. g. Place soil samples in a box, which you can obtain from the County Extension Office along with Soil Sample Information sheet, send the box and information to Agronomic Division Soil Test Lab in Raleigh for a free soil test.

Soil Profile Review

Review What are the 3 soil textures? Which is the largest soil particle? Which has the largest water holding capacity?