Horticulture I: Soil Part 11. Types of Growing Media

a. Peat mossi. Peat moss is organic and has a slightly acidic pHii. Is partially decomposed material mined from the swampsiii. Peat moss has good moisture holding properties

b. Vermiculitei. Vermiculite is inorganic and has a slightly alkaline pHii. Is a light-weight mica mineral matter commonly used to start seed and cuttingsiii. Vermiculite holds moisture and has a neutral pH

c. Perlitei. Perlite is inorganic and has a slightly alkaline pHii. Is a natural volcanic materialiii. Perlite helps with soil aeration and drainage

d. Organic matteri. Is dead plant or animal tissueii. Organic matter contains carbon

e. Composti. Is decayed organic matterii. Compost is used for soil conditioning and fertilizer

f. Barki. Bark is organic and has a slightly acid pHii. Is larger matter added to some horticulture media to promote drainageiii. Adding bark to a soilless mix usually makes the mix heavieriv. It is widely used in tree and shrub production

g. Sphagnum mossi. Sphagnum is organic and is very acidicii. Is dehydrated remains of acid bog plantsiii. Sphagnum moss holds moistureiv. Sphagnum moss is commonly used to line wire hanging baskets

2. Advantages of horticultural soils (mixes that may or may not include soil)a. The soil is sterileb. The pH is neutral for most commercial blends of media mixesc. The soil is disease and weed freed. It is good for starting disease sensitive seeds (tomato)e. It is easy to control the nutrient content of the soilf. It improves crop uniformityg. It is easy to create a horticulture soil for particular plant needs

3. Disadvantages of horticultural soilsa. It is expensiveb. It is light weight

4. Additional materials used in soilless media mixesa. Sawdust and Wood Shavings

i. High carbon to nitrogen ratio

ii. Makes nitrogen unavailable for plant useb. Organic materials

i. Must be well rotted or decomposed to avoid problems with nitrogen tie-up

Horticulture I: Soil Part 21. Soil Profile

a. Soil layers (horizons)i. All soil profiles do not have the same number or level of horizons

1. Sandy soil may not have an “O” horizon if it has been under cultivation2. Other soils may have a horizon missing due to erosion3. Most typical soils in North Carolina will have a minimum of the A, B and C or

R horizonsb. O Horizon

i. Rich soil found where a plant cover has been in place for an extended timeii. Is rich in organic matter in various stages of decomposition and is dark in coloriii. It is the most fertile layer in the soil profile

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

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

e. C Horizoni. Is parent materialii. C Horizon consists mainly of clumps of un-weathered rocks

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

2. Soil Structure a. Soil structure is how the soil particles fit together

i. Sandy soils typically have a loose soil structureii. Silty soils have a granular soil structureiii. Clayey soils have a blocky or platy structureiv. 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

3. Soil Texturea. Sand

i. Largest particles. Sandy soils have low moisture and nutrient holding capacityb. Silt

i. Medium sized particles. Silt has a good moisture and nutrient holding capacityc. Clay

i. Smallest sized particles. Clayey soils have high water and nutrient holding capacityd. Loam

i. Almost equal parts of sand, silt and clay. This is the ideal texture for most non-container outside plants

4. Soil pHa. Soil pH is a measure of the acidity or alkalinity of soilsb. Soil pH ranges from 0-14:

i. 0-6.9 (low pH) is considered an acid soilii. 7 indicates a neutral soiliii. 8-14 (high pH) is considered an alkaline soil

c. Lime will raise the pH value in soils (make the soil less acidic)d. Calcium or sulfur will lower the pH value in soils (make the soil more acidic)e. The ideal pH value for vegetable garden soils are 5.5 to 7.0

5. Physical Properties of Soilsa. Permeability

i. The rate at which water moves through the soilb. Water holding capacity

i. The ability of a soil to hold water for plant usec. Porosity

i. The amount of air space between soil particlesd. 50% of soil should be pore space

i. 25% water space and 25% air spacee. 50% of soil should be soil particles

i. 45% mineral matter and 5% organic matter

6. Soil Samplinga. Soil sampling and testing is essential for an accurate fertilizer recommendation for growing

plantsb. Soil sampling procedures

i. Create a visual grid of the area to be plantedii. For gardens and landscapes, take 5-10 subsamples from the site to be evaluatediii. Sample before the growing seasoniv. Use a stainless steel soil-sampling probev. Take the surface sample to tillage depth or about 3-4 inches for lawns and 6-8

inches for cropsvi. Mix the soil samples togethervii. Remove any grass, rocks or other material besides soilviii. Avoid unusual spots in the lawn or field

1. Those areas need to be sent in a separate boxix. 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