Envirothon Soil

Topics Soil Soil Formation Soil Texture Soil Color Organic Matter pH Salinity Soil Air Compaction/Shrink-Swell Drainage Erosion Soil Surveys-How to Use Them References

Typical Loamy Soil

Typical Clayey Soil

Typical Sandy Soil

Forming Factors Climate Living Organisms Parent Material Topography Time

Climate Most influential factor Temperature and precipitation in particular Determines the nature and speed of formation High Heat, High humidity, abundant rain=a lot of power

Living Organisms Plants and animals Grasses vs trees Microorganisms

Parent Material Geology Gulf Coast was a fluvial deltaic system Soils are derived from loamy and clayey sediments About 14,000 years old

Topography Nearly level Slope occurs along drainage

Time Soils on flood plains and coast line are youngest Stable landscapes have older soils Takes about 500 years to form an inch of soil from hard parent material

Texture USDA % of Sand, Silt and Clay Key factor chemically and physically

Clayey Soils High Shrink-Swell High Organic Content High Water Holding Capacity Agriculturally productive Difficult to work with

Sandy Soil High pore space Low organic matter Low fertility Low water holding capacity Easy to work with

Loamy Soil Wide array of soils Low to High Fertility Low to High Organic content Low to High Water Holding Content Moderate to work with

Soil Color Dark=high organic content Light=low organic content Red, yellow, brown is well drained Gray could mean excessive wetness

Dark= High Organic Most clayey soils in our area are dark and have high organic content

Light=Low organic content <1 percent Most loamy and sandy soils in our area are low in organic content

Well Drained High on the landscape Ridges and sloping areas Yellow, red or brown Black is usually well drained

Gray Could be Wet Gray surface Contains mottles (oxidized or reduced iron) Concave landscape Wet soils could be associated with wetlands!

Organic Matter Accumulation of partially decomposed plant and animal residues Loosens soil Nutrient source for plants Increases water holding capacity Food for microbes

Soil Organic Matter Highest in the surface where the majority of biotic activity occurs Important to stockpile surface layer Easily destroyed when disturbed

Increasing Organic Content Warm and humid conditions are ideal for microorganisms Constant struggle Leave grass clippings, leaves, and twigs Add mulch

Organic Matter Considerations Carbon to Nitrogen ratio Microbes use nitrogen to eat carbon Could cause nitrogen difficiency in plants Add nitrogen fertilizer Will correct over time Use good compost

Soil pH Ideal pH range is 5.5 to 7.5 pH >8.5 could mean high salt content pH<4 Aluminum and Iron toxicity pH meters Add lime for soils less than 5.5 and sulfur for soils above 7.5 Local soils are in good pH range Best to not get too worried about changing pH

Salinity A localized problem on Gulf Coast Almost all soils have some salinity Causes soil to become hard Damages roots and stunts plants Damages steel

Soil Air Well aerated soils support better plant growth Mechanical aerator Incorporate organic matter into the soil for a long term solution

Soil Compaction Occurs in high traffic areas Occurs when soils are manipulated when wet Plowing or incorporating organic matter decreases compaction Minimize hazard of compaction by having a good thick layer of mulch on surface

Shrink and Swell All clayey soils do it swell when wet and shrink when dry $$$$$ to fix damage

Soil Drainage Classes Very poorly Drained-Water is at or near the surface during much of the growing season Poorly drained-The soil is wet at shallow depths periodically during the growing season or remains wet for long periods. Somewhat Poorly drained-The soil is wet at a shallow depth for significant periods during the growing season. Moderately Well drained-Water is removed from the soil somewhat slowly during some periods of the year Well drained-Water is removed from the soil readily, but not rapidly. Somewhat Excessively Drained-Water is removed from the soil rapidly. Excessively Drained-Water is removed from the soil very rapidly.

Drainage Poorly drained soils are gray with oxidized iron zones Concave landscapes Usually have water loving plants

Drainage Well drained are brown, yellow or red and most black soils Convex landscapes Avoid making depressions if you want the soil to stay well drained

Erosion Soil moved by wind or water Occurs in high traffic areas where surface vegetation is gone Areas with more than 3 percent slope are susceptible Mulch and terraces (anything to slow wind and water down)

Soil Surveys An inventory of soils that includes maps, interpretative tables, and soil descriptions for use in general land use planning

Using a Soil Survey Locate your area of interest in the soil map section Identify all of the soil map unit symbols at your area of interest

How to Use Soil Surveys Go to the table that contain the information you seek Find your map unit symbol and then find the land use practice Table provides information on suitability for that soil for that particular land practice

References The Nature and Properties of Soils, by Nyle C. Brady

Contacts USDA-Natural Resources Conservation Service –Rosenberg= ext 3 –Angleton= –Temple State Soils Staff= –Rosenberg Soil Survey Office= ext 5