What is Soil

What is SOIL???? The relatively thin surface layer of the Earth’s crust consisting of mineral and organic matter. Soil is not DIRT!

Q: What’s the difference between soil and dirt? A.Location, location, location! Dr. Greg Pillar, Queens College

The 5 Soil-Forming Factors climate (water, wind, temperature) biology (macro- and microorganisms, plants) relief (topography) parent material (rocks/minerals) time Which is the MOST important?? CLIMATE!!! Formed from parent material (bedrock) that’s slowly broken down through weathering processes.

What is Soil? How would you describe soil? Color Texture Dr. Greg Pillar, Queens College Texture

Soil Composition Water (~25%) Air (~25%) Mineral (~45%) Humus (~5%) Mineral matter comes from parent material Air & Water percents are interchangeable Humus is organic matter!

Soil Composition continued… Mineral Matter –Provides nutrient minerals for plants –Provides pore space for water & air Older soils are: –More weathered –Lower in certain essential nutrient minerals Humus: black/dark brown organic material remaining after decomposition –Leaf litter, animal dung, & decaying organisms –Increases the soil’s water-holding capacity by acting like a sponge

Soil Composition continued… As water infiltrates the soil, it can carry dissolved materials with it. Leaching: Removal of dissolved materials from the soil by water percolating downward Illuviation: Deposition of leached material in lower layers –Some substances completely leach out of the soil because they’re so soluble that they migrate right down to the groundwater.

Observe this SOIL PROFILE through soil Soil layers are horizons and assigned letters O: Organic material (may be absent) (may be absent) A: Topsoil - Organic material & mineral grains E: Leached zone (may be absent) (may be absent) B: Subsoil – rich in clay, iron, aluminum C: Weathered bedrock R: Bedrock (parent material) (parent material)

Soil Color – Variation by Geography Red soils: Southeast US Dr. Greg Pillar, Queens College

Soil Color – Variation by Geography Brown/black soils: Midwest Dr. Greg Pillar, Queens College

Soil Color – Variation by Geography White (gypsum) sands: New Mexico Dr. Greg Pillar, Queens College

Soil Organisms Ex: bacteria, fungi, algae, microscopic worms, protozoa, plant roots, insects, earthworms, moles, snakes, groundhogs, etc. Soil organisms provide several Ecosystem Services (important environmental functions). –maintaining soil fertility –preventing soil erosion –breaking down toxic materials –cleansing water –affecting atmospheric composition

Earthworms & Ants: –Cycle minerals –Aerate the soil –Decomposing corpses contribute organic matter –Assist plants in reproduction by burying seeds Mycorrhizae –Symbiotic relationship between fungi and the roots of vascular plants –Fungus absorbs nutrients from the soil, and provides it for the plant. –Plant produces food (photosynthesis), and provides it for the fungus.

Dr. Greg Pillar, Queens College

Physical Soil Properties PHYSICAL properties: Texture (%sand, silt, clay) Porosity & Permeability Ionic Charge

Texture is determined by its % sand, silt, and clay. Texture determines the type of soil, and the soil’s properties. Physical Property: Texture Loam: ideal for agricultural soil

Fine Texture - Clay Dr. Greg Pillar, Queens College

Course Texture - Sand Dr. Greg Pillar, Queens College

Soil Texture The relative portions of sand, silt, and clay-sized particles Sand: 2.0 – 0.05 mm Silt: 0.05 – mm Clay: < mm Dr. Greg Pillar, Queens College

B Soil Texture Diagram Practice What type of soil has: 1.20% clay, 40% silt, 40% sand 2.40% clay, 10% silt, 50% sand 3.30% clay, 60% silt, 10% sand Find the % of each particle at: 1.A 2.B 3.C A C 60%clay, 20%silt, 20%sand 30%clay, 40%silt, 30%sand 10%clay, 30%silt, 60%sand (1) Loam (2) Sandy clay (3) Silty clay loam

PropertySandSiltClay Water holdingLowMed-highHigh AerationGoodMedPoor Nutrient supplyingPoorMed-highHigh Pollutant FilteringLowMedHigh Why is Soil Texture Important?

Physical Characteristics (review) Why would 100% sand be undesirable for plants? Why would 100% clay be undesirable for plants? Answer SAND / SILT / CLAY for the following: –A soil with a lot of _____ would have good drainage, but poor nutrient-holding characteristics. –A soil with a lot of _____ would have poor drainage, but good nutrient-holding characteristics. –A soil with a lot of _____ would have low porosity. –A soil with a lot of _____ would have high permeability.

Two soil cores Bottom of core contains filter paper and cheese cloth Demonstration

Two unknown liquids Pollutant #1 Pollutant #2 Demonstration Liquids passed through soil cores Leachate collected below What will you observe?

Demonstration What happened to the original liquids? What does a change or no change in color mean? To what extent did the soil contribute to this change? Soil

Adsorption of Organic Dyes Chlorophenol red Methylene blue CR - MB +

Soil CR - MB +

Chemical Property: Acidity Most soil pH is 4-8. Plants are happiest at 6-7. Plants are affected by soil pH. (1) The solubility of certain nutrient minerals varies with differences in pH Low pH = Al & Mn are more soluble, and can be absorbed in toxic amounts. High pH = some salts are less soluble, and are less available to the plants. (2) Soil pH affects the leaching of nutrient minerals. Acidic soil = positively charged ions are less soluble and are unavailable for plants.

Soil stores important nutrients Phosphorus (P) Nitrogen (N) Potassium (K) Calcium (Ca) Magnesium (Mg) Dr. Greg Pillar, Queens College

Soil Conditioners (Lime) CaCO 3 or MgCO 3 Soil amendment / conditioner… not a fertilizer! Important functions: 1.Corrects soil acidity 2.Adds important plant nutrients— Ca & Mg 3.Reduces solubility & toxicity of certain elements in the soil Al, Mn, Fe This toxicity could reduce plant growth under acid conditions. 4.Promotes availability of major plant nutrients. Zn, Cu, P 5.Increases bacterial activity & mutualistic relationships.

Soil Conditioners (Compost) Decayed organic matter Replaces some nutrients Improves soil structure –The soil becomes more porous, increasing air circulation and the ability of the soil to absorb and hold moisture. –Makes the soil more spongy!