Land, then, is not merely soil; it is a fountain of energy flowing through a circuit of soils, plants, and animals.

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1 Soil Science Land, then, is not merely soil; it is a fountain of energy flowing through a circuit of soils, plants, and animals. - Aldo Leopold, A Sand County Almanac, 1949

2 The Rock Cycle IGNEOUS ROCK Erode & Weather SEDIMENT MAGMA Melt SEDIMENTARY ROCK METAMORPHIC ROCK

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

4 Q: What s the difference between soil and dirt? A.Location, location, location! Dirt is found under your nail, soil is found beneath your feet

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

6 What is Soil? How would you describe soil? Color Texture Texture

7 Why the color? Hematite: red Goethite: yellowish brown Ferrihydrite: reddish brown Calcite: off white Quartz: white Organic matter: black

8 Soil Color Variation Did you know?????? There are more than 20,000 different soil types in the United States

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

10 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

11 Soil Composition continued Porosity POROSITY = amt of soil pore spaces Pore spaces occupy ~50% of a soil s volume Filled with varying proportions of soil water and soil air Soil Air contains the same gases as atmospheric air, but in different proportions. More CO 2 and less O 2 (from organism respiration) Some bacteria need nitrogen (why??) The CO 2 can accelerate weathering CO 2 + H 2 O H 2 CO 3 (carbonic acid)

12 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.

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

14 Soil Pedon

15 Soil Color by Horizon A horizon: organic coatings B horizon: Iron coatings Fun Fact: It takes 100 to 600 years to form an inch of topsoil. C horizon: little coating

16 Soil Color Variation by Geography Red soils: Southeast US

17 Soil Color Variation by Geography Brown/black soils: Midwest

18 Soil Color Variation by Geography White (gypsum) sands: New Mexico

19 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

20 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.

21 Dr. Greg Pillar, Queens College

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

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

24 Soil Components Q: What did the shy pebble say to the big rock? A. Do you think I ll ever be a little boulder?

25 Fine Texture - Clay

26 Course Texture - Sand

27 Soil Texture The relative portions of sand, silt, and clay-sized particles Sand: mm Silt: mm Clay: < mm

28 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 (1) Loam (2) Sandy clay (3) Silty clay loam Find the % of each particle at: 1. A 2. B 3. C 60%clay, 20%silt, 20%sand 30%clay, 40%silt, 30%sand 10%clay, 30%silt, 60%sand C A B

29 Why is Soil Texture Important? Property Sand Silt Clay Water holding Low Med-high High Aeration Good Med Poor Nutrient supplying Poor Med-high High Pollutant Filtering Low Med High

30 Physical: Porosity & Permeability again Think it is important?? Porosity Definition? amt of soil pore spaces Permeability Definition? ability of water to percolate through porosity = permeability

31 Physical: Ionic Charge Soil minerals are often present as ions. Minerals ions are either positively or negatively charged. Clay particles have mostly negative charges on their outer surfaces. Positively charged mineral ions are attracted to the soil particles and are held for plant use. potassium K + and magnesium Mg 2+ Negatively charged mineral ions are repelled by the soil particles and are washed away from roots. nitrate NO 3 -

32 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.

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

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

35 Demonstration Soil Soil 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?

36 Adsorption of Organic Dyes HO Cl Cl OH O S O O Chlorophenol red CR - N Cl - N S + N Methylene blue MB +

37 MB + MB + MB+ MB + MB + CR - CR - CR - CR - MB + MB + MB+ MB + MB + Soil

38 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.

39 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.

40 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!

41 Why is Soil Important? Soil supports life Fun Fact: There 1 teaspoon are more of living good organisms soil contains a more cubic than foot 1 of million soil then bacteria! all of China! Dr. Greg Pillar, Queens College L. Clarke and Corbis, 2008

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

43 Soil Holds Water Dr. Greg Pillar, Queens College

44 Soil provides support for buildings Dr. Greg Pillar, Queens College

45 Soil filters, buffers, detoxifies. Soil Dr. Greg Pillar, Queens College

46 Inputs/Outputs Are these Soil Inputs or Soil Outputs? Mass Movements (landslides, etc) Precipitation Parent Material Leaching Infiltration Uptake by Plants Organic Matter Energy I O I I I I O O

47 Transfers/Transformations Recall: Transfers simply MOVE things they reorganize the soil! Transformations CHANGE things they alter the soil s makeup in some way. Are these Soil Transfers or Transformations? Decomposition transformation Erosion transfer Deposition transfer Weathering transformation Nutrient Cycling transformation

48 Soil Pollution Part II

49 Soil Pollution = any physical or chemical change in soil that adversely affects the health of plants and other organisms living in and on it. Many soil pollutants ARE MOBILE! move into groundwater, surface water, or air ARE PERSISTENT! seep into tiny cracks called micropores and adhere to the soil particles COME FROM FERTILIZERS / PESTICIDES! CAN ACCUMULATE! Sustainable Agriculture practices can help more on this later

50 Salinization of Irrigated Soil Irrigation water soaks through the soil area where the plant roots grow, adding to the existing water. The additional irrigation water causes the underground water-table to rise, bringing salt to the surface. When the irrigated area dries & the underground water table recedes, salt is left on the surface soil. Each time the area is irrigated this salinity process is repeated. ALL IRRIGATION WATER CONTAINS SOME DISSOLVED SALTS.

51 Salinization of Irrigated Soil This is in Australia occurred not from irrigation, but from lack of water-loving plants. Extra water flows through the soil, mixing w/ salt underground, and bringing it to the surface. Irrigation salinization is basically the same concept, and the ground would look just like this.

52 Effects of Salinized Soil on Plants Normally, the water concentration inside plant cells is lower than that in the soil resulting in a net movement of water into the root cell. When soil contains a high amount of salt, its relative water concentration can be lower than the water concentration inside cells. This causes water to move out of the roots into the soil, even when the soil is wet.

53 Soil Remediation Until recently, the only way to remove soil contaminants was to DIG IT UP & INCINERATE IT! Why is this a bad thing to do?? Impractical, kills all beneficial organisms, creates waste, expensive

54 Soil Remediation Techniques Dilution Add lots of water; leach out pollutants Vapor extraction Inject air into soil to remove volatile organic compounds Bioremediation Use microorganisms to degrade organic contaminants (oil, sludge) Phytoremediation Use plants to absorb contaminants such as salts or heavy metals.

55 DILUTION: Pump & Treat / Soil Washing Water GROUND LEVEL Extraction well Pollutant low sorption potential = not attracted to soil easily washed away Pollutant high sorption potential = not easily washed

56 But what s the problem here? GROUND LEVEL How can this problem be fixed??? Source Identification and Removal!!!!

57 12-32 Bioremediation (Bioventing)

58 Activities that Threaten Soil b Overgrazing Removing vegetation Erosion Control Soil contamination

59 Preventing Soil Erosion Agricultural: 10% of the worlds best agricultural land damaged due to soil erosion and overuse over last 50 years. - contour plowing - no-till agriculture (no plowing) - terracing slopes - crop rotation - fallow