NRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties11NRES 201Soils & Soil Properties2Today’s lecture topics- What is soil?- Soil components- Functions of soil- Soil as an environmental interfaceSoils & Soil PropertiesNRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties23What is soil?Two distinct meaningsSoil as a material Soil as found in natureSource: Brady and Weil (2010)4What is soil?Some definitions- The upper part of the Earth’s crustNRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties35What is soil?Some definitions- The upper part of the Earth’s crust- The upper part of the Earth’s crust composed ofmineral and organic matter6What is soil?Some definitions- The upper part of the Earth’s crust- The upper part of the Earth’s crust composed ofmineral and organic matter- The upper part of the Earth’s crust composedof mineral and organic matter and formed by the interaction of:- Climate-Organisms- Topography- Parent material-TimeThe five soil-forming factorsNRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties47How a soil looks in the field- Solum, consistingof 3 horizons (layers):- O = organic- A = plow layer- B = subsoil- C horizon- Parent material- But not yet soil- Regolith (O + A + B + C)truesoil†Source: Brady and Weil (2010)†Also includes E horizon, if present8Soil components:The solid phaseComposed of- Inorganic minerals- Primary minerals present in the original rock- Secondary minerals formed by weathering- Organic matter- Living organisms (biomass)- Organismal remains (residues)- Decay products (humus)NRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties59Properties- Texture- Proportion of particles by size:• Sand (coarse)• Silt (medium)• Clay (fine) Different types with different properties- Structure- Aggregation of soil particles- Important to:• Soil air and water movement• Root growth 10- Organic matter content- Many important effects on soil physical, chemical, and biological properties, including:• Aggregation of soil particlesSource: Buckman and Brady (1969)NRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties611- Organic matter content- Many important effects on soil physical, chemical, and biological properties, including:• Aggregation of soil particles• Water storage and availabilitySource: Brady and Weil (2010)12- Organic matter content- Many important effects on soil physical, chemical, and biological properties, including:• Aggregation of soil particles• Water storage and availability• Microbial energy source• Nutrient-supplying power- These properties interactNRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties713Soil components:The liquid phaseCharacteristics- Water + dissolved ions, molecules, and gases- Known as the soil solution- Medium for chemical andbiological processes- Vital to plant growth- Held within soil pores- Mobile in large pores- But immobile in smallporesSource: Troeh and Thompson (2005)14Soil components:The gaseous phaseCharacteristics- Gases occupy soil pores not filled with water- Known as the soil atmosphere- Isolated, not continuous- Differs from ambient air by having:- Less O2-More CO2- More humidity- Critical to biological processesNRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties815Soil components:Typical compositionSource: Brady and Weil (2010)Percentages by volume for a loam surface soil16Functions of soil- Medium for plant growthNRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties917Functions of soil- Medium for plant growth- How the soil affects plant growth:• Physical support• Aeration (O2& CO2)• Water availability• Thermal insulation• Control of toxicities• Nutrient supply18From air or water- Carbon (C)- Hydrogen (H)- Oxygen (O)From soil solids- Nitrogen (N)- Phosphorus (P)- Potassium (K)- Calcium (Ca)- Magnesium (Mg)- Sulfur (S)- Boron (B)- Copper (Cu)- Iron (Fe)- Manganese (Mn)- Molybdenum (Mo)- Zinc (Zn) The essential nutrientsNRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties1019- Medium for plant growth- Regulator of water suppliesFunctions of soil20Functions of soil- Medium for plant growth- Regulator of water supplies- Waste recycling systemNRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties1121Functions of soil- Medium for plant growth- Regulator of water supplies- Waste recycling system- Habitat for soil organisms22Functions of soil- Medium for plant growth- Regulator of water supplies- Waste recycling system- Habitat for soil organisms- Engineering mediumNRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties1223- Medium for plant growth- Regulator of water supplies- Waste recycling system- Habitat for soil organisms- Engineering medium- Atmospheric modifierFunctions of soil24Soil as an environmental interfaceFour spheres of the Earth- Lithosphere = rocks- Atmosphere = air- Hydrosphere = water- Biosphere = living creaturesA fifth sphere- Pedosphere = soil- The outermost layer of theEarth, where soil forms and life beginsSource: NASA (http://ares.jsc.nasa.gov)NRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties1325The pedosphere interfaces at different scalesSource: Brady and Weil (2010)Scalea = kilometerb = meterc = millimeterd = micrometer26Environmental consequences of soil degradation- For the atmosphere- Dust storms-CO2enrichmentPhoenix dust storm (2012)Source: http://twistedsifter.comNRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties1427Environmental consequences of soil degradation- For the atmosphere- Dust storms-CO2enrichment- For the hydrosphere- Sedimentation- Nutrient pollutionSource: http://earthobservatory.nasa.govsediment discharge from the Mississippi River28Today’s lecture topics- What is soil?- Soil components- Functions of soil- Soil as an environmental interfaceSoils & Soil PropertiesNRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties1529Today’s key concepts- Soils are critical to life on Earth.- They provide essential ecosystem services.30Today’s lecture topics- Introduction to soil physical properties- Soil color- Soil texture- Soil structure- Soil consistenceSoils & Soil PropertiesNRES 201 Lectures 2-3 (Fall 2014): Soils & Soil Properties1631The basic properties- Color- Described by hue, value, and chroma- Texture- Size distribution of soil particles- Structure- Arrangement of soil particles to formaggregates or peds- Consistence- Cohesiveness holding soil particles togetherIntroduction to soil physical