What are Soils? PDF

Earth’s Soil [email protected] Alfred Hartemink Department of Soil Science Earth’s Soil: Natural Science and Human Use Earth’s Soil [email protected] What you will learn § gain appreciation, knowledge and synthesis of the diversity of soils in the world, § be able to describe what are important so...

Earth’s Soil [email protected] Alfred Hartemink Department of Soil Science Earth’s Soil: Natural Science and Human Use Earth’s Soil [email protected] What you will learn § gain appreciation, knowledge and synthesis of the diversity of soils in the world, § be able to describe what are important soil characteristics § discuss how the soils relate to the grand environmental challenges that confront humanity. Earth’s Soil [email protected] How you will learn § Attend lectures § Discuss and participate § Read and prepare § Write an essay § Exams Mid-term 40% Final 40% Essay 20% § Appointments: [email protected] Earth’s Soil [email protected] Essay Choose ONE of the following topics for a 600 words essay: How can we produce enough food for a growing world population, and maintain our soil resources? Imagine you are working in a rural area in Tanzania. What would you do in terms of soil advice to make a better life for people? If you were to win a large sum of money and you could buy 1,000 acres of land, where would you buy it, and why? In the essay you need to focus on soil aspects, grading will be based on correctness of facts and ideas, originality and precise use of language. As follows: Soil aspects 35% Correctness of facts and ideas 35% Originality 15% Precise use of language 15% Total points for the essay are 110. Earth’s Soil [email protected] § January 29 – What are soils? § February 5 - Soils & the grand environmental challenges (recorded) § February 12 - Soils and people § February 19 - Soils of the tropics § February 26 - Soils of the drier regions March 4 – Mid Term Exam § § § § § § March 11 Soils of temperate regions March 18 - Soils of the cold regions March 25 - Spring Break April 1 - Soils of the USA April 8 - Soils of Wisconsin April 15 - How to obtain soil information April 22 – Final Exam Important dates Earth’s Soil [email protected] Mid-term exam March 4 (first 5 lectures) Essay April 1 (printed, in my mailbox, corridor) Final exam April 22 (cumulative 10 lectures) Multiple choice. No re-exam Grading based on 2 exams, 1 essay Earth’s Soil [email protected] Earth’s soil What are soils? Soils & the grand environmental challenges Introduction Soils and people Soils of the tropics Soils of the drier regions Soils of temperate regions Across the globe Soils of the cold regions Soils of the USA Soils of Wisconsin How to obtain soil information Wrap up Earth’s Soil [email protected] Alfred Hartemink Department of Soil Science What are soils? Earth’s Soil [email protected] Earth’s Soil [email protected] Earth’s Soil [email protected] But also… Some soils are dry, some are wet Some are hard, some are soft Some are productive, some are not Some are under forest, some are under grass Some are found here, and not there How come? Does it matter? Earth’s Soil [email protected] Definition of soil Soils are the thin layer covering our planet earth. They are complex blends of living and mineral materials. Just like birds or plants there are thousands of kinds of soil. Earth’s Soil [email protected] Different for different people To the agriculturist, forester or gardener: soil is what plants grow on To the engineer: a material to be moved, built on, or consolidated To the ecologist: a home for animals To the geologist: a material with a particular history of formation, to be moved Soil Earth’s Soil [email protected] Soil: physical, biological and chemical properties Soil: solids, liquid, gas Air Gas Mineral soil Solid Liquid Soil Organic Inorganic Water Organic matter Life - fauna and flora Death - fauna and flora Lifeless - mineral Clay < 2μm Silt 2-50 μm Sand >50-2000 μm Gravel Stones Boulders Earth’s Soil [email protected] How we study soils Dig a pit Auger Probe truck Road cut Quarry Earth’s Soil [email protected] Soil characteristics § Soils are alive § Soils have chemical and physical properties § Soils change with depth and across the landscape § Soils change over time § Soils are not random § So soils can be mapped and classified Earth’s Soil [email protected] Soil characteristics Soil biological properties Transforms and recycles Biodiversity pool Soil physical properties Soil texture Soil colour Soil structure Soil chemical properties Nutrients Exchange capacity (clay and organic matter) Soil organic matter (C) pH (acidity or alkalinity) Earth’s Soil [email protected] Soils are alive The recycling factory Earth’s Soil [email protected] CO2 atmosphere nutrients Soil organisms Dead organic material and nutrients Earth’s Soil [email protected] Soil food web Earth’s Soil [email protected] Soil physical properties § Texture (sand, silt, clay) § Soil color § Soil structure Earth’s Soil [email protected] Sand, silt and clay Earth’s Soil [email protected] Influence of soil texture Sand Water-holding capacity Aeration Drainage Nutrient retention Silt Clay Low Medium High Good Medium Poor Fast Low Slow Medium Very slow High Earth’s Soil [email protected] Soil colour Colour is caused by coatings: Organic matter Minerals Iron Moisture Earth’s Soil [email protected] Soil Structure § The arrangement of soil particles (sand, silt, clay) into aggregates or peds § Binding agents provided by plant roots (exudates), soil organic matter, and clays § Most important contributor is organic matter Earth’s Soil [email protected] Soil structures 1. nnnnnnnnnn Columnar Blocky Granular Platy cm 26 Earth’s Soil [email protected] Soil chemical properties § Nutrients § Nutrient retention (clay and organic matter) § Soil organic matter (C) § pH (acidity or alkalinity) Earth’s Soil [email protected] Nutrients N P K Ca Mg S (6) Mo Bo Cl Fe Mn Zn Cu (7) Earth’s Soil [email protected] No nutrients no crops Manure Inorganic fertilizer, lime Compost Earth’s Soil [email protected] Soil characteristics § Soils are alive § Soils have chemical and physical properties § Soils change with depth and across the landscape § Soils change over time § Soils are not random § So soils can be mapped and classified Earth’s Soil [email protected] Soil changes with depth Earth’s Soil [email protected] Changes across the landscape Earth’s Soil [email protected] Soil pH Soil changes over time Soil change – as a result of human activities Tillage, weeding, terracing, subsoiling, deep ploughing, manure and fertilizer addition, liming, drainage, irrigation Soil change – natural Acidification, clay movement, organic matter accumulation, weathering Earth’s Soil [email protected] Mapped and classified Earth’s Soil [email protected] Mapped and classified Earth’s Soil [email protected] Soil orders Permanently frozen soil Gelisols Soils that consists of organic material Histosols Acid forest soils Spodosols Volcanic soils Andisols Highly weathered soils of the tropics Oxisols Clay soils with strong shrink/swell Vertisols Soils in dry areas Aridisols Strongly leached soils Ultisols Grassland soils, thick dark topsoil Mollisols Moderately leached soils Alfisols Weakly developed soils Inceptisols Soils with little or no development Entisols Earth’s Soil [email protected] Soil orders Permanently frozen soil Gelisols Soils that consists of organic material Histosols Acid forest soils Spodosols Volcanic soils Andisols Highly weathered soils of the tropics Oxisols Clay soils with strong shrink/swell Vertisols Soils in dry areas Aridisols Strongly leached soils Ultisols Grassland soils, thick dark topsoil Mollisols Moderately leached soils Alfisols Weakly developed soils Inceptisols Soils with little or no development Entisols Earth’s Soil [email protected] Soil functions § Determine agricultural and forestry production § Physical and cultural environment for humans § Biodiversity pool § Sources, transformers and stores of plant nutrients § Storing and filters and water § Soils are buffers and filters for pollutants § Soils are archives of past climates and human activities § Source of raw material § Carbon pool, moderating the climate Earth’s Soil [email protected] Food production Biodiversity pool Construction environment Cultural environment Source plant nutrients Pollutants buffer Water store and filter Raw material Past climates and cultures