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Soils for Plant Growth. A Unit of the Michigan State University Extension Master Gardener Curriculum. Soils for Plant Growth. Objectives. Define soil Understand its composition Understand its physical properties Understand its chemical properties
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Soils for Plant Growth A Unit of the Michigan State University Extension Master Gardener Curriculum
Soils for Plant Growth Objectives • Define soil • Understand its composition • Understand its physical properties • Understand its chemical properties • Identify essential plant nutrients and their management
Soils for Plant Growth Objectives • Understand management practices related to changing soil properties • Understand environmental implications of soil management practices • Use knowledge gained to analyze and assess concerns related to soil properties
Soils for Plant Growth What Is Soil?
Soils for Plant Growth What Is Soil?
Soils for Plant Growth What Is Soil?
Soils for Plant Growth What Is Soil?
Soils for Plant Growth What Is Soil? • Not DIRT!!! • Precious resource • Loose, unconsolidated material on the earth’s surface • Soil scientist’s definition
Soils for Plant Growth What Is Soil? “A natural body of the earth’s surface having characteristics resulting from climate and living organisms acting upon parent material as conditioned by slope over periods of time”
Soils for Plant Growth What Is Soil? • Parent material • Organisms
Soils for Plant Growth What Is Soil? • Parent material • Organisms • Climate • Topography • Time
Soils for Plant Growth Soil Provides • Anchorage • Water • Air • Nutrients • Growth-producing chemical environment
Soils for Plant Growth Soil Is Composed of • Mineral solids • Organic solids • Pore spaces
Soils for Plant Growth Ideal Soil Composition 5% Water Air 25% 45% Mineral 25% Organic
Texture Structure Pore space Density Temperature Color Soil organisms Organic matter Groundwater Soils for Plant Growth Physical Properties of Soil
Soils for Plant Growth Soil Texture • Sand • Silt • Clay
Soils for Plant Growth Coarser Loamy Sand Sandy Loam Silt Loam Clay Loam Sand Loam Clay Finer
Soils for Plant Growth 100 90 10 20 80 30 70 clay 40 60 Percent Silt Percent Clay 50 50 silty clay sandy clay 60 40 silty clay loam clay loam 70 30 sandy clay loam 80 20 loam silt loam sandy loam 90 10 loamy sand silt 100 sand 100 90 80 70 60 50 40 30 20 10 Percent Sand
Soils for Plant Growth Soil Structure Loose Aggregated
Soils for Plant Growth Influence of Soil Structure
Soils for Plant Growth Texture Vs Structure • Texture is unchangeable • Structure can be improved or destroyed
Soils for Plant Growth Compaction Good Structure Compressed Structure
Soils for Plant Growth Excessive Tillage Too Much Tillage
Soils for Plant Growth Porosity Porosity Water holding capacity Porosity Drainage Porosity Aeration Porosity Density
Soils for Plant Growth Macro- and Micropores Water-filled microprore Air-filled macropore
Soils for Plant Growth Water Movement Sand Loam Clay
Soils for Plant Growth Soil Density Clay Sand
Soils for Plant Growth Soil Temperature
Soils for Plant Growth Soil Color • Affects soil temperature • Indicates how much organic matter is present • Predicts natural drainage conditions
Dark High organic matter Formed under cool, wet conditions Light Low organic matter Formed under warmer, drier conditions Soils for Plant Growth Topsoil Color
Soils for Plant Growth Soil Organisms • Bacteria • Fungi • Mycorrhizae • Lichens • Protozoa • Invertebrates • Vertebrates
Leaves Manure Grass clippings Decomposes rapidly Highly decomposed Stable Rich in nitrogen Slowly degradable Soils for Plant Growth Organic Matter Vs Humus decomposes to form humus Organic matter
Soils for Plant Growth Groundwater • Stored in aquifers, water-saturated zones beneath the earth’s surface • Part of the soil environment if close to the surface - high water table • Easily contaminated
Soils for Plant Growth Points to Remember • Know the physical characteristics of your soil • Adding organic matter is usually beneficial • Don’t over till • Don’t compact • Maintain groundcover on slopes • Avoid bringing in soil of drastically different texture
Soils for Plant Growth Chemical Properties of Soil Capacity - Cation Exchange Capacity CEC Availability pH Intensity - Electroconductivity EC Balance - Nutrient ratios Ca:Mg
Soils for Plant Growth Chemistry 101 Atom • The smallest unit of a substance that has all the properties of that substance • No net electrical charge • Model behaves a bit like our solar system Electron (-) - + Proton (+) Neutron
Soils for Plant Growth Chemistry 101 • Molecule • A group of atoms connected by chemical bonds • No net electrical charge • Example: H2O - water H O H
Soils for Plant Growth Chemistry 101 Ion - An atom or molecule that has an electrical charge due to the loss or gain of electrons H2OH+ + OH-
Soils for Plant Growth Chemistry 101 • Ion • Cation - an ion with a positive charge • Ca++ Mg++ H+ K+ NH4+ • Anion - an ion with a negative charge • OH- NO3- SO4-- Cl-
Soils for Plant Growth Chemistry 101 • Unlike charges attract • Like charges repel _ + + +
Soils for Plant Growth Chemical Properties of Soil Capacity - Cation Exchange Capacity CEC • ++Ca Soil particle • +K • ++Mg
Soils for Plant Growth Cation Exchange Capacity +H +K +NH4 +H +K NH4+ ++Ca Mg++ ++Mg NH4+ ++Ca Clay Humus
Soils for Plant Growth Cation Exchange Capacity CEC 1 - 5 6 - 10 10+ 20+ • Very low with not much clay or humus • Intermediate loamy texture or sandy with more humus • Progressively more clay and/or humus • Probably an organic soil
Soils for Plant Growth Chemical Properties of Soil CEC Availability pH
Soils for Plant Growth What Is pH and Why Is It Important? H2O H+ + OH- Remember: Everything is dissolved in water
Soils for Plant Growth Neutral Acid Alkaline 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Vinegar Ammonia Bleach Lye Battery acid Orange juice Pure water Baking soda
Soils for Plant Growth Neutral Acid Alkaline 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Blueberries Alfalfa Most plants
Soils for Plant Growth Factors Influencing Soil pH • Components of the soil • Lime • Water quality • Type of nitrogen applied • Amount of fertilizer • Crop species
Soils for Plant Growth What Does This Plant Tell You about the pH of the Soil?
Soils for Plant Growth What Does This Plant Tell You about the pH of the Soil?