Introduction to Soils - PDF Free Download

Introduction to Soils Jackson County Master Gardeners, 2013 From Symphony of the Soil, Courtesy of Lily Films Elizabeth Murphy OSU Extension Small Farms Department of Crop and Soil Science Elizabeth.murphy@oregonstate.edu

Class Outline What is a soil Why study soil Soil physical properties and processes Soil chemical properties and processes Soil biology Soil ecology Soil organic matter Soil management & practical considerations Part II: Soil Fertilizers and Amendments March 6 th, 9-12 am

What is a soil? Photo from Mars Rover

What is a soil? Photo from Mars Rover soil - (i) The unconsolidated mineral or organic material on the immediate surface of the Earth that serves as a natural medium for the growth of land plants. (ii) The unconsolidated mineral or organic matter on the surface of the Earth that has been subjected to and shows effects of genetic and environmental factors of: climate (including water and temperature effects), and macro- and microorganisms, conditioned by relief, acting on parent material over a period of time. A product-soil differs from the material from which it is derived in many physical, chemical, biological, and morphological properties and characteristics (Soil Science Soceity of America, 2012)

Why Study Soil For Environment: Food Security Water Quality Air Quality Contaminant mitigation Reduced Inputs For Plants: Nutrients Water Support Air for plant roots Increased Yields Closed Loop

Components of a Soil

Components of a Soil Water Mineral Air Organic Matter

Mineral Component Makes up less than 50% of a soil Depends on the parent material (fine, coarse, organic) Varies in chemical composition (aluminum, calcium) Contains particles of several size ranges (small to really really small)

Soil Water Held to varying degrees depending on amount of water, soil texture, pore size and pore distribution Not all soil water is available to plants H 2 O

Soil Air High variability Anaerobic v. Aerobic Soils High CO 2 content Low O 2 contentds What other gases? Nitrogen (N 2 ) Nitrous oxide - N 2 O Methane (CH 4 ) Hydrogen sulfide - (H 2 S)

Organic Matter Small constituent by weight, but huge influence on soil properties Made up of partially decomposed plant & animal residues + organic compounds synthesized by soil microbes

Soil Forming Factors What are the most important conditions that influence the formation of the soil?

Soil Forming Factors What are the most important conditions that influence the formation of the soil? Parent Material Relief Organisms Climate Time Humans

Soil Forming Factors What are the most important conditions that influence the formation of the soil?

Soil Characteristics

Soil Physical Properties Moisture, warmth, and aeration; soil texture,; soil fitness; soil organisms; its tillage, drainage, and irrigation; all these are quite as important in the make up and maintenance of the fertiility of the soil as are manures, fertilizers, and soil amendments. J.L. Hills, C. H. Jones, and C. Cutler, 1908 Soil Texture Soil Structure Soil Density Soil Depth Water Holding Capacity Available Water Permeability Porosity

Soil Physical Properties: Soil Texture Soil Texture - percentage of sand silt and clay in a soil

Soil Physical Properties: Soil Texture The jar method Texture by feel

Soil Physical Properties: Soil Texture The jar method You try Texture by feel

Soil Physical Properties: Soil Texture

Soil Physical Properties: Soil Texture INFLUENCE OF SOIL TEXTURE: 1. Soil wetness 2. Soil drainage 3. Soil compaction 4. Soil fertility (nutrient availability and retention) 5. Available water 6. Soil structure 7. Soil organic matter 8. Soil temperature 9. Gardening and Management Decisions

Soil Physical Properties: Soil Texture Can a gardener change soil texture through management?

Soil Physical Properties: Soil Structure Soil structure: the arrangement of particles in a soil

Soil Physical Properties: Soil Structure Good soil structure affects: Soil Organic Matter Content Soil organisms Soil Water Erosion Drainage Nutrient supply to plants

Soil Physical Properties: Soil Structure Drainage rates of different soil structures

Soil Physical Properties: Soil Structure Can a gardener change soil structure through management?

Soil Physical Properties: Soil Structure Can a gardener change soil structure through management? Organic matter Cover crop (Roots! and organic matter)/bare soil Tillage/Compaction Mulch/Raindrop Impact Overwatering/Underwatering Gypsum? Fertilization/Excessive salts

Soil Physical Properties: Porosity and Permeability Soil Porosity - pore space between particles - Amount of pore space = amount of water held in soil Which has greater porosity: clay or sand?

Soil Physical Properties: Porosity and Permeability Permeability - Rate at which water moves through soil Which has greater permeability: clay or sand?

Soil Physical Properties: Water Holding Capacity Water Holding Capacity The ability of micropore s to hold water for plant use Plant Available Water - Soil water available for uptake by plant Which has greater water holding capacity? Plant available water?

Soil Physical Properties & Water

Water and Air at Different Moisture Levels Field capacity: when water has drained from the macropores Wilting point: water there, but held too tightly for the plants to access it

Soil Physical Properties & Water Greatest water holding capacity Greatest available water

Soil Physical Properties: Water

Irrigation Scheduling Irrigation needs depends on available soil water. Avoid under or overwatering by estimating soil moisture by feel.

Irrigation Scheduling

Soil Physical Properties: Bulk Density Non-compacted compacted What important quality changes?

Soil Physical Properties: Bulk Density Non-compacted compacted What important quality changes? WATER and AIR

Soil Physical Properties: Why should I care? Irrigation o Sandy soils need frequent, light irrigation o Clay soils need less frequent, deep irrigation Drainage o Clay soils take longer to drain, longer to warm, longer to work o Sandy soils will drain rapidly and leach added nutrients Tillage o Risk of compaction is much greater on clay soils

Soil Physical Properties: Soil Texture Property/Behavior Sand Silt Clay Ability to hold water Low Medium High Aeration Good Medium Poor Drainage High Medium Very Slow Decomposition of Organic Matter Rapid Moderate Slow Organic Matter level Low Medium High Warm-up in spring Rapid Moderate Slow Shrink/swell potential * Very Low Low High Compactability Low Medium High Ability to store plant nutrients Poor Medium High Resistance to ph change Low Medium High

Soil Physical Properties: Soil Texture Can any soil texture be sutiable for gardening? Can you change the physical properties of a soil with management?

Soil Physical Properties: It all comes down to Soil Tilth Tilth - Physical condition of the soil in relation to plant growth Aggregate formation and stability Bulk density Soil moisture content Soil aeration Infiltration rate Water-holding capacity Friability

Soil Chemical Properties

Why Soil Chemistry? Properties Cation Exchange Capacity (CEC) ph Nutrient status Resistance to change Affects: Plant growth and nutrition Soil structure Fertilizer management Environmental Contamination/Mitigation

The Exchange Soil Texture

The Exchange Electric Clay Soil Particle SDSU Electron Microscope Facility

Cation Exchange Capacity (CEC) Cation Exchange Capacity: A soil s capacity to hold nutrients (cations) based on electric charges What s missing from this list? Cations (+): Sodium - Na + Calcium - Ca ++ Magnesium - Mg ++ Ammonium - NH + 4 Potassium - K + Aluminum - Al +++ Hydrogen - H +

Cation Exchange Capacity (CEC) Cation Exchange Capacity: A soil s capacity to hold nutrients (cations) based on electric charges Cations (+): Sodium - Na + Calcium - Ca ++ Magnesium - Mg ++ Ammonium - NH + 4 Potassium - K + Aluminum - Al +++ Hydrogen - H + What s missing from this list? NITRATE!!! NO 3 -, neg. charge

Cation Exchange Capacity (CEC) Cation Exchange Capacity: A soil s capacity to hold nutrients (cations) based on electric charges Affected by: Clay amount Clay type ph Organic Matter Competitive Ions

Cation Exchange Capacity (CEC) Cation Exchange Capacity: A soil s capacity to hold nutrients (cations) based on electric charges Affected by: Clay amount Clay type ph Organic Matter Competitive Ions Soil Organic Matter: ENORMOUS external surface area! (but no internal surface all edges)

Cation Exchange Capacity (CEC) Cation Exchange Capacity: A soil s capacity to hold nutrients (cations) based on electric charges Measured by: charge (meq)/100g soil Types of clay Type Kaolinite 3-20 Illite 10-40 Montmorillonite 80-120 Vermiculite 100-150 Humus 200-300 CEC (meq/100g) Tropical potter s clay Shrink-swell Black sticky

Base Saturation Base saturation: is the percent of soil CEC occupied by nutrients (base cations) Base cations include K +, Mg ++, Ca ++, Na + Base saturation is a measure of your soil s inherent fertility and ability to buffer change

Nutrient Mobility = Leaching

Nutrient Mobility = Leaching Mobile o N (NO 3- ), S (SO 4 2- ), Cl - Somewhat Immobile o N (NH 4+ ), S 2- (organic), K +2, Ca +2, Mg +2 Immobile o P, Fe +2, Mn, Zn +2, Cu +2, Mo

Soil ph Measure of Hydronium ions Potential and Active Acidity

Affected by: Rainfall/irrigation Fertilizers and Lime Soil ph Organic matter decomposition Nutrient Uptake and Transformation Base cations Temperature Weathering and parent material

Soil ph Low or High ph can create nutrient imbalances

Soil Chemistry: Why should I care? Nutrient availability o CEC and base saturation determine inherent fertility Nutrient application o Ability of soil to hold and release nutrients determined by CEC, therefore texture o Sandy soils more frequent, lighter nutrient applications to avoid leaching (just what the plant needs) Managing ph o CEC (texture) affects how hard or easy it is to change ph o Heavy clay soils require huge lime applications for small changes in ph

Soil Chemistry: What can I manage? A soil s charge (CEC) is the driving force for soil chemical properties. Good soil chemical properties can include: Neutral ph Nutrient retention Inherent fertility Chemical buffering

Soil Chemistry: What can I manage? This depends on your goals

Soil Chemistry: What can I manage? A soil s charge (CEC) is the driving force for soil chemical properties. Soil organic matter raises CEC, increases nutrient & water retention, raises inherent fertility, improves soil structure, and increases soil biological activity

Soil Biology IT S ALIVE - Beyond the boundaries of physics and chemistry

Soil Biology IT S ALIVE - Beyond the boundaries of physics and chemistry Can modify both chemical and physical properties Living and dead organisms Nutrient cycling and retention Nitrogen fixation Symbiotic relationships Soil structure Pathogen control

The Living Soil From NRCS Soil Biology Primer

A cup of soil contains... Microflora, or microbes microfauna macro- and mesofauna { { { Bacteria Fungi Protozoa Nematodes Arthropods Earthworms 200 billion 100,000 meters 20 million 100,000 50,000 <1 Note: Two earthworms may have more effect on the soil than a billion protozoa because they aerate the soil, improve water infiltration, and mix in OM

Soil is an Ecosystem Drawing courtesy of Hinterland Who s Who. www.hww.ca

Soil Biological Diversity Courtesy of The Living Soil

Soil Biology Classified based on size and grouped based on what they eat Critical functions: o translocation and mixing of OM and mineral soil o shred plant litter (speeds up decomposition) o increased aeration and improved water infiltration o population control of smaller organisms Example of function: Dung beetles can bury up to 78% of the cattle feces in a pasture within weeks. The amount of N added by burial can equate to ~158 lbn/acre (more than industrial fertilization).

Type of Organism Photosynthesizers (plant, algae, bacteria) Decomposers (bacteria, fungi) Mutualists (bacteria, fungi) Pathogens (bacteria, fungi) Parasites (nematodes, arthropods) Root-feeders (nematodes, arthropods) Soil Biology: Functions Functions Capture energy Fix CO 2 Add organic matter Break down residue Immobilize nutrients in biomass Create new organic compounds Bind soil aggregates (hyphae and exudates) Nitrogen cycling Compete with or inhibit pathogens Enhance Plant Growth Protect plant roots from disease-causing organisms Fix N 2 Mycorrhyzal associations with plants Promote Disease Consume roots and other plant parts, causing disease Parasitize beneficial micro-organims Consume plant roots Cause significant crop loss

Type of Organism Bacterial-Feeders (protozoa, nematodes) Fungal Feeders (nematodes, microarthropods) Shredders (earthworms, macroarthropods) Higher-Level Predators (Nematode-feeding nematodes, arthropods, mammels, birds) Soil Biology: Functions Functions Graze Release plant-available N (NH 4+ ) Control parasites and pathogens Stimulate and control bacterial populations Graze Release plant-available N (NH 4+ ) Control parasites and pathogens Stimulate and control fungal populations Break down residue and enhance soil structure Shred plant litter as they feed on bacteria and fungi Provide habitat for bacteria in guts and fecal pellets Enhance soil sturcture through burrowing and fecal pellets Control populations Control the populations of lower trophic-level predators Improve soil structure through burrowing and digestion Carry smaller organisms long distances From NRCS Soil Biology Primer

Soil Biological Properties

Bacteria and Actinomycetes NRCS Soil Biology Primer Size: 1/1000 mm Single celled organisms 1 million 1 billion/ tsp. Actinomycetes

Rhyzobium Mutualist N fixation Anaerobic nodules on roots of N-fixing plants Energy Expensive Favored by P fertilization Suppressed by N fertilization Inoculant is species-specific

Size: 1/1000 mm to miles long Several yards of hyphae in 1 tsp Decomposers Symbiotic and parasitic relationships Mycorrhyzhae root associations improve plant P uptake and water availability Hyphae - Important in binding aggregates Fungi Favored by dry conditions Favored by Nitrogen fertilization Reduced by tillage, fallow, and broadspectrum fungicides

Examples: Amoeba and ciliates Bacterial grazers Release N by consuming N- concentrated bacteria Stimulate bacterial populations Suppress Disease through competition or feeding Require water (management responsive) Size relative to soil texture Protozoa NRCS Soil Biology Primer

Nematodes Size: 1/500 to 1/20 in. Many trophic levels Bacterial-feeders Fungal-feeders Predatory nematodes Omnivores Release N by consuming N- concentrated microbes Regulate prey populations Beneficial and parasitic species Disperse microbes Food source for higher tropic levels Require water (management responsive) Used as soil quality indicator NRCS Soil Biology Primer

Size: micro to macroscopic Arthropods Shredders break-up OM, disperse OM, inoculate OM Predators- regulate pathogens Herbivores can be pests Aerate and mix soil Enhance aggregation Regulate microbial populations Release N by consuming bacteria and fungi

Bury and shred plant residues Vertically mix soil: Epigeic surface Endogeic-upper Anecic deep Earthworms Soil structure, water movement, root growth Create channels for root growth Improve aggregation Increase water holding capacity and water movement Indicator of soil health Earthworm casts Stimulate microbial populations

Plant Roots Sites for exchange chemically active Favorable conditions for microbes in rhizosphere http://biology.kenyon.edu Root exudates feed microbes

Plant Roots x Mycorrhyzae http://biology.kenyon.edu

Soil Biological Properties

Soil Biology Ecosystem Functions Nutrient Cycling (decomposition, mineralization) Nutrient Retention (immobilization) Nitrogen Fixation Soil structure o o o Porosity Infiltration Water holding capacity Disease Prevention Buffering and Filtering (clean water) Carbon Sequestration

Building a Healthy Soil Food Web Add Organic Matter Retain residue Mulch plantings Cover soil yearround Use proper irrigation Reduce tillage Reduce erosion Plant Cover crops Use crop rotations

Building a Healthy Soil Food Web Diversify Your Garden and Landscape to Diversify Soil Organisms Manage for an ecosystem, not a plant

Building a Healthy Soil Food Web Protect soil habitat o Reduce tillage o No-till o Minimize compaction o Minimize fallow periods o Proper irrigation o Improved drainage

Building a Healthy Soil Food Web Minimize Pesticide Use o Impacts to non-target organisms o Reduces biological complexity http://fwcb.cfans.umn.edu

Building a Healthy Soil Food Web Nutrient Management o Manage ph o Maximize plant productivity o Minimize salt effect o Avoid excessive applications o Combine mineral fertilizers with organic amendments From Brady and Neil, 1990.

Building a Healthy Soil Food Web Soil Inoculation o Inoculate N-fixers with proper rhyzobium o Introduce predator bacteria, nematodes, insects o Mycorrhyzal inoculant http://www.eurekalert.org

Soil is an Ecosystem Drawing courtesy of Hinterland Who s Who. www.hww.ca

Soil Organic Matter The way we care for, or nuture, a soil modifies its inherent nature Practices that promote good soil organic matter management are, thus, the very foundation for a more sustainable and thriving agriculture

Soil Organic Matter Improves soil structure Improves water holding capacity Improves aeration and drainage Increases biological activity Reduces compaction Nutrient availability Nutrient retention Reduces inputs more sustainable system

Managing Soils: Guides 1. Use a number of practices that add organic materials to the soil 2. Use diverse sources of organic materials 3. Reduce unneeded losses of native soil organic matter 4. Use practices that leave the soil surface protected from raindrops and temperature extremes 5. When using equipment, use practices that develop and maintain good soil structure 6. Manage soil fertility status to maintain optimal ph levels for your crops and a sufficient supply of nutrients without resulting in water pollution From Buidling Soils for Better Crops

Managing Soils Add Organic Matter Improve Soil Quality.Nuff said

Managing Soils Avoid Compaction Change depth of tillage Never work on waterlogged soils Manage irrigation properly

Use Proper Irrigation Avoid waterlogged soils Determine soil moisture by feel Managing Soils Soil Texture affects irrigation schedule Improper irrigation affects: Compaction Plant Growth Microbial Activity

Managing Soils Avoid excess fertilization Wasted money Environmental pollutant Excessive plant growth/burn Excessive salts cause drought stress Excessive salts degrade soil structure

Managing Soils Cover the Soil Protect from erosion Conserve moisture Add organic matter Cover for organisms Ways to cover: Garden residue Cover crops Intercropping Leaf or Bark Mulch Compost

Managing Soils Modify texture effects by adding organic matter Not sand or topsoil

Managing Soils When you can t deal with the texture you ve got Is this a soil? USE A RAISED BED INSTEAD

Managing Soils When to Use Raised Beds: To improve drainage for heavy soils To improve nutrient and water holding for decomposed granitic soils or poorly developed topsoil To raise garden to a more convenient height To warm soil and plant sooner in the spring Management Issues More frequent watering Replace decomposed organic matter Replace nutrients

Raised Bed Medium Soil based mix 1 pt soil 1 pt organic matter (screened compost or manue) 1 pt vermiculite/perlite 1 cup fertilizer

Part II: Soil Fertilizers and Amendments March 6 th, 9-12 am

QUESTIONS