Plant 14 🪴😭

PARENT MATERIAL - ROCKS AND MINERALS

Rocks

• Igneous -

  • Solidified Magma

  • Granite, gabbro

  • Composed of primary mineral

• Sedimentary -

  • Weathered minerals

    • sediment in lakes and oceans

  • Cemented into rock

  • Sandstone, shale

  • Composed of secondary minerals

• Metamorphic -

  • Once igneous and sedimentary rocks

  • high temperature and pressure change form and structure

  • Gneiss, schist, slate

• Primary Mineral

  • Formed during original crystallization of igneous rock

  • Quartz, feldspar, mica, hornblende, biotite

• Secondary Mineral -

  • Weathered primary minerals

WEATHERING PROCESSES

• Weathering Defined -

  • physical & chemical change occurring in rocks & minerals leading to disintegration &/or decomposition:

• Erosion Defined -

  • The removal &/or transport of minerals from rock formation, as a result of environmental factors ex. Water, ice, wind, etc

• Physical (weathering) -

  • Disintegration into smaller particles

  • Without much change to chemical composition

• Chemical (weathering) -

  • Decomposition of primary minerals

  • Can form secondary through recrystallization

  • Can lead to disintegration

PHYSICAL WEATHERING

• Causes - climate

  • Temperature fluctuations

    • exfoliation - peeling of layers from parent mass

  • Wind

  • Water, ice

    • Cryofracturing

CHEMICAL WEATHERING AGENTS

Carbonation-

• CO2 combines with water

  • From air or Biota

• Forms carbonic acid (HCO3)

• Dissolves Rock

Oxidation-

• Dependant on Parent Material

  • Oxygen combines with minerals in rock

  • Form Iron Oxides (FeO)

• Oxidation weakens rocks - causes disintegration

Hydrolysis

• Water splits into H+ (acidic) or OH- (corrosive) ions

• Replaces other mineral ions in rock

• Forms new solutions

Hydration

• Bonding of water and mineral

• Rocks swells causing disintegration

• Forms new mineral compound

Both related to Climate and Topography

MOVEMENT OF WEATHERED PARENT MATERIAL

• Alluvium/alluvial - material moved by water streams

• Marine - under oceans

• Lacustrine - under fresh water lakes

• Glacial Till - Material collected and moved by glaciers

• Eolian - material moved by wind

• Colluvium - material moved by gravity (downhill)

SOIL FORMATION

• Soil formation is variable across locations around the world

  • Heterogeneity

• Soil formation is impacted by environmental factors

• Highly dependent upon

  • Geological parent material

  • Four processes which transform parent material to soil

    • Soil forming factors

FORMATION OF SOIL

1. Parent Material - Originating sources of mineral matter

2. Climate - Temperature and precipitation

3. Biota - Plant and animal life of region

4. Topography - Slopes, plains, depressions —> runoff, erosion, infiltration, excess water

5. Time - Duration material subjected to weathering and other processes

1. Magma escapes through the seems due to geological events. It becomes rock, parent material (solidifies)

2. Rock or parent material gets subjected to the soil forming factors. Such as climate, Biota, and Topography, over time. Will eventually form Topography and land masses.

3. Disintegration through weathering.

4. Transportation or erosion because of climate. Such as alluvial, eolian, colluvial, etc.

5. Deposited and mixes with organic matter and then becomes soil

UNIT 3

*SOIL ARCHITECTURE AND PHYSICAL PROPERTIES*

SOIL PROFILE AND HORIZONS

Profile-

• Vertical cross-section of soil

Horizons-

• Distinct layers withing profile

• O-Organic layer

  • Most biological activity

• A-top soil/root zone

  • 90% plant roots and nutrients exist here

• B-Subsurface

  • Fewer roots

  • Mostly soil with some rock

• C-Mostly rock

  • Almost no organic matter

SOIL COLOR

What influences the color of soil?

1. Organic matter

   • Dark/black soils: typically rich in organic matter

2. Moisture

   • Moist: darker soil

   • Dry: lighter soil

3. Presence of salts and metals

   • Light soils

     • Typically calcareous:

       • High in calcium (Ca)

     • Can be affected by other salts:

       • Sodium (Na) and potassium (K)

4. Oxidation or Reduction of salts and metals

   • Red soils-

     • Iron oxide/rust:

       • Iron (Fe) gaining/reacting with oxygen (O)

   • Gray/Green Soils-

     • Iron oxide reduction:

       • Iron losing oxygen

       • Iron oxide + carbon —> iron + carbon dioxide

       • 2Fe2O3 + 3C —> 4Fe +3CO2

SOIL TEXTURE

• Soil texture-

  • Determined by the amount of sand, silt, and clay particles in soil

  • Describes the relative size of soil particles

• Particle Sizes (micrometers):

  • 1 micrometer = 0.001 millimeter

  • Sand > 0.05mm

  • Silt 0.05-0.002mm

  • Clay < 0.002mm

• Textural Classes:

  • 12 designations of the soil texture triangle

  • Percentage of sand, silt, and clay in a soil

Physical Characteristics: Soil Particles

• Surface area - area of matter exposed to air

• Porosity - total volume of pore space

• Smaller particles (clay) have

  • more surface area

  • greater porosity

  • micro pores

• Larger particles (sand) have:

  • less surface area

  • lower porosity

  • Macro pores

Practically thinking…

• What happens in pore space?

  • Water holding

  • air exchange

  • plant root growth

  • organism habitation

  • nutrient ionization

• Larger pore spaces (Sand):

  • Increased

    • water movement

    • air exchange

• Greater porosity (clay):

  • Increased holding capacity of

    • water, air, roots, organisms, nutrients

Soil Particles

• Sand

  • Largest particle

  • No electrical charge

  • Most macro pores

  • Best tilth: ability to cultivate

  • Highest rate of

    • Drainage, water infiltration, gas exchange

  • Facilitates root diameter and length

• Clay

  • Smallest soil particle

  • Only soil particle with a charge

    • Negatively charged

    • Exchange of cations and anions

  • Best holding capacity of:

    • Water, nutrients, air, organism habitat

• Silt

  • Size between sand and clay

  • No electrical charge

  • Similar shape and minerals as sand

  • High weathering potential

    • Increase nutrient availability

Soil Structure

• Soil Structure-

  • Arrangement of soil particles into peds/aggregates

  • Sand, silt, clay, and organic matter

  • Categorized by:

    • Type: shape of structure

    • Size

    • Strength: penetration resistance

Impacts of Soil Structure

Soil structure can influence:

1. Water movement

2. Aeration (air movement)

3. Root Growth

4. Heat transfer

5. Tilth

6. Micro-organisms

Poor soil structure (compaction) can inhibit or worsen these factors

Improving Soil Structure

Preventing Compaction

1. Conservation tillage and reduced tractor usage

   1. Mowing weeds instead of discing

2. Planting cover crops

3. Avoid walking on when wet

4. Adding organic matter

Remediating Compaction

1. Conservation tillage and reduced tractor usage

2. Deep ripping

3. Planting cover crops

4. Soil amendments to break up soil

5. Adding organic matter

Measurements: of Soil Structure
■ Particle Density- Mass of soil particle by volume
■ Bulk density-
– Mass per unit volume of soil sample
– Measures pore space (compaction levels)
■ Aggregate stability-
– Ability of soil peds/aggregates to retain structure
– Determines soil ability to resist compaction
– Impacted by organic matter content
■ Porosity- Volume of pore space (ideally 50%)

Soil aggregate refers to a cluster of soil particles that bind together to form a stable, larger structure. These aggregates can vary in size and shape and play a crucial role in soil health, affecting water retention, aeration, and nutrient availability. They are formed through biological activity, organic matter, and physical processes.

*UNIT 4 SOIL ORGANIC MATTER*

The Global Carbon Cycle and Soil

Soil’s role in the carbon cycle

Repository for carbon -

• Point of accumulation

  1. Source of carbon -

     1. Plant and Animal residues

  2. Sink for carbon -

     1. Carbon from atmosphere

Mitigates greenhouse effect

• Carbon sequestration (Collection & Storage/ When C is stored in soil it is inhibited or delayed from entering atmosphere )

• Oxidation of organic matter

Role of Soil Organic Matter

OM’s role in soil quality and health:

• Formation and stabilization of soil aggregates

  • Increase soil macroporosity

  • The ‘glue’ holding particles together

• Habitat and food for soil organisms

• Cation Exchange Capacity CEC-

  • Nutrient pools

  • Slow release of ionized nutrients

• WHC-water holding capacity

• Buffers soil pH

Organic Matter in the Soil

O horizon: 20-30% OM by weight

Arable soils (AKA Farmable soils)

• contain 1-4% OM

• Ideal target 5%

15-33% of plant residues become stabilized soil humus

Decomposition of Plant Residues

Green plant residues

• 60-90% water

Dry plant matter

• 90% carbon, hydrogen, oxygen

• 10% mineral nutrients

• Cellulose, lignin, hemicellulose, fat (slow to decompose)

• Protein, sugar, starch (easily decomposed)

In aerobics soils —>

Organic compounds become

• CO2, water, energy, humus

During the oxidation process

• Nutrient elements

  • released into soil

  • assimilated by plants

In anaerobic soils (without oxygen) —>

Organic compounds become:

• methane- CH4

• alcohols like ethanol- CH3CH2OH

• other organic compounds

Organic matter decomposition slows

Factors Influencing OM Decomposition

1. Geographical location

2. Residue particle size

3. pH

4. Microbial diversity

5. Microbial viability

6. C:N ratio

7. Temperature

8. Moisture

The Carbon to Nitrogen Ratio

Influences:

• Rates of OM decomposition

• Rates of N mineralization and immobilization

Ideal ratio:

• 25:1

• C:N

* Too much carbon slows decomposition and ties up nitrogen

Composting

Practice of creating humus-like materials from raw materials

Requires

• Nitrogen (wet or green waste)

• Carbon (dry or brown waste)

• Moisture

• Air

• Surface area-outside of soil

Humus

Characteristics:

• Dark colored

• Heterogenous

• Amorphous

• Colloidal mixture

• Microscopic particle suspended in solution

Composition:

• Lignin - wood

• Humic Acids

• Complex with clay

Function of Humus

High water holding capacity

Enhances soil fertility

• Not a true nutrient

• Stimulates mineral weathering

• Complexing with metallic ions

  • Increases CEC

Management of OM

Methods to encourage OM accumulation:

1. Continual addition of organic materials

   1. Cover crops

   2. Animal manure

   3. Crop residues

   4. Retention of crop roots

2. Maintain adequate Nitrogen

   1. Legumes

   2. Nitrogen fertilizers

   3. Encourage microbial populations

3. Minimum tillage and/or soil pertubation

4. Perennial vegetation

UNIT 5 - SOIL WATER

Features of Water

• Chemically Considered A Universal Solvent

  • Solvents: Solution with ability to dissolve other substances -solute

• Asymmetric molecular configuration

  

• Polarity: Charges are unevenly distributed

  • H: Electropositive O: Electronegative

  • Responsible for attraction of other water molecules

• Exists as molecule and compound

  • Chemical bonding

    • Molecule

      • Strong covalent bond

      • Sharing unpaired electrons

    • Compound:

      • Weak hydrogen bond

• Exhibits both cohesion and adhesion forces

  • Cohesion-strongly bonds to itself

  • Adhesion- Bonds to other materials

  • Enables water to move through soil in any direction

• 

Capillary Movement

• Capillary Movement-

  • Ability of water to move through soil in any direction

  • Against the force of gravity and plant roots

  • Occurs in micropores - capillary tubes of soil

Features of Water Continued

• Surface Tension-

  • Tendency of water to behave as if it has a membrane

  • Result of the high attraction between water molecules (cohesion)

  • Influences water behavior in soils via capillary movement

Soil Water

• Infiltration- Process by which water enters soil profile through precipitation and irrigation

• Percolation or drainage- Process by which water moves through soil profile via gravity

Soil Water Content

• Saturation Point- (States of soil water)

  • All soil pores are full of water

• Field Capacity-

  • Percolation has occurred

  • Air replaces water in macro-pores

  • Soil holds optimal water available to plants

• Permanent Wilting Point- (PWP)

  • Water in capillaries of soil

  • Water unavailable to plants

• Hygroscopic Water-

  • Occurs after pwp

  • Water molecules tightly held by soil particles (adhesion)

  • Movement only through vapor

Influences of plant available water

• Water holding capacity (WHC)-

  • Soil’s ability to hold plant - Available water (PAW)

  • Varies by soil texture (relates to pore space)

• Organic Matter Content

  • Micropores hold water

  • Higher OM = Higher WHC

• Soil Structure - influenced OM content

  • Impacts infiltration and percolation rates

  • Relates to OM content

  • Compaction

    • Decreases total pore space

      • Run off

• Osmotic Potential-

  • Soil solute (salt) concentrations

  • Impacts water movement

    • Water moves on a gradient

Soil Texture and Water Holding Capacity

(water holding capacity) WHC:

• Increases as particle sizes decrease (micropores)

• Decrease as particle sizes increase (macropores)

• What does this tell you about how texture influences WHC?

1. In Unit 1 we learned that the ideal water content of soil is 25%. How did the moisture content of the soil tested compare? 

   1. The moisture content of the soil tested had a lower percentage that the ideal water content of soil.

2. If there is a substantial difference, why do you think that is?

   1. Think in terms of seasonal climate and soil properties such as texture and organic matter content. 

      1. I think it might be because even though we are in the fall season, there has been extreme heat which may have caused for more drayage of the soil.

3. What implications does this water content have on soil productivity and its ability to sustain life? 

   1. The soil is not very suitable to sustain life since it is too little too dry.

4. Can you think of any factors that may limit the results of this test? Are there other factors to consider, like season, time of sampling, or any thing else?

   1. As previously mentioned, even if the season is fall, there has been extreme heat which may have factored in.

5. Do you think this test provides enough information about the soil-water relationship? What is something you learned from lecture or reading that substantiates your position on this?  

   1. I do believe that the test provides enough information about the soil-water relationship. I learned from the lecture about the importance of proper moisture for plant growth as well as about porosity, macropores, micropores, and the difference between infiltration and drainage. Meaning that it may be that my soil has an increase in particle size which decreases the water holding capacity of my soil.

Soil Moisture % of a Given Sample

UNIT 6

- Drought reduces snowpack and results in decreased reservoir volume. Here, the effect of drought on 56 of California's more than 700 reservoirs is shown through time.

- Snowpack is an accumulation of snow that compresses with time and melts seasonally, often at high elevation or high latitude. Snowpacks are an important water resource that feed streams and rivers as they melt, sometimes leading to flooding.

• How long has California been consistently experiencing drought conditions?

  • California started being consistently in drought conditions in 2012 but signs were more severe by mid-2013 up until 2017. Totaling up to around 3-4 years.

• Based on the data you've observed, what effect has the drought had on our state's reservoirs, snow-pack, and stream flow?

  • The reservoir volume, as a percentage of total capacity, kept substantially decreasing. The water typically is from the snowpack, meaning that there most likely was also a decrease in wintertime snowpack. Snowpacks feed streams meaning less stream flow.

• Based on what you now know about the water cycle, how do you think these conditions have influenced or changed California's water cycle? 

• What are the primary usages/withdrawals of water in California? What is your opinion on these usages?

Unit 6 - SOil and the Hydrologic Cycle

The Earths Water

The Earths Water exists in:

• Oceans

• Glaciers

• Soil

• Deep groundwater aquifers

• Exchange between atmosphere and lithosphere

The Water Cycle - Water Returns to the Atmosphere

Evaporation- Vaporation of soil water; returns to atmosphere as gas

Transpiration - Vaporization of water from leaf surface; returns to atmosphere as gas

Evapotranspiration- Total evaporative loss from soil and leaf surface; returns to atmosphere as gas

Condensation- Water droplets bonding together to form clouds

Precipitation- Water released from clouds as rain, sleet, or snow

Infiltration- Water entering the soil; responsible for groundwater recharge

Runoff- Water flowing over the landscape; creates watersheds

Hydrologic Cycle- Cycling of water from earths surface to atmosphere driven by solar energy

Watershed - An area of land drained by a system of streams

ex. San Joaquin Delta Watershed

Water Table- The depth at which groundwater can be accessed

SOIL AND THE WATER CYCLE

Groundwater

• Portion of water cycle resides in soil via infiltration

  • Soil pore space

    • Point of access for plants

  • Water bearing rock

    • Point of access for humans- wells

Soil properties and management impact how water behaves.

• Gravitational water percolates through soil profile

  • Can carry solutes with it

    • Nitrogen and Phosphorus

      • Fertilizers and Ag byproducts

    • Heavy metals and pollution

    • Sodium

Water returns to the atmosphere from the soil via:

• Evaporation

• Transpiration

  • Roots take IP soil-water

  • Releases through openings on leaves called stomata

• Evapotranspiration

Soil properties and management impact how water behaves

• Runoff

  • Removes topsoil (erosion)

  • Deposits runoff into bodies of water

  • Can contain solutes and pollution

Unit 6 Lecture 1

1. its difficult to measure with varying depths and areas, its always in flux between the atmosphere and lithosphere, its always in varying phases of matter

2. 30.1%

3. True

4. False

Lecture 2

1. Evaporation of water from soil surface, Evaporation of water from leaf surfaces due to transpiration, Quantifiable measurement of total evaporative water loss

2. water entering the soil vs running over it

3. True

Lecture 3

How does soil structure and texture influence infiltration, percolation and runoff?

Infiltration is affected by the soil structure and texture since depending on the texture there is a higher level of infiltration such as in sandy due to its loose structures, and lower with clay. Consequently, clay has the most runoff. In silt soils there is higer percolation than in clay but slower than sandy. Silt typically is moderate and in between of sandy and clay texture.

UNIT 7 — SOIL AERATION AND TEMPERATURE

Soil Composition

1. Mineral Matter

2. Organic Matter

3. Water

4. Air

What is Air?

• Gaseous envelope surrounding the earth

• Commonly referred to as air

• The gas called “air” is:

  • A mixture of gasses

  • Similar to that found in soil, but

Air Composition

Earth-

78% nitrogen (N2)

21% oxygen (O2)

0.04% Carbon Dioxide (CO2)

Soil-

78% Nitrogen (N2)

20% oxygen (O2)

CO2 can be 10x greater than atmosphere

Air Composition

Atmospheric and Soil Air Contains:

• Trace amounts of other gases- <1%

  • argon, freon, neon, helium, methane

• Water vapor- Remember the ater cycle?

Air Composition

Air pollutants

• Smog- combusted fuels reacting with solar radiation

• Soot- Particulate matter

  • ash

  • dust

  • pollen

  • mold

Soil Aeration

Aerated soils- constant gas exchange with atmosphere

Air movement:

• Mass flow- movement of gas related to pressure and temperature

• Diffusion- gradual dispersal of gas molecules to lower concentrations

Why is soil air important?

Gas exchange with atmosphere necessary in biological processes:

• Photosynthesis

• Cellular respiration

The ratio of CO2 and O2 in soil determines its suitability for life

O2 crucial in ionization and mineralization of elements

• Ionization- Atom that has gained an electrical charge either through loss or gain of electrons

• Mineralization- The release of minerals-plantessential nutrients through the decomposition of OM

Soil organisms:

• Require O2- for respiration

• Will use other elements in its absence

  • Ex. iron, nitrogen, sulfur, carbon

• Responsible for ionization and mineralization of plant nutrients via respiration

  • Ex. nitrogen cycle

O2 influences decomposition of OM

• Aerobic vs Anaerobic

  • With or without O2

• Soul organisms present

• Mineralization

Aeration allows water to move through profile

• Infiltration, percolation, run-off

• Water carries nutrients

Aeration allows plant root development

• Pore space

• O2 uptake via root

Gas concentrations determine form and availability of plant essential nutrients.

• Presence of O2 impacts redox reactions

  • Redox-

    • Reduction- gain electrong

    • Oxidation- loss of electrong

^Fe and Mn can be toxic in reduced form, or unavailable in oxidized form

Factors Affecting Soil Aeration

Soil heterogeneity-

• Macropore volume

  • Soil texture, structure, density

  • OM content

  • Presence of deep cracks

• Higher O2 concentrations in upper horizons

Drainage-

• Air cannot occupy pores filled with water

  • Hardpan/compaction

  • Water table depth

  • Porosity

Organism respiration rates-

• Use O2 and CO2

• Impact diffusion rates

Plant roots-

• Decrease soil O2

• Remove soil water

Soil management-

• Tillage

  • Increase aeration short-term

  • Can lead to compaction

    • lower aeration over time

  • OM sequestration

Management to improve soil aeration

Improve drainage and avoid compaction-

• Add and retain OM

• Avoid working wet soil

• Conservation tillage and equipment use

• Deep ripping

• Aeration equipment

Measuring Soil Aeration Status

1. Redox: oxidation-reduction potential of soil

2. Volume of macro pores

3. CO2 and O2 levels

4. Soil Saturation- pores occupied by water cannot be occupied by air

Soil Temperature

Temperature impacts biological, chemical, and physical properties of soil

Biological-

Plant processes

• Seed germination

• Root function

• Shoot growth

  • Warm vs cool season

Biological and Chemical-

Microbial Processes in warm temps

• Increase respiration

  • Alter soil aeration levels

• Impacts nutrient cycling

Microbial Processes in cool temps:

• Lower decomposition rates/mineralization

• Lower ion oxidation

• Impacts nutrient cycling

Physical-

• OM Content

  • Influences soil structure

• Freezing and thawing

  • Increases granular structure

Factors Influencing Soil Temperature

1. Solar radiation

   1. Primary source of soil heat

2. Specific heat of soil

   1. Dry soil requires less energy to heat

3. Vaporization of soil water

   1. Evaporation cools soil

4. Fire

   1. Temporary heating of soil

Managing Soil Temperature

• Insulate soil with mulch

  • Living, organic, plastic

  • Solarization

• Provide adequate drainage and aeration

• Raise soil level

  • “Bed-up” soil: Manteca farm example

  • Raised beds

Unit 7 Lecture 1

1. Gaseous mixture known as air. Gaseous envelope surrounding earth.

2. CO2

3. it contains water vapor

4. driven by temperature vs. gas concentrations. movement in large volume vs. gradual dispersal

Unite 7 Lecture 2

1. Photosynthesis. Cellular respiration.

2. increase of plant available nutrients through cellular respiration

3. slow or cease ionization, slow decomposition of OM and mineralization, decrease cellular respiration, substitute other nutrients for O2

4. False

Unit 7 Lecture 3

1. False

2. Pore space

3. Oxidations is losing electrons, Determine form and availability of plant nutrients, Reduction is gaining electrons, Related to the sharing of electrons

UNIT 8 - SOIL COLLOIDS

Colloidal Particles

Colloid-

• Microscopic particles dispersed in solution

• Particles will not settle

• Organic and inorganic

• Soil Solution- Aqueous / water phase of soil contains dissolved organic & inorganic particles (colloids)

Soil Colloidal Particles

Soil colloids-

Organic and inorganic particles in soil solution

• Very small —> <2mm

• High surface area

• Highly reactive

Types of Soil Colloids

Inorganic Colloid- the clay fraction of colloids MM

• Crystalline Silicate Clays

• Non-crystalline Silicate Clays

• Iron and Aluminum Oxides

Organic Colloid- the humus (carbon) fraction OM

Soil Colloid Properties

High surface area- Concentration of micro pores:

• Electrically charged surfaces

• Increase water holding capacity

• Microbiological activity

  • Nutrient formation and ionization

• Aeration and gas exchange

• Root growth

Highly reactive- Carry negative and positive charges

• Negatively charged surfaces

  • Adsorb- Attraction of ions, including H2O, to colloid surfaces

    • ability to attract and hold nutrient ions

Cation Exchange Capacity (CEC)

Cation exchange- cations moving between colloidal surfaces and soil solution

CEC- Measurement of the total quantity of cations able to adsorb to soil particle surface -Nutrient holding capacity

In other words…CEC measures how fertile or potentially fertile a soil is, or quantifies the Nutrient Pool!

Two major problems associated with low CEC

1. Nutrients not adsorbed can become pollutants

   1. Nitrate (NO3)

   2. Phosphate (P2O5)

2. Nutrients —> fertilizers:

   1. Fertilizers are costly and can be overapplied

Colloids and CEC

CEC expressed in values 0-250 cmol/kg (molecular/mass)

Organic Matter (OM) -humus

• 150 to 250 cmol/kg

Clay

• 10-50 cmol/kg

Practically thinking, what would you do to improve soil CEC??

Nutrient Pools

Measurable state of plant nutrients in the soil

—> quantifiable

• Soluble- Readily available = dissolved into solution

  • Exchangeable cations (CEC)

  • Carbonates, sulfates, chlorides ionized nutrients

• Insoluble- Available over long periods of time —> slow release fertilizer

  • OM- mineralization yet to occur *raw materials*

  • Feldspars, apatite, mica —> primary minerals * raw materials*

Soil Nutrient Relationships

Possible fate of soil nutrients:

• Plant root uptake

• Cycling through plant development and decomposition

• Removal through harvest and tillage

• Holding in soil colloids - adsorption

• Leaching and runoff - Nutrients are carried by water either through percolation or via runoff

Unit 8 Part 1

1. True

2. Organic

3. High surface area

4. False

Unit 8 Part 2

what would you do to improve soil CEC??

In order to improve my soil CEC I would add organic matter to it such as humus. Which will consequently create fertility in the plant, prevent pollutants, and be a cheaper method than utilizing fertilizer.

Unit 8 part 3

1. soluble

2. OM, Mineral Matter, CEC, Surface adsorption, Soil Organisms

UNIT 9 SOIL ACIDITY, ALKALINITY, AND SALINITY

pH

Measurement of hydrogen ion (H+) concentration

• H+ increases/decreases by 10x with each level

  • Ex. increase of pH from 5 to 7 increases H+ exponentially by 10²

Indication of hydroxyl ion (OH-) ion concentration

• Inverse relationship with H+

Soil pH

Degree of acidity or alkalinity in a soil

• Acid VS base forming ions

Master variable in chemical reactivity

• Affects all soil properties

  • Chemical

  • Biological

  • Physical

    • Agricultural soils ideal range: 6.2-7.3

The importance of pH

Determines: Chemical Properties of Soil

Ion availability and CEC

• pH influences whether nutrient levels are:

  • Optimum, Deficient, or Toxic

• Increase in pH increases CEC

  • OH- on colloid surfaces exchange H+ and other cations

Mobility of soil pollution

• rate of biochemical breakdown

• solubility

• Adsorption

Toxins destroyed in the soil VS Toxins passed into groundwater

Determines: Biological Properties of Soil

Soil suitability for life

• Which plants dominate the landscape

  • Root uptake availability

  • most prefer neutral

• Activity of microbes

• Presence of fungi

Determines: Physical Properties of Soil

Soil structure

• Alkalinity causes particles dispersal

  • Associated with Na+ (sodium)

Soil Acidity

Result of:

1. Production of H+ ions

   1. Rain water

   2. Accumulation of OM

   3. Oxidation of N and S

   4. Plant uptake of …

2. Leaching of base ions via percolation

   1. High precipitation

      1. (Percolation + soil solids = leaching)

The role of Aluminum (A13+)

Adsorbed-

• H+ releases A13+ from minerals

  • (colloid via wethering)

• A13+ cleaves water molecule

  • Frees H+ to acidify soil

• Causes toxicity in plants

Soil Alkalinity

Result of reactions that consume(bonding w/anion) H+ or produce OH-

1. Weathering and accumulation of base forming cations

   1. calcium (Ca2+), sodium (Na+)

      1. Weathering consumes H+

   2. Low precipitation

      1. Avoid leaching

2. Production of base forming anions

   1. carbonates (CO3)

   2. bicarbonates (HCO3-)

   3. React with water to form OH-

pH and Soil

pH problems are chemical imbalances-

• Excessive fertilizers

• Loss of OM

• Poor farming practices

• Biological activity

• Acid rain

• Pollutants

Buffering

Soils ability to resist pH change when acid/base is added

• Mechanisms-

  • Cation exchange react

  • A13+ reactions

  • OM reactions

  • H+ on clay colloids

  • Carbonate reactions

Importance of Soil Buffering

Maintain stable pH environment

• Soil biota

Influences agricultural management

• process of neutralizing acid or base environments or correcting a chemical imbalance

• Buffer- Material that will neutralize an acid or base

• Amendment- Addition to the soil which is incorporated into the profile

Correcting Acidic Soils

Amending to buffer acidic soils-

1. Add Ag Lime (limestone) - calcium carbonate (CaCO3)

2. Add Dolomite Lime- calcium carbonate and magnesium carbonate (CaCO3MgCO3)

Correcting Acidic Soils: How it works…

CaCO3 (+) clay

H+Clay

Ca2+ (+) HCO3

1. Ca+ and/or Mg+ cations replace H+ cations on soil colloids

2. Carbonate (CO3) reacts with H+ to form bicarbonates (HCO3-)

3. The bicarbonate dissociates in water forming OH-ions

4. The H+ is consumed raising pH

Correcting Alkaline Soils

Add OM

Add sulfur- two chemical reactions associated with sulfur buffering

1. Involves water: 2S + 302 + 2H2O —> 4H + 2SO4

2. Oxidation reaction:

   1. microorganisms

      1. metabolize sulfur and release sulfate

      2. sulfate reacts with water to produce sulfuric acid = lowered pH:

Salinity and Sodicity

Defined: concentration of salts dissolved in solution

What are salts?

• Chemical definition: solid crystalline structured precipitate formed through an acid/base reaction

• Thousands of salt types

  • vary in color, composition, reactivity, solubility, and other physical and chemical …

Salts are formed by cations and anions-

• They are potential plant nutrients

• Can be toxic in excess concentrations

Plant nutrient salts

• Ca, K, Mg

Toxic/detrimental salts

• Al, Se, Cl, Na

Saline(desert) Soils- Ca, K, Mg, Al, Se, Cl

Sodic Soils(salt water encroachment)- Na (sodium)

Management of Saline Soils

Plant salt tolerant crops

• Sugar beets, wheat, barley

Improve DRainage- Leaching

• Amend soil with gypsum CaSO4

  • SO4 bonds with Na

  • Leaches through profile

• Deep ripping

• Raise beds

• Apply pure water to leach slats

Salts are measured using electro-conductivity (EC)

Salts conduct electricity; can easily be measured in solution

U.9 L.1

1. As pH values decrease = H+ ions increase, Solution becomes more acidic

2. pH is a measurement of H+ and indicator of OH- due to their ___ relationship = Inverse

3. Due to its influence on the chemical properties of solutions, pH is termed a Royal Variable = False

U.9 L.2

1. CEC increases as pH = increases

2. What is the ideal pH range for agricultural soils? = 6.3-7.3

3. What are the primary effects of pH on soil chemical properties? = ionization, CEC, pollution mobility

4. pH determines a soils suitability for life = True

U.9 L.3

1. Select the following ways that H+ ions are produced in the soil = rain water mixing with CO2, OM accumulation, Oxidation of N and S, Plant uptake

2. How does precipitation contribute to acidification = percolation + soil slids = leaching

3. A13+ contributes to soil pH because it is an acid forming ion = false

U.9 L.4

1. What does ‘consuming’ H+ mean? = H+ bonding with an anion, H+ becomes unable to further acidify a solution

2. Bicarbonates alter pH because they react with water to form OH- = True

3. What is the difference between calcareous and sodic soils? = high in calcium salts vs. sodium salts

U.9 L.5

1. How does fertilization alter soil pH? = all answers are correct

2. Cation exchange and colloids play a role in soil buffering capacity because accumulation of acid and base ions is responsible for pH changes = True

3. Compare and contrast buffers and an amendments? = buffers neutralize acids and bases, amendments can be buffers, amendments are added to the soil profile

4. Calcium and magnesium are plant nutrients and are directly responsible for changing pH = False

5. What are the differences between sulfur buffering reactions in the soil? = involving water vs. oxidation, oxidation commonly occurs naturally, water reaction with S is a common agricultural practice

UNIT 10 Organisms and Ecology of the Soil

The Soil Ecosystem

Ecosystem- Complex systems with biodiversity

Key terms-

Biodiversity- the wide variety of organisms in a system

Fauna- general term for animals

Flora- general term for plants and non-animal organisms

The Soil Ecosystem and its Organisms

Flora and Fauna-

Macro > 2mm

Meso 0.1-2.mm

Micro < 0.1mm

Eukarya-

• Organisms with cellular nucleus and organelles

• Multicellular and unicellular

• Plants, animals, fungi, protists

Prokarya-

• Organisms without cellular nucleus and organelles

• Unicellular

• Bacteria

THE SOIL FOOD WEB

Food Web-

• Complex system of interdependent food chains

  • Many organisms are omnivorous

• Organisms grouped by their sources of carbon and energy

• Trophic Levels- Consumption, energy/carbon sources

  • Primary Producers

  • Primary Consumers

    • Decomposers

  • Secondary Consumers

  • tertiary consumers

First trophic level-Primary Producers

Autotrophs:

Photoautotrophs:

• Rely on CO2 for carbon

• Photosynthesis for energy

• Plants, phytoplankton

Chemoautotrophs:

• Rely on CO2- or CO3- for carbon

• Oxidation of NH4+, S, Fe for energy

• Some bacteria

Second trophic level- Primary Consumers

Heterotrophs:

Rely on organic compounds for energy and carbon

Herbivores:

• Consume plants

• Nematodes

• Insects-termites, larva

• Shredders- rodents, earthworms

Detrivores: decomposers

• Consume decaying plant matter

• Insects, fungi, bacteria

Fungivores: Consume fungi

Bacterivores: Consume bacteria

Saprotrophic: Consume dead tissue

Third trophic level-Secondary Consumers

Low level Predators and Parasites:

• Consume primary consumers

• Omnivores and carnivores

• Carnivores- Centipedes, mites, bacteria, fungi, nematodes, spiders, snails

• Parasites- mites, bacteria, fungi, nematodes, protozoa don’t consume prey; feed off of host

Fourth and Fifth trophic level-Tertiary Consumers

Higher Level Predators:

• Consume secondary consumers

• Omnivores, Obligatory Carnivores

• Ants, spiders, scorpions, birds, moles

Functions of Soil Organisms

• Nutrient Cycling

• Formation of Soil Structure

• Weed Suppression

• Inhibiting Pests and Diseases

• Carbon Sequestration

Healthy soil organisms —> Nutrient cycling:

• Improve and support healthy plant growth

• Provides nutritional value of crops

• Sustains agricultural and natural systems

• Supports and maintains biodiversity

• Provides ecosystem stability

Nutrient Cycle

• Sequestration-

  • collection of nutrients to soil

• Cycling-

  • Mineralization

  • Bioturbation

• Transformation-

  • Ionization

• Assimilation-

  • Solubilize nutrients for plant uptake

Healthy soil organisms —> Suppress Weeds:

Functioning nutrient cycles —> nutrition for crops

• NO3- feeds weeds

• NH4+ feeds crops

• Nitrifying bacteria convert:

  • NH4+—> NO2—>NO3

  • Fungi predates on bacteria

Healthy soil organisms —> Inhibit pests and diseases:

Functioning nutrient cycles —> healthy plants

• Healthy vigorous plants resist insect pests and pathogens

Sustained biodiversity —> microbial populations

• Microbes

  • Suppress soil borne pathogens

  • Predate on pathogenic species

  • Actinomycetes

Formed Soil Structure —> improved aeration

Aerobes-

• Organisms require high volumes of O2

• Mostly beneficial

Anaerobes-

• Organisms do not require high volume of O2

• Mostly detrimental

healthy soil organisms —> Sequester carbon:

Soil Macrofauna

Role of macrofauna-

• To mix organic matter with soil

  • Complex MM with OM

• To increase aeration through channeling and burrowing

• To accelerate decomposition of organic matter

Role of Macrofauna

Macrofauna and the acceleration of OM decomposition

1. Springtails, termites, fly larvae: Puncture leaf epidermis and open leaf to microorganisms

2. Mollusks, termites, millipedes, earwigs, fly larvae, earthworms eat OM, pulverize it through excretion

3. Earthworms, insects, and burrowers transport the OM into soil

4. Earthworms and potworms consume OM in soil and further mix it

5. Microbes take over from there

Types of Macrofauna

Earthworms-

• Consume detritus

• Do not harm plants

• Increase macroporosity

  • Drainage, infiltration, aeration, root penetration

• Increase availability of nutrients and aggregates

  • Castings- partially digested OM and soil

Common Types of Macrofauna

• Termites- feed on carbon

• Springtails- detritivores

• Mollusks- feed on plant material

• Earwigs- feed on plant material

• Pill Bugs- detritivores

• Millipedes- Omnivores: detritus, fungi, plant juices, some predatory

Soil Fungi

• Mycology- Study of fungi

• Myco- Prefix for fungi: Greek root word ‘Mykes’

  • Includes:

    • Mold, mildew, rusts, smuts, yeast, puffball, mushroom

  • Multi celled- Eukaryotic

  • Mostly consume detritus

  • Micro and macro floral species

Role of Fungi in Soil

Functions of fungi (bacterial)

• Antibiotic production

• Decomposition of OM

• Predate on insects, fungi, bacteria

• Nutrient cycling and formation

• food source

• degradation of pollution

• Mycelium- Roots of fungi

• Mycorrhizae— A group of beneficial fungi living symbiotically on plant roots

  • Increase root surface area- extended access to water and nutrients

  • Element ionization —> nutrient formation

  • Provides tolerance for plant against salts, pesticides, diseases, parasites

  • Some deliver nutrients to plants

Soil Microfauna

Role of microfauna-

• Decompose OM

  • Mineralization

• Nutrient ionization

• Pollution degradation

• Control populations

  • Predation and parasitization

Nematodes-

• Microscopic unsegmented worms

• Found in almost all soils

• Can be beneficial or agricultural pests

• Impacts fungal and bacterial populations

• Alters nutrient cycling

• Food sources:

  • Fungi, bacteria, algae, plants, nematodes, protozoa, insect larvae

Soil Organisms- Bacteria

Bacteria-

• Single celled

  • Prokaryotic

• Measured in:

  • Micrometers

  • Gram positive vs gram negative

Morphology

• Cocci- spherical shape

• Bacilli- rob shaped

• Spirilla- tightly coiled or spiraled

Colonies

• Staphs- colonize in clusters

• Filamentous- form filaments

• Form biofilm networks

Bacteria

• Found in most habitats on earth

• Largest populations and species diversity exist in the SOIL

  • Healthy soil —> 40-50 million bacteria per gram

• <10% of bacteria is pathogenic (disease causing)

• Roughly 90% of bacteria is beneficial or benign (harmless)

Bacterial Ecological Fuctions-

• Recycling nutrients

• Key role in Nitrogen fixation and cycling

• Decompose animal proteins

• Predation/parasitism manages populations

• Antibiotic production help plants manage diseases

  • Actinomycetes key antibiotic producers

U.10 L.1

1. The soil ecosystem is diverse because all kingdoms of life are represented there = True

2. What is the characteristic which makes eukaryotic cells unique? = possess organelles

3. Select the characteristics which may prokaryotic cells unique = do not possess organelles, unicellular

U.10 L.2

1. A food chain is a complex system of interdependent organisms = false

2. What is the primary characteristic of autotrophs? = they synthesize their own carbon

3. What is the primary characteristic of heterotrophs? = they rely on other organisms for their carbon

4. What is the primary characteristic of detritivores? = they consume decomposing carbon

5. Predators and parasites both keep populations of other organisms regulated by feeding and infecting them. = True