Soil Organisms

22 species

What creatures live in soil?What creatures live in soil?

Harvester Ant Colony

Fauna

Macro

Mammals, reptiles, insects, earthworms

Micro

Nematodes, Protozoa, Rotifers

Flora

Plant roots, algae, fungi, actinomycetes (filamentous bacteria), bacteria

unicellular

20,000 species

Macrofauna: EarthwormsMacrofauna: Earthworms

Earthworm castEarthworm castCasts: earthworm’s wastesCasts: earthworm’s wastesEat soil organics: 2-30 times of their own wt.Eat soil organics: 2-30 times of their own wt.

five pairs of hearts

1,000,000 per acre

Mostly intestine

22 ft. long (Afr. and Aus.)

EarthwormsEarthworms

Abundance of earthwormsAbundance of earthworms

– 10-1,000/m10-1,000/m33

– 3,000 species3,000 species

Benefits of earthwormsBenefits of earthworms- soil fertility by producing castsoil fertility by producing cast- aeration & drainageaeration & drainage- size & stability of soil aggregatessize & stability of soil aggregates

Mycorrhizae symbiosisMycorrhizae symbiosisAssociation between fungi & plant rootAssociation between fungi & plant root

Increased SA (up to 10 times)Increased SA (up to 10 times)Increased nutrient uptake, Increased nutrient uptake, especially Pespecially P

Soil FungiSoil Fungi

10 - 100 billion/m2

Cell with a nuclear membrane and cell wallMost versatile & most active in acid forest soils

Yeasts, molds, mushrooms

Tolerate extremes in pH (bacteria do not)

Mycorrhizae FungiMycorrhizae Fungi

1. Ions in solution2. Movement from solution to root (diffusion)

Phosphorous granule

Root hair

Fungalhyphae

– Fungi provide nutrientsFungi provide nutrients– Plant root provides carbonPlant root provides carbon– EctomycorrhizaEctomycorrhiza Root surfaces and cortex in forest trees Root surfaces and cortex in forest trees

– EndomycorrhizaEndomycorrhiza Penetrate root cell wallsPenetrate root cell walls

agronomic crops- agronomic crops-

corn, cotton, wheat, & ricecorn, cotton, wheat, & rice

Symbiosis

Soil BacteriaSoil Bacteria10-100 trillion/m10-100 trillion/m22

Single-celled organismsSingle-celled organisms

Rapid reproductionRapid reproduction

Small (<5 Small (<5 µµm)m)

Mostly heterotrophicMostly heterotrophic

Autotrophic BacteriaImpact the availabilityof soil nutrients (N,S)

Quantification of Soil OrganismsQuantification of Soil Organisms

Numbers of organismsNumbers of organisms– Extremely numerousExtremely numerous– 1,000,000-1,000,000,000 /g soil1,000,000-1,000,000,000 /g soil– 10,000 species /g soil10,000 species /g soil

BiomassBiomass– 1-8% of total soil organic matter1-8% of total soil organic matter

Metabolic activityMetabolic activity – Respiration: Respiration: COCO22

– Proportional to # & biomassProportional to # & biomass

Quantification of Soil OrganismsQuantification of Soil Organisms

Three Criteria

OrganismsOrganisms #/g soil#/g soil Biomass (g/mBiomass (g/m22))MicrofloraMicroflora

BacteriaBacteria 10108 8 -10-1099 40-50040-500ActinomycetesActinomycetes 10107 7 -10-1088 40-50040-500FungiFungi 10105 5 -10-1066 100-1,500100-1,500AlgaeAlgae 10104 4 -10-1055 1-501-50

FaunaFaunaProtozoaProtozoa 10104 4 -10-1055 2-202-20NematodesNematodes 1010 -10-1022 1-151-15MitesMites 11 -10 -10 1-21-2EarthwormsEarthworms 11 -10 -10 10-15010-150

Soil Organisms in Surface SoilsSoil Organisms in Surface Soils

Note those in White

Basic Classification of Organisms

FoodOxygen

Energy Source

Based on food: live or deadBased on food: live or dead

Detritivores

• Eat dead tissues:• Fungi, bacteria

Herbivores– Eat live plants Insects, mammals, reptiles

PredatorsPredators– Eat other animalsEat other animals Insects, mammals, reptilesInsects, mammals, reptiles

AerobicAerobic– Active in OActive in O22 rich environment rich environment– Use free oxygen for metabolismUse free oxygen for metabolism

AnaerobicAnaerobic– Active in OActive in O22 poor environment poor environment– Use combined oxygen (NOUse combined oxygen (NO33

- - , SO, SO44-2-2))

Based on OBased on O22 demand demand

Autotrophic (COAutotrophic (CO22))– Solar energy (photoautotrophs)Solar energy (photoautotrophs)– Chemical reaction w/inorganic elementsChemical reaction w/inorganic elements N, S, & Fe (chemoautotrophs)N, S, & Fe (chemoautotrophs)

Based on energy & C sourceBased on energy & C source

Heterotrophic Energy from breakdown of organic matter

Most Numerous

Organisms are Major Determinants of Water Qualityand the Impact or Availability of Water Pollutants

Metals (Hg, Pb, As)Nutrients (N, P)

Organic Chemicals (PCBs, Dioxins)

Autotrophic: produce complex organic compounds from simple inorganic molecules and an external source of energy.

The Earliest Organisms

Chemoautotrophs, Cyanobacteria, Plants

Organic = Carbon-containing

3.5 bya

Autotrophs – Plants, Algae, Cyanobacteria

Produce complex organic compounds fromcarbon dioxide using energy from light.

6CO2 + 6H2O C6H12O6 + 6O2

light

simple inorganic molecule complex organic compound

energy

Primary producers – base of the food chain

Heterotrophs

Derive energy from consumption of complex organic compounds produced by autotrophs

Autotrophs store energy from the sun in carbon compounds (C6H12O6)Heterotrophs consume these complex carbon compounds for energy

carbon compounds (C6H12O6)

autotrophs Heterotrophs

Organisms

Anaerobic live in low-oxygen environments

Aerobic live in high oxygen environments

Heterotrophs

Heterotrophs: use carbon compounds for energy - consumers

Aerobic heterotrophs Anaerobic heterotrophs

Aerobic Heterotrophs and Anaerobic Heterotrophs

Aerobic Heterotrophs

Obtain the energy stored in complex organiccompounds by combining them with oxygen

C6H12O6 + Oxygen = energy

Live in high-oxygen environmentsConsume organic compounds for energy

C6H12O6 + 6O2 → 6CO2 + 6H2O

Aerobic Respiration

+ energy

C6H12O6 + 6O2 → 6CO2 + 6H2O

Electron poor

Electron rich Electron poor

Electron rich

The energy is obtained by exchanging electrons during chemical reactions.

2880 kJ of energy is produced

Aerobic respiration is very efficient, yielding high amounts of energy

Anaerobic Heterotrophic Organisms

Can use energy stored in complex carbon compounds in the absence of free oxygen

The energy is obtained by exchangingelectrons with elements other than oxygen.

Nitrogen (NO3)Sulfur (SO4)Iron (Fe3+)

Live in low-oxygen environmentsConsume organic compounds for energy

C6H12O6 + 3NO3- + 3H2O = 6HCO3

- + 3NH4+

Anaerobic respiration

C6H12O6 + 6O2 → 6CO2 + 6H2O

Electron poor

Electron rich Electron poor

Electron rich

Aerobic Respiration

Electron rich

Electron poor

Electron poor

Electron rich

C6H12O6 + 3NO3- + 3H2O = 6HCO3

- + 3NH4+ 1796 kJ

C6H12O6 + 3SO42- + 3H+ = 6HCO3

- + 3HS- 453 kJ

C6H12O6 + 6O2 → 6CO2 + 6H2O 2880 kJ

Anaerobic respiration is less efficientand produces less energy.

The oxygen status of soil/water determines the type of organisms

aerobic or anaerobic

High-oxygen Low-oxygen

Oxygen status impacts availability of nutrients as wellAs the availability and toxicity of some pollutants

Example: Eutrophication

Photosynthetic life

O2

bacteria

Nutrient AdditionsNutrient addition increasesprimary productivity (algae)

Sunlight is limited at greater depth

Photoautotrophs die and becomefood for aerobic heterotrophs

Aerobic autotrophs consume oxygenOxygen content in water is reduced

If oxygen is reduced sufficiently,aerobic microbes cannot survive,and anaerobic microbes take over

SO4-2 HS-

O2

NO3-

SO4-2

Respiration and Still Ponds

C6H12O6 + 3SO42- + 3H+ = 6HCO3

- + 3HS-

Heterotrophic Organisms

oxygen

Aerobic heterotrophsconsume oxygen

Anaerobic heterotrophsUse nitrate instead of O2

Anaerobic heterotrophsUse sulfate instead of O2

Organisms and Nutrients

NitrogenNitrogen

The most limiting essential element in the environment

Nitrogen and Soil Nitrogen and Soil

Surface soil range: 0.02 to 0.5%

0.15% is representative

1 hectare = 3.3 Mg

Biological/Plant NitrogenBiological/Plant Nitrogen

Amino acidsProteinsEnzymesNucleic acids (DNA)Chlorophyll

Component of living systems

Strongly limiting in the Environment

DeficiencyDeficiency

Chlorosis – pale, yellow-green appearance primarily in older tissues.

ExcessExcess

Enhanced vegetative growth – lodgingOver production of foliage high in N Delayed maturityDegraded fruit quality

N Distribution/CyclingN Distribution/Cycling

Atmosphere Soil / soil O.M. Plants, animals

N2, NO, N2O

NH4+, NO3

-, R – NH2

Proteins, amino acids

Organic Nitrogen (plant tissue, Soil Organic Matter): R – NH2

During organic decomposition, R – NH2 is usually broken down to NH4+

NH4+ is converted to NO3

- by soil microorganisms

Mineralization: Decomposition of organic forms releasing nitrogen into the soil, generally as NH4

+

Immobilization: Plant uptake of mineral nitrogen, removing it from the soil and incorporating into plant

tissue.

Forms: mineral and organic

Organic: plant/tissue N R-NH2

Mineral: soil N NH4+, NO3

-

Cycling in the Environment

Ammonium and NitrateAmmonium and Nitrate

NH4+R – NH2

organic mineral

Mineralization

Immobilization

NH4+ or NO3

- R – NH2

Cycling of Nitrogen

N2

XR-NH2R-NH2

R-NH2 is organically bound form of nitrogenR-NH2 is organically bound form of nitrogen

NH4+

DecompositionOf O.M.

Uptake byplant

Uptake byplant

NO2- NO3

- nitrosomonas nitrobacter

NH4+ is exchangeable, NO3

- is not

Atmospheric Nitrogen Fixation

Forms of Nitrogen

N2

XR-NH2R-NH2

R-NH2 is organically bound form of nitrogenR-NH2 is organically bound form of nitrogen

NH4+

DecompositionOf O.M.

Uptake byplant

Uptake byplant

NO2- NO3

- nitrosomonas nitrobacter

NH4+ is exchangeable, NO3

- is not

Rhizobium

Symbiotic Biological Nitrogen Fixation

Symbiosis between plant roots and rhizobium bacteria

Nodules are packed with Rhizobium

N2 NH4+

Residue from legume crops is usually high in N when compared with residue from other crops and can be a major source of N for crops that follow legumes in rotation.

Most of the N contained in crop residue is not available to plants until microbes decompose the plant material.

alfalfa range from 100 to 150 lbN/acre

Soybeans range from 20-40 lb/acre

N Contributions

Nitrogen and Legumes

Nitrogen Fixation is Difficult and SpecializedNitrogen Fixation is Difficult and Specialized

NN22 + 6H + 6H22 2NH 2NH33

Fixing NFixing N22 is energetically “expensive” is energetically “expensive”

NN NN Triple bondTriple bond– Must use energy to break these bondsMust use energy to break these bonds

Artificial Nitrogen FixationArtificial Nitrogen Fixation

Haber - Bosch ProcessHaber - Bosch Process - Artificial Fixation of - Artificial Fixation of Nitrogen Gas:Nitrogen Gas:– 200 atm200 atm– 400-500 400-500 ooCC– no oxygenno oxygen

yield of 10-20%

Produces 500 million tons of artificial N fertilizer per year. 1% of the world's energy supply is used for it Sustains roughly 40% of the world’s population

Nitrogen and Food

Irrigated land expected to expand by 23% in 25 years

70% of water used

Food production hasgrown with population

Crop VarietiesFertilizers

Nitrogen FertilizationNitrogen Fertilization

NO3- Negative Exchange sites

Loss of ProductivityLeaching to groundwater, surface water

NO3-NH4

+

Some Areas of Florida are Susceptible

Approximately 250 million years ago

Approximately 150 - 200 million years ago

Flooded, stable platformSubject to marine sedimentation

FL platform/plateau

For the next several million years the platform was dominated by carbonate sedimentation

Late Jurassic

Sedimentation: settling of particles from a fluid due to gravity

Carbonate Deposition/Sedimentation

Marine Calcium and Magnesium Carbonate

CaCO3

MgCO3

Florida platform was a flooded, submarineplateau dominated by carbonate deposition

FL platform

CaCO3

Between about 150 Mya and 25 Mya

*

The Eocene and Oligocene limestone forms theprincipal fresh water-bearing unit of the Floridan Aquifer,one of the most productive aquifer systems in the world

Eocene: 55 – 34 million years ago

Oligocene: 34 – 24 million years ago

The Eocene and Oligocene Limestone

carbonates

Prior to 24 Mya

Marine Carbonates

Between 150 and 25 Mya, Florida was dominated by carbonate deposition

Continental Influences

highlands

Sediments

Isolation of the Florida Peninsula

Suwannee Current

Georgia Channel

Sediments

Lowering of Sea Levels, Interruption of Suwannee Current

Suwannee Current

Events of the Late Oligocene Epoch, approximately 25 Mya

Raising of the Florida Platform

Exposure of Limestone

The Oligocene marked thebeginning of a world wide cooling trend and lower seaLevels.

Erosion cavitiesDue to acidity

Rejuvenation of Appalachians, weathering, increased sediment load

sediments

Miocene Epoch: began approximately 24 Mya

Sediments were sands, silts, clays

Sediments

Filling in the Georgia Channel

Early Miocene(~ 24 Mya)

Sediments

Rising sea levels allow sediments to becomesuspended in water and drift over the platform

Siliciclastics Covered the Peninsula

Sands And

Clays

1. Deposition of Eocene/Oligocene Limestone (55 – 24 Mya)2. Raising of the Florida platform3. Lowering of sea levels, interruption of the Suwannee Current4. Infilling of the Georgia Channel with sediments derived from Appalachian/continental erosion5. Sea level rise, lack of Suwannee current.6. Suspended siliciclastic sediments settle over the peninsula7. These sediments blanket the underlying limestone forming the upper confining layer for the Floridan Aquifer.

Summary

55 – 24 million years ago

Clays and Sands(low permeability)

Surface Siliciclastics (sandy)(highly permeable)

The Floridan aquifer is a confined aquifer.The water-bearing unitis permeable limestone.

Low PermeabilityConfining Unit(poor water movement)

Unconfined aquifer isextensive throughoutthe state of Florida

Low permeability rock (confining)

Permeability: the ease with which water moves through material

Calcium Carbonate CaCO3

The Water-bearing Unit is Extremely Productive

Magnesium Carbonate MgCO3

How does this material hold and deliver water?

limestone

Carbonate Dissolution

Acid (H+) dissolves calcium carbonate

Carbonates are made porous by acid dissolution

Carbon dioxide dissolved in water produces carbonic acid

CO2 + H2O = H2CO3 (carbonic acid)

H2CO3 => H+ + HCO3-

Acid

Rainfall is naturally acidic

CaCO3 + H+ = HCO3- + Ca2+

Acidity from rainfall reacts with CaCO3

and dissolves the carbonate rock.

(solid) (solution)(acid) (solution)

CO2 + H2O = H2CO3

H2CO3 => H+ + HCO3-

Dissolution Cave

Dissolution Cavities

Caves andSolution Cavities

Acid dissolves calcium carbonate

CaCO3 + H+ = HCO3- + Ca2+

Carbonates

Clayey Deposits

Channels and Caves

Karst Topography

Characterized by sinkholes, springs, depressions, lakes

Sinkhole Lakes

Florida is Dominatedby Karst Topography

Sinkhole formation depends on the material overlying the carbonate water-bearing unit

Thin, sandy covering

Thick sands up to 200 ft thick and some clays

Cohesive clays up to 200ft

Very thick clays> 200ft.

Miocene clays have been eroded and shaped throughout their historyresulting in extreme variability in thickness across the state.

The Importance of Sinkholes and Sinkhole Lakes

Hydrologic connections between the surfaceand the underlying limestone are maintained.

Florida: Nitrates (NO3-)

Nitrates do not interact significantly with soilmaterial and can move rapidly to groundwater.

Areas where the aquifer confining unitis thin are also particularly vulnerable.

What areas are particularly vulnerable?

Areas where natural groundwater recharge occurs

The unconfined, surficial aquifer

• residential and commercial septic systems in rural areas• about 300 row crop and vegetable farms• 44 dairies with more than 25,000 animals • 150 poultry operations with more than 38 million birds

Lower Suwannee River Watershed

Nitrates

NO3 Drinking water standard: 10 ppm

Possible sources of nitrate in the ground water in the vicinity of the riverinclude fertilizer, animal wastes from dairy and poultry operations, and septic-tank effluent.

Nitrate concentrations were higher in the measured springs than in the river.

Flow

Groundwater Nitrate Discharge to Rivers

Next: Phosphorus