Soil Science Lecture 10 after (midterm 2)

Phyotosynthesis

autotrophic transformation converting light energy into chemical energy useable by living organisms

Photosynthesis Chemical Equation

6CO2 + 6H2O →C6H12O6 + 6O2

The Carbon Cycle consists of

Co2 in plant tissue death to organic residues, Photosynthesis goes to animal tissue then organic residues, ???

Respiration in Carbon Cycle

Moves Organic residues and animal tissue to Co2

Combustion in Carbon Cycle

Fossil fuels to carbon

Herbivory in Carbon Cycle

organic residues tpo soil humus to animal tissue

Immobilization

herbivory, consumption and metabolism of plant material, eating organic source, animals and bugs/organisms

Carbon Nitrogen Ratio

how much carbon relative to N in organic material, every 10 units of C microbes need one unit of N

If there is a high C:N ratio then what do microbes do?

find another N source for balance or stop eating

What is considered a high C:N ratio?

30:1

Humus

conceptual mixture of organic substances but may not reflect reality

Fresh Organic Residue Functions and Decoposition

rapid decomposition, 1-2 years, nutrient release, food for microbes

Active Fraction OM Functions and Decomposition

slow decomposition, 15-100 years, some nutrient release, some CEC water holding capacity

Stabilized OM Functions and Decomposition

500-5,000, holds water and nutrients, maintains soil structure, sloe nutrient release 2-5% decomposes per year

Respiration (Decomposition) 

mineralization=conversion from organic to inorganic form

SOM content depends on what

the balance between inputs and outputs

SOM can eventually

top out, rea ch its equilibrium point

Effects of SOM on Soil Properties

Color, Physical Properties, Cation Exchange Capacity, Nutrient Supply, and lots more

Plant Essential Macronutrients

Sulfur, Phosphorus, Magnesium, Calcium, Potassium, Nitrogen

Plant Essential Micronutrients

Cobalt, Molybdenum, Copper, Zinc, Iron, Boron, Chlorine

Where do plants get Carbon,Oxygen and Hydrogen

water and air, N from organic sources

Main point of measuring fertility in soils is that

elements can come in different formes

Nitrogen Plant Functions

Enzymes (amino acids, protein, DNA), Chlorophyll, Vegetative and root growth

Nitrogen Cycle

N2 gas, Biomass N, Soil Organic N, NH4+/ammonium, goes to NH3 gas or NO2-, NO3-, NO2-, N2O back to beginning 

In the nitrogen cycle what happens to allow N2 to get to Biomass N

Nitrogen Fixation

Nitrogen Fixation does what to the triple bonded N?

breaks the bonds and attaches the N to hydrogens and something else

Nitrogen Fixation: Symbiotic

inoculation with correct bacteria, infection of legume roots, nodulation, legume feeds bacteria, bacteria provide fixed nitrogen

Nitrogen Fixation: Nonsymbiotic

nitrogen fixation by free-living microorganisms, cyanobacteria main 

Nitrogen Fixation: Abiotic nitrogen fixation

lighting, haber bosch process, human making of N fixation

Nitrogen Mineralization

a process of decomposition, makes N more available for plants, takes the organic nitrogen that’s attached to something and turns into NH4+ or NO3-

Nitrification

conducted by autotrophic bacteria (and archaea), has an oxidation reaction happen, turns NH4+ to highly leachable NO3-

Immobilization

Uptake of inorganic nitrogen by soil microbes/plant uptake changed into organic N

Carbon to Nitrogen Ratio

determines net immobilization, higher carbon ratio to nitrogen

Leaching

downward movement of soluble substances with percolating water

Denitrification

a respiration process conducted by anaerobic bacteria, flooded with water=denitrification, anaerobic conditions and available C are required

Phosphorus: Plant Functions

Nucleic Acids, ATP, Cell Membranes

Phosphorus Cycle inputs

fertilizer P mined from phosphate deposits, found in mineral apatite

Phosphorus Fixation

formation of insoluble calcium, aluminum, and iron phosphates

Phosphate Availability and pH

after 5 pH then more available

5 Components of the Phosphorus Cycle

Phosphate Inputs, Soluble Phosphate, Biomass Phosphate or Fixed Phosphate, Soil organic phosphate

Potassium Plant Functions

Enzyme control, Salt/water balance, transport of compounds within plant cells

N Deficiency

stunted growth, general yellowing, mostly in older leaves

P deficiency

Stunted growth, Dark green to purpling of older leaves

K deficiency

Yellowing/tissue death on edges of older leaves, white spots on some plants

Most Limiting Factor Barrel

the shortest supply nutrient inhibits plant growth, sets threshold to max effeciny

pH impact on nutrient availability

ideal pH is 6.5-7.0, pH needs to allow all plant nutrients to be available