1.
 BiochemicalTransformation in Soil
Nitrogen Cycle (N2)
Sulfur Cycle (S)
Iron Cycle (Fe)
Carbon Cycle (C)
Phosphorus Cycle (P)
By: Dr. MohammedAzim Bagban
Asst. Prof. (Microbiology)
C. U. SHAH INSTITUTE OF SCIENCE
MI 202 (Unit -2)

2.
 Earth is a closed system, where the over all quantity of
matter remains constant.
 Microorganisms need electron, energy and nutrients to
grow.They are responsible for cyclic transformation of
compounds, and therefore they are called
biogeochemical agents.
 They carryout transformation of carbon, nitrogen,
sulphur phosphorus, iron etc.This cycling of elements is
called biogeochemical cycling.
 Both biological and chemical process are involved in
biogeochemical cycling.
 The oxidation reduction reactions are mainly
responsible for biogeochemical, cycling of compounds.
 This changes the chemical and physical characteristics of
different compounds.

3.
Biochemical
Transformation
Mineralization
Elemental
mineralization
Assimilation
Immobilization

4.
Rotation of Elements in Nature
Elements
Nitrogen
Carbon
SulfurIron
Phosphorus

5.
What is Nitrogen?
Nitrogen makes up about 78%
of our atmosphere.
Nitrogen in the atmosphere it is mostly in the form of
______, which is a compound that plants and animals cannot
use.
The process of converting nitrogen into compounds that
can be used by plants and animals is called the
________________.
N2
Nitrogen Cycle

6.
N2
Cycle
Nitrogen
Fixation
Proteolysis
AmmonificationNitrification
Denitrification
By traveling through
one of the ________
processes in the
Nitrogen Cycle!
How does atmospheric nitrogen (N2) get changed into a form
that can be used by most living organisms?
Four

7.
Process 1: Nitrogen Fixation
___________________ is the process in which the N2 compound
in the atmosphere breaks and combines with other compounds.
The nitrogen is _________ when it combines with
______________ or _______________.
N
N
H
N
HH
N2
Nitrogen Fixation
“fixed”
hydrogen oxygen
Ammonia (NH3)
Nitrous Oxide (N2O)

8.
Three ways to “fix” Nitrogen
Main process: Special ____________
convert the nitrogen gas (N2) to ammonia
(NH3), which only ________ plants can use
(peas, beans).
__________ strikes convert N2 to NO2 or
NO3.
Industrial production. ____________
manipulation turns N2 into NH3 (Fertilizer)
bacteria
some
Lightning
Chemical

9.
Types of Nitrogen Fixation

10.
Non biological Fixation

11.
Biological Fixation

12.
Non-Symbiotic

13.
Non-Symbiotic

14.
Symbiotic

15.
Nodule formation in Leguminous Plants

16.
Non-Nodulation

17.
Symbiotic Nitrogen Fixation

18.
Rhizobium

19.
Biochemistry of Nitrogen Fixation

20.
Nitrogenase Enzyme

21.
Biochemistry of Nitrogen Fixation
o The product of N2 fixation is ammonia, which is immediately
incorporated into organic matter as an amine (glutamine).
These amino atoms are converted into amino acids and
proteins, nucleic acid and other biomolecules in plants, animals
and microorganisms.
o The N2 cycle continues with the degradation of these
molecules into NH within many microbes through many
pathways including proteolysis.

22.
Proteolysis
o Plants use ammonia produced by symbiotic nitrogen fixers,
non-symbiotic nitrogen fixers, and ammonia available
through assimilatory reduction of nitrates to synthesize
amino acids and eventually plant proteins. When plants are
consumed by animals the plant protein are converted to
animal proteins.

23.
o This immobilized nitrogen in animal and plant proteins
and other nitrogenous compounds can be released only
when plants and animals die. These proteins and other
nitrogenous compounds are decomposed in the soil.
o The process of enzymatic breakdown of proteins is
called proteolysis. Proteolysis is carried out by microbes
which produce extracellular enzymes called proteases.
Proteolysis

24.
Process 2:Ammonification
Ammonification is the process in which release of ammonia
takes place from complex organic nitrogenous compounds. It
usually occurs under aerobic condition.
N
H
H
H
Bacteria
Ammonia
Organic Nitrogen (proteins)

25.
Ammonification
o The microorganisms responsible are Proteus, Bacillus, Micrococcus, etc.
o The ammonia produced has different fates :
(1) As it is volatile, it may leave the soil.
(2) It may be solubilized in water and ammonium ions are produced.
(3) Ammonium ions can be utilized both by plants and microorganisms.
(4) It may be oxidized to nitrates by a process called nitrification.

26.
Ammonification
o Putrefaction is the anaerobic degradation of amino acid
resulting into formation of amines.
o This is mainly carried out by anaerobic bacterium belonging
to genus Clostridium.
o One more important fate of NH4
+ is its conversion to
nitrates (NO3
-) through a process called nitrification,

27.
Process 3: Nitrification
_______________ is the process that converts
ammonia (NH3) into nitrites (NO2) and
nitrates (NO3) which ____ plants _______
use.
Note: Ammonia comes from ______ nitrogen
fixation and ammonification
How is it done?
_____________________ N
N
N
H
H
H
O O
O
O O
Nitrification
most can
Both
Bacteria!

28.
Nitrification
o This is a two step process carried out by chemolithotrophs.
o The first step is sometimes described as Nitrosofication where NH4
+
first oxidized to nitrite by bacterial genera Nitrosomonas, Nitrobacter,
Nitrosolobus, Nitrosococcus, etc.
o These bacteria are chemolithotrophic, gram negative, aerobic, motile,
rod-shaped bacteria, sensitive to acidity.
o The second step described as Nitrification is carried out by nitrite
oxidizing bacteria.
o Bacterial genera Nitrobacter, Nitrospira and Nitrococcus are responsible for
this reaction. They are chemolithotrophic gram negative, nonmotile
bacteria, rods, sensitive to alkaline conditions.

29.
Process 4: Denitrification
Denitrificaiton: Process in which nitrogen
compounds convert back into atmospheric
nitrogen (N2 or N2O).
The main process is performed by bacteria in the
soil. It can also happen by burning fossil fuels.
N2ONO3
N2

30.
Denitrification
o This process results in a net loss of N2 from soil into the atmosphere.
The microbes responsible are Achromobacter, Agrobacterium, Alcaligenes,
Bacillus MicrococcusPseudomonas,Thiobacillus,Vibrio etc.
o Several anaerobic bacteria in soil carry out dissimilative nitrate reduction
in which nitrate is reduced to ammonia.
o The process is enhanced by:
(1) Presence of organic matter
(2) Temperature between 25-60°C.
(3) Neutral to alkaline pH.
(4) Anoxic condition.

31.
Nitrogen
Cycle
(4) Denitrification (1) Nitrogen Fixation
(2) Ammonification
Nitrates in Soil Organic nitrogen is converted
to ammonia.
N2
NH3
NO3
N2O
Ammonia is converted to
nitrites and nitrates.
(3) Nitrification

32.
Nitrogen in
the air
animal protein
dead plants & animals
urine & feces
ammonia
nitrites
nitrates
plant made
protein
decomposition by bacteria & fungi
bacteria
(nitrifying bacteria)
nitrates absorbed
denitrifying
bacteriaroot nodules
(containing nitrogen
fixing bacteria)
nitrogen fixing plant
eg pea, clover
bacteria

33.
Sulfur Cycle:
(Sulfur oxidation & Reduction)

34.
• The sulfur cycle is the collection of processes by
which sulfur moves between rocks, waterways and
living systems. Such biogeochemical cycles are
important in geology because they affect many
minerals.
• Biochemical cycles are also important for life
because sulfur is an essential element, being a
constituent of many proteins and cofactors, and
sulfur compounds can be used as oxidants or
reductants in microbial respiration.
• The global sulfur cycle involves the transformations
of sulfur species through different oxidation states

35.
• Sources of sulfur to the global cycle
• Weathering & volcanism & sea-spray
• Biological emission of Dimethyl Sulfide (DMS) from
oceans.
• Fossil fuel combustion (photo-oxidation of SO2).
• Most sulfur is in seawater and sedimentary
rocks.
• Assimilatory sulfate reduction:
• Incorporates sulfate into methionine and cystein
(amino acids).
• Only some anaerobes assimilate S-2 directly to
organic matter.

36.
Global
Input and
Outputs

37.
Steps Involved in Sulfur cycle
1. 'S' in elemental form cannot be utilized by plants or animals.
Bacteria Thiobacillus thiooxidans and similar can oxidize S to SO4
-2
2S + 2H20 + 302 2H2SO4
They can also oxidize ferrous sulfide. This causes the lowering
pH of soil/environment to pH 1.0 to 2.0. This process causes
the problem of acid-mine drainage due to release of acidic
waste water from mines containing sulfide ores.

38.
Steps Involved in Sulfur cycle
II. Sulfate is assimilated by plants and incorporated into sulfur
containing amino acids and into proteins.
Degradation of proteins (proteolysis) liberates sulfur in the
form of H2S which is released due to the enzymatic activity
of some microorganisms on sulfur containing amino acids.

39.
Steps Involved in Sulfur cycle
III. Sulfate (S04
2-) is reduced to H2S by sulfate-reducing
bacteria in soil e.g. Desulfotomaclulum, Desulfovibrio,
Desulfomonas,etc.
4H2 + CaSO4 H2S +Ca(OH)2 + 2H2O.

40.
Steps Involved in Sulfur cycle
IV. Hydrogen sulfide (H2S) is toxic to living organisms and hence
must be oxidized rapidly.
V. H2S is oxidized to elemental sulfur by photosynthetic
bacteria.
Co2 + 2H2S Light (CH20)x + H2O + S

41.
S
u
l
f
u
r
c
y
c
l
e

42.
S
u
l
f
u
r
c
y
c
l
e

43.
Carbon Cycle

44.
• An element
• The basis of life of earth
• Found in rocks, oceans, atmosphere, and all living
organisms.
• The same carbon atoms are used repeatedly on earth.
They cycle between the earth and the atmosphere.
What Is Carbon?

45.
Plants Use Carbon Dioxide
 Plants pull carbon dioxide (CO2) from the
atmosphere.
 Using sunlight with the CO2 they make glucose.
 This process is photosynthesis.
 The carbon can be used by the plant (food) and used
to build the plant (cellulose).
 Also gives off CO2 from cellular respiration.

46.
Animals Eat Plants
 When organisms eat plants, they take in the carbon and
some of it becomes part of their own bodies.
 They generate CO2 from cellular respiration(break
down of glucose) and exhale this CO2 into the
atmosphere.

47.
Animals Eat Animals
 When organisms eat animals, they take in the carbon and
some of it becomes part of their own bodies.
 They generate CO2 from cellular respiration (break down
of glucose) and exhale this CO2 into the atmosphere.

48.
Plants and Animal Die
 When plants and animals die, most of their bodies are
decomposed and carbon atoms are returned to the
atmosphere.(CO2)
 Some are not decomposed fully and end up as deposits
underground (oil, coal, etc.= fossil fuels=Carbon)

49.
Carbon Slowly Returns to Atmosphere
 Carbon in rocks and underground
deposits is released very slowly into the
atmosphere.
 This process takes many years.

50.
Carbon in Oceans
 Additional carbon is stored in the ocean.
 CO2 passes into the water from the atmosphere.
 Plants & phytoplankton use for photosynthesis.
 Many animals pull carbon from water to use in
shells, etc.
 Animals die and carbon substances are deposited
at the bottom of the ocean.
 Oceans contain earth’s largest store of carbon.

51.
Burning wood and Fossil Fuels
 Releases carbon compounds in air, water, and
soil
 * one gallon of gas burned in a car=19lbs of
CO2

52.
Cycle – Repeats Over and Over
and Over and Over …

53.
StepsInvolvedinCarboncycle
Plants, algae and photosynthetic bacteria fix CO2 into organic
compounds through photosynthesis.
Atleast, half the carbon present in earth is fixed mainly by
marine photosynthetic bacteria namely by Prochlorococcus,
Synechococcus and Diatoms.
I. Organic Carbon formation

54.
The other examples of CO2 transformation are by :
(1) Autotrophic bacteria as per the following reaction:
CO2 + 4H (CH20)n+ H20
(2) Heterotrophic microorganisms can fix CO2 by following reaction:-
CH3COCOOH + CO2 COOHCH2COCOOH
Pyruvic acid Oxaloacetic acido
(3) Plant organic carbon is converted into animal organic carbon when
animals feed on plant.
I. Organic Carbon formationStepsInvolvedinCarboncycle

55.
• Deposition of all this organic carbon occurs in soil.
• Decomposition of organic compounds from soil occurs by microbial
processes.
• Microbial mineralization in aerobic conditions results into complete
oxidation of these compounds with major end products CO2 and
H2O.
• Under anaerobic condition incomplete degradation of organic
compounds produce CH4, H2, various organic acids and alcohols.
• CH4 is formed by Methanobacterium, Methanococcus,Methanosarcina
and Clostridium spp.
I. Organic Carbon formationStepsInvolvedinCarboncycle

56.
• CH4 can be oxidized to CO2 by two rare species of
Pseudomonas and Methylomonas.
• Thus, by the activity of microbes the immobilized organic
carbon is mineralized to CO2.
• The plant and animal organic compounds are of different
types. All these compounds are degraded and mineralized
differently by different microorganisms.
I. Organic Carbon formationStepsInvolvedinCarboncycle

57.
The organic constituents of plants are divided into the
following different categories:
I. Organic Carbon formation
Plant Organic
compunds
Cellulose
33%
Hemicellulose
15-25%
Lignin
5-30%
Water soluble
compounds
5-10%
StepsInvolvedinCarboncycle

58.
• A molecule of cellulose consists of 1900 to 10,000 units of
glucoseIt is degraded by bacteria and fungi.
• In the first step cellulose is converted into cellobiose by
enzyme cellulase.
• Cellobiose is then converted into glucose by the enzyme
B-glucosidase.
• Glucose is then converted into CO2 and H2O by enzyme
systems of many microbes during catabolism.
II. Cellulose DegradationStepsInvolvedinCarboncycle

59.
• Alternaria
• Aspergillus
• Fusarium
• Rhizopus
• Penicillium
• Achromobacter
• Cellfalcicura
• Cellulomonas
• Cellvibrio
• Cytophaga
• Pseudomonas
• Bacillus
• Micromonospora
• Streptomyces
II. Cellulose Degradation
• Microbes involved in cellulose degradation:
StepsInvolvedinCarboncycle

60.
• It is a polymer of pentose sugar especially of xylose and
arabinose linked by B - 1, 4 linkage.
• Enzyme responsible for its degradation is hemicellulase.
• Final end - products are CO2 and H20.
• The organisms that degrade hemicellulose are:
Bacteria - Bacillus, Pseudomonas, Cytophaga
Fungi - Alternaria, Fusarium,Aspergillus, Rhizopus etc.
III. Hemicellulose DegradationStepsInvolvedinCarboncycle

61.
• It is a polymer of aromatic alcohol and is highly resistant
to degradation.
• Lignin is a very complex molecule. Assaying and
purifications of lignin fraction from soil is difficult.
• The end-product of lignin degradation are vanillin and
vanillic acid.
• Microorganism responsible for lignin degradation are
Clavaria, Hypholoma,Agaricus, Streptomyces, etc.
IV. Lignin DegradationStepsInvolvedinCarboncycle

62.
• Pectin is a polymer of methyl D-galacturonate.
• It is degraded by enzymes protopectinase,
polygalacturonase and pectin methyl esterase.
• The end-product of degradation is galacturonic acid, The
microorganisms involved are Bacillus, Clostridium,
Pseudomonas, Fusarium, etc.
V. Pectin DegradationStepsInvolvedinCarboncycle

63.
• When plant and animal residue decompose in soil, the
product formed is called Humus.
• It is soft, spongy, amorphous dark colored substance made
up of residual organic matter which is not capable of
further degradation by microorganisms. It consists of
heterogeneous group of substances having an unknown
chemical structure.
VI. HumusStepsInvolvedinCarboncycle

64.
Iron Cycle

65.
• The iron cycle (Fe) is the biogeochemical cycle of iron
through the atmosphere, hydrosphere, biosphere and
lithosphere. While Fe is highly abundant in the Earth's
crust.
• Iron is a key micronutrient in primary productivity.
• It is a key component of hemoglobin, important to
nitrogen fixation as part of the Nitrogenase enzyme
family, and as part of the iron-sulfur core of ferredoxin it
facilitates electron transport in chloroplasts, eukaryotic
mitochondria, and bacteria.

66.
• Iron is transformed between ferrous (Fe2+) and Ferric
(Fe3+) oxidation states by microorganisms.
• Ferric compounds are less soluble than ferrous
compounds.
• Both ferrous and ferric ions are inter-convertible.
• This conversion is based on pH and redox potential of
soil.

67.
StepsInvolvedinIroncycle
• Under aerobic condition some bacteria obtain energy by
oxidizing Fe2+.
• They are Thiobacillus ferrooxidans, Leptospirillum ferrooxidans,
Sulfolobus acidocaldarius, etc.
• 2Fe+2+ ½ O2 + 2H+ 2Fe+3 + H2O.
• T. ferrooxidans oxidizes ferrous sulfate to produce ferric
sulfate [Fe2(SO4)3].
• The ferric sulfate is hydrolysed to ferric hydroxide and
acid is released [Fe(OH)2].
• The ferric hydroxide accumulates outside the cell forming
a gelatinous coat.
I. Iron oxidation

68.
StepsInvolvedinIroncycle
• The reduction of F+ to Fe+ occurs when redox potential
value is very high.
• The example of microbes capable of iron reduction are :
Alternaria, Fusarium, Bacillus, Clostridium, Klebsiella,
Pseudomonas, etc.
• The reaction involves:
• 2Fe+3 + H2 2Fe2+ + 2H+
II. Iron Reduction

69.
Ironcycle

70.
Phosphorus Cycle

71.
• The phosphorus cycle is the biogeochemical cycle that
describes the movement of phosphorus through the
lithosphere, hydrosphere, and biosphere.
• Phosphorus is an essential nutrient for plants and animals.
Phosphorus is a limiting nutrient for aquatic organisms.
• Phosphorus does enter the atmosphere in very small
amounts when the dust is dissolved in rainwater and
seaspray but remains mostly on land and in rock and soil
minerals.

72.
• Eighty percent of the mined phosphorus is used to make
fertilizers. Phosphates from fertilizers, sewage and detergents
can cause pollution in lakes and streams.
• Phosphorus occurs most abundantly in nature as part of the
orthophosphate ion (PO4)3−
• On land most phosphorus is found in rocks and minerals.
• The primary biological importance of phosphates is as a
component of nucleotides, which serve as energy storage
within cells (ATP) or when linked together, form the
nucleic acids DNA and RNA.

73.
• The double helix of our DNA is only possible because of
the phosphate ester bridge that binds the helix.
• Besides making biomolecules, phosphorus is also found in
bone and the enamel of mammalian teeth, whose strength
is derived from calcium phosphate in the form of
hydroxyapatite.
• It is also found in the exoskeleton of insects, and
phospholipids (found in all biological membranes)

74.
• Phosphorus cycle is the alternation between
inorganic and organic state of phosphorus occurs
within living cell of plants, animals and
microorganisms.
• The alternation between soluble and insoluble
forms of phosphorus occur in soil.

75.
StepsInvolvedinPhosphoruscycle
• Most organic phosphate forms present in soil cannot be
taken up directly by living cells.
• The phosphorus requirements are met by the uptake of
soluble inorganic ion orthophosphate (PO3-) from soil.
• It is utilized for synthesizing nucleotides, orthophosphate
nucleic acids, phospholipids, etc. by both plant and
microorganisms.
I. Inorganic to organic

76.
StepsInvolvedinPhosphoruscycle
• This conversion of inorganic phosphorus to organic form
is done by process of esterification within living cell.
• Upon death of organisms, phosphate ions are released
rapidly by hydrolysis of nucleic acid, phospholipids, etc.
• This cycle functions very rapidly and therefore inorganic
soluble phosphate ions should be provided to the living
cells constantly.
I. Inorganic to organic

77.
StepsInvolvedinPhosphoruscycle
• In soil and rocks, relatively large quantities of inorganic
phosphates occur as insoluble calcium, iron or aluminium
salts.
• Furthermore soluble forms of phosphate are constantly
transferred from terrestrial life to sea by drainage and
leaching.
II. Insoluble to Soluble form

78.
StepsInvolvedinPhosphoruscycle
• Very little amount of soluble phosphates are available for
terrestrial life, and therefore phosphorous often becomes
a limiting factor for growth of living organism.
• Solubilization of insoluble phosphate is necessary for life
of soil microflora. Some microorganisms like nitrifying and
sulfur oxidizing bacteria play a very important role.
II. Insoluble to Soluble form

79.
StepsInvolvedinPhosphoruscycle
• These organisms produce strong acids like nitric sulphuric
acid which help solubilization of insoluble phosphates as
shown below :
Ca3(PO4)2 + 2HNO3 2CaHPO4 + Ca(NO3)2
Ca3(PO4)2 + 4HNO3 → Ca(H2PO4)2 + 2Ca(NO3)2
Ca3(PO4)2 + H2SO4 2CaHPO4 + CaSO4
II. Insoluble to Soluble form

80.
StepsInvolvedinPhosphoruscycle
• This soluble form of phosphate is taken up by living cells.
• Thus, through the activity of nitrifying and sulphur oxidizing bacteria
the phorphorus is available to living organisms.
• Some bacterial species belonging to the genus Pseudomonas has been
found to be phosphate solubilizing.
• Other phosphate solubilizers are Micrococcus, Bacillus, Flavobacterium
and some fungi.
• Phosphate Solubilizing Bacteria (PSB) are also used as biofertilizers.
II. Insoluble to Soluble form

81.
StepsInvolvedinPhosphoruscycle
II. Insoluble to Soluble form

82.
Soil Fertility: Biofertilizers

83.
• Soil fertility refers to the ability of soil to sustain
agricultural plant growth, i.e. to provide plant habitat and
result in sustained and consistent yields of high quality.
• A fertile soil has the following properties:
• The ability to supply essential plant nutrients and
water in adequate amounts.
• The absence of toxic substances which may inhibit
plant growth.

84.
• A biofertilizer (also bio-fertilizer) is a substance which
contains living micro-organisms which, when applied to seeds,
plant surfaces, or soil, colonize the rhizosphere or the interior
of the plant and promotes growth by increasing the supply or
availability of primary nutrients to the host plant.
• Biofertilizers add nutrients through the natural processes of
nitrogen fixation, solubilizing phosphorus, and stimulating plant
growth through the synthesis of growth-promoting substances.
• The microorganisms in biofertilizers restore the soil's natural
nutrient cycle and build soil organic matter.

85.
• Biofertilizers are means of fixing the nutrient availability in the soil.
Generally Nitrogen deficiencies.
• Since a bio-fertilizer is technically living, it can symbiotically associate
with plant roots. Involved microorganisms could readily and safely
convert complex organic material into simple compounds.
• It has also been shown that to produce a larger quantity of crops,
biofertilizers with the ability of nitrogen fixation and phosphorus
solubilizing would lead to the greatest possible effect.
• No adverse side effects on crop, less labour, and non-toxic .
Benefits:

86.
1. Azolla-Anabena symbiosis: Azolla is a small, eukaryotic, aquatic fern
having global distribution. Prokaryotic blue green algae Anabena azolla
(BGA) resides in its leaves as a symbiotic. Azolla is an alternative
nitrogen source. This association has gained wide interest because of
its potential use as an alternative to chemical fertilizers
Groups of biofertilizers:

87.
II. Rhizobium: Symbiotic nitrogen fixation by Rhizobium with legumes
contribute substantially to total nitrogen fixation. Rhizobium inoculation is
a well-known agronomic practice to ensure adequate nitrogen.
Groups of biofertilizers:

88.
III. Phosphate solubilizing bacteria (PSB) are beneficial
bacteria capable of solubilizing inorganic phosphorus from
insoluble compounds. Many different strains of these
bacteria have been identified as PSB, including Pantoea
agglomerans (P5), Microbacterium laevaniformans (P7)
and Pseudomonas putida (P13) strains are highly efficient
insoluble phosphate solubilizers.
Groups of biofertilizers:

89.
IV. Plant growth-promoting rhizobacteria (PGPR) were first
defined to describe soil bacteria that colonize the roots of
plants following inoculation onto seed and that enhance plant
growth. Rhizobacteria are root-associated bacteria that form
symbiotic relationships with many plants.
PGPR bacteria include Pseudomonas putida, Azospirillum
fluorescens, and Azospirillum lipoferum.
Groups of biofertilizers:

90.
V. Mycorrhiza:
• A mycorrhiza is a symbiotic association
between a green plant and a fungus. The
plant makes organic molecules such as
sugars by photosynthesis and supplies
them to the fungus, and the fungus
supplies to the plant water and mineral
nutrients, such as phosphorus, taken
from the soil.
Groups of biofertilizers:

91.
V. Mycorrhiza:
• Mycorrhizas are commonly divided into ectomycorrhizas and
endomycorrhizas.
• The two types are differentiated by the fact that the hyphae of
ectomycorrhizal fungi do not penetrate individual cells within
the root, while the hyphae of endomycorrhizal fungi penetrate
the cell wall and invaginate the cell membrane.
Groups of biofertilizers:

92.
• Fowler, David; Coyle, Mhairi; Skiba, Ute; Sutton, Mark A.; Cape, J. Neil; Reis, Stefan; Sheppard, Lucy J.; Jenkins, Alan; Grizzetti, Bruna; Galloway, JN; Vitousek, P; Leach,
A; Bouwman, AF; Butterbach-Bahl, K; Dentener, F; Stevenson, D; Amann, M; Voss, M (5 July 2013). "The global nitrogen cycle in the twenty-first century". Philosophical
Transactions of the Royal Society of London. Series B, Biological Sciences. 368 (1621): 20130164. doi:10.1098/rstb.2013.0164. PMC 3682748. PMID 23713126.
• Galloway, J. N.; Townsend, A. R.; Erisman, J. W.; Bekunda, M.; Cai, Z.; Freney, J. R.; Martinelli, L. A.; Seitzinger, S. P.; Sutton, M. A. (2008). "Transformation of the
Nitrogen Cycle: Recent Trends, Questions, and Potential Solutions" (PDF). Science. 320 (5878): 889–892. Bibcode:2008Sci...320..889G. doi:10.1126/science.1136674.
ISSN 0036-8075. PMID 18487183. S2CID 16547816. Archived (PDF) from the original on 2011-11-08. Retrieved 2019-09-23.
• Vitousek, P. M.; Menge, D. N. L.; Reed, S. C.; Cleveland, C. C. (2013). "Biological nitrogen fixation: rates, patterns and ecological controls in terrestrial ecosystems".
Philosophical Transactions of the Royal Society B: Biological Sciences. 368 (1621): 20130119. doi:10.1098/rstb.2013.0119. ISSN 0962-8436. PMC 3682739. PMID
23713117.
• Voss, M.; Bange, H. W.; Dippner, J. W.; Middelburg, J. J.; Montoya, J. P.; Ward, B. (2013). "The marine nitrogen cycle: recent discoveries, uncertainties and the potential
relevance of climate change". Philosophical Transactions of the Royal Society B: Biological Sciences. 368 (1621): 20130121. doi:10.1098/rstb.2013.0121. ISSN 0962-8436.
PMC 3682741. PMID 23713119.
• Fowler, David; Coyle, Mhairi; Skiba, Ute; Sutton, Mark A.; Cape, J. Neil; Reis, Stefan; Sheppard, Lucy J.; Jenkins, Alan; Grizzetti, Bruna; Galloway, JN; Vitousek, P; Leach,
A; Bouwman, AF; Butterbach-Bahl, K; Dentener, F; Stevenson, D; Amann, M; Voss, M (5 July 2013). "The global nitrogen cycle in the twenty-first century". Philosophical
Transactions of the Royal Society of London. Series B, Biological Sciences. 368 (1621): 20130164. doi:10.1098/rstb.2013.0164. PMC 3682748. PMID 23713126.
• Vuuren, Detlef P van; Bouwman, Lex F; Smith, Steven J; Dentener, Frank (2011). "Global projections for anthropogenic reactive nitrogen emissions to the atmosphere:
an assessment of scenarios in the scientific literature". Current Opinion in Environmental Sustainability. 3 (5): 359–369. doi:10.1016/j.cosust.2011.08.014.
hdl:1874/314192. ISSN 1877-3435.
• Pilegaard, K. (2013). "Processes regulating nitric oxide emissions from soils". Philosophical Transactions of the Royal Society B: Biological Sciences. 368 (1621):
20130126. doi:10.1098/rstb.2013.0126. ISSN 0962-8436. PMC 3682746. PMID 23713124.
• Levy, H.; Moxim, W. J.; Kasibhatla, P. S. (1996). "A global three-dimensional time-dependent lightning source of tropospheric NOx". Journal of Geophysical Research:
Atmospheres. 101 (D17): 22911–22922. Bibcode:1996JGR...10122911L. doi:10.1029/96jd02341. ISSN 0148-0227.
• Sutton, M. A.; Reis, S.; Riddick, S. N.; Dragosits, U.; Nemitz, E.; Theobald, M. R.; Tang, Y. S.; Braban, C. F.; Vieno, M. (2013). "Towards a climate-dependent paradigm of
ammonia emission and deposition". Philosophical Transactions of the Royal Society B: Biological Sciences. 368 (1621): 20130166. doi:10.1098/rstb.2013.0166. ISSN
0962-8436. PMC 3682750. PMID 23713128.
References

93.
• Dentener, F.; Drevet, J.; Lamarque, J. F.; Bey, I.; Eickhout, B.; Fiore, A. M.; Hauglustaine, D.; Horowitz, L. W.; Krol, M. (2006). "Nitrogen and sulfur deposition on regional
and global scales: a multimodel evaluation". Global Biogeochemical Cycles. 20 (4): n/a. Bibcode:2006GBioC..20.4003D. doi:10.1029/2005GB002672.
• Duce, R. A.; LaRoche, J.; Altieri, K.; Arrigo, K. R.; Baker, A. R.; Capone, D. G.; Cornell, S.; Dentener, F.; Galloway, J. (2008). "Impacts of Atmospheric Anthropogenic
Nitrogen on the Open Ocean". Science. 320 (5878): 893–897. Bibcode:2008Sci...320..893D. doi:10.1126/science.1150369. ISSN 0036-8075. PMID 18487184. S2CID
11204131.
• Bouwman, L.; Goldewijk, K. K.; Van Der Hoek, K. W.; Beusen, A. H. W.; Van Vuuren, D. P.; Willems, J.; Rufino, M. C.; Stehfest, E. (2011-05-16). "Exploring global changes
in nitrogen and phosphorus cycles in agriculture induced by livestock production over the 1900-2050 period". Proceedings of the National Academy of Sciences. 110
(52): 20882–20887. doi:10.1073/pnas.1012878108. ISSN 0027-8424. PMC 3876211. PMID 21576477.
• Solomon, Susan (2007). Climate change 2007 : the physical science basis. Published for the Intergovernmental Panel on Climate Change [by] Cambridge University
Press. ISBN 9780521880091. OCLC 228429704.
• Madigan MT, Martino JM (2006). Brock Biology of Microorganisms (11th ed.). Pearson. p. 136. ISBN 978-0-13-196893-6.
• Poore J, Nemecek T (June 2018). "Reducing food's environmental impacts through producers and consumers". Science. 360 (6392): 987–992. Bibcode:2018Sci...360..987P.
doi:10.1126/science.aaq0216. PMID 29853680
• "An Introduction to the Global Carbon Cycle" (PDF). University of New Hampshire. 2009. Archived (PDF) from the original on 8 October 2016. Retrieved 6 February 2016.
• Riebeek, Holli (16 June 2011). "The Carbon Cycle". Earth Observatory. NASA. Archived from the original on 5 March 2016. Retrieved 5 April 2018.
• Jickells TD, An ZS, Andersen KK, Baker AR, Bergametti G, Brooks N, et al. (April 2005). "Global iron connections between desert dust, ocean biogeochemistry, and climate".
Science. 308 (5718): 67–71.
• Raiswell R, Canfield DE (2012). "The iron biogeochemical cycle past and present" (PDF). Geochemical Perspectives. 1: 1–232. doi:10.7185/geochempersp.1.1.
• Wang T, Müller DB, Graedel TE (2007-07-01). "Forging the Anthropogenic Iron Cycle". Environmental Science & Technology. 41 (14): 5120–5129.
• Turner BL, Frossard E, Baldwin DS (2005). Organic phosphorus in the environment. CABI Publishing. ISBN 978-0-85199-822-0.
• Schlesinger WH (1991). Biogeochemistry: An analysis of global change.
• "Eutrophication - Soil Science Society of America". www.soils.org. Archived from the original on 2014-04-16. Retrieved 2014-04-14.
• Peltzer DA, Wardle DA, Allison VJ, Baisden WT, Bardgett RD, Chadwick OA, et al. (November 2010). "Understanding ecosystem retrogression". Ecological Monographs. 80
(4): 509–29. doi:10.1890/09-1552.1.
• "Phosphorus Cycle - The Environmental Literacy Council". enviroliteracy.org. Archived from the original on 2006-11-08.
References