from this ppt you will learn about phosphorus its cycle , its mechanism ,all organism and its effect if the p-cycle is disturb.

1. Semester -5th
Paper – Environmental Microbiology
Topic- Phosphorus cycle
BY: KHAN SHAH RUKH
Roll no : 4181457022
Submitted to: Dr. Anjana Kapoor
College / Department: MICROBIOLOGY, SSN College ;University of Delhi

14. CONTENT

37. Schematic representation of the importance of microorganisms to P availability in soil.
©2011 by American Society of Plant Biologists

39. Inorganic P Compounds
(precipitates)
Acid soils
Fe and Al phosphates
FePO4
l2H2O , AlPO4
l2H2O
Alkaline soils
Ca and Mg phosphates

40. Ca(H2PO4)2 monocalcium phosphate
CaHPO4 dicalcium phosphate
Ca3(PO4)2 tricalcium phosphate
3Ca3(PO4)2
lCa(OH)2 hydroxyapatite
3Ca3(PO4)2
lCaCO3 carbonate apatite

41. Organic Soil Phosphorus
* 20 - 50% of total soil P is organic
• Mostly inositol phosphates,
• Humic acid
• Phospholipids
• Phosphate sugars
• Nucleic acids

42. • Immobilization (or demineralisation) in soil
science is the conversion of inorganic
compounds to organic compounds by micro-
organisms , by which it is prevented from
being accessible to plants . Immobilization is
the opposite of mineralization.

43. Factors affecting immobilization:-
Soil organic and inorganic matter
pH of soil
Presence of microbs in soil

44. MINERALIZATION OF ORGANIC P
• Mineralization is the microbial conversion of
organic P to H2PO4-or HPO4
2-, forms of plant
available P known as orthophosphate.
• Mixed cultures of PSMs (Bacillus, treptomyces,
Pseudomonas etc.) are most effective in
mineralizing organic phosphate (Molla et al., 1984).
• Enterobacter agglomerans solubilizes
hydroxyapatite and hydrolyze the organic P (Kim et
al .,1998).

45. P-mineralizing microorganisms

46. P-solubilizing microorganisms
• Bacteria
e.g. Actinomycetes,
Pseudomonas, and
Bacillus spp.
• Fungi
e.g. Aspergillus and
Penicillium spp.
• A nematofungus Arthrobotrys oligospora also has
the ability to solubilize the phosphate rocks
(Duponnois et al., 2006).

47. • Phosphorus solubilizing activity is determined by
the ability of microbes to release metabolites such
as organic acids, which through their hydroxyl and
carboxyl groups chelate the cation bound to
phosphate, the latter being converted to soluble
forms

48. Mechanisms of phosphate solubilization
• Chelating-mediated mechanism

49. Organic and inorganic acids
secreted by PSB in which have
hydroxyl and carboxyl groups
Hydroxyl and carboxyl groups
of acids chelate cations (Al, Fe,
Ca)
Decrease the pH in basic
soils

50.  Ca(H2PO4)2
 monocalcium phosphate
 CaHPO4
 dicalcium phosphate
 Ca3(PO4)2
 tricalcium phosphate
 3Ca3(PO4)2
lCa(OH)2
 hydroxyapatite
 3Ca3(PO4)2
lCaCO3
carbonate apatite
decreasing solubility
Inorganic P Compounds
pH
6
8

51. • Inorganic acids e.g. hydrochloric acid can also
solubilize phosphate but they are less effective
compared to organic acids at the same pH (Kim et
al., 1997).
• In certain cases phosphate solubilization is induced
by phosphate starvation (Gyaneshwar et al., 1999).

55. PHOSPHORUS CYCLE
MICROBIAL SINK
Eutrophication WATERBODIES and
SEDIMENTS
Aidedby
Mycorrhiza
MINERAL
FERTILIZER
HUMAN and ANIMAL EXCREMENT
(~50% of P in phytic acid form)
ROCKBOUND
•Apatite
•Fluorapatite
•Chlorapatite
•Hydroxlapatite
PLANT UPTAKE as H2PO4
-
or HPO4
2-
SOIL
INORGANIC PORGANIC P
•Humic acid
•Inositol phosphates
•Phospholipids
•Phosphate sugars
•Nucleic acids
Non-Labile Labile Soil Solution
•Specific adsorption to
Fe, Al,+ Mn oxides and
broken clay edges
• Precipitation of Ca or
Mg-P at pH>7
•Precipitation of Fe, Al,
or Mn-P at pH<5
•Weakly sorbed
phosphates
•Newly-precipitated Fe,
Al, or Mn-P in
acid soils
•Newly precipitated
Ca or Mg-P in
alkaline soils
•Phosphate
released from
labile pool or
added via
fertilizer
LEACHING
SURFACE
RUNOFF
WIND
EROSION
PLANT and ANIMAL
RESIDUES
HUMAN and ANIMAL
CONSUMPTION
By: Damon Wright, 2000; Clyde Alsup and
Michelle Armstrong, 1998; Asrat Shaiferaw,
1994; and Jerry Speir, 1996
Summary

56. Additional Information on Phosphorus
• Form taken up by plant: H2PO4
-, HPO4
=
• Mobility in soil: None; roots must come in direct
contact with orthophosphate P
• Mobility in plant: Yes
• Deficiency symptoms: Lower leaves with purple leaf margins
• Deficiency pH range: <5.5 and >7.0
• Toxicity symptoms: None
Toxicity pH range: Non toxic (optimum availability pH 6.0-6.5)
• Role in plant growth: Important component of phospholipids and
nucleic acids (DNA and RNA)
• Role in microbial growth: Accumulation and release of energy during
cellular metabolism
• Concentration in plants: 1,000 – 5,000 ppm (0.1 –0.5%)
• Effect of pH on availability: H2PO4
- at pH < 7.2
• HPO4
= at pH > 7.2
• Interactions with other P x N, P x Zn at high pH, in anion
nutrients: exchange P displaces S, K by mass action
displaces Al inducing P deficiency (pH<6.0)
MORE INFO

57. • P fertilizer sources: Rock phosphate, phosphoric acid, Ca
orthophosphates, ammoniumphosphates, ammonium
poly-phosphates, nitric phosphates, K phosphates,
microbial fertilizers (phosphobacterins) increase P
uptake
• Additional categories:
• Mineralization/ C:P ratio of < 200: net mineralization of
immobilization: organic P; C:P ratio of 200-300: no gain/loss of
inorganic P; C:P ratio of >300: net immobilization of
inorganic P
• P fixation: Formation of insoluble Ca, Al, and Fe phosphates
• Al(OH)3 + H2PO4
-  Al(OH)2HPO4
• (Soluble) (Insoluble)
• Organic P sources: Inositol phosphate (Esters of orthophosphoric acid),
phospholipids, nucleic acids, phosphate sugars
• Inorganic P sources: Apatite and Ca phosphate (unweathered soils) and Fe
and Al sinks from P fixation (weathered soils)
• Waste: Poultry litter (3.0 to 5.0%), steel slag (3.5%), electric
coal ash (<1.0%)
Additional Information on Phosphorus (Cont.)
MORE INFO

58. • Total P levels in soil: 50 – 1500 mg/kg
• Solution concentration range: < 0.01 to 1.0 ppm
• Applied fertilizer: < 30% recovered in plants, more P
must be added than removed by crops
Additional Information on Phosphorus (Cont.)

59. References:
• Alexander, M., 1977. Introduction to Soil Microbiology. 2nd Edition. John Wiley and Sons, NY.
• Brady, N.C., 1990. The Nature and Properties of Soils. 10th Edition. Macmillan Publishing Co., NY.
• Brigham Young University. 1997. The Phosphorus Cycle.
http://ucs.byu.edu/bioag/aghort/214pres/geochem.htm
• Harrison, A.F., 1987. Soil Organic Phosphorus. A Review of World Literature. C.A.B. p.39.
• Pierre, W.H., 1948. The Phosphorus Cycle and Soil Fertility. J. Amer. Soc. of Agron., 40:1-14.
• Pierzynski, G.M., Sims, J.T., and Vance, G.F., 1994. Soil and Environmental Quality. Lewis
Publishers, FL.
• Stewart, J.W.B., and Sharpley, A.N., 1987. Controls on Dynamics of Soil and Fertilizer Phosphorus
and Sulfur in Soil Fertility and Organic Matter as Critical Components of Production Systems, SSSA
Spec. Pub. No.19, 101-121.
• Tiessen, H., 1995. Phosphorus in the Global Environment – Transfers, Cycles and Management.
John Wiley and Sons, NY.
• Tisdale, S.L., Nelson, W.L., Beaton, J.D. and Havlin, J.L., 1993. Soil Fertility and Fertilizers.
Macmillan Publishing Co., NY.
 MICROBIAL ECOLOGY:
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 SOIL MICROBIOLOGY:
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