The phosphorus cycle describes the movement of phosphorus among the biosphere, lithosphere, and hydrosphere of Earth. Phosphorus weathers from rocks and enters the soil, where it is absorbed by plants and animals through the food chain. Upon the death and decomposition of organisms, phosphorus is released back into the soil to be reabsorbed by plants, completing the cycle. Phosphorus is an essential nutrient for all living things, as it is a component of cell membranes, nucleic acids, and ATP used in cellular respiration.

2. INTRODUCTION
• IT IS A BIOGEOCHEMICAL CYCLE THAT DESCRIBES THE
MOVEMENT OF PHOSPHOROUS IS EXCHANGED AMONG THE
BIOSPHERE, LITHOSPHERE,AND HYDROSPHERE OF EARTH.
• UNLIKE MANY OTHER BIOGEOCHEMICAL CYCLE THE
ATMOSPHERE DOES NOT PLAY A SIGNIFICANT ROLE IN THE
MOVEMENT OF PHOSPHOROUS
• PHOSPHOROUS IS AN IMPORTANT CONSTITUENT OF
PROTOPLASM AND REQUIRED FOR METABOLISM OF ALL
LIVING ORGANISM.
• CARBON : NITROGEN : PHOSPHOROUS – 98 : 8.3 : 1
CARRINGTON SALT LOAM SOIL.

3. SOURCES
• ROCK DEPOSITS (SEDIMENTS)
• AGRICULTURE CROPS CONTAIN 0.05-0.5%
• ORGANIC FORMS- IN FORM OF PHYTIN, PHOSPHOLIPIDS,
NUCLEIC ACID, PHOSPHORYLATED SUGAR, COENZYMES,
ACID
• ADENOSINE TRIPHOSPHATE(ATP)
• SOIL IS RICH IN ORGANIC PHOSPHOROUS

6. STEPS OF PHOSPHOROUS CYCLE
• WEATHERING OF ROCKS – THE PHOSPHATE SALTS ARE
BROKEN DOWN FROM ROCK FROM THEIR THEY WASHED
AWAY INTO THE GROUND WHERE THEY MIX IN THE SOIL.
• ABSORPTION BY PLANTS- PHOSPHATE SALT FROM SOIL
ARE ABSORBED BY PLANTS . PLUS ADDED FERTILIZERS
ARE SOURCE OF PHOSPHOROUS.
• ABSORPTION BY ANIMALS – ANIMALS ABSORB IT FROM
PLANTS.
• RETURNING TO THE ENVIRONMENT THROUGH
DECOMPOSITION- AFTER THE DEATH OF PLANTS AND
ANIMALS BY THE PROCESS OF DECOMPOSITION IT GET
MIXES INTO THE SOIL AGAIN. WHICH ENDS UP INTO
SEDIMENTS AGAIN.

7. PROCESS INVOLVED
ALTERATION OF SOLUBILITY OF INORGANIC COMPOUNDS
OF PHOSPHOROUS
MINERALISATION OF ORGANIC PHOSPHATE COMPOUNDS
WITH THE RELEASE OF INORGANIC PHOSPHATE
IMMOBILISATION OF PHOSPHOROUS – CONVERSION OF
INORGANIC PHOSPHOROUS INTO ORGANIC FORM
ASSIMILATION- UTILISATION OF PHOSPHOROUS BY
MICROBIAL CELL TO MAKE CELL COMPONENTS
OXIDATION/REDUCTION REACTION OF INORGANIC
PHOSPHOROUS (PI) - EXIST IN TWO FORMS – (-3 FORM OF
PHOSPHINE AND +5 FORM OF ORTHOSPHOSPHATE)

8. ORGANIC PHOSPHATE COMPOUNDS(PHYTIN, PHOSPHOLIPIDS,
NUCLEIC ACID) ARE MINERALIZED TO ORTHOPHOSPHATE BY A
WIDE RANGE OF MICROORGANISMS THAT INCLUDE BACTERIA
(Bacillus subtilis, Arthrobacter), ACTINOMYCETES
(Streptomyces) AND FUNGI (Aspergillus, Penicillium)
CLEAVAGE OF PHOPHOROUS FROM ORGANIC MATTER IS DONE
BY PHOSPHATASE
MYCORRHIZAL FUNGI EXTRACT PHOSPHOROUS FROM SOIL
PHOSPHATE ALSO RETURN TO SOIL AND WATER THROUGH
DECAY EXCRETA AND DEAD BODIES OF ORGANISM
MINERALISATION

9. IMPORTANCE OF PHOSPHOROUS CYCLE
• VERY IMPORTANT FOR ALL ORGANISM
• COMPONENTS OF CELL MEMBRANE, NUCLEIC ACID,
• AS ATP PARTICIPATES IN RESPIRATION.
• IN ANIMALS- PART OF BONES AND TEETH