SUBMITTED TO:Dr. LAKSHMIPATHIDEPT OF MICROBIOLOGY

SUBMITTED BY:PRABHAKARA REDDY A VI BSC SERIID NO.SLC3031COLLEGE OF SERICULTURE,CHINTAMANI

Phosphorous cycle

INTRODUCTION

Phosphorous is one of the essential nutrient which is required for energy storage and transfer system in the plant.

P is a component of building blocks of genes and chromosomes.

P increases the root growth, enhances crop maturity improves development of reproductive parts.

DEFICIENCY OF ‘P’

Shown by stunted growth of plants, becomes

dark green colour of leaves, then changes to grey and then to purple colour because accumulation of sugars. This sugar reacts with anthocyanin pigment and forms purple colour (or) bronzing.

Phosphorous is mobile in plants and relatively immobile in soils.P is less in soils compared to N and K.It varies between 0.005% to 0.15%.The total phosphorous present in the soil includes both organic and inorganic phosphorous.

Organic ‘ P ‘ comes from organic components like enositol phospholipids, nucleic acids and nucleoproteins.

Inorganic ‘ P’ comes from minerals, fertilisers,

Appetite has the highest amount of ‘P’ followed by granite,gneiss,limestone,mica.

The inorganic ‘P’present in soil in different pools i.e present in 3 forms ‘P’ bound to alluminium,’P’ bound to iron,’P’ bound to calcium.

IMPORTANCE OF ‘P’. study of p-cycle is essential to know the various p-

transformations occurring in the soil when any ‘P’ fertilizer (or)organic manure are applied.

1.The p-cycle is shown by simple reaction as follows

Soil solution P labile P non-labile P.

2.Depletion of labile P some non-labile P becomes labile at a very slow rate in order to buffer both org-p and inorg-p the primary and secondary P-minerals dissolved to resupply these 2 ionic form in solution.

3.The inorg-P gets adsorbed on the clay surfaces as H2Po4- and HPo4-- so this get desorbed and helps in buffering the soil solution P.

Continue….

4.The soil mo’s digest the plant residues containing P mineralized and supplies the available form to the soil solution.

5.By this 2 reactions-mineralization, adsorption and desorption,P concentration in the solution is maintained (or)referred as P intensity. The amount of P present in inorganic form referred as quantity.

6.The P-nutrition depends on quantity and intensity factor.

7.The ratio of quantity and intensity is defined as buffering capacity.

P-fixation

Thomas way(1850) observed P-fixation in neutral, alkaline and acidic soil.

Ca(H2PO4)2 + 2CaCO3------ Ca3(PO4)2+2Co2+2H2O

Al+3+H2PO4- +2H2O------2H+ Al(OH)2H2PO4 Fe+3 +H2PO4-+2H2O-------2H+Fe(OH)2H2PO4-

Fe3PO4

FACTORS AFFECTING P-FIXATION.

1.Soil temperature

2.PH

3.Organic matter.

4.Liming.

5.Nature and amount of soil component.

P-management in soil-PUE

PUE=Amo.of P taken up by DM/Amo.of fertilizers applied.

PUE is approximately 20-30%. To increase PUE

1.Timely application.

2.Method of application.

3.Liming of acidic soil.

4.Treatment of plant material.

5.Use of Bio-fertilizers.

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