Role and deficiency symptoms of phosphorus (P) in Rice

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Role and deficiency symptoms of phosphorus (P) in Rice

Introduction

Phosphorus deficiency is widespread in all major rice ecosystems and is the major growth-limiting cause in acid upland soils.

P management should be considered as a long-term investment in soil fertility, and it is more effective to prevent P deficiency than to treat P deficiency symptoms.

The residual effect of P fertilizer application can persist for several years, and management must emphasize the buildup and maintenance of adequate soil-available P levels to ensure that P supply does not limit crop growth and N use efficiency.

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Essential constituent of Adenosine Triphosphate (ATP), Adenosine Diphosphate (ADP), nucleotides, nucleic acids, and phospholipids.

Involved in energy storage and transfer and membrane integrity.

Promotes tillering, root development, early flowering, and ripening (especially where the temperature is low).

Increases straw strength and disease resistance.

Role of Phosphorus in rice

Role and deficiency symptoms of phosphorus (P) in Rice

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It is important to note that:

P is particularly important in early growth stages of rice. 

The addition of phosphatic fertilizer is required when the rice plant’s root

system is not yet fully developed and the native soil P supply is less.

P is remobilized within the rice plant during later growth stages if adequate P has been absorbed during early growth stages.

Role and deficiency symptoms of phosphorus (P) in Rice

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P deficiency symptoms

Stunted growth of rice plants with reduced tillering.

Leaves, particularly older ones, are narrow, short, very erect, and dark green.

Stems are thin and spindly and plant development is reduced.

The numbers of leaves, panicles, and grains per panicle are also reduced.

Young leaves appear to be healthy but older leaves turn brown and eventually may die.

(Contd….)

Role and deficiency symptoms of phosphorus (P) in Rice

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P deficiency symptoms

Red and purple colours may develop in leaves, especially when the variety has a tendency to produce anthocyanin pigment.

Leaves may have pale green colouration when P and N deficiency occur simultaneously.

P deficiency is often associated with other nutrient disorders such as Fe toxicity at low pH , Zn deficiency, Fe deficiency , and at high pH .

(Contd….)

Role and deficiency symptoms of phosphorus (P) in Rice

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P deficiency symptoms

Delayed maturity.

In severe P deficiency , plants may not flower at all.

Increased number of empty grains in a panicle. In severe deficiency, grain formation may not occur.

Decreased 1000-grain weight and grain quality.

Decreased uptake of nitrogen and potassium by rice plants.

Role and deficiency symptoms of phosphorus (P) in Rice

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Role and deficiency symptoms of phosphorus (P) in Rice

P deficiency in rice

Less vigorous growth of P deficient plot (right) than P sufficient plot (left)

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Role and deficiency symptoms of phosphorus (P) in Rice

Excess of Phosphorus

Excess phosphorus may cause micronutrient deficiencies,

especially iron or zinc.

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Low inherent capacity of soil to supply P.

Inadequate use of P fertilizers and organic matter.

Low efficiency of applied P fertilizer use due to high P-fixation capacity or losses by soil erosion losses.

P immobilization in Ca phosphates due to excessive liming.

Crop establishment method (P deficiency is more likely in direct-seeded rice due to high plant densities and shallow root systems).

Imbalanced use of fertilizers. For example, excessive use of N fertilizer with insufficient P application.

Causes of P deficiency

Role and deficiency symptoms of phosphorus (P) in Rice

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P deficiency is the major growth-limiting factor in acid upland soils where soil P-fixation capacity is generally high.

Soils particularly prone to P deficiency include the following types:

Coarse-textured soils containing small amounts of organic matter and small P reserves (e.g., sandy soils)

Highly weathered, clayey, acid upland soils with high P-fixation capacity (e.g., Ultisols and Oxisols) Calcareous, saline, and sodic soils Acid sulphate soils in which large amounts of active Al and Fe result in the

formation of insoluble P compounds at low pH . Soils having intensive cropping without using adequate P application.

Occurrence of P deficiency

Role and deficiency symptoms of phosphorus (P) in Rice

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Apply the appropriate dose of phosphatic fertilizers

Add organic manures/ green manures before transplanting / sowing of rice.

Use biofertilizers like , phosphate solubilizing bacteria, and /or mycorrhiza for better phosphorus uptake and utilization.

Follow strictly the fertilization schedule recommended for rice, particularly suitable for the region.

Corrective measures (P)

Role and deficiency symptoms of phosphorus (P) in Rice

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Role and deficiency symptoms of phosphorus (P) in Rice

Name Formula Content Comments

Single superphosphate Ca(H2PO4)2 . H2O +

CaSO4 . 2H2O

7–9% P, 13–20% Ca,

12% S

Soluble, neutral (16–

21% P2O5)

Triple superphosphate Ca(H2PO4)2 . H2O 18–22% P, 9–14% Ca,

1.4% S

Soluble, neutral (41–

50% P2O5)

Monoammonium

phosphate (MAP)

NH4H2PO422% P, 11% N Soluble, acidifying

(51% P2O5)

Diammonium phosphate

(DAP)

(NH4)2HPO420–23% P,18–21% N Soluble, acidifying

(46–53% P2O5)

Sources of phosphatic fertilizers

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Role and deficiency symptoms of phosphorus (P) in Rice

Sources of phosphatic fertilizers

Name Formula Content Comments

Urea phosphate (UP) CO(NH2)2 + H3PO420% P, 18% N Soluble (46% P2O5)

Partly acidulated rock

phosphate

Ca3(PO4)210–11% P >1/3 water-soluble

(23–26% P2O5)

Rock phosphate,

finely powdered

Ca3(PO4)211–17% P, 33–36%

Ca

Very slow acting (25–

39% P2O5)

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Appropriate P management results in better yield of rice

Role and deficiency symptoms of phosphorus (P) in Rice

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Let Us Sum Up

P is essential for growth, cell division, root lengthening, seed and fruit development, and early ripening. It is a part of several compounds including oils and amino acids. The P compounds adenosine diphosphate (ADP) and adenosine triphosphate (ATP) act as energy carriers within the plants. Plant growth is markedly restricted under P deficiency, which retards growth, tillering and root development and delays ripening.

The deficiency symptoms usually start on older leaves. Extremely high levels of P can result in toxicity symptoms. Use of organic manures and chemical fertilizers should be done to prevent phosphorus deficiency.

Role and deficiency symptoms of phosphorus (P) in Rice

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