Transcript 3-Role_and_deficiency_symptoms_of_Phosphorus_in_Rice_corr

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
the major growth-limiting cause in acid upland soils.
and is
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 soilavailable P levels to ensure that P supply does not limit crop growth and N use
efficiency.
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Role and deficiency symptoms of phosphorus (P) in Rice
Role of Phosphorus in rice
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.
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Role and deficiency symptoms of phosphorus (P) in Rice
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.
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Role and deficiency symptoms of phosphorus (P) in Rice
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.
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(Contd….)
Role and deficiency symptoms of phosphorus (P) in Rice
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 .
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(Contd….)
Role and deficiency symptoms of phosphorus (P) in Rice
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.
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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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Role and deficiency symptoms of phosphorus (P) in Rice
Causes of P deficiency
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.
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Role and deficiency symptoms of phosphorus (P) in Rice
Occurrence of P deficiency
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.
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Role and deficiency symptoms of phosphorus (P) in Rice
Corrective measures (P)
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.
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Role and deficiency symptoms of phosphorus (P) in Rice
Sources of phosphatic fertilizers
Name
Single superphosphate
Triple superphosphate
Monoammonium
Formula
Content
Comments
Ca(H2PO4)2 . H2O + 7–9% P, 13–20% Ca,
Soluble, neutral (16–
CaSO4 . 2H2O
12% S
21% P2O5)
Ca(H2PO4)2 . H2O
18–22% P, 9–14% Ca, Soluble, neutral (41–
NH4H2PO4
1.4% S
50% P2O5)
22% P, 11% N
Soluble, acidifying
phosphate (MAP)
(51% P2O5)
Diammonium phosphate (NH4)2HPO4
20–23% P,18–21% N Soluble, acidifying
(DAP)
(46–53% P2O5)
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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 + H3PO4
20% P, 18% N
Soluble (46% P2O5)
Partly acidulated rock Ca3(PO4)2
10–11% P
>1/3 water-soluble
phosphate
Rock phosphate,
(23–26% P2O5)
Ca3(PO4)2
finely powdered
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11–17% P, 33–36%
Very slow acting (25–
Ca
39% P2O5)
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Role and deficiency symptoms of phosphorus (P) in Rice
Appropriate P management results in better yield of rice
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Role and deficiency symptoms of phosphorus (P) in Rice
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.
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