Role and Deficiency Symptoms of Secondary Nutrients in Rice

Role and Deficiency Symptoms of Secondary Nutrients in Rice


Introduction

In today’s agriculture with the emphasis on higher crop yields, there is an increased need for calcium, magnesium and sulphur, called secondary nutrients.

Some of the factors responsible for this increased need are:

Increased use of higher analysis fertilizers.

Increased crop yields.

High crop utilization of calcium, sulphur and magnesium.

Introduction

Decreased use of sulphur containing insecticides and fungicides

Government restrictions on sulphur emissions to the atmosphere.

Many soils are acidic and need limestone, which provides calcium.


Many soils are deficient in sulphur and magnesium.

Increased awareness of sulphur and magnesium needs.

Sulphur (S): role in rice

It is a constituent of essential amino acids (cysteine, methionine, and cystine) involved in chlorophyll production and is thus required for protein synthesis, and plant function and structure.

Sulphur is also a constituent of coenzymes required in protein synthesis. It is contained in the plant hormones thiamine and biotine, both of which are involved in carbohydrate metabolism.

S is also involved in some oxidation-reduction reactions.

It is less mobile in the plant than N so that deficiency tends to appear first on young leaves. S deficiency affects human nutrition by causing a reduction in cysteine and methionine content in rice.


Sulphur deficiency in rice:


http://www.flickr.com/photos/philrice/3176059128/

http://www.flickr.com/photos/philrice/3176059128/

Causes of S deficiency

Low status of S in the soil.

Depletion of soil S as a result of intensive cropping systems.

Use of S-free fertilizers

S concentrations in groundwater, however, may range widely. Irrigation water contains only small quantities of SO4

2-.

S contained in organic residues is lost due to burning.


Occurrence of S deficiency in soils

Soils containing allophane (e.g., Andisols)

Soils with low organic matter status.

Highly weathered soils containing large amounts of Fe oxides.


Sandy soils, which are easily leached.

Corrective measures of S deficiency S deficiency is easily corrected or prevented by using S-containing fertilizers (Table 1)

Table 1. Sulphur containing fertilizers for rice


Name Formula Content CommentsAmmonium sulphate (NH4)2SO4 24% S Quick-acting

Single superphosphate Ca(H2PO4)2 . H2O

+ CaSO4 . 2 H2O

12% S, 7–9 % P, 13–20% Ca

Soluble, quick-acting

Potassium sulphate K2SO4 18% S Quick-acting

Magnesium sulphate (Epsom salt)

MgSO4 . 7 H20 13% S, 10% Mg Very quick-acting

Kieserite MgSO4 . H20 23% S, 17% Mg Quick-acting

Langbeinite K2SO4 . MgSO4 18% K, 11% Mg, 22% S Quick-acting

Gypsum CaSO4 × 2 H2O 17% S Slow-acting

Elemental S S 97% S Slow-actingS-coated urea CO(NH2)2 + S 6–30% S, 30–40% N Slow-acting

Magnesium (Mg): role in rice

Magnesium activates several enzymes.

It is a constituent of chlorophyll, and is involved in CO2 assimilation and protein synthesis.

Mg also regulates cellular pH and the cation-anion balance.


Magnesium deficiency symptoms in rice


It is very mobile and is retranslocated easily from old leaves to young leaves. Deficiency symptoms therefore tend to occur initially in older leaves.

Mg-deficient plants are pale-coloured with interveinal chlorosis first appearing on older leaves, and later on younger leaves as deficiency becomes more severe.

Green coloring appears as a "string of beads" compared with K deficiency, in which green and yellow stripes run parallel to the leaf.


With moderate deficiency, plant height and tiller number are not affected greatly.

Reduced number of spikelets and reduced 1,000-grain weight. May reduce grain quality (% milled rice, protein, and starch content).


Leaf number and leaf length are greater in Mg-deficient plants and Mg-deficient leaves are wavy and droopy due to an expansion in the angle between the leaf sheath and leaf blade.



Orange-yellow interveinal chlorosis usually appears first on older leaves

Chlorosis may also appear on the flag leaf.


Mg deficiency may also be induced by large applications of K fertilizer on low Mg status soils (IRRI, Phillipines)


Causes and occurrence of Mg deficiency

Important cause of Mg deficiency is low available soil Mg. Furthermore, decreased Mg uptake due to a wide ratio of exchangeable K:Mg (i.e., >1:1) causes its deficiency.

Mg deficiency is more common in rainfed lowland and upland rice where soil Mg has been depleted because of the continuous removal of Mg in crop products without recycling crop residues or replacing removed Mg with mineral fertilizer. Many rainfed rice soils are inherently deficient in Mg.


Corrective measures of Mg deficiency Apply Mg-containing fertilizers (Table 2). Rapid correction of Mg deficiency symptoms is achieved by foliar application of liquid fertilizers containing Mg (e.g., MgCl2).

Table 2. Magnesium containing fertilizers for rice.

Name Formula Content CommentsKieserite MgSO4 . H20 17% Mg, 23% S Soluble, quick-acting

Langbeinite K2SO4,

MgSO4

18% K, 11% Mg, 22%S

Quick-acting

Magnesium chloride

MgCl2 9% Mg Soluble, quick-acting

Magnesium oxide

MgO 42% Mg Slow-acting, for foliar application

Magnesite MgCO3 25-28% Mg Slow-acting

Dolomite MgCO3.

CaCO3

13% Mg, 21% Ca Slow-acting, content of Ca and Mg varying


Calcium (Ca): role in rice

Calcium is a constituent of Ca pectates, important cell wall constituents also involved in biomembrane maintenance.

Helps in cell wall stabilization as an enzyme activator, in osmoregulation, and in the cation-anion balance.

Ca is less mobile in rice plants than Mg and K. Because Ca is not retranslocated to new growth, deficiency symptoms usually appear first on young leaves. Ca deficiency also results in impaired root function and may predispose the rice plant to Fe toxicity.

An adequate supply of Ca increases resistance to diseases such as bacterial leaf blight or brown spot.


Calcium deficiency symptoms in rice

Symptoms are usually visible only under severe Ca deficiency (e.g., pot experiments, exhaustion experiments).

The tips of the youngest leaves become white or bleached, rolled, and curled.

Necrotic tissue may develop along the lateral margins of leaves and old leaves eventually turn brown and die.

Ca deficiency may resemble B deficiency and plant tissue analysis may be required to distinguish the cause of symptoms.


The tips of the youngest leaves may become chlorotic-white (IRRI, Phillipines)

Calcium deficiency symptoms in rice


Causes of Ca deficiency

Small amounts of available Ca in soil (degraded, acid, sandy soils)

Alkaline pH with a wide exchangeable Na:Ca ratio resulting in reduced Ca uptake. Use of irrigation water rich in NaHCO3.

Excessive N or K fertilizer application resulting in wide NH4:Ca or K:Ca ratios and reduced Ca uptake.

Excessive P fertilizer application, which may depress the availability of Ca (due to formation of Ca phosphates in alkaline soils).


Occurrence of Ca deficiency in soils

Acid, strongly leached, low-CEC soils in uplands and lowlands

Soils derived from serpentine rocks

Coarse-textured sandy soils with high percolation rates and leaching

Leached, old acid sulphate soils with low base content


Corrective measures of Ca deficiency

Apply CaCl2 (solid or in solution) or Ca-containing foliar sprays for quick treatment of severe Ca deficiency.

Apply gypsum on Ca-deficient nonacidic soils, e.g., on sodic and high-K soils.

Apply lime on acid soils to raise pH and Ca availability.

Apply Mg or K in conjunction with Ca because Ca may cause deficiencies in these nutrients.

Apply pyrites to mitigate the effects of NaHCO3-rich water on Ca uptake.


Corrective measures of Ca deficiency

Table 3. Calcium containing fertilizer sources for rice.

Name Formula Content Comments

Calcium chloride

CaCl2 .. 6

H2O

18% Ca Soluble, quick-acting, does not raise pH

Gypsum CaSO4 .. 2

H2O

23% Ca, 18% S

Slightly soluble, slow-acting, for saline and alkaline soils

Dolomite MgCO3 +

CaCO3

13% Mg, 21% Ca

Slow acting , content of Ca and Mg varying

Lime CaCO3 40% Ca Slow-acting, for acid soils


Let us sum up

Calcium, magnesium and sulphur are essential for rice crop.

Variety of roles are being played by these secondary nutrients in rice

Their deficiency under certain situations produces varying symptoms, which eventually affect the growth and yielding ability of rice.

The deficiency of sulphur is more common than deficiency of calcium and magnesium in rice soils in India.

The deficiency of these nutrients can be corrected by applying appropriate fertilizers and crop management practices.


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Role and Deficiency Symptoms of Secondary Nutrients in Rice