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SALINITY MANAGEMENT IN

COASTAL SOILS

M A SALEQUE

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Outline

What is salinity?

Types of salinity.

Causes of salinity. Measurement of salinity.

How salinity causes harm to plants?

Adaptive mechanisms of plants to saline soils. How to manage saline soils?

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What is soil salinity?

Accumulation of salts in soils at a level higher

than 4 dS/m.

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Types of salinity

Inland salinity

Coastal salinity

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Inland salinity

Due to groundwater irrigation.

Due to natural salinity in landscape.

Industrial waste disposal.

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Coastal salinity

Salt water intrusion.

Flooding with saline tidal water.

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Coastal salinity

Sea floor (max

1340 m)

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Coastal salinity

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Coastal salinity

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Coastal salinity

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Measurement of salinity

Saturation extract

Field measurement

Caution calibration of machine

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Unit of salinity

Deci simen/m (dS/m)

ppm

ppt

1 dS/m = 670 ppm

1 dS/m = 0.67 ppt

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How salinity harms plant

Water stress due to osmotic effect

Toxicity from excess Na uptake

Imbalance Na/K and Na/Ca ratio. Leakage of K from cytoplasm.

Affect enzymatic activity that are mediated by

K.

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Symptoms of salt injury in rice plant

Stunted growth

Reduced number of tillers

Reduced root growth

Rolling of leaves Drying of leaves

White leaf tips

White blotches on the leaves

Sterile spikelets

Delayed flowering or no flowering at all.

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Symptoms of salt injury in rice plant

Stunted growth

Reduced number of tillers

Reduced root growth

Rolling of leaves Drying of leaves

White leaf tips

White blotches on the leaves

Sterile spikelets

Delayed flowering or no flowering at all.

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Symptoms of salt injury in rice plant

Stunted growth

Reduced number of tillers

Reduced root growth

Rolling of leaves Drying of leaves

White leaf tips

White blotches on the leaves

Sterile spikelets

Delayed flowering or no flowering at all.

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Symptoms at different salinity

EC

(dS/m)

Salinity

level

Symptoms

3.0 4.5 Medium

salinity

Nearly normal growth; some

reduction in tillering; someleaves are rolled.

5.0 8.5 High

salinity

Reduced growth and tillering;

most leaves are rolled; very

few are elongating

9.0 14.5 Very high

salinity

Growth completely ceased;

most leaves get dry and wither

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Sensitivity of rice plants to salinity at

different growth stages

Growth phase Growth stage Sensitivity

Vegetative Germination Tolerant

Seedling Sensitive

Tillering Tolerant

Stem elongation Tolerant

Reproductive Panicle initiation Sensitive

Flowering SensitiveHeading Sensitive

Ripening Milk grain Tolerant

Dough grain Tolerant

Mature grain Tolerant

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How salinity harms plant

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Irrigation water quality

Classes Quality EC (dS/m)

Class 1 Excellent 0.25

Class 2 Good 0.25 0.75

Class 3 Permissible (leaching needed ifused)

0.76 2.0

Class 4 Doubtful (good drainage needed

if used)

2.01 3.00

Class 5 Unsuitable 3.00

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Annual salinity trend

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Adaptive mechanisms of plants to

salinity

Osmotic adjustment by the accumulation ofhigh concentrations of either inorganic ions orlow molecular weight organic solutes.

Restricted uptake of Na ions exclusion effect.

Rapid vegetative growth dilution effect

Accumulation of salt in older leaves so that

young leaves can grow compartmentalization.

Maintaining high K/Na ratio.

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Management of coastal saline soils

Embankment to protect intrusion of saline

water.

Irrigation with non-saline water. Flushing with non-saline water.

Growing salt-tolerant variety.

Growing cover crops during rabi season. Gypsum application if soils pH > 8.5.