2. About 2.8 million hectares of land in Bangladesh is
within the grip of salinity which is equal to about one
fifth of the total area.
Out of these coastal areas about 0.833 million hectares
of the arable lands, which constitutes about 52.85% of
the net cultivable area in 64 upazillas of 13 districts
are affected by varying degrees of soil salinity.
3. A considerable success in boosting up of food production
could be achieved by the efficient utilization of this vast
area of land.
The salinity prevalent in Noakhali, Khulna, Comilla,
Barisal and Patuakhali districts has penetrated upto
about 151.4 km and 46.3 km inland from coasts of Khulna
and Barisal, respectively.
It is the view to the experts, that with the introduction of
high yielding varieties of different crops these lands may
become suitable for crop lands following proper planned
cultivation.
7. The soils which contain sufficient water-soluble salts
in the root zone affect or impair plant growth in
general, may be termed as saline soil.
According to Biswas and Mukherjee (1987), saline soils
are soils containing excess of nutral soluble salts
dominated by chlorides and sulfates that affect plant
growth.
Definition of saline soil
8. Formation of Saline Soil
According to Boyer (1970) the most important sources of
salts in the formation of saline soils are
•Intrusion of sea water
•Marine sediments
•Saline ground water
•Saline irrigation water
•Poor drainage
•Seepage from canals, and
•Arid climate
9. In areas of low rainfall, salts formed during the
weathering of soil minerals are not fully leached.
The salinity sources in Bangladesh are quite different
from the other saline areas of arid and semi arid
regions of the world. Here, the main cause of salinity is
marine origin. Sea water salinity surrounding the
coastal areas of Bangladesh is induced by
1) salt water intrusion during cyclone or typhoon,
2) direct inundation by saline or brackish water,
10. 3) heavy withdrawal of water upstream by neighboring
country, which results saline water movement along
the main rivers and tributaries,
4) upward or lateral movement of saline ground water
during the dry season and
5) withdrawal of ground water in the northwest for
irrigation which encourages saline water movement in
the aquifers, and since fresh water is costly and rare,
farmers have tendency to irrigate land with saline
water flowing through rivers.
11. Patchy stand and stunted growth are the most obvious
features observed in plants due to salinity. No yield
enhancement at any salinity level.
Sodium chloride and sodium sulphate salinities
suppressed the growth of peanut. High concentration
of both NaCl and Na2SO4 greatly reduced the shoot
growth, biomass and dry weight of all plant parts.
Shoot length was also reduced at all concentrations of
both salts
12. Salt tolerance of plants is associated with salt
exclusion, which is the ability of plants to restrict the
uptake and/or transport of salt between roots & shoots.
Evidence has shown that shoot growth of Etrog citron
and Kharna khatta was reduced significantly by 50mm
NaCl, but growth of Ranpur lime plants showed a
marked reduction only at 100ml NaCl
Salinity treatment with 48 mM NaCl in solution culture
reduced dry matter production by 65% in shoots and
43% in roots of sunflower plants.
13. The aim of reclamation is to remove salinity from the root
zone within permissible limits, so as to restore the
productivity of salt-affected soil.
Before starting the reclamation of saline soil knowledge
of the following is essential.
1. Quality of irrigation water.
2. Nature and distribution of salt in the coastal zone.
3. Level of sub-soil water.
4. Drainage condition.
14. Reclamation of Saline Soil
Eradication or
removal of the salts
-Leaching
-Irrigation
management
-Drainage
management
-Beneficial use of
multiple water
resources
Conversion of some
of the salts to less
injurious forms
-By using gypsum
-By using elemental
sulfur and sulfuric
acid
Designated
control
-Mulching
-Crop choice
-Pre-plant
irrigation
15. The most common method used to the free soil of
excess salts is installation of drainage systems and
leaching or flushing.
A combination of two, flooding after field drainage
ditches have been installed, is the most through and
satisfactory.
The salts that dissolve are leached from the solum and
drained away.
Eradication or Removal of the Salts
16. Application of excess water, above evapotranspiration
requirements to leach salts from the root zone of soils
may effectively control salinity.
The most common method by which salt is removed is
by leaching it out of the root zone with water.
An equation for this is
DiCi – DdCd = 0
Di (the volume of water per unit area of land is
expressed by its depth),
Ci , initial salt concentration,
Dd, the volume of water drained out of the soil,
Cd the salt concentration which drained out by water.
Leaching
Salinity Control during Irrigation
17. While it is difficult to forecast accurately the tolerance of
crops, the comparative data presented in the following
table may be helpful.
Table : Relative tolerance of certain plants to salty soils:
Tolerant Moderately
tolerant
Moderately
sensitive
Sensitive
Barley, grain
Bermuda grass
Bougainvillea
Cotton
Date
Barley, forage
Beet, garden
Broccoli
Brome grass
Clover, berseem
Alfalfa
Broad bean
Cauliflower
Cabbage
Clover
Apple
Apricot
Bean
Blackberry
Carrot celery
18. Source: Cited by Nyle C. Brady (1990) in
“The Nature and Properties of Soil” as
modified from Carter (1981).
Tolerant Moderately
tolerant
Moderately
sensitive
Sensitive
Natal plum
Mutall alkali grass
Rescue grass
Rosemary
Sugar beet
Salt grass
Wheat grass
Wild rye
Wheat grass, tall
Fig
Orchard grass
Oats
Rye, hay
Sorghum
Sudan grass
Wheat
What grass, western
Trefoil, birds foot
Corn
Cowpea
Cucumber
Lettuce
Pea
Peanut
Rice, paddy
Soya-bean
Sweet clover,
timothy
Grape fruit
Lemon
Onion
Orange
Peach
Pineapple, Guava
Potato
Rose
Strawberry,
Tomato
19. Bangladesh is a vast delta having 14.2 million ha, of which
roughly coastal brackish waters cover 17%.
At present only 5% of the coastal brackish water region is
under coastal aquaculture mainly for shrimp farming.
Gradually shrimp production is increasing through horizontal
expansion of the farming area.
So that, coastal aquaculture would develop as a good source
of animal protein for the growing population.
A foreign currency earner and as well as maintainer of
ecological balances in the brackish-water region.
Correct planning, regulation and motivation are needed to
develop an environment friendly coastal aquaculture
program to avoid ecological disasters in a land scarce and
densely populated like Bangladesh.
20. Development of coastal area soils for agricultural purposes
is of great importance for a small country like Bangladesh.
The reclamation of saline soils and practicing cultivation
of salinity resistant crop varieties should be emphasized.
Another potentiality of our coastal soils is the shrimp
production and export of which can earn substantial
foreign currency.
So, the soils’ potentialities should be explored as well as
managed for agricultural sustainability of future
Bangladesh.
