In saline soil excess amount of salts are present. Mainly NaCl is present in high amount. Salts of Mg, K, Ca also present in saline soil at low concentration. A white crust of salts is deposited on the surface of soil due to salinity. So other name of saline soil is white alkali.
Characteristics of saline soil:
Normally pH remains below 8.5 ( 7.0 to 8.5 ) in saline soil. Electrical conductivity values remain greater than 4dS/m. In saline soil exchangeable sodium percentage is less than 15 at 250 c. The surface of coastal soils are slightly to moderately saline and sub-surface layers and substrata of the soils are highly saline.
Salinisation:
The process by which salts are accumulated in the soils is known as salinisation. Flooding of coastal water is the main cause of salinisation. There are some others factors such as a) tidal action, b) depth of the ground water table and salt deposits, c) the nature of the soils, d) the effect of the river system and their discharges, e) precipitation and f) the slope of the ground and the proximity to drainage channels.
Causes of salinity:
1. Poor drainage system of agricultural lands and seepage of saline water to the lands.
2. Irrigation with the high salt containing water to the agricultural fields.
3. Continuous shrimp cultivation in agricultural land is a major cause of introducing salt in soils.
4. High water table with high salt concentration in coastal area increases the possibility of introduction of saline water in coastal area.
5. High temperature and low rainfall also increase the salinity in saline soils.
6. Weathering of salt containing parent materials is one of the major cause of the increasing salinity in soils.
7. Tidal flooding is the main cause of introduction of saline water.
8. In dry season, capillary movement of saline water ( upward ) causes salinity in soils.
Location of saline soil:
More than 2.9 ha land of Bangladesh is affected by saline water. Every year it is increasing. Chittagong, Barishal, Noakhali, Khulna and Patuakhali districts are mostly affected by saline water.
The AEZs that are affected by saline water are
1. Gangas Tidal Floodplain ( AEZ 13 )
2. Young Meghna Estuarine Floodplain ( AEZ 18 )
3. Chittagong Coastal Plain ( AEZ 23 )
4. St Martin’s Coral Island (AEZ 24 )
Constrains to crop productions:
1. Water use efficiency is reduced.
2. Occurrence of organic soil and extreme acid sulphate soil is one of the major constrains.
3. It reduces nitrate absorption.
4. In dry season that means in Robi season crop cultivation is hampered.
5. There is lack of fresh surface and ground water.
6. It inhibits germination of crop seeds.
7. Breakdown of soil aggregates is occurred.
8. Also ionic imbalance in soil is occurred.
Management of saline soil for crop production:
1. Flooding with fresh water is very effective though it is sometimes difficult.
2. Fertilizers should be applied in balance.
3. Irrigation must be done before sowing seeds or transplanting.
4. Higher seed rate and close planting is a effective practice against saline soils.
5. We have building embankment to control saline water in coastal area.
6. Application of organic matter and green manure during dry season.
7. Reducing shrimp cultivation in coastal area.
8. Cultivating salt tolerant crops.
Result of salinity:
1. Growth of plants and yield reduced detrimentally.
2. Degradation of land is occurred.
3. The quality of water is reduced.
4. Infrastructures near the coastal area or saline soil are damaged rapidly than non coastal area.
