what is soil salinity their effect on crop and soil

1. Muneeb Ur Rehman
Saline Soil
Agricu
Agricultural University Plovdiv, Master’s Student of
Soil Science, Department of Agronomy
Plovdiv, Bulgaria, 2023

2. Contents
• Salinity
• The effect of saline soil on plant growth
• Crop response to salinity
• Relative salt tolerance crops
• Salinity; Alarming situation in Pakistan
• Recommendations for managing soil salinity

3. What is soil salinity and how does the soil becomes saline
• Soil salinity is the salt content in the soil; increasing the salt content is known
as salinization.
• Salinization; A soil may be rich in salts because the parent rock it was formed
contains salts.
• Sea water is another source of salt in low-lying areas along the coast.
• Irrigation water is a very common source of salts in irrigated soils. Most irrigation
waters contain some salts.
• After irrigation, the crop uses the water added to the soil or evaporates directly
from the moist soil.
• The salt, however, is left behind in the soil. If not removed, it accumulates in the
soil; this process is called salinization.
• Very salty soils are sometimes recognizable by a white layer of dry salt on the soil
surface.

5. Cont..
• Salty groundwater may also contribute to salinization.
• When the water table rises the salty groundwater may reach the upper
soil layers and, thus, supply salts to the root zone.
• Soils that contain a harmful amount of salt are often called salty or
saline soils.
• Soil, or water, with a high salt content is said to have a high salinity.

6. The effect of saline soil on plant growth
• Most crops do not grow well on soils that contain salts.
• Salt causes a reduction in the rate and amount of water the plant roots can take up
from the soil.
• Water moves into plant roots by a process known as osmosis, which is controlled by
the level of salts in the soil water and in the water contained in the plant.
• If the level of salts in the soil water is too high, water may flow from the plant roots
back into the soil. This results in dehydration of the plant, causing yield decline or
even death of the plant.
• Salinity affects crop production, pastures and trees by interfering with nitrogen
uptake, reducing growth and stopping plant reproduction.

9. Other common effect

10. Crop response to salinity
• Some crops are more sensitive to salinity than others.
• Crops such as pulses, row crops and special crops are particularly sensitive
to salinity.
• Sensitive crops may exhibit negative effects of salinity at levels <4 dS/m
• An EC of 4 is a general salinity rating for traditional annual crops (wheat,
canola) not significantly affected by soil salinity below 4 dS/m.
• Non-saline (0-2 dS/m)
• Slightly saline (2-4 dS/m)
• Weakly saline (4-8 dS/m)
• Moderately saline (8-15 dS/m)
• Strongly saline (>15 dS/m)

11. Relative salt tolerance crops
EC dS/m Field crops Forages Vegetables Trees/Shrubs
High (16)
Tall wheatgrass Russian wildrye
Slender wheatgrass
Sea buckthorn Silver
buffalo-berry
moderate (8)
6-row barley 2-row barley Fall
rye Winter wheat Spring wheat
Oats Flax Canola
Birds foot trefoil Sweet clover Alfalfa
Bromegrass Crested wheatgrass
Intermediate wheatgrass Meadow
fescue Reed canary grass
Garden beets
Asparagus Spinach
Tomatoes Broccoli
Cabbage
Russian olive Poplar
Apple
Low (4)
Sunflowers Soybeans Corn
Peas Field beans
Timothy White Dutch clover Alsike
clover Red clover
Potatoes Carrots
Onions Strawberries
Raspberries
Common lilac
Manitoba maple
Colorado blue spruce
Cottonwood Birch

12. Salinity; Alarming situation in Pakistan
• The total geographical areas of Pakistan is 80.0 million hectares with a very
good canal irrigated system of about 62,400 km long and mainly confined to
Indus plain, covering an area of 19.43 million hectares.
• In Pakistan, about 6.30 million hectares of land are salt-affected and of which
1.89 hectare is saline, 1.85 million hectares is permeable saline-sodic, 1.02
million hectares is impermeable saline-sodic and 0.028 million hectares is
sodic in nature.
• The location of Pakistan is in arid and semi-arid climatic zones. Generally
high evapotranspiration accumulation on the soil surface. The average summer
temperature is about 40°C.
• The annual rainfall varies between 100 mm to 700 mm throughout the
country.
• The evaporation rate is generally very high and exceeds that of precipitation.
Thus, insufficient rainfall, followed by high evaporative demand and shallow
groundwater depth, enhances the movement of salts toward the soil surface.

13. Recommendations for managing soil salinity
• The only real reclamation procedure for saline soils is to drain the excess
water off the bottom and pour fresh water on the top to flush the salts out
and away” Les Henry, 1990.
• There are no quick or easy solutions to soil salinity. Saline soils can only
be reclaimed by rinsing the salts down and out of the root zone.
• Primary salinity: Due to primary salinity, salinity soils often have high EC
values. These soils are not suited to crop production. The best action for
primary salinity is to leave the affected area in its natural state. If the land
has been tilled, salt-tolerant vegetation should be established.
• Secondary salinity: Saline soils due to secondary salinity may have lower
EC values and may be improved with management.

14. Cont…
• To optimize production in saline discharge areas, water must be utilized
in the adjacent, non-saline recharge areas. This will decrease the
movement of excess water from recharge areas to discharge areas.
• The following are additional recommendations for managing secondary
salinity:
• Eliminate summer fallow – this reduces evaporation, drawing water and
salts to the soil surface.
• Improve drainage to lower the water table and minimize the upward
movement of salts.
• Use recommended fertilizers according to soil test information. There
are no quick chemical fixes to cure soil salinity.

15. Cont..
• Select salt-tolerant crops to grow in discharge areas to reduce evaporation
and maximize soil water use
• Crops that use large amounts of soil water (such as alfalfa, perennial
grasses, corn, sunflowers, and winter wheat) should be planted in recharge
areas – this reduces the amount of excess water that percolates through the
soil and prevents the water table from rising in discharge areas
• Avoid deep tillage on saline soils because it will bring salts to the soil
surface.
• Use manure and crop residues to provide additional organic matter to the
soil. Although increased organic matter does not cure salinity, it reduces
evaporation, improves water infiltration, water holding capacity and tilth
of the soil