What is soil salinity.pptx

what is soil salinity their effect on crop and soil

1. Muneeb Ur Rehman Saline Soil Agricu Agricu ltural 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.

4. 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 .

5. 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.

6. Other common effect

7. 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)

8. 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

9. 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.

10. 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.

11. 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.

12. 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