Soil salinization decreases the production potential of up to 46 million ha per year.
What is soil salinization?
Salt-affected soils consist of saline and sodic soils, occur in all continents and under almost all climatic conditions, but their distribution is relatively more extensive in the arid and semi-arid regions compared to the humid regions. Soil salinization and sodification are major soil degradation processes threatening ecosystem and are recognized as being among the most important problems at a global level for agricultural production, food security and sustainability in arid and semi-arid regions. There are extensive areas of salt-affected soils on all the continents but their extent and distribution have not been studied in detail. At a global span, according to the report of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) of 2018:
- about 190 million acres are completely lost;
- 150 million acres are damaged;
- 2.5 billion acres are impacted by salinization.
What Causes Soil Salinization?
Soil salinization occurs when soluble salts are retained in the earth. It happens either naturally or because of improper anthropogenic activities, particularly farming practices. Besides, some earths are initially saline due to low salt dissolution and removal. Soil salinization causes include:
- dry climates and low precipitations when excessive salts are not flushed from the earth;
- high evaporation rate, which adds salts to the ground surface;
- poor drainage or waterlogging when salts are not washed due to a lack of water transportation;
- irrigation with salt-rich water, which amplifies salt content in earths;
- removal of deep-rooted vegetation and a raised water table as a consequence;
- leakage from geological deposits and penetration into groundwater;
- sea-level rise when sea salts seep into lower lands;
- breezes in the coastal areas that blow salty air masses to the nearby territories;
- seawater submergence followed by salt evaporation;
- inappropriate application of fertilizers when excess nitrification accelerates soil salinization.
What are the impacts of soil salinization?
Salt-affected soils have serious impacts on soil functions leading to an array of consequences, including significant decreases in agricultural productivity, water quality, soil biodiversity, and soil erosion. Salt-affected soils have a decreased ability to act as a buffer and filter against pollutants. The degradation of soil structure and functions of global ecological systems such as the hydrological, nutrient and biogeochemical cycles, impair the provision of ecosystem services, which are critical for supporting human life and biodiversity. Salt-affected soils reduce both the ability of crops to take up water and the availability of micronutrients. They also concentrate ions that are toxic to plants and may degrade the soil structure.