Читать книгу Physiology of Salt Stress in Plants - Группа авторов - Страница 15

Primarily, hydro‐geological activities contribute in escalating soil salinity and sodicity. Moreover, the soil is generated because of the weathering actions on intermediate and basic igneous rocks; sandstones already carry salt as a primary constituent. In the regions with moderate to low rainfall, a greater rate of evapotranspiration induces higher salinity and sodicity. Furthermore, coastal regions with tidal exposure may also develop salinity problems. A study conducted by Sultana et al. (2001) depicted that rice yield in coastal Asia gets often impaired due to the intrusion of saline Indian Ocean water. Inland precipitation also surprisingly elevates the soil sodicity. It is evidenced that rainwater can constitute up to a few milligrams of salt against each kilogram of a downpour with an electrical conductance (EC) value of 0.01 dS/m (Cucci et al. 2016; Corwin and Yemoto 2017; Hossain, 2019).

However, the deteriorating impacts of artificially induced salinity are more predominant. Over‐irrigation or saline water irrigation is cited as one of the prima facie reason for human‐induced salinity. Roughly, it is estimated that globally half of the irrigated lands are anyhow saltaffected. Other than irrigation, probable sources of inland salinity are the following:

1 Salt accumulation: Effluent and waste discharged into the surface water bodies from the industries and effluent treatment plants (ETPs) beyond absolute concentrations can accumulate and form salt films downstream to cause acute saline toxicity (Naidoo and Olaniran 2013).

2 Reduction of greenbelt: Deforestation accelerates the salinization process by facilitating salt movement both through upper and lower soil layers. It further results in depleted annual precipitation and elevated soil temperature. Subsequent heating and cooling promote wear and tear, higher runoff, and substantial sedimentation to cause flooding and salt assimilation.

3 Overdosing fertilizers: Post‐Green Revolution, the usage of chemical fertilizers, herbicides, and pesticides has abruptly increased. Overdosing often results in underutilization and accumulation.

4 Excessive grazing: Areas with scarce soil cover often suffer the root zone saline toxicity due to overgrazing. Surface waterlogging (i.e. either due to over‐irrigation or riverbed sedimentation) in such areas can cause elevation of the water table and thereby facilitating salt migration from the deep aquifers.