Abstract
Salinity and sodicity have been a major environmental hazard of the past century since more than 25% of the total land and 33% of the irrigated land globally are affected by salinity and sodicity. Adverse effects of soil salinity and sodicity include inhibited crop growth, waterlogging issues, groundwater contamination, loss in soil fertility and other associated secondary impacts on dependent ecosystems. Salinity and sodicity also have an enormous impact on food security since a substantial portion of the world’s irrigated land is affected by them. While the intrinsic nature of the soil could cause soil salinity and sodicity, in developing countries, they are also primarily caused by unsustainable irrigation practices, such as using high volumes of fertilizers, irrigating with saline/sodic water and lack of adequate drainage facilities to drain surplus irrigated water. This has also caused irreversible groundwater contamination in many regions. Although several remediation techniques have been developed, comprehensive land reclamation still remains challenging and is often time and resource inefficient. Mitigating the risk of salinity and sodicity while continuing to irrigate the land, for example, by growing salt-resistant crops such as halophytes together with regular crops or creating artificial drainage appears to be the most practical solution as farmers cannot halt irrigation. The purpose of this review is to highlight the global prevalence of salinity and sodicity in irrigated areas, highlight their spatiotemporal variability and causes, document the effects of irrigation induced salinity and sodicity on physicochemical properties of soil and groundwater, and discuss practical, innovative, and feasible practices and solutions to mitigate the salinity and sodicity hazards on soil and groundwater.
Highlights
Introduction iationsIrrigation water usually contains salts that accumulate in the soil over time, causing various problems, including plant growth inhibition, changes in soil properties, and groundwater contamination
Practices such as wastewater irrigation have further exacerbated the problems associated with salinity and sodicity in Australia as it significantly deteriorates the quality of soil and the integrity of the ecological systems [60,61,62]
Both salinity and sodicity have a combined effect on the infiltration rates (Figure 1), and the swelling factor is used to assess the potential impact of irrigation water quality on the infiltration rate
Summary
Quantifying and identifying irrigation-induced salinity and sodicity hotspots is quite challenging because of the high geographic variability and net changes in the salinity and sodicity levels; certain regions mostly in semi-arid and arid regions are at higher risk because of the inherent saline and sodic nature (chemical composition) of the soil [37]. 6.73 million ha of land has been degraded due to salinity and sodicity, which were mainly catalyzed by the introduction of irrigation in western parts of the country [42] It is a major threat in irrigated arid and semi-arid regions of Latin America [43]. Sodicity hazard in Australia has scaled up above 60% of the cultivable land (20 million ha) even though farming is practiced without irrigation under dry conditions [9,59] Practices such as wastewater irrigation (sewage farming) have further exacerbated the problems associated with salinity and sodicity in Australia as it significantly deteriorates the quality of soil and the integrity of the ecological systems [60,61,62]
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