Abstract
Salinization and sodification are important processes of soil degradation affecting irrigated lands. A large proportion of the global irrigated area is affected by some degree of soil salinity or sodicity caused by the intensification of irrigation. The increase of the frequency of adverse climatic conditions, like high temperatures and variations in precipitation patterns caused by climate change, will potentially amplify these processes in arid, semi-arid, and Mediterranean areas. The use of integrated approaches for the spatial and temporal prediction of the risk of salinization and sodification in irrigated areas is of great value, helping in the decision-making regarding land uses and choice of more suitable agricultural practices. In this study, based on key criteria for the assessment of irrigation-related salinization processes (e.g., climate, topography, soil drainage, water quality for irrigation, and crop irrigation method), we developed a methodology for the prediction of soil salinity and sodicity risk in irrigated lands, using two composite indices, the Salinization Risk (RSA) index and the Sodification Risk (RSO) index. The application of these indices to a real scenario (a Mediterranean area in Southern Portugal) showed that 67% of the potentially irrigated area presented a low risk of salinity development, 68% had a moderate risk of sodification, and 16% was of high risk of sodicity development. Areas under moderate risk of salinization (26%) were mostly characterized by low slopes and fine-textured soils, like Luvisols and Vertisols, with limited drainage conditions. Areas with high risk of soil sodification presented a large incidence of low slope terrain, moderate-to-restricted soil drainage, in high clay content Luvisols, Vertisols and Cambisols, and land use dominated by annual crops irrigated with surface or sprinkler systems. These risk prediction tools have the potential to be used for resource use planning by policymakers and on-farm management decision by farmers, contributing to the sustainability of irrigated agriculture in Mediterranean regions.
Highlights
Salinization and sodification are major processes of soil degradation threatening land productivity and global food security [1]
We aimed to: (i) present an overview of major criteria and respective indicators related with soil salinity and sodicity induced by irrigation; (ii) propose two composite risk indices, for soil salinization and soil sodification assessment in large areas, based on climate, irrigation water quality, soil information, and land-use data; (iii) present the risk indices when applied in a real scenario in a Mediterranean area in Southern Portugal
A temporal trend of degradation in water quality for irrigation was reported [11,12], that could be attributed to the expansion of the irrigation area, with the concomitant intensification of agriculture, and to the increase of drier conditions resulting from climate change
Summary
Salinization and sodification are major processes of soil degradation threatening land productivity and global food security [1]. According to Zhou et al [29], the use of risk indices or frameworks for soil salinity assessment may facilitate communication among scientists, policymakers, and practitioners by providing a basis for evaluating the environmental impact of agricultural practices and government programs and policies These risk indices are GIS-based in order to ascertain priority areas, predict where it may occur in the future, and determine appropriate management options to mitigate salinity risk [30]. We aimed to: (i) present an overview of major criteria and respective indicators related with soil salinity and sodicity induced by irrigation; (ii) propose two composite risk indices, for soil salinization and soil sodification assessment in large areas, based on climate, irrigation water quality, soil information, and land-use data; (iii) present the risk indices when applied in a real scenario in a Mediterranean area in Southern Portugal
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