The role of halophytes in phyto-desalination: mechanisms and potential

Cultivating edible salt-tolerant plants (halophytes) for human consumption is increasingly important due to climate change and soil salinization, and offers sustainable agricultural solutions. Optimizing seed germination, the crucial initial stage of crop growth, is essential for enhancing crop production. This study aimed to optimize the germination of edible halophytes under greenhouse conditions, focusing on select soil (salinity and substrate) and non-soil-related factors (chemical and mechanical treatments). The target species were selected for their commercial value and included Mesembryanthemum crystallinum L. (crystalline iceplant), Salicornia ramosissima J. Woods (sea asparagus), Medicago marina L. (sea medick), Ammophila arenaria (L.) Link (European beachgrass), Portulaca oleracea L. (common purslane), and Atriplex halimus L. (Mediterranean saltbush). Salinity negatively impacted germination rates (GRs) and delayed mean germination time (MGT) across species. P. oleracea had the highest GR (95.6%) in coco peat under freshwater irrigation, and the shortest MGT (5.2 days). A. halimus did not germinate under the tested conditions. Scarification with sulfuric acid improved the GR of M. marina by 42.2%, while scarification with ultrasounds improved the GR of A. arenaria by 35.5%. Our results indicate that the choice of substrate and the application of specific treatments like scarification can significantly improve the germination of certain halophyte species under variable saline conditions.

Irrigated areas, mainly in arid regions, are threatened by salinization processes. Climate change inducing temperature rise and rainfall depletion are expected to enhance these processes. Numerical models are often used to predict salinization in the root zone as well as water and solute fluxes reaching groundwater. Climatic data, mainly rainfall, have an important influence on the estimation of those fluxes. The present paper studies the impact of rainfall structure and climate change on soil and groundwater salinization. Soil samples were collected in three drip-irrigated plots in Korba semi-arid coastal plain in Tunisia during dry and wet seasons. Collected field data (water contents and soil salinities) are used to define the initial solute and flow conditions and to estimate the soil hydraulic parameters for numerical modeling. Daily rainfall structure and annual rainfall transition under both Markov Chain and climate change (RCP4.5 and RCP8.5) are assessed. Different climatic scenarios are then introduced as boundary conditions in HYDRUS-1D, to test the influence of rainfall on the salinity evolution in the soil profile and groundwater. Results show that both annual rainfall amounts and daily structure have an impact on soil concentrations and solute fluxes quantities reaching groundwater. The influence of rainfall paths is more important for larger unsaturated zone thickness when considering the dry and median rainfall conditions. Climate change scenarios show significant accumulation of salts in the root zone implying the imperative use of adequate irrigation practices.

The on-going climatic variability and climate change is modifying the environment, farming practices, farmer’s income and overall livelihoods of Bangladesh people particularly crucial for southern coastal region where 30 million people lives near the coast mostly dependent on agriculture and fisheries. A study was conducted to capture the farmer’s perception about climate change, climatic variation, soil salinity, tidal water effect, other bio-physical factors and adaptation measures against the changing environments. Six FGD was conducted in different villages of Jhalokati, Pirojpur, Bagerhat and Satkhira district of Bangladesh where climate change effect is more critical. Available climatic and soil salinity data was collected from concerned organizations for evaluation. For collating agricultural adaptation options different agricultural research organization scientists was contacted along with communities own experience and innovation. Community members(both men and women) believe that climate is continuously changing, creating unbearable heat wave round the year except in short winter period, rainfall is erratic and often excessive rainfall in a day/ week, more cyclonic storm, higher tidal water pressure and increased water height in rivers, canal, increased soil and water salinity which causing loss of lives, crops, cultured fish, trees, livestock, houses and other properties. Farmers also reported very limited natural fish availability, increased pest and diseases of crops and diversified health hazards for human.

Observing the influences of climatic and environmental variability over soil salinity changes in the Noakhali Coastal Regions of Bangladesh using geospatial and statistical techniques

The online version contains supplementary material available at 10.1007/s43657-022-00061-2.

In maize fields, few studies have been conducted to identify the temporal trend of soil salinity and formulate optimal irrigation plans under climate change. Therefore, the main goals of this study were to predict changes in soil salinity over 2022–2050 and to formulate an optimal supplemental irrigation plan preventing soil salinity in a South African rainfed maize field. The study used the Global Climate Model (GCM) MPI-ESM1-2-LR to obtain future climate data for the study area from 2022 to 2050 and applied the HYDRUS-1D model to project the effects of these future climate data on soil salinity over the same period and to identify the best irrigation plan under climate change. Two key findings were revealed: first, the combined use of GCMs (i.e., MPI-ESM1-2-LR model) and soil-water models (i.e., HYDRUS-1D) was a powerful tool to identify soil salinity trends and formulate optimal irrigation plan under climate change. Second, in addition to rainfall amount, supplying a limited supplemental irrigation amount equal to 8% of the actual evapotranspiration of maize at the mid-season stage of maize growth can significantly reduce soil salinity (<1.7 dS m−1) and enhance soil moisture under climate change by 2050. These findings will be useful for preventing soil salinity in rainfed maize fields.

Chapter 12 - Soil salinization and climate change

Deficit irrigation (DI) strategies using moderately saline waters save water, but may enhance soil salinization. Based on data gathered during years 2007–2012 in three drip-irrigated grapevine, peach, and nectarine crops subjected to several irrigation and soil-mulching treatments, we assessed trends in root-zone soil salinity [saturation extract electrical conductivity (ECe)], related the changes in soil salinity (ΔECe) to field-wide leaching fraction (LF), evaluated management strategies for soil salinity control, and examined the sustainability of DI strategies under present and expected climate change (CC) scenarios in the Middle Ebro River Basin (ERB, Spain). ECe increased in 82 % of the irrigation seasons and decreased in 75 % of the non-irrigation seasons examined. Soil salinization trends were not apparent during the study years due to these annual salt accumulation–salt leaching cycles. ECe increases were higher in the more severe DI treatments and in the geotextile-mulched soil and lower in the full and less severe irrigation treatments and in the organic-mulched soil. As expected, ΔECe and LF were linearly and negatively correlated (P < 0.01), indicating that soil salinization increased with decreasing LF. These linear relationships provided a way to evaluate best management strategies (increased irrigation, rainfall harvesting, and soil mulching) for soil salinity control. These strategies decreased soil salinization, but did not guarantee the sustainability of severe DIs in the study area. The application of these relationships to the CC precipitation and crop evapotranspiration projections in the ERB shows that the examined DI strategies will be unsustainable due to soil salinization.

&amp;lt;p&amp;gt;Sea level rise (SLR) is a well-documented aspect of anthropogenic climate change which is primary due to the thermal expansion of seawater and melting of ice caps and glaciers (1). Climate change is expected to exacerbate sea-level rise within the next century, much larger than the observations since the beginning of the recordings. Next to various natural hazards and extreme environmental events such as flooding, the sea level rise poses serious long-standing and possibly irreversible consequences on human timescales in coastal regions. For example, soil salinity is expected to increase near shorelines due to sea level rise. Soil salinization, referring to excess accumulation of salt in soil, is a global problem (2) adversely affecting many environmental and hydrologic processes such as terrestrial ecosystem functioning, water cycle and biodiversity. SLRs shift the saltwater-freshwater boundary in coastal regions which will increase the risk of soil salinization further inland. Considering the growing population living in coastal regions, SLR-driven soil salinization has a severe socio-economic impact posing significant threat to farmlands, wetlands, coastal marshes, forests and other ecosystems. Motivated by the importance of the interaction between SLR, climate change and soil salinization, this study aims to determine how the saltwater-freshwater interface moves under different Representative Concentration Pathways (RCP) scenarios in coastal regions. Groundwater data of coastal wells, Digital Elevation Model&amp;amp;#8217;s and satellite images will be used to highlight areas under high risk of soil salinization. The results will enable us to quantify the possible extent of the soil salinization as a result of SLR under different climate scenarios with the associated socio-economic consequences. Such information could support decision making and sustainable resource management under different RCPs.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;1. Moftakhari H.M., Salvadori G., AghaKouchak A., Sanders, B.F., Matthew, R.A. (2017). Compounding Effects of Sea Level Rise and Fluvial Flooding. Proc. Nat. Acad. Sci., 114 (37), 9785-9790.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;2. Hassani, A., Azapagic, A., Shokri, N. (2020). Predicting Long-term Dynamics of Soil Salinity and Sodicity on a Global Scale. Proc. Nat. Acad. Sci., 117 (52) 33017-33027.&amp;lt;/p&amp;gt;

Drivers of soil salinity and their correlation with climate change

In this study, the usability of some herbaceous halophytes grown naturally in salt marshes that dry most of the year in Central Anatolia Region were investigated in landscape design. Within the scope of the research, in the years of 2016 and 2017, seasonal field studies were carried out in saline habitats in the vicinity of Konya, Ankara, Aksaray and Nevşehir, and taken photographs and herbarium samples of halophytic plant species. The general botanical and ecological characteristics of the selected species are given and the values used in landscape design have been determined considering the aesthetic and functional properties. As a result of the field studies carried out during the vegetation periods, 59 halophytic plant species, belonging to 38 genera and 19 families that could be used in landscape design were identified. The most representative family was the Asteraceae with 11 species, followed by Plumbaginaceae (9 species) and Chenopodiaceae (8 species). The genus Limonium from Plumbaginaceae family is well represented with 8 species for landscape use. The endemism rate of halophytes used in landscape design is 42% (25 species) in the research area. The most common uses in landscape design are determined in roof gardens by 49 species, followed in ground conservation and erosion prevention by 31 species. Since these halophytic species, which are mostly succulent and endemic, are well adapted into both wet and dry areas. Their use in landscape design is of great importance for restoration of arid and barren land, which may increase as a result of global climate change, conservation of biodiversity as well as sustainable agricultural practices.

Changes in climate patterns are dramatically influencing some agricultural areas. Arid, semi‐arid and coastal agricultural areas are especially vulnerable to climate change impacts on soil salinity. Inventorying and monitoring climate change impacts on salinity are crucial to evaluate the extent of the problem, to recognize trends and to formulate irrigation and crop management strategies that will maintain the agricultural productivity of these areas. Over the past three decades, Corwin and colleagues at the U.S. Salinity Laboratory (USSL) have developed proximal sensor and remote imagery methodologies for assessing soil salinity at multiple scales. The objective of this paper is to evaluate the impact climate change has had on selected agricultural areas experiencing weather pattern changes, with a focus on the use of proximal and satellite sensors to assess salinity development. Evidence presented in case studies for Californiaʼs San Joaquin Valley (SJV) and Minnesotaʼs Red River Valley (RRV) demonstrates the utility of these sensor approaches in assessing soil salinity changes due to changes in weather patterns. Agricultural areas are discussed where changes in weather patterns have increased root‐zone soil salinity, particularly in areas with shallow water tables (SJV and RRV), coastal areas with seawater intrusion (e.g., Bangladesh and the Gaza Strip) and water‐scarce areas potentially relying on degraded groundwater as an irrigation source (SJV and Murray‐Darling River Basin). Trends in salinization due to climate change indicate that the infrastructure and protocols to monitor soil salinity from field to regional to national to global scales are needed. Highlights Climate change will have a negative impact on agriculture, particularly in arid regions. Proximal/remote sensors are useful to assess climate change impact on soil salinity across scales. Salt‐water intrusion, shallow water tables and degraded water reuse will increase soil salinity. Infrastructure and protocols to monitor soil salinity across multiple scales are needed.

Soil salinization, referring to the excessive accumulation of soluble salts in soil to a degree that adversely influences vegetation and environmental health, is an unfolding challenge threatening soil health, vegetation and consequently food security with serious socio-economics implications (Hassani et al., 2020, 2021). High salinities in the root zone reduce water and nutrient uptake and result in soil infertility, freshwater contamination at the surface and the loss of biodiversity.Here, we concentrate on soil salinization in coastal areas due to saltwater intrusion and the groundwater salinization, partly influenced by climate change. &amp;#160;In low-lying coastal regions where, saline groundwater levels are shallow, saltwater intrusion poses risks to vegetation and soil health since the soluble salt could be transported toward the surface. This causes soil salinization depending on the competition between upward capillary forces and the limiting downward gravity and viscous forces. Several parameters influence such a competition including soil texture and heterogeneity. We developed a quantitative framework, using software package FEFLOW, to delineate the regional impact of soil textures and arrangements on salt transport toward the surface in low-lying coastal regions. The model includes a wide range of hydrologic, soil and climate related factors such as hydraulic heads, soil properties, and groundwater recharge. We evaluated the performance of the developed model using field data measured in the &amp;#8220;Alte Land&amp;#8221; located in north Germany near the Elbe estuary - an agriculturally significant low-lying region threatened by increasing soil surface salinity.The evaluation of the model against field-data was followed by conducting the simulation under several hypothetical scenarios differing in soil textures, layering and arrangements to investigate how these parameters would influence soil surface salinity driven by the saltwater intrusion in coastal areas. &amp;#160;Our results highlight the prominent effects of different soil textures and arrangements on the regional surface soil salinity and the amount of salt deposited close to the surface. This agrees with the conclusions of laboratory experiments which were conducted in other studies at scales much smaller than the one investigated in our analysis (Shokri-Kuehni et al., 2020). Our results suggest that an effective soil remediation strategy for salinity treatment would require high resolution 3D mapping of soil properties which influences soil salinization. Our findings shed new light on the dominant parameters influencing surface soil salinity in coastal areas threatened by the saltwater intrusion as a result of the projected climate changes.&amp;#160;ReferencesHassani, A., Azapagic, A., Shokri, N. (2020). Predicting Long-term Dynamics of Soil Salinity and Sodicity on a Global Scale, Proc. Nat. Acad. Sci., 117 (52), 33017-33027.Hassani, A., Azapagic, A., Shokri, N. (2021). Global Predictions of Primary Soil Salinization Under Changing Climate in the 21st Century, Nat. Commun., 12, 6663.Shokri-Kuehni, S.M.S., Raaijmakers, B., Kurz, T., Or, D., Helmig, R., Shokri, N. (2020). Water Table Depth and Soil Salinization: From Pore-Scale Processes to Field-Scale Responses. Water Resour. Res., 56, e2019WR026707.

Simulation for response of crop yield to soil moisture and salinity with artificial neural network

The on-going climatic variability and climate change is modifying the environment, farming practices, farmer’s income and overall livelihoods of Bangladesh people particularly crucial for southern coastal region where 30 million people lives near the coast mostly dependent on agriculture and fisheries. A study was conducted to capture the farmer’s perception about climate change, climatic variation, soil salinity, tidal water effect, other bio-physical factors and adaptation measures against the changing environments. Six FGD was conducted in different villages of Jhalokati, Pirojpur, Bagerhat and Satkhira district of Bangladesh where climate change effect is more critical. Available climatic and soil salinity data was collected from concerned organizations for evaluation. For collating agricultural adaptation options different agricultural research organization scientists was contacted along with communities own experience and innovation. Community members(both men and women) believe that climate is continuously changing, creating unbearable heat wave round the year except in short winter period, rainfall is erratic and often excessive rainfall in a day/week, more cyclonic storm, higher tidal water pressure and increased water height in rivers, canal, increased soil and water salinity which causing loss of lives, crops, cultured fish, trees, livestock, houses and other properties. Farmers also reported very limited natural fish availability, increased pest and diseases of crops and diversified health hazards for human.