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Salt accumulation in bare strips under film-mulched drip irrigation is a global concern as it adversely affects soil quality and hinders sustainable agricultural development in arid and semi-arid regions. This study aims to investigate the spatial distribution of soil moisture and salt under various planting patterns and assess the lateral salt accumulation effect in bare strips. Seven treatments were implemented based on the local cotton planting pattern, including the local classical planting pattern (LTP), mulch width of 220 cm (WFM-220), spacing of 90 cm (SFM-90), mulch width of 40 cm (WFM-40), spacing of 10 cm (SFM-10), ridge tillage (TFM-RT), and ditching (TFM-D), varying in mulch width, spacing, and tillage method in bare strips. Additionally, the performance of the HYDRUS-2D model was evaluated by comparing simulated and observed values using field data. The results revealed that (I) the WFM-220 cm treatment exhibited the best water content retention under mulched film, with lower salt accumulation in the surface bare strip (0–20 cm soil layer); (II) all treatments with narrow rows showed desalination effects in the 0–40 cm soil layer, with salt content reductions ranging from approximately 13% to 38% compared to the initial values; (III) under the LTP treatment, the lateral salt discharge effect in the bare strip of the 0–40 cm soil layer was the best, regardless of mulch width and spacing, with a salt accumulation rate up to three times higher than the initial value, and even up to four times higher in the 0–10 cm layer; (IV) the TFM-RT treatment exhibited the best salt accumulation ability on the surface bare strip; and (V) the HYDRUS-2D model proved to be an effective tool for studying the dynamic regulation mechanism of water and salt with root mean square error values ranging from 0.079 to 0.106 cm3·cm−3 for soil water content and from 0.044 to 0.079 dS·m−1 for electrical conductivity, indicating good agreement between simulations and observations. [ABSTRACT FROM AUTHOR]

With the increasing shortage of water resources, the current management of saline–alkali lands in semi-arid and arid areas has gradually transformed from "flooding irrigation with drainage" in the past to the combination of controlling regional water and salt balance, phytoremediation, and comprehensive utilization of halophyte resources. However, soil salinization caused by natural and anthropogenic factors has still been a major global environmental problem, which changes the chemical and physical properties of soil, deteriorates the quality of underground water, and decreases biodiversity, contributing to the loss of soil productivity and the succession of the halotolerant species. Euhalophytes, as the materials for phytoremediation, have been confirmed to be effective species in improving saline–alkali soils. They can redistribute salts in soil profile through the interaction of their desalinization potential and irrigation water leaching, thereby preventing secondary salinization and improving soil productivity for long-term reclamation of saline soil. In this review, the adaptation mechanisms of euhalophytes to saline soils are generalized from the views of morphological, physiological, and molecular aspects and evaluated for their potential to remediate saline soil through salt removal and promoting leaching. Euhalophytes can not only sequestrate salts inside the central vacuole of cells to tolerate higher salt stress by means of organ succulence, ion compartmentalization, and osmotic adjustment but facilitate water infiltration and salts leaching through root–soil interaction. The root system's mechanical penetration increases soil porosity, decreases soil density, as well as stabilizes soil aggregates. Moreover, the suitability of phytoremediation in arid situations with low precipitation and non-irrigation and some agricultural practices need to be taken into account to avoid salts returning to the soil as forms of litter and deep tillage altering salt distribution. Hence, euhalophytes planting in semi-arid and arid areas should be evaluated from their adaptation, desalinization, and prospective commercial values, such as foods, biofuels, and medical development to alleviate soil secondary salinization crisis and enhance the productivity of arable agricultural land. [ABSTRACT FROM AUTHOR]

Halophytes are capable of resisting salinity, and their root system is the part in direct contact with the saline soil environment. The aim of this study was to compare the responses of root morphology and rhizosphere characteristics to salinity between a halophyte, Suaeda salsa (suaeda), and a glycophyte, Beta vulgaris L. (sugar beet). The soil salt content was set to four levels (0.7, 1.2, 1.7, and 2.7%) by NaCl-treated plants. We investigated the soil pH, EC, nutrients and soil, plant ion (Na+, Cl−, K+, and Mg2+) concentration to evaluate the rhizospheric processes, and salt tolerance of suaeda by the root mat method. The highest biomass was in the 1.2% salt level for suaeda and in the 0.7% salt level for sugar beet. The root length and root surface area of suaeda showed similar trends to biomass, but the root diameter decreased by 11.5–17.9% with higher salinity. The Na+, Cl−, and K+ accumulations in the shoot of suaeda displayed higher than that in sugar beet, while the Mg2+ accumulation was lower in suaeda than that in sugar beet. High salinity resulted in increased pH and EC values in the rhizosphere for suaeda, but lower values of these parameters for sugar beet. Under high salinity, the Olsen phosphorus content was 0.50 g·kg−1 and 0.99 g·kg−1 higher in the rhizosphere than in the non-rhizosphere for suaeda and sugar beet. We concluded that the two species [halophyte, Suaeda salsa (suaeda), and a glycophyte, B. vulgaris L. (sugar beet)] showed diverse approaches for nutrient absorption under salinity stress. Suaeda altered its root morphology (smaller root diameter and longer roots) under salt stress to increase the root surface area, while sugar beet activated rhizospheric processes to take up more nutrients. [ABSTRACT FROM AUTHOR]

Halophytes possess the capacity to uptake high levels of salt through physiological processes and their root architecture. Here, we investigated whether halophyte/non-halophyte intercropping in saline soil benefits plant growth and contains root-dialogue between interspecific species. Field and pot experiments were conducted to determine the plant biomasses and salt and nutrient distributions in three suaeda (Suaeda salsa)/maize (Zea mays L.) intercropping systems, set up by non-barrier, nylon-barrier, and plastic-barrier between plant roots. The suaeda/maize intercropping obviously transferred more Na+ to the suaeda root zone and decreased salt and Na+ contents. However, the biomass of the non-barrier-treated maize was significantly lower than that of the nylon and plastic barrier-treated maize. There was lower available N content in the soil of the non-barrier treated groups compared with the plastic barrier-treated groups. In addition, the pH was lower, and the available nutrient content was higher in the nylon barrier, which suggested that rhizospheric processes might occur between the two species. Therefore, we concluded that the suaeda/maize intercropping would be beneficial to the salt removal, but it caused an adverse effect for maize growth due to interspecific competition, and also revealed potential rhizospheric effects through the role of roots. This study provides an effective way for the improvement of saline land. [ABSTRACT FROM AUTHOR]

Euhalophytes, such as Suaeda salsa, are ideal candidates to remediate heavy metal-polluted saline soils. However, the metal tolerance ability of dimorphic seeds and subsequent seedlings is largely unknown. This study investigated the tolerance of S. salsa seeds to different concentrations of Cu2+ (0–300 mM) and Zn2+ (0–300 mM) during germination and seedling growth stages. Results showed that dimorphic seeds of S. salsa had high metal tolerance during germination, and even germinated under 300 mM Cu and Zn treatments. However, seedling growth was more sensitive to metal solutions and radicle growth was almost completely inhibited by Cu at 10 mM, and by Zn at 50 mM. Germinating seeds and seedlings of S. salsa had a higher metal toxicity threshold of Zn than that of Cu. In all indexes, indexes of radicle were the most sensitive and effective indicator of metal tolerance. Seeds of S. salsa germinated successfully and seedlings survived under high Zn and Cu stress. The results suggest that S. salsa could be sown directly in heavy metal-contaminated soils for phytoremediation. [ABSTRACT FROM AUTHOR]

Soil salinization causes the degradation of soil structure, which seriously affects the global agricultural production. Currently, planting halophytes to improve saline soil has been widely used. However, most of the experiments were short-term, and the effect of long-term continuous cropping of halophytes on soil is still uncertain. This study aimed to investigate the multi-year effect of continuous cropping of euhalophyte Suaeda salsa on soil physicochemical properties. The space-for-time substitution approach was used to compare changes in soil physicochemical indicators under 3-year, 5-year, and 7-year continuous cropping periods of Suaeda salsa under drip irrigation, with bareland(0-year) serving as the control. In the 0–20 cm soil layer, the soil moisture content increased from 10.76% to 11.72–14.92%; in the 0–40 cm soil layer, the average bulk density decreased from 1.61 g cm−3 to 1.45–1.46 g cm−3 (P < 0.05), the average total porosity increased from 40.54% to 45.63–46.82% (P < 0.05), the average content of soil water-stable macroaggregates rose from 2.38% to 3.07–7.42%, and the average clay particle content declined from 20.88% to 16.63–18.63%; in the 0–60 cm soil layer, the average total salt content decreased from 48.11 g kg−1 to 12.43–22.01 g kg−1, and the average soil organic matter(SOM) content decreased from 8.73 g kg−1 to 7.40–8.15 g kg−1; in the 0–100 cm soil layer, the average pH value increased from 7.33 to 7.38–7.75, and the average content of Ca2+, Mg2+, Na+, K+, SO 4 2-, and Cl- all decreased, whereas the average HCO 3 - content increased from 0.16 g kg−1 to 0.25–0.29 g kg−1. After 7 years of continuous cropping, the mean weight diameter (MWD) of 0–40 cm soil layer increased by 19.01%, the sodium adsorption ratio (SAR) of 0–40 cm soil layer decreased by 53.57% (P < 0.05), and the soil hydro-chemical type of 0–100 cm soil layer changed from Cl--Na+·Ca2+ to Cl-·SO 4 2--Na+·Ca2+. The salt accumulation in the aboveground part of Suaeda salsa accounted for only 1.85–4.36% of the annual desalination quantity in the 0–100 cm soil layer. The continuous cropping of Suaeda salsa improved the soil structure and promoted salt leaching, which was the main mechanism of soil salt reduction. The results showed continuous cropping of Suaeda salsa under drip irrigation in arid regions is an effective method to improve saline soil, providing a theoretical reference for long-term continuous cropping of halophytes to improve saline soil in arid regions. • Effects of different planting years of Suaeda salsa on soil quality under drip irrigation were investigated. • Continuous cropping of Suaeda salsa can significantly improve soil structure. • Continuous cropping of Suaeda salsa can sustainedly reduce the average salt content of 0–100 cm soil profile. • Mechanism of saline soil improvement by halophytes under drip irrigation was analyzed. • Continuous cropping of Suaeda salsa will cause SOM reduction and soil alkalization in the early stage. [ABSTRACT FROM AUTHOR]

• Apocynum is widely distributed and geographically diverse plant species. • Apocynum exhibits several medical and economic benefits. • Salt tolerance in Apocynum is associated with better redox- and osmo-regulation. • Apocynum can be used to remediate saline area due to its better ability to remove salts from soil and sequester in leaves. • Both sexual and asexual propagation methods make Apocynum cultivation a great opportunity for the vegetation restoration on saline soils Apocynum belongs to Apocynaceae family, is known as highly stress tolerant plant genus. Apocynum venetum L. and Apocynum pictum Schrenk, locally known as luobuma in China, are used as traditional medical plants and cash crops, and used for the phytoremediation of degraded saline lands. This review was aimed to critically analyzed the biological uses, salt tolerance mechanisms, and propagation methods of both Apocynum species to highlight the significance of the cultivation of Apocynum as a great opportunity for the vegetation restoration in saline soils in the arid region. In saline area, where arable crop production is nearly impossible due to high salt toxicity in soil, cultivation of Apocynum can reduce the levels of salt in soils and can also provide livelihood in the form of high-quality fibre. Critical literature analysis showed that overall salinity tolerance in Apocynum is associated with the regulation of redox regulation and ionic homeostasis, however their molecular regulation has not been identified yet. Findings such as removal of Na+ from soils and enhanced accumulation of flavonoids and antioxidants in leaves under saline environment, are useful in understanding the complex network of salt tolerance in Apocynum. Moreover, the practical adoption and application of different sexual and asexual propagation methods also play an important role in the successful cultivation of Apocynum in saline soils. To sum up, there are broad prospects for vigorously developing Apocynum industry by utilizing saline-alkali lands and carrying out research on cultivation technology and conservation strategy of Apocynum resources in arid lands. [ABSTRACT FROM AUTHOR]

Soil salinization threatens agricultural sustainability, especially for arid and semiarid regions. Planting euhalophytes with drip irrigation is proposed to be a feasible solution for the reclamation of saline soils. Thus, by planting an annual halophyte Suaeda salsa with drip irrigation, we assessed the potential of S. salsa to accumulate high amount of salt from soil and change in soil salinity levels in a three-year field study in arid northwestern China. The aboveground parts of S. salsa contained >20% ash salt on a dry weight basis and Na+ and Cl− were the main components. For each year, salt extraction by the aboveground part of S. salsa was ranged from 3749 to 3911 kg ha−1. Soil salinity dramatically decreased year by year by the cultivation of S. salsa , especially in the topsoil layer (0–40 cm). Our study suggested that consecutive cultivation of S. salsa with drip-irrigation is an efficient method to reclaim saline soil in arid and semiarid regions. [ABSTRACT FROM AUTHOR]

• Bacterial communities were geographically distributed along the longitude gradient. • Salinity affected bacterial diversity but not bacterial abundance. • Salinity was the main environmental driver of bacterial communities. • Salinity levels altered the modularity in the bacterial co-occurrence network. Saline soils suppress plant growth and reduce yield worldwide, thereby pose a serious threat to agriculture. Although microbes drive major biogeochemical cycles and play an integral role in agricultural production, understanding of the microbial distribution patterns in saline agricultural systems remains limited. Here we investigated the co-occurrence and biogeographical patterns of bacterial communities in saline agricultural soils at a regional scale in north-west China. Our results revealed a trend towards increasing bacterial abundance at higher longitudes. By contrast, bacterial diversity exhibited different spatial patterns and declined with increasing salinity. Bacteroidetes , Gammaproteobacteria , Alphaproteobacteria and Gemmatimonadetes were the dominant groups across all soil samples (>5% of all sequences). Additionally, members belonging to Flavobacteriaceae , Cytophagaceae , Halomonadaceae , Acidobacteria and Gemmatimonadetes were identified as indicators across the salinity gradient. Salinity levels also affected the modularity of bacterial co-occurrence networks, with module composition differing between soil salinity levels. Bacteria belonging to Acidobacteria subgroup 4, Acidobacteria subgroup 6, Gemmatimonadetes and Rhodospirillales were statistically identified as the keystone taxa. Geographical distance explained 5.08% of the community variation, whereas soil parameters explained 27.26% variation, with salinity as a major driver explaining 15.18% of the variation. Therefore, bacterial communities were geographically distributed along the longitude gradient, and soil salinity was more important than geographical isolation in shaping soil bacterial communities. Taken together, our results indicate that salinity alters bacterial network modularity and drives spatial distribution in saline agricultural soils. [ABSTRACT FROM AUTHOR]