Artificial utilization of saline-sodic land promotes carbon stock: The importance of large macroaggregates.

Soil aggregates are essential functional units involved in soil carbon sequestration, particularly in saline-sodic soils prone to severe carbon loss. In the present study, the distribution of aggregate-associated carbon fractions and their influencing factors were investigated after artificial utilization of saline soil in the Songnen Plain, Northeast China. Physicochemical properties, enzymatic activities, and bacterial communities were measured in various hierarchical aggregates among two natural land-use types (saline wasteland and degraded grassland) and three anthropogenic land-use types (artificial forest, upland field, and paddy field). The results indicated that, compared to saline wasteland, anthropogenic land use was witnessed an increase in macroaggregate proportions, and PF in large macroaggregates increased the most, while UF and FL were mainly increased in small macroaggregates. After transforming from natural land to anthropogenic land, the aggregate-associated carbon fractions (total organic carbon, readily soluble organic carbon, dissolved organic carbon, and microbial biomass carbon) increased, especially in small macroaggregates. All enzyme activities increased after artificial utilization, hydrolase (urease, amylase, and invertase), catalase, and ß-glucosidase activities were highest in the small macroaggregates. Bacterial biomass was increased in all three aggregate types compared to natural land. Due to the influence of various factors on soil carbon storage, through partial least squares path modeling revealed that large macroaggregates were conducive to carbon storage. These findings suggested that artificial utilization of saline soil can increase large macroaggregate proportions and the abundance of aggregate-associated carbon, resulting in increased soil carbon stocks, with PF having the greatest carbon sequestration capacity.

Irrigation water quality, gypsum, and city waste compost addition affect P dynamics in saline-sodic soils.

The amendments used for sodicity reclamation also profoundly influence P dynamics and leaching losses. This study characterized the effect of irrigation water quality on P dynamics and leaching from saline-sodic soil during reclamation utilizing gypsum alone or in combination with manure and city compost. Changes in properties of unleached and leached soils were fitted with labile P pools using redundancy analysis. The relation between leachate properties and P loss was explained by means of monitoring leachate properties up to ten pore volumes. During incubation, the water-extractable P (PH2O) concentration was greater than Olsen's P (PNaHCO3) in all treatments. The PNaHCO3 decreased in proportion to the amount of gypsum applied. Applying the organics with gypsum increased the PNaHCO3, PH2O, and organic P concentration compared to gypsum alone. The labile P pools in soil were positively correlated with HCO3- content (r = 0.39-0.77; P < 0.05) of leached and unleached soils. Adding gypsum and compost caused a 10-14% decrease in cumulative P leaching. The cumulative P leaching were greater with rainwater compared to saline water of SAR (sodium adsorption ratio) 5 and 15. The CO32-, HCO3-, pH, and SO42-content of the leachate explained about 71% variability in total P leaching (adj. R2 = 0.71; P < 0.001). This study concludes that low electrolyte water had a greater risk of P leaching and associated environmental pollution. Leaching of the saline-sodic soil amended with gypsum and city waste compost with low SAR saline water can reduce P leaching compared to good quality rainwater.

Desulfurization steel slag improves the saline-sodic soil quality by replacing sodium ions and affecting soil pore structure.

Flue gas desulfurization steel slag (DS), a solid waste produced by coal power plants and steelworks, was proposed as an amendment for the remediation of saline-sodic soil. A pot experiment including three dosages of DS alone (1%, 5%, 10% w/w) and their combination with fulvic acid (FA, 1%, w/w) was conducted to evaluate the potentials of DS as an amendment and to explore remediation mechanism of DS combined with FA on saline-sodic soil. The soil salinity, nutrition, pore structure, water retention, consistency, and desiccation cracking of DS and FA-amended soils were determined. Application of DS resulted in a significant reduction of pH, sodium adsorption ratio (SAR), and exchangeable sodium percentage (ESP) of saline-sodic soil. The DS amendment significantly increased the 6-15 µm pore volume of soil. The combination application of DS and FA showed better effect than the DS alone. The DS amendments at 5% and 10% significantly increased the field water capacity, permanent wilting point, and available water content of the soil, whereas significantly decreased the plastic limit, liquid limit, and plastic index. The DS alone and combined with FA could effectively control the development of desiccation cracking, reduced significantly the crack area density and average width of cracks of the soil. Consequently, the improvement of alkalinity and soil physical properties by DS amendment significantly increased the yield of alfalfa grown on saline-sodic soil. The remarkable improvement of physical properties of saline-sodic soil contributed to the decrease of SAR and ESP by the Ca2+ in DS replacing the Na + at soil colloid sites. Our results suggested that DS amendments alone or combined with fulvic acid have great potential as saline-alkali soil amendment.

Reclamation effects of distinct volumes and concentrations of CaCl2-amended brackish ice in different saline-sodic soils.

The proper usage of marginal soil and water resources has major implications for the sustainability of agriculture, such as brackish water and saline-sodic soils. The saline soils can be ameliorated though melting process of calcium-containing brackish ice, however, the optimum concentration and volume of brackish ice (water) for the reclamation of different saline-sodic soils remain to be determined. In this study, 108 soil columns representing four Ice salinity levels (16, 26, 36, 46 mmolc L-1) and three Pore Volumes (2/3, 1.5, 2.5 PV) of calcium-amended brackish ice were tested to reveal the reclaiming effect on a range of saline-sodic soils. The linear mixed model (LMM), multiple regression equation, and principal coordinate analysis (PCoA) were applied to calculate the amelioration effect in terms of three factors: Ice volume, Ice salinity and Column depth. Our results showed that the soil salinity and sodicity generally decreased with increasing Ice volume and Ice salinity, and the saline-sodic soils with low exchangeable sodium percentages (i.e. ESP 20) were more sensitive to Ice salinity, with high salinity (26-46 mmolc L-1) and large volume (2.5 PV) of brackish ice reaching a better amelioration effect. The effect of Ice volume became more dominant in medium and high ESP soils (ESP 40 and ESP 70), whereas the high salinity combined with low volume of brackish ice would lead to worse soil properties, especially at the bottom layers. Meanwhile, the Column depth factor had a considerable effect on the soil chemical properties, with the variance explained ranging from 18.6% to 36.0%. These results provide theoretical guidance in the rational use of calcium-amended brackish ice and highlight the necessity to take layer effect into consideration for reclaiming saline-sodic soils.

Heavy metal pollution risk of desulfurized steel slag as a soil amendment in cycling use of solid wastes.

The by-product of wet flue gas desulfurization, desulfurized steel slag (DS), had chemical characteristics like natural gypsum that can be used to improve saline-sodic soil. However, contamination risk of heavy metals for cycling utilization of DS in agriculture was concerned mostly. Both pot and field experiments were conducted for evaluating the potential pollution risk of DS as the amendment of saline-sodic soil. Results showed that application of DS decreased the contents of Cd, Cu, Zn, and Pb, while significantly increasing chromium (Cr) content in DS-amended soils. The field experiment demonstrated that the migration of heavy metals (Cd, Zn, Cu, and Pb) in the soil profile was negligible. The application of DS at the dosage of 22.5-225 tons/ha significantly increased the Cr content in alfalfa (Medicago sativa L.) but lower than the national standard for feed in China (GB 13078-2017). DS altered the chemical fraction of heavy metals (Zn, Cu, and Pb), transferred exchangeable, reducible into oxidizable and residual forms in DS-amended soil. Application of DS combined with fulvic acid (FA) could effectively reduce the movement of heavy metals in soil and the accumulation of Cr in alfalfa. Based on our results, DS was a safe and feasible material for agricultural use and presented relatively little pollution risk of heavy metals. However, the results also showed that DS to a certain extent had a potential environmental risk of Cr if larger dosages of DS were used.

Effective removal of sodium ion as efflorescence at soil surface using ammonium salts.

The existing methods for reclamation of saline-sodic soils are expensive, time-consuming, and require skilled engineering approaches. Therefore, new and fast techniques should be developed for the reclamation of these soils. This study was undertaken to evaluate if harvesting excessive salts via the soil with ammonium hexacyanoferrate (II) (AH) and ammonium perchlorate (AP) [0, 10, 20 and 40 mmol kg-1] is possible through dendritic crystal growth above the soil surface. Application of crystallization inhibitors increased the concentration of salts on the outer surface and thereby increased pHe at the top of the soil. Whereas the pHe of 0-5 cm layers were obtained as 7.30, 7.36 and 7.84, it increased to 9.94, 9.84 and 8.45 in 15-20 cm layers with 10, 20 and 40 mmol kg-1 AH application doses, respectively. Except for 5-10 cm of control and 10 mmol kg-1 AP application, the lowest pHe values were obtained from the 0-5 cm and gradually increased from bottom to top. For all AH and AP application doses, the highest electrical conductivity (ECe) values were obtained from the 15-20 cm and significantly increased from bottom to top. Application of AH and AP have transformed exchangeable Na+ to water-soluble Na+ and this situation has caused an increase in the concentration of water-soluble Na+ throughout the soil column. AH and AP applications have decreased exchangeable sodium percentage (ESP) in all of the layers. Whereas the ESP of control was 70.07% in 0-5 cm layer, it decreased to 62.44, 55.63 and 53.76% with 10, 20 and 40 mmol kg-1 AH application doses, respectively. Similar decreases were obtained for 5-10, 10-15 and 15-20 cm layers. Results obtained have shown that application of AH and AP to saline-sodic soil is an effective reclamation material to remove salts from soil surface within a short time, particularly in arid climates.

Impact of using magnetic water on the micro structure of leached saline-sodic soil.

Structural changes in the porous media are critical in evaluating the soil pore system and other physical properties of leached soil. In this work, the combination of selected physical parameters such as bulk density and hydraulic conductivity with images of scanning electron microscopic (SEM) was used to study the impact of five levels (1, 3, 5, 7, and 9 magnets) of magnetically treated water (MTW) on the structural changes in pore spaces of leached high saline-sodic soil, compared with leached soil with non- magnetically treated water (NMTW) and unleached soil. Results show that leaching saline-sodic soil with MTW leads to a remarkable increase in soil pore network as confirmed by SEM observations and ImageJ software program. The influence of MTW is important in all cases but the changes in pores of leached soil were mainly observed when the magnetic fields of 7 and 9 were used. It has been found that the value of total percentage area of pores in the leached soil was found to be 7.55 and 9.53, respectively, while the total percentage area of pores in both leached soil with NMTW and unleached soil were 0.69 and 0.1 respectively. It can be concluded that MTW can improve the physiochemical properties of soils in two ways: first, it accelerates the solubility of salts and increases calcium ion available on the soil exchange surface which displaced a higher concentration of adsorbed sodium ions. Second, the changes in the microstructure lead to improved soil porosity combined with saturated hydraulic conductivity and bulk density. This study will provide a method for using magnetic water technology to improve soil properties greatly by increasing soil porosity. Through this porosity, water, solutes, and gases can diffuse through the ground, thus increasing exchange processes.

Soil bacterial microbiota predetermines rice yield in reclaiming saline-sodic soils leached with brackish ice.

BACKGROUND: Saline-sodic lands threaten the food supply and ecological security in the western Songnen Plain of northeast China, and the gypsum is commonly adopted for restoration. However, the dynamics of soil bacterial community and the correlation with crop yield during restoring processes remain poorly understood. Here, we elucidated the soil chemical properties and bacterial communities and their associations with rice yield under different flue gas desulphurization gypsum (FGDG) application rates combined with brackish ice leaching. RESULTS: The increased application rate of FGDG generally improved soil reclamation effects, as indicated by soil chemical properties, bacterial diversity, and rice yield. Compared with fresh ice irrigation, the rice yield in brackish ice treatment increased by 15.84%, and the soil alkalinity and sodium adsorption ratio (SAR) decreased by 35.19% and 10.30%, respectively. The bacterial alpha diversity significantly correlated and predicted rice yield as early as brackish ice melt, suggesting the bacterial diversity was a sensitive indicator in predicting rice yield. Meanwhile, the bacterial communities in the control possessed a high abundance of oligotrophic Firmicutes, while eutrophic bacterial taxa (e.g. Proteobacteria) were enriched after brackish water irrigation and FGDG application. Moreover, we also established a Random Forest model and identified a bacterial consortium that explained an 80.0% variance of rice yield. CONCLUSION: Together, our results highlight the reclaiming effect of brackish ice in the saline-sodic field and demonstrate the sensitivity and importance of the soil bacterial community in predicting crop yield, which would provide essential knowledge on the soil quality indication and bio-fertilizer development for soil reclamation. © 2021 Society of Chemical Industry.

Use of a stabilized sewage sludge in combination with gypsum to improve saline-sodic soil properties leached by recycled wastewater under freeze-thaw conditions.

Soil salinization is a major environmental hazard that limits agricultural production. Using sewage sludge and recycled wastewaters in amelioration of saline-sodic soils is one of the most effective ways to dispose waste. However, a very low initial permeability of soil in the freeze-thaw conditions can make improvement difficult. Therefore, column experiments at a soil depth of 15 cm have been conducted to determine the effects of the combination of four stabilized sewage sludge doses (0, 50, 100, 150 t ha-1), three freeze-thaw cycles (0, 5, 10 times) and two water types (FW: freshwater, RWW: recycled wastewater) on gypsum-treated saline-sodic soil properties. The effects of non-saline-sodic RWW on the soil properties were similar to the FW in total 22.5 cm leaching amount. Compared to gypsum alone and initial values, sewage sludge increased wet aggregate stability, organic matter, total N and exchangeable Ca + Mg while it decreased pH, exchangeable Na and CaCO3. Saturated hydraulic conductivity was not induced by sewage sludge although exchangeable sodium percentage and electrical conductivity were reduced by 44% and 63.6%, respectively. Negative effects of freeze-thaws on hydraulic conductivity and salinity and sodicity elimination were not observed, while pH and aggregate stability were negatively affected from ten freeze-thaws. Overall, it can be concluded that the improvement of hydraulic conductivity is attributed to the further improvement of soil structure from more strong wet aggregate stability via additional sewage sludge and leaching amounts.

Desodification from calcareous saline sodic soil through phytoremediation with Phragmites australis (Cav.) Trin. ex Steud. and gypsum.

The reclamation of saline sodic soils requires sodium removal and the phytoremediation is one of the proven low-cost, low-risk technologies for reclaiming such soils. However, the role of Phragmites australis in reclaiming saline sodic soils has not been evaluated extensively. The comparative reclaiming role of P. australis and gypsum was evaluated in a column experiment on a sandy clay saline sodic soil with ECe 74.7 dS m-1, sodium adsorption ratio (SAR) 63.2, Na+ 361 g kg-1, and pH 8.46. The gypsum at 100% soil requirement, planting common reed (P. australis) alone, P. australis + gypsum at 50% soil gypsum requirements, and leaching (control without plant and gypsum) were four treatments applied. After 11 weeks of incubation, the results showed that all treatments including the control significantly reduced pH, EC, exchangeable Na+, and SAR from the initial values, the control being with least results. The gypsum and P. australis + gypsum were highly effective in salinity (ECe) reduction, while sodicity (SAR) and Na+ reductions were significantly higher in P. australis + gypsum treatment. The reclamation efficiency in terms of Na+ (83.4%) and SAR (86.8%) reduction was the highest in P. australis + gypsum. It is concluded that phytoremediation is an effective tool to reclaim saline sodic soil.

Use of textile waste water along with liquid NPK fertilizer for production of wheat on saline sodic soils.

A field experiment in collaboration with a private textile industry (Noor Fatima Fabrics Private (Ltd.), Faisalabad) was conducted to evaluate the effect of disposed water from bleaching unit, printing unit and end drain for improving growth and yield of wheat under saline sodic soil. Textile waste water along with canal water (control) was applied with and without liquid NPK fertilizer. The application of liquid NPK fertilizer with end drain waste water increased plant height, spike length, flag leaf length, root length, number of tillers (m(-2)), number of fertile tillers (m(-2)), 1000 grain weight, grain yield, straw yield and biological yield up to 21, 20, 20, 44, 17, 20, 14, 44, 40 and 41%, respectively compared to canal water (control). Similarly, the NPK uptake in grain was increased up to 15, 30 and 28%, respectively by liquid fertilizer treated end drain water as compare to canal water with liquid fertilizer. Moreover, concentration of different heavy metals particularly Cu, Cr, Pb and Cd was decreased in grains by application of waste water along with liquid NPK. The result may imply that waste water application along with liquid-NPK could be a novel approach for improving growth and yield of wheat in saline sodic soils.

Remediation of saline-sodic soil with flue gas desulfurization gypsum in a reclaimed tidal flat of southeast China.

Salinization and sodicity are obstacles for vegetation reconstruction of coastal tidal flat soils. A study was conducted with flue gas desulfurization (FGD)-gypsum applied at rates of 0, 15, 30, 45 and 60Mg/ha to remediate tidal flat soils of the Yangtze River estuary. Exchangeable sodium percentage (ESP), exchangeable sodium (ExNa), pH, soluble salt concentration, and composition of soluble salts were measured in 10cm increments from the surface to 30cm depth after 6 and 18months. The results indicated that the effect of FGD-gypsum is greatest in the 0-10cm mixing soil layer and 60Mg/ha was the optimal rate that can reduce the ESP to below 6% and decrease soil pH to neutral (7.0). The improvement effect was reached after 6months, and remained after 18months. The composition of soluble salts was transformed from sodic salt ions mainly containing Na(+), HCO3(-)+CO3(2-) and Cl(-) to neutral salt ions mainly containing Ca(2+) and SO4(2-). Non-halophyte plants were survived at 90%. The study demonstrates that the use of FGD-gypsum for remediating tidal flat soils is promising.

Remediation of soda-saline-alkali soil through soil amendments: Microbially mediated carbon and nitrogen cycles and remediation mechanisms.

Due to the high salt content and pH value, the structure of saline-sodic soil was deteriorated, resulting in decreased soil fertility and inhibited soil element cycling. This, in turn, caused significant negative impacts on crop growth, posing a major challenge to global agriculture and food security. Despite numerous studies aimed at reducing the loss of plant productivity in saline-sodic soils, the knowledge regarding shifts in soil microbial communities and carbon/nitrogen cycling during saline-sodic soil improvement remains incomplete. Consequently, we developed a composite soil amendment to explore its potential to alleviate salt stress and enhance soil quality. Our findings demonstrated that the application of this composite soil amendment effectively enhanced microbial salinity resistance, promotes soil carbon fixation and nitrogen cycling, thereby reducing HCO3- concentration and greenhouse gas emissions while improving physicochemical properties and enzyme activity in the soil. Additionally, the presence of CaSO4 contributed to a decrease in water-soluble Na+ content, resulting in reduced soil ESP and pH by 14.64 % and 7.42, respectively. Our research presents an innovative approach to rehabilitate saline-sodic soil and promote ecological restoration through the perspective of elements cycles.

Quantitative evaluation and mechanism analysis of soil chemical factors affecting rice yield in saline-sodic paddy fields.

Salinization and sodication have become an important abiotic stress affecting soil fertility and crop production in the western of the Songnen Plain in Northeast China. And rice cultivation is considered as one of the most effective biological methods to reclaim saline-sodic soils and ensure food security. However, it is difficult to select the optimal measures to regulate rice growth for increasing yield, because the independent and comprehensive influences of the soil limitation factors on rice yield are not quantitatively evaluated. In this study, the hierarchical partitioning (HP) and the structural equation model (SEM) were used to quantitatively evaluate the influences of salinization parameters, salt ion concentrations and soil nutrients to identify the dominant limitation factors and obstacle mechanism for rice yield. The results showed that soil pH was the key index in salinization parameters, [CO32- + HCO3-] was the key index in salt ion concentrations and available nitrogen (AN) was the key index in soil nutrients to impact rice yield, which independent influences reached 53.7 %, 45.4 % (negative) and 53.2 % (positive), respectively. Soil pH was determined by [CO32- + HCO3-], and the negative effect of alkali stress on rice yield mainly caused by [CO32- + HCO3-] was greater than that of salt stress mainly caused by [Na+] in saline-sodic paddy fields. Among the soil chemical factors, soil pH and AN were the most important explanatory variables of rice yield in saline-sodic paddy fields, which standardized total effects were - 0.32 and 0.40, respectively. Furthermore, the AN showed a more significant negative correlation with soil pH and a higher yield-increasing potential in severe saline-sodic soils (9 ≤ pH < 10) than that in moderate saline-sodic soils (8 ≤ pH < 9). Therefore, decreasing [CO32- + HCO3-] and increasing the content of AN are key to improve rice yield in saline-sodic paddy fields.

A review of organic and inorganic amendments to treat saline-sodic soils: Emphasis on waste valorization for a circular economy approach.

Soil salinization poses a significant challenge to the sustainable advancement of agriculture on a global scale. This environmental issue not only hampers plant growth and soil fertility but also hinders the advancement of the national economy due to restrictions on plant development. The utilization of organic and/or inorganic amendments has demonstrated the ability to mitigate the detrimental impacts of salt stress on plant life. At the outset, this review, in addition to summarizing current knowledge about soil amendments for saline-sodic soils, also aims to identify knowledge gaps requiring further research. The organic or inorganic amendments modify soil conditions and impact plant development. For instance, organic amendments have the potential to improve the structure of the soil, augment its capacity to retain water, and stimulate microbial activity. As this occurs, salts gradually leach through the porous structure of the soil. Conversely, inorganic amendments, such as gypsum and phosphogypsum, displace sodium from soil-negative sorption sites reducing the salinity, they also increase base saturation, altogether positively impacting plant growth conditions. This review emphasizes that, under adequate rates, the combination of organic and inorganic amendment has a high potential to enhance the poor physicochemical properties of saline-sodic soils, thereby reducing their salinity. Consequently, an in-depth examination of the mineral composition, texture, and chemical composition of the soil is required to choose the most effective amendment to implement. Future research necessitates a thorough investigation of techno-economic and life cycle assessment, with active involvement from stakeholders, to enhance the decision-making process of the amendments in specific localities.

Effects of irrigation and nitrogen fertilization on mitigating salt-induced Na+ toxicity and sustaining sea rice growth.

This study investigated the effects of irrigation and nitrogen (N) fertilization on mitigating salt-induced Na+ toxicity and sustaining sea rice growth for perfecting irrigation and fertilization of sea rice. Three irrigation methods (submerged irrigation, intermittent irrigation, and controlled irrigation), three kinds of N fertilizers (urea, controlled release urea, and mixed N fertilizer), and control treatment without NaCl were set up in a pot experiment of sea rice with NaCl stress. The electrical conductivity in root layer soil of treatment with mixed N fertilizer and intermittent irrigation decreased slowly with the growth of rice and was significantly smaller than that of other treatments with NaCl. The Na+ content in sea rice of intermittent irrigation was the least, and that of submerged irrigation was significantly smaller than that of controlled irrigation, but the K+ and Ca2+ contents of three irrigation treatments were opposite to the Na+ content. The Na+ content of treatment with mixed N fertilizer and intermittent irrigation was the lowest, while the K+, Ca2+, and Mg2+ contents of mixed N fertilizer and intermittent irrigation were the highest in treatments with NaCl. The cell membrane permeability and malondialdehyde contents of rice leaves of mixed N fertilizer and intermittent irrigation were significantly smaller than those of other treatments with NaCl. The rice yield of mixed N fertilizer was significantly greater than that of urea and controlled release urea, and that of mixed N fertilizer and intermittent irrigation was increased by 104, 108, 277, 300, and 334% compared with mixed N fertilizer and submerged irrigation, urea and intermittent irrigation, urea and submerged irrigation, controlled release urea and intermittent irrigation, and controlled release urea and submerged irrigation, respectively. Therefore, the treatment of mixed N fertilizer and intermittent irrigation is worth recommending for being used for planting sea rice on coastal saline-sodic soil.

Structural and Predicted Functional Diversities of Bacterial Microbiome in Response to Sewage Sludge Amendment in Coastal Mudflat Soil.

The study investigated the influence of sewage sludge application at rates of 0 (CK), 30 (ST), 75 (MT), and 150 (HT) t ha-1 to mudflats on bacterial community diversity and predicted functions using amplicon-based sequencing. Soils under sewage sludge treatments, especially the HT treatment, exhibited lower pH, salinity and higher nutrient contents (C, N, and P). Moreover, restructured bacterial communities with significantly higher diversities and distinct core and unique microbiomes were observed in all sewage sludge-amended soils as compared to the control. Specifically, core bacterial families, such as Hyphomicrobiaceae, Cytophagaceae, Pirellulaceae Microbacteriaceae, and Phyllobacteriaceae, were significantly enriched in sewage sludge-amended soils. In addition, sewage sludge amendment significantly improved predicted functional diversities of core microbiomes, with significantly higher accumulative relative abundances of functions related to carbon and nitrogen cycling processes compared to the unamended treatment. Correlation analyses showed that modified soil physicochemical properties were conducive for the improvement of diversities of bacterial communities and predicted functionalities. These outcomes demonstrated that sewage sludge amendment not only alleviated saline-sodic and nutrient deficiency conditions, but also restructured bacterial communities with higher diversities and versatile functions, which may be particularly important for the fertility formation and development of mudflat soils.

Remediation of saline-sodic soil by plant microbial desalination cell.

Saline-sodic soil is widely distributed around the world and has induced severe impacts on ecosystems and agriculture. Plant microbial desalination cell (PMDC) and soil microbial desalination cell (SMDC) were constructed to migrate excessive salt in the soil in this study. Compared with SMDC, PMDCs generated higher voltage ranging from 150 mV to 410 mV (500Ω) and the maximum power density reached 34 mW/m2. Higher desalinization efficiency was obtained by PMDCs, the soil conductivity reduced from initial 2.4 mS/cm to 0.4 ± 0.1 mS/cm and pH decreased from initial 10.4 to 8.2 ± 0.1. Soils desalination in PMDCs was achieved through multiple pathways, including ion migration in PMDCs driven by electrokinetic process, plant absorption and bioremediation by plant roots and anode microorganism activity. Geobacter was the dominant electrogenic bacteria at the PMDC anode. The electrochemical and desalinating performance of PMDCs was enhanced by plants and provided a new method for remediation of saline-sodic soil.

Salt-Tolerant Compatible Microbial Inoculants Modulate Physio-Biochemical Responses Enhance Plant Growth, Zn Biofortification and Yield of Wheat Grown in Saline-Sodic Soil.

A wide range of root-associated mutualistic microorganisms have been successfully applied and documented in the past for growth promotion, biofertilization, biofortification and biotic and abiotic stress amelioration in major crops. These microorganisms include nitrogen fixers, nutrient mobilizers, bio-remediators and bio-control agents. The present study aimed to demonstrate the impact of salt-tolerant compatible microbial inoculants on plant growth; Zn biofortification and yield of wheat (Triticum aestivum L.) crops grown in saline-sodic soil and insight of the mechanisms involved therein are being shared through this paper. Field experiments were conducted to evaluate the effects of Trichoderma harzianum UBSTH-501 and Bacillus amyloliquefaciens B-16 on wheat grown in saline-sodic soil at Research Farm, ICAR-Indian Institute of Seed Sciences, Kushmaur, India. The population of rhizosphere-associated microorganisms changed dramatically upon inoculation of the test microbes in the wheat rhizosphere. The co-inoculation induced a significant accumulation of proline and total soluble sugar in wheat at 30, 60, 90 and 120 days after sowing as compared to the uninoculated control. Upon quantitative estimation of organic solutes and antioxidant enzymes, these were found to have increased significantly in co-inoculated plants under salt-stressed conditions. The application of microbial inoculants enhanced the salt tolerance level significantly in wheat plants grown in saline-sodic soil. A significant increase in the uptake and translocation of potassium (K+) and calcium (Ca2+) was observed in wheat co-inoculated with the microbial inoculants, while a significant reduction in sodium (Na+) content was recorded in plants treated with both the bio-agents when compared with the respective uninoculated control plants. Results clearly indicated that significantly higher expression of TaHKT-1 and TaNHX1 in the roots enhances salt tolerance effectively by maintaining the Na+/K+ balance in the plant tissue. It was also observed that co-inoculation of the test inoculants increased the expression of ZIP transporters (2-3.5-folds) which ultimately led to increased biofortification of Zn in wheat grown in saline-sodic soil. Results suggested that co-inoculation of T. harzianum UBSTH-501 and B. amyloliquefaciens B-16 not only increased plant growth but also improved total grain yield along with a reduction in seedling mortality in the early stages of crop growth. In general, the present investigation demonstrated the feasibility of using salt-tolerant rhizosphere microbes for plant growth promotion and provides insights into plant-microbe interactions to ameliorate salt stress and increase Zn bio-fortification in wheat.

Flue gas desulfurization (FGD) steel slag ameliorates salinity, sodicity, and adverse physical properties of saline-sodic soil of middle Yellow River, China.

Saline-sodic soil is considered the most important low-yield soil in arid and semi-arid regions. Flue gas desulfurization (FGD) steel slag is a kind of by-product from wet FGD process, in which steel slag powder replaces lime as sorbent of SO2 emitted from coal-fired power plants. It could potentially be used to ameliorate saline-sodic soil. In this study, a large-scale field experiment of applying FGD steel slag as a new amendment of saline-sodic soils was conducted in the middle Yellow River, Inner Mongolia, China. The FGD steel slag was applied at a rate of 180 t/ha in 2015, 2016, and 2018, respectively. After FGD steel slag application for 1, 3, and 4 years, the soil samples were collected. The saline-sodic field without FGD steel slag amendment was used as the control treatment (CK). Compared with control, the application of FGD steel slag significantly (p < 0.05) decreased soil pH, electric conductivity (EC), salt content, sodium adsorption ratio (SAR), and exchangeable sodium percentage (ESP) of surface soil in saline-sodic soil. However, FGD steel slag increased the EC and salt content at the lower depth of soil profile because of the salt accumulation leached from surface soil. The FGD steel slag significantly increased the concentration of Ca2+ and reduced the concentrations of Na+, Cl-, CO32-, and HCO3- ions. FGD steel slag was beneficial for improving adverse physical properties of saline-sodic soil. The application of FGD steel slag significantly reduced the plastic index, tensile strength, and the formation of cracking in saline-sodic soil. The FGD steel slag reduced surface area density of crack (Dc) and average crack width (AW) by 49.1% and 58.7%, compared with the control. The reduction of soil cracking was contributed to the release of Ca2+ from FGD steel slag to exchange the Na+ on the soil cation exchange sites, which decrease the clay dispersion in soil. The findings of this study confirmed that FGD steel slag could effectively and rapidly remediate saline-sodic soils through decreasing soil sodicity and improving poor physical properties.