Non-saline Soil Research Articles

Impact of Neem-Coated Urea on NO₃-N and NH₄-N Availability and Growth Performance of Maize in Saline and Non-Saline Soils

This study investigates the effects of neem-coated granular urea on nitrogen volatilization and leaching in maize (Zea mays L.), focusing on nutrient availability (NO3-N and NH4-N) in both normal and saline soils. The pot experiment was conducted in a glass-panelled wire house CRD design with three replications. The experimental treatments included T1 (control without fertilizer), T2 (0.05 % neem-coated granular urea @ 200 kg ha⁻¹ + recommended P and K), T3 (0.08 % neem-coated granular urea @ 200 kg ha⁻1 + recommended P and K), T4 (0.01 % neem-coated granular urea @ 200 kg ha-1 + recommended P and K), and T5 (recommended NPK: 200 kg N ha⁻¹, 90 kg P₂O₅ ha⁻¹, and 60 kg K₂O ha⁻¹). Soil samples were taken prior to planting, one month later, and following harvest in order to examine key chemical components. The results demonstrated that maize growth and nutrient uptake were significantly enhanced by T3 (0.08 % neem-coated urea). Under T3, there was an increase of 34.32 % in shoot length, 50.48 % in fresh weight, and 22.40 % in dry weight. There were notable increases in root length, fresh weight, and dry weight of 36.68 %, 21.32 %, and 46.53 %, respectively. Additionally, in comparison to the control, the T3 treatment increased the plant membrane stability index (MSI), chlorophyll content, and nitrate retention by 21.32 %, 22.13 %, and 17.29 %, respectively. Treatment T3 enhanced potassium content, phosphorus absorption, and nitrogen concentration. According to data, applying 0.08 % neem-coated urea along with recommended levels of potassium and phosphate enhances maize growth, and overall crop productivity. This makes it a feasible substitute for long-term and effective fertilizer application in both normal and salinized soils.

Retrieval of soil moisture in salinized farmland soil by multi-polarization SAR

ABSTRACT Synthetic Aperture Radar (SAR) is a potent instrument for estimating soil moisture across vast farmland areas. However, when soil salinity rises, existing SAR retrieval models for soil moisture become less accurate. Soluble salts in soil water alter the inherent correlation between the SAR backscattering coefficients and soil water, thus compromising the performance of retrieval models. The need to get surface roughness parameters from the field also limits the widespread application of the model. To address these issues, we developed a retrieval model for salty soil moisture assessment under small-scale roughness surfaces. First, we found a method to distinguish between slightly rough and rough surfaces using scattering entropy obtained from full-polarization decomposition. Then, we harnessed the co-polarization ratio to mitigate the effect of surface roughness in slightly rough conditions. Later, we developed a soil moisture retrieval model based on the co-polarization ratio, considering incidence angle, residual roughness, and soluble salt content. The validation of the model was verified using field surveying data, yielding an RMSE of 0.026 cm3 ·cm− 3 for the estimated soil moisture. This accuracy is comparable to or surpasses the level achieved by SAR for non-salinized soil moisture retrieval. Our findings showed that Scattering entropy is an effective parameter for distinguishing scattering mechanisms on farmland surfaces effectively. Specifically, when the scattering entropy of farmland is less than 0.5, the co-polarization ratio can mitigate some surface roughness effects. Additionally, when the soil-soluble salt content is incorporated, our model can accurately estimate the soil moisture of salty soil.

Influence of composted manures and co-composted biochar on growth performance of saffron and soil nutrients under varying electrical conductivity soil conditions: A two-year field study

The stigmas of saffron (Crocus sativus L.) are known as “red gold” for being the most expensive spice of the world. This medicinal crop grows well in the regions with cold winter Mediterranean climate. However, salinity can be one of the limiting factors for its cultivation in these regions. Composted manures and their co-compost with wood-derived biochar as fertilizers in saline soil can reduce the salinity stress on saffron. In this study, the composted manures from dairy farms (FYM), sheep and goats (SG) and poultry (PM) and their co-compost with wood-derived biochar (FYM-B, SG-B and PM-B) were amended in non-saline (EC1:2 0.25 dS m−1, SOM; 9.9 g kg−1) and soil with natural slight salinity (EC1:2; 1.95 dS m−1, SOM; 30.9 g kg−1) soil for two consecutive years with the total amendment rate of 65 t ha−1 for each fertilizer. The saline soil was transported from an agricultural farm (30 km away from research field); whereas, the non-saline soil was not transported and was not cultivated before. The amendment of fertilizers and sowing of corms were conducted at the same time in the mid of August. The stigma yield in saline control soil was significantly lower than non-saline control in both cropping years. In non-saline soil, all fertilizers reduced stigma yield of first-year crop by 14–60 % (P < 0.05). No differences between treatments for the stigma yield of second year crop in non-saline and of first year crop in saline soil were observed. In saline soil, FYM and PM fertilizers increased stigma yield of second year crop by 44 % and 41 %, respectively (P < 0.05). The two-year cumulative agronomic efficiencies for nitrogen and phosphorus and the nitrogen use efficiency for leaf biomass were lower under fertilizer treatments than control in non-saline and saline soil. In non-saline soil the PM-B; whereas, in saline soil all fertilizers (except SG) increased the phosphorus use efficiency of leaves (P < 0.05). The two-year amendment of composted manures and FYM-B in non-saline soil resulted in high uptake of sodium in leaves (P < 0.05); whereas, such effect was not observed for saline soil. Almost all fertilizers increased ∼2–5 fold the concentration of bioavailable phosphorus and ∼2–3 fold the concentration of potassium in non-saline and saline soil (P < 0.05). The positive influence of fertilizers on stigma yield and PUE of leaves of second year crop was observed only for saline soil. Furthermore, contrary to the results for non-saline soil, these fertilizers did not cause an increased uptake of Na in leaves in saline soil. We attribute this effect to the high concentration of SOM and gradual decline in EC (0.94–1.71 dS m−1) over time in saline soil. The gradual improvement in yield (from negative to neutral in non-saline and from neutral to positive in saline soil) was observed over time. Amendment of fertilizers and sowing of corms at same time may be the reason for their negative influence on stigma yield in low SOM-containing non-saline soil.

Inoculation of halotolerant plant-growth-promoting bacteria improved the growth of chia (Salvia hispanica L.) in saline and nonsaline soils

Context Chia (Salvia hispanica L.), a nutrient-rich crop with potential application in different industries, is sensitive to salinity. Halotolerant plant-growth promoting bacteria could be a biotechnological strategy to increase chia’s salinity tolerance. Aims The aim of this study was to determine the morphological and physiological response of chia plants inoculated with free-living halotolerant plant-growth promoting bacteria and grown in saline soils under greenhouse conditions. Methods A total of 15 bacterial treatments were inoculated to plants potted in soils with three electrical conductivity levels: 0.5, 4, and 6 dS m−1. Mortality and morphological and physiological parameters were evaluated. The measured variables were used to calculate a relative growth index. Key results Bacterial inoculation had a positive effect on plants at 4 dS m−1. Plants inoculated with Pseudomonas sp. AN23, Kushneria sp. T3.7, and C6 (Halomonas sp. 3R12 + Micrococcus luteus SA211) exhibited the best morphological and physiological performance (51% longer shoots, up to 90% heavier roots and up to 400% higher photosynthetic rate than control plants). Moreover, plants inoculated with Kushneria sp. T3.7 and C5 (Halomonas sp. 3R12 + Pseudomonas sp. AN23) showed significant increase in stomatal conductance and transpiration rate (up to 12 times) and in proline production (up to 345 μg g−1 leaf fresh weight) with respect to control plants (8 μg g−1 leaf fresh weight) under saline conditions. Conclusions The analysed extremophilic plant-growth promoting bacteria enhanced growth and stress tolerance in chia, a salt-sensitive crop. Implications Free-living plant-growth promoting bacteria isolated from hypersaline environments have potential for bioinoculant formulation for salinity-sensitive crops.

Optimal groundwater depth and irrigation amount can mitigate secondary salinization in water-saving irrigated areas in arid regions

Secondary salinization poses a significant threat to the sustainable development of water-saving irrigation districts. This study aims to explore the spatial and temporal variations in soil salinity and the factors influencing these changes in water-saving irrigation areas in the inland arid regions of Northwest China. The Manas River Irrigation District was selected as the study area. A grid measuring 10 km × 14 km grid was designed to determine the latitude and longitude coordinates of the grid centers, resulting in 66 sample points. Soil samples were collected from these points in 2013, 2014, 2020, and 2021 from the 0100 cm layer to obtain salinity data. Based on existing research and practical conditions in water-saving irrigation areas, 11 factors influencing soil salinity changes were identified, including irrigation area and irrigation amount. Classical statistical methods and interpretable machine learning techniques were employed to analyze the distribution characteristics of soil salinity and the influencing factors. This analysis proposes effective solutions to mitigate potential secondary salinization in irrigation areas. The results revealed that soil salinity in the irrigation area belonged to moderate variation (Cv = 46.74 %51.80 %). The horizontal direction of the irrigation area shows higher salt content in the upstream and downstream areas, and a gradual decrease in variability with increasing depth characterizes the vertical direction. From 2013–2021, soil salinization in the irrigation area gradually decreased. In 2013 and 2014, the area was predominantly covered by mild saline-alkali soil, accounting for 75.1 % and 76.6 % of the total area, respectively. However, in 2020 and 2021, non-saline soils became dominant, covering 60.9 % and 66.5 % of the total irrigation area, respectively. In order of importance, the factors affecting the spatial and temporal evolution of soil salinity are groundwater depth, annual water surface evaporation, water-saving irrigation area, underground water diversion amount, mineralization of groundwater, irrigation amount, surface water diversion amount, and annual rainfall. In the oasis irrigation area, maintaining a groundwater depth of 4.06.0 m and an irrigation amount of 55006000 m3 ha−1 can alleviate the problem of secondary salinization that may result from large-scale development of water-saving irrigation. The findings of this study provide a basis for the prevention and control of soil salinization in water-saving irrigation areas and the development and management of saline land in oasis areas.

Calculating the Soil Freezing Characteristic Curve of Saline Soil With Equivalent State of Bulk Solution

AbstractThe relationship between unfrozen water content and temperature, called as soil freezing characteristic curve (SFCC), is of importance for hydrologic, engineering, environmental issues related to frozen soil. The SFCC of saline soil is essentially a result of phase equilibrium of pore solution, which is similar but not identical to that of bulk solution. However, there is still a vacancy of study on the phase equilibrium of pore solution in frozen soil. In this study, image transformation was used to establish the relationship of phase equilibrium between bulk solution and pore solution, with four introduced parameters. Then, the new model of SFCC for saline soil was proposed based on the equivalent state of bulk solution with Pitzer model and SFCC of nonsaline soil. The model was validated by the experimental data from published articles and showed good performance in calculating SFCC of saline soils regardless of soil type, phase transition path, and soil initial water‐salt condition, and some advantages when compared to other three models. All the four introduced parameters have clear physical meanings and their relationships with soil type and initial salt concentration were discussed. Finally, the evolution of phase diagram from bulk solution to pore solution at icing stage was figured out. Further studies are needed for their relationship at salt crystallization stage. Shifting the research perspective from unfrozen water content to pore solution, this study gives a new approach to research of freezing characteristic of saline soil and could promote hydrological and engineering research in cold regions.

Interactive effects of soil salinity and nitrogen fertilizer types on nitrous oxide and ammonia fluxes

Soil salinization, impaired by climate change and poor management practices, poses a global threat, particularly in arid and semi-arid regions, leading to significant land degradation. This study aims to investigate the effects of different nitrogen (N) fertilizer sources (urea, ammonium-sulfate, and biogas waste) on CO2, N2O, and NH3 emissions and soil enzyme activities in two soil types varying in salinity level (non-saline: EC = 1.15 dS m−1, and saline: EC = 35.80 dS m−1) in a robotized continuous-flow soil incubation system. Our results showed a sharp increase in N2O and CO2 emissions (up to 0.51 ± 0.02 g N2O-N ha−1 day−1, 28.1 ± 3.9 kg CO2-C ha−1 day−1) in non-saline soils following soil rewetting, attributed to bacterial denitrification. However, this pattern was not observed in saline soils, suggesting that salinity causes partial inhibition to the regeneration of soil organic matter mineralization and denitrification processes after rewetting. Although salinity did not alter the overall cumulative N2O losses in any fertilizer treatment, it significantly delayed the evolution of N2O peak during the incubation period. On the other hand, NH3 volatilization was significantly higher in N-fertilized saline soils compared to non-saline soils (241% and 157% in ammonium-sulfate and biogas waste treatments, respectively), except for urea treatment, likely due to the decrease in nitrification rates. Furthermore, the study clearly showed lower soil enzyme activity levels for both nitrate reductase and urease activity. Interestingly, the lowest NH3 emissions were measured in urea treatment in both soils. Overall, our findings highlight the complex interplay between soil salinity, nitrogen fertilizer sources, and microbial processes, significantly influencing gaseous nitrogen emissions and N cycling in agricultural soils. Identifying the specific fertilizer treatments that minimize or maximize gaseous nitrogen losses in varying soil salinity, may guide the selection of appropriate fertilization strategies for farmers and policymakers to mitigate environmental impacts of fertilizer use during agricultural production.

Unveiling the salinity tolerance potential of Armenian Dandur (Portulaca oleracea L.) genotypes: Enhancing sustainable agriculture and food security

This study examines the adaptation of an undocumented halophyte, Dandur, to salt stress in different soil mediums. The Dandur plant physiological, morphological, and biochemical analyses show that it can withstand salinity stress. Dandur plants grown in clay and clay loam soil experienced significant decreases in height and stem diameter under extreme salinity conditions compared to non-saline soil. The fresh weight of root and shoot decreased by 70.4% and 84.8%, respectively, and dry weight by 48.5% and 79.7%. These findings underscore the importance of maintaining saline soil conditions for plant growth. Dandur unique ability to avoid dehydration and maintain growth traits, particularly in clay soil, holds promise for further exploration in agricultural research and food security-related issues caused by climate change in saline areas of Armenia and other European countries.

Growth and production of M6 and M7 black soybean mutant genotypes

Abstract. Anwar S, Kusmiyati F, Lukiwati DR, Sas MGA, Arifah YN. 2024. Growth and production of M6 and M7 black soybean mutant genotypes. Biodiversitas 25: 2541-2546. The seed coat colors of soybeans are yellow, black, green, brown, or bicolor, and in Indonesia, black seed coat color is for used soy sauce. Our black soybean mutation breeding research started with irradiating soybean cultivar Detam 3 with gamma rays at 160, 208, 256, 304, 352, 400, 448, 496, 544, and 592 Gy. Genotypes were selected from M1 (first generation) to M5 (fifth generation) based on saline and/or nonsaline soil productions. This research aims to evaluate the growth and production of sixth-generation (M6) and seven-generation (M7) black soybean mutant genotypes. The research was conducted in Karangharjo Village, Pulokulon Sub-district, Grobogan District, Central Java Province, Indonesia. The plant material was three genotypes of M6 black soybean mutants (BSMG VQ 05-256/1-6-2-28, BSMG VQ 05-400/1-2-2-6 and BSMG VQ 05-256/1-2-9-29), four genotypes of M7 black soybean mutants (BSMG VQ 06-256/1-6-2-28, BSMG VQ 06-400/1-2-2-6 and BSMG VQ 06-256/1-2-9-29 and BSMG VQ 06-256/1-4-2-21) and three cultivar checks (Detam 1, Detam 3/parent variety and Detam 4 variety). The parameters measured consist of plant growth, components, and production. All data collected were subjected to statistical Analysis of Variance (ANOVA); if significantly different, it continued by Duncan Multiple Range Test (DMRT). The results showed that the genotype treatment affected all observed characters except plant height. Selected lines based on the number of leaves, number of pods, number of seeds, weight of 100 seeds, weight of seed, and production were BSMG VQ 05-256/1-2-9-29, BSMG VQ 05-256/1-2-9-29 and BSMG VQ 06-256/1-4-2-21. These selected genotypes provided the prospective source of soy sauce material and needed to examine its stability at different locations (multilocation test).

Nghiên cứu trồng thử nghiệm một số loài tre trong điều kiện đất nhiễm mặn tại huyện Cần Giờ, Thành phố Hồ Chí Minh

Vietnam is one of the most biodiverse countries with high bamboo species and has the potential for planning bamboo to harvesting bamboo shoots. The purpose of this study is to evaluate the growth ability of Dendrocalamus latiflorus and Bambusa cf. beecheyana under 3 salty soil conditions comprising non-saline soils (0.12±0.12 g/kg), slightly saline soils (1.58±0.39 g/kg), and moderately saline soils (2.96±0.87 g/kg) at Can Gio Applied Research and Testing Station, located in Can Gio District, Ho Chi Minh City. The results showed that the survival rate of bamboo species tends to decrease with planting time and the increase of salinity in the soil environment. Tree height, trunk diameter, and number of trees per clump were significantly higher on non-saline soils than on slightly saline soils and both were significantly higher than moderately saline soils (p-value &lt; 0.05). The primary result provides the research base for further planning bamboo to harvesting bamboo shoots in Can Gio district, Ho Chi Minh City.

A simple model of the soil freezing characteristic curve for saline soils with two freezing stages

Soil freezing characteristic curve (SFCC) describes the relationship between unfrozen water and subzero temperature, which is of significance for the simulation of heat, water, salt migration in cold regions. There are two phase transition stages in some saline soils, which is often explained by the phase equilibrium of bulk solution. However, the second phase transition and chemical characteristic of solute are ignored in the current coupling numerical models for freezing-thawing soils. The newest SFCC methods considering abovementioned two items are not applicable to numerical models due to complex calculation or irregularly changeable parameters. To solve those problems, a simple model was proposed in this paper. Firstly, the complete phase diagram of pore solution at icing stage was speculated from published experimental SFCCs of saline soils. Then, the temperatures of saline soils at freezing and eutectic points were quantitative expressed with phase diagram of bulk solution and SFCC of nonsaline soil, and the criteria determining whether single icing stage or icing-eutectic stage occurs in saline soils was proposed. A synthetic index was used to describe the effects of soil matrix and initial solute concentration on the exponent. Only three constant parameters were introduced to reflect the soil matrix effect on phase transition points of pore solution and the influence of chemical characteristic of solute on pore water freezing process. Finally, the model was validated by the experimental data of saline soils and showed good results and ease of use compared to a widely used theorical model for saline soil with single freezing stage and other two models both considering two phase transitions. The work provides a deeper view of freezing process in saline soils and promote the improvement of numerical simulation effect for heat, water and salt migration in seasonal freezing-thawing areas.

Hydrogen sulfide-mitigated salinity stress impact in sunflower seedlings was associated with improved photosynthesis performance and osmoregulation

BackgroundSalinity is one major abiotic stress affecting photosynthesis, plant growth, and development, resulting in low-input crops. Although photosynthesis underlies the substantial productivity and biomass storage of crop yield, the response of the sunflower photosynthetic machinery to salinity imposition and how H2S mitigates the salinity-induced photosynthetic injury remains largely unclear. Seed priming with 0.5 mM NaHS, as a donor of H2S, was adopted to analyze this issue under NaCl stress. Primed and nonprime seeds were established in nonsaline soil irrigated with tape water for 14 d, and then the seedlings were exposed to 150 mM NaCl for 7 d under controlled growth conditions.ResultsSalinity stress significantly harmed plant growth, photosynthetic parameters, the structural integrity of chloroplasts, and mesophyll cells. H2S priming improved the growth parameters, relative water content, stomatal density and aperture, photosynthetic pigments, photochemical efficiency of PSII, photosynthetic performance, soluble sugar as well as soluble protein contents while reducing proline and ABA under salinity. H2S also boosted the transcriptional level of ribulose 1,5-bisphosphate carboxylase small subunit gene (HaRBCS). Further, the transmission electron microscope showed that under H2S priming and salinity stress, mesophyll cells maintained their cell membrane integrity and integrated chloroplasts with well-developed thylakoid membranes.ConclusionThe results underscore the importance of H2S priming in maintaining photochemical efficiency, Rubisco activity, and preserving the chloroplast structure which participates in salinity stress adaptation, and possibly sunflower productivity under salinity imposition. This underpins retaining and minimizing the injury to the photosynthetic machinery to be a crucial trait in response of sunflower to salinity stress.

Enhancing Bean (Phaseolus vulgaris L.) Resilience: Unveiling the Role of Halopriming against Saltwater Stress

Common bean (Phaseolus vulgaris L.), one of the most important cultivated legumes, requires a high level of water. It is included among the most sensitive species to climate change; drought and salinity cause a reduction in photosynthesis, metabolic and enzymatic alterations, and oxidative stress. To improve crop tolerance to salt, seed priming and acclimation can be useful tools. To test the salt tolerance of beans, a preliminary screening was undertaken on four cultivars of P. vulgaris (Black Turtle, Cargamanto, Bola Roja, Borlotto) by exposing the seeds to different levels of salinity. The salt-sensitive cultivar Borlotto was chosen for experimental greenhouse trials to study the effects of halopriming and acclimation. Primed and non-primed seeds were sown in non-saline soil and acclimated for 2 weeks; then, the plants were watered with non-saline and saline solutions for 4 weeks. At the end of this growth period, the primed plants showed a marked increase in salt stress tolerance, improving the chlorophyll content, phenolic compounds, and many enzymes’ activities, in turn reducing the effect of salt on growth and fruit production compared to the non-primed controls. In conclusion, halopriming can be considered a useful tool to enhance salinity tolerance in beans and other salt-sensitive crops.

Characterization and Classifications of Soils in an Experimental Farm in the Tiruvannamalai District, Tamil Nadu, India

It is essential to characterize and classify soil resources in order to plan agricultural land use agroforestry, agri-horticulture and silvipastoral farming systems. In the present study, an attempt was made to characterize and classify the soils occurring on different topography in an experimental farm in Tiruvannamalai District of Tamil Nadu, India. A detailed soil survey was carried out using cadastral map. Physiographically, the area has been characterized into Pediplain shallow weathered and Pediplain moderately weathered which were further subdivided based on slope and erosion categories. Six typical pedons were identified based on landform and their soil morphological properties. The soils were very shallow to moderately deep, dark reddish brown to yellowish red (red soils) in colour with sub-angular blocky in structure, These soils were sandy loam to sandy clay loam in texture, slightly acidic to mildly alkaline (3.28-7.70) in reaction (non-saline soils) and had low to medium (1.2 to 6.4 g/kg) organic carbon content. Calcium and magnesium were the dominant exchangeable cations followed by sodium and potassium. Taxonomically these soils were classified as Typic Rhodustalfs, Typic Haplustalfs, Vertic Haplustepts and Typic Haplustepts at the subgroup level.

ENHANCING SPINACH (SPINACIA OLERACEA L.) SEED GERMINATION, LEAF BIOMASS PRODUCTION UNDER SALINE WATER STRESS: THE IMPLICATIONS OF ZINC AND COW MANURE

Plant growth and productivity is restricted due to significant influence of salt stress on the essential physiological processes. Zinc supplementation holds promise as a technique to improve the resilience under salt stress. An open field experiment was conducted to assess the leaf growth parameters of spinach (Spinacia oleracea) including seed germination, plant area, leaf area, length, width, leaf fresh weight as well as dry weight, and Number of leaves per plant. Spinach plants were irrigated with a defined electrical conductivity (EC) level of 4.16 dSm-1 in clay loam, non-saline soil. Cow manure, a form of organic waste rich in macronutrients and micronutrients was also investigated. This study focuses on examining the response of zinc and cow manure on spinach growth under salinity stress. Salinity stress resulted in reduction in seed germination, leaf area, width, length, leaf fresh and dry weight, with no significant effect on the number of leaves. High doses of zinc and cow manure (0.20g Zinc+ 150g Cow Manure + Salinity) meaningfully enhanced performance by increasing seed germination by 15-20%, leaf area 130 cm2, length 8.41 cm, width 4.8 cm , leaf fresh 0.67g and leaf dry weight 0.51g but didn’t affect the number of leaves. Overall, our results demonstrate that the application of zinc and cow manure induced resistance to salinity stress and impacts positively on Spinach growth. Future research can focus on how zinc affects enzymatic activities and various mechanisms under salt stress.

Salinity decreases the contribution of microbial necromass to soil organic carbon pool in arid regions

Saline soils are widely distributed in arid areas but there is a lack of mechanistic understanding on the effect of salinity on the formation and biochemical composition of soil organic carbon (SOC). We investigated the effects of salinity on the accumulation of microbial necromass under natural vegetation and in cropland in salt-affected arid areas stretching over a 1200-km transect in northwest China. Under both natural vegetation and cropland, microbial physiological activity (indicated by microbial biomass carbon normalized enzymatic activity) decreased sharply where the electrical conductivity approached 4 ds m−1 (a threshold to distinguish between saline and non-saline soils), but microbial biomass was only slightly affected by salinity. These indicated that a larger proportion of microbes could be inactive or dormant in saline soils. The contribution of fungal necromass C to SOC decreased but the contribution of bacterial necromass C to the SOC increased with increasing soil salinity. Adding fungal and bacterial necromass C together, the contribution of microbial necromass C to SOC in saline soils was 32–39 % smaller compared with non-saline soils. Fungal necromass C took up 85–86 % of microbial necromass C in non-saline soils but this proportion dropped to 60–66 % in saline soils. We suggested that the activity, growth, and turnover rate of microbes slowed by salinity was responsible for the decreased accumulation of fungal necromass in saline compared with non-saline soils, while the increased accumulation of bacterial residue in saline soils could be induced mainly by its slower decomposition. Soil microbial biomass was a poor predictor for the accumulation of microbial necromass in saline soils. We demonstrated a reduced contribution of microbial necromass to SOC and a shift in its composition towards the increase in bacterial origin in saline relative to non-saline soils. We concluded that salinity profoundly changes the biochemistry of SOC in arid regions.

Biochar Amendment Alleviates the Combined Effects of Salinity and Drought Stress on Water Productivity, Yield and Quality Traits of Sugar Beet (Beta vulgaris L.)

Salinity and drought are two commonly occurring major threats to agricultural yields worldwide, including sugar beet production. Therefore, this work aimed to determine the effectiveness of biochar amendment in improving soil health and alleviating the combined effects induced by salinity and drought on morphological, physiological and biochemical responses of sugar beet plants. Two field studies were established at the experimental farm of Fayoum University, Egypt over two successive winter seasons (2019/2020 and 2020/2021). The experiments were carried out in a split-split plot design with triplicate including three factors: 1) soil salinity, with two levels of ECe (< 4 dS m−1 as control and 10 dS m−1) as main-plot factor; 2) deficit irrigation regimes (I100, I80, and I60) representing 100%, 80%, and 60% of crop evapotranspiration (ETc), respectively as sub-plot factor; and 3) biochar amendment with three application levels (B0 as control, B10, and B20) corresponding to 0, 10, and 20 t ha−1, respectively as sub-sub plot factor. Drought and salinity stress induced significant reduction in growth attributes, relative water content, membrane stability, relative chlorophyll content (SPAD), yield and yield components of sugar beet plants. Meanwhile, the contents of sucrose, proline, Na, K, α amino-N were substantially increased with increasing stress severity. The application of biochar amendment improved the soil physical and chemical properties, resulting in better morphological, physiological and biochemical responses of saline-drought stressed sugar beet plants. Biochar at level (B20) produced the highest values of root yield (95.02 t ha−1) and sugar yield (20.24 t ha−1) for full irrigated sugar beet plants in non-saline soil. Moreover, the application of biochar enhanced water productivity for drought and saline stressed sugar beet plants. Biochar amendment could be effectively used as a helpful agro-management strategy in alleviating the detrimental impacts of salinity and water stress on sugar beet plants, improving soil quality and enhancing water productivity to ensure water sustainability and food security, especially in areas of limited water supply.

Effects of Land-Use Type and Salinity on Soil Carbon Mineralization in Coastal Areas of Northern Jiangsu Province

Sea level rise due to glacier melting caused by climate warming is a major global challenge, but the mechanism of the effect of salinity on soil carbon (C) mineralization in different land types is not clear. The pathways by which salinity indirectly affects soil carbon mineralization rates need to be investigated. Whether or not the response mode is consistent among different land-use types, as well as the intrinsic links and interactions between soil microbial resource limitation, environmental stress, microbial extracellular enzyme activity, and soil carbon mineralization, remain to be demonstrated. In this paper, three typical land-use types (wetland, forest, and agroforestry) were selected, and different salinity levels (0‰, 3‰, 6‰, and 32‰) were designed to conduct a 125-day laboratory incubation experiment to determine the soil CO2 release rate, soil physicochemical properties, and soil enzyme activities, and to correlate C mineralization with biotic and abiotic factors. A correlation analysis of soil physical and chemical properties, extracellular enzyme activities, and carbon mineralization rates was conducted to investigate their intrinsic linkages, and a multiple linear regression of C mineralization at different sites was performed to explore the variability of mineralization among different site types. Structural equation models were established in the pre- and post-incubation stages to study the pathways of soil C mineralization at different incubation times, and the mechanism of mineralization was further verified by enzyme stoichiometry. The results showed that, at the end of 125 days of incubation, the 32‰ salinity addition reduced the cumulative mineralization of forest and agroforestry types by 28.41% and 34.35%, respectively, compared to the 0‰ salinity addition. Soil C mineralization in the three different land-use types was highly correlated with the active C fractions of readily oxidizable C (ROC), dissolved organic C, and microbial biomass C (MBC) in the soil, with the standardized coefficients of multivariate linear regression reaching 0.67 for MBC in the wetland and −0.843 for ROC in the forest. Under long-term salinity additions, increased salinity would reduce the microbial respiratory quotient value by inhibiting β-glucosidase activity, thus indirectly affecting the rate of CO2 release. With added salinity, the mineralization of non-saline soil was more susceptible to the inhibitory effect of salinity, whereas the mineralization of salinized soil was more controlled by soil C pools.

Greenhouse gas emissions, carbon stocks and wheat productivity following biochar, compost and vermicompost amendments: comparison of non-saline and salt-affected soils

Understanding the impact of greenhouse gas (GHG) emissions and carbon stock is crucial for effective climate change assessment and agroecosystem management. However, little is known about the effects of organic amendments on GHG emissions and dynamic changes in carbon stocks in salt-affected soils. We conducted a pot experiment with four treatments including control (only fertilizers addition), biochar, vermicompost, and compost on non-saline and salt-affected soils, with the application on a carbon equivalent basis under wheat crop production. Our results revealed that the addition of vermicompost significantly increased soil organic carbon content by 18% in non-saline soil and 52% in salt-affected soil compared to the control leading to improvements in crop productivity i.e., plant dry biomass production by 57% in non-saline soil with vermicompost, while 56% with the same treatment in salt-affected soil. The grain yield was also noted 44 and 50% more with vermicompost treatment in non-saline and salt-affected soil, respectively. Chlorophyll contents were observed maximum with vermicompost in non-saline (24%), and salt-affected soils (22%) with same treatments. Photosynthetic rate (47% and 53%), stomatal conductance (60% and 12%), and relative water contents (38% and 27%) were also noted maximum with the same treatment in non-saline and salt-affected soils, respectively. However, the highest carbon dioxide emissions were observed in vermicompost- and compost-treated soils, leading to an increase in emissions of 46% in non-saline soil and 74% in salt-affected soil compared to the control. The compost treatment resulted in the highest nitrous oxide emissions, with an increase of 57% in non-saline soil and 62% in salt-affected soil compared to the control. In saline and non-saline soils treated with vermicompost, the global warming potential was recorded as 267% and 81% more than the control, respectively. All treatments, except biochar in non-saline soil, showed increased net GHG emissions due to organic amendment application. However, biochar reduced net emissions by 12% in non-saline soil. The application of organic amendments increased soil organic carbon content and crop yield in both non-saline and salt-affected soils. In conclusion, biochar is most effective among all tested organic amendments at increasing soil organic carbon content in both non-saline and salt-affected soils, which could have potential benefits for soil health and crop production.

Enhancing salt stress tolerance in kidney beans: The synergistic effects of biochar and salicylic acid in arid and semi-arid regions

Salt stress is one of the most damaging environmental stresses of recent times and poses a significant threat to food security. Here, we conducted an experimental study over two consecutive years (2022–2023) to evaluate the physiological and biochemical characteristics of kidney beans. The study used a randomized complete block design with 4 replications (n = 4). The experiment included three levels of salicylic acid (SA): SA0 (0 mM), SA0.5 (0.5 mM) and SA1 (1 mM). The study also used biochar in four levels, without biochar as the control treatment (B0), regular biochar (Rb) by 2.5 % per soil weight, modified biochar with phosphoric acid (PA) by 1.25 % per soil weight, and modified biochar with sulfuric acid (Sb) by 1.25 % per soil weight. Additionally, salt stress (SS) was induced using NaCl in three levels, SS0 (distilled water), SS4 (4 4 dS m−1), and SS8 (8 dS m−1). The results showed that salt stress, biochar, and salicylic acid significantly affected the measured parameters. Salt stress (SS4 and SS8) negatively affected the measured parameters compared to the control. However, the application of biochar and salicylic acid regulated the alleviation of the impact of salt stress. Under SS4, the application of Rb along with SA1 resulted in the highest value of proline content. The highest enzymatic activity of catalase was observed due to the use of PA in combination with SA0.5 under non-saline soil conditions. The use of PA under SS8 increased the hydrogen peroxide and caused the highest activity, while the lowest activity was obtained under non-saline soil conditions with the application of Sb. In the first year of the experiment, it was found that the use of SA1 without biochar under non-stress conditions resulted in the highest levels of malondialdehyde. Likewise, in the second year, the highest malondialdehyde activity was observed by applying Rb and SA1 under SS8. The research concludes that kidney bean plants are significantly impacted by salt stress, which affects their biochemical characteristics. Nonetheless, the combined application of biochar and salicylic acid showed promise in addressing these challenges. This approach could be particularly effective in managing salinity issues in arid and semi-arid regions, highlighting the potential of biochar and salicylic acid for improving plant resilience under such conditions.