Soil Electrical Conductivity Research Articles

Analysis of Bacterial Community Characteristics in Maize Root Zones Under Maize-soybean Compound Planting Mode

Maize-soybean compound intercropping has the potential to increase yield and is being tested for spreading in Huang-Huai-hai Plain. However, the main regulatory regions of this cropping pattern on soil microbial communities have not been clarified. In the present study, the tested samples were collected from three maize root zones of bulk soil, rhizosphere soil, and roots under mono- and intercropping planting modes, respectively. The non-rhizosphere soil chemical properties and enzyme activities were determined, and bacterial communities were characterized using high-throughput sequencing of the 16S rRNA gene V3-V4 region. Compared with monocropping, the maize bulk soil electric conductivity （EC）, soil organic matter （SOM）, available potassium （AK）, available phosphorus （AP）, total nitrogen （TN）, and enzyme activities of intercropping were significantly increased. The α diversities and β diversity of the bacterial community in rhizosphere soil were significantly different between the two planting modes. There were 11 bacteria genera with significantly higher abundance in the rhizosphere soil of compound planting than that of monoculture, and TN, AP, and catalase were the three most important factors contributing to their distribution. The abundances of 8 genera among the 11 genera mentioned above, unclassified Vicinamibacterales, unclassified Geminicoccaceae, MND1, unclassified Gemmatimonadaceae, Acidibacter, unclassified Vicinamibacteraceae, Sphingomonas, and unclassified Comamonadaceae were significantly positively correlated with TN. As for the bacteria distribution in maize root, AK contributed the most and had a significantly negative correlation with unclassified Rhizobiaceae and unclassified Microscillaceae and a positive correlation with Haliangium. Maize-soybean compound intercropping affected mainly the bacterial community of maize rhizosphere and had an evident effect on soil fertilizer cultivation and microbial diversity regulation, which provides a theoretical basis and practical guidance for rational intercropping to maintain agroecosystem biodiversity.

Mitigating the detrimental impacts of low- and high-density polyethylene microplastics using a novel microbial consortium on a soil-plant system: Insights and interactions

The accumulation of polyethylene microplastics (PE-MPs) in soil has raised considerable concerns; however, the effects of their persistence and mitigation on agroecosystems have not been explored. This study aimed to assess the detrimental effects of PE-MPs on a soil-plant system and evaluate their mitigation using a novel microbial consortium (MC). We incorporated low-density polyethylene (LDPE) and high-density polyethylene (HDPE) at two different concentrations, along with a control (0 %, 1 %, and 2 % w/w) into the sandy loam soil for a duration of 135 days. The samples were also treated with a novel MC and incubated for 135 days. The MC comprised three bacterial strains (Ralstonia pickettii (MW290933) strain SHAn2, Pseudomonas putida strain ShA, and Lysinibacillus xylanilyticus XDB9 (T) strain S7–10F), and a fungal strain (Aspergillus niger strain F1–16S). Sunflowers were subsequently cultivated, and physiological growth parameters were measured. The results showed that adding 2 % LDPE significantly decreased soil pH by 1.06 units compared to the control. Moreover, adding 2 % HDPE resulted in a more significant decrease in soil electrical conductivity (EC) relative to LDPE and the control. A dose-dependent increase in dissolved organic carbon (DOC) was observed, with the highest DOC found in 2 % LDPE. The addition of higher dosages of LDPE reduced soil bulk density (BD) more than HDPE. The addition of 2 % HDPE increased the water drop penetration time (WDPT) but decreased the mean weight diameter of soil aggregates (MWD) and water-stable aggregates (WSA) compared to LDPE. The results also revealed that higher levels of LDPE enhanced soil basal respiration (BR) and microbial carbon biomass (MBC). The interaction of MC and higher MP percentages considerably reduced soil pH, EC, BD, and WDPT but significantly increased soil DOC, MWD, WSA, BR, and MBC. Regarding plant growth, incorporating 2 % PE-MPs significantly reduced physiological responses of sunflower: chlorophyll content (Chl; −15.2 %), Fv/Fm ratio (-25.3 %), shoot dry weight (ShD; −31.3 %), root dry weight (RD; −40 %), leaf area (LA; −38.4 %), and stem diameter (StemD; −25 %) compared to the control; however, the addition of novel MC considerably reduced and ameliorated the harmful effects of 2 % PE-MPs on the investigated plant growth responses.

Soil Solution Properties of Tropical Soils and Brachiaria Growth as Affected by Humic Acid Concentration

The soil solution is the compartment where plants uptake nutrients and this phase is in equilibrium with the soil solid phase. Changes in nutrient content and availability in the soil solution can vary among soil types in response to humic acid concentrations, thereby affecting Brachiaria growth. However, there are no studies demonstrating these effects of humic acid application on different soil types and how they affect Brachiaria growth. Thus, the aim of this study was to evaluate the effects of humic acid concentrations (0, 5, 10, 25, and 60 mg kg−1 carbon-humic acid) on Brachiaria brizantha growth and soil solution properties of contrasting tropical soils. Plants were grown for 35 days in greenhouse conditions in pots containing Sandy Entisol, Clayey (Red Oxisol), and Medium Texture (Red-Yellow Oxisol). Soil solution was assessed for pH, electrical conductivity (EC), carbon, and nutrient content. Shoot and root dry matter, as well as macro and micronutrients accumulation in the shoot, were determined. In a soil type-dependent effect, pH, EC, and concentrations of nutrients in solutions changed in response to carbon-humic acid concentration. In the less-buffered soils, Sandy Entisol and Red-Yellow Oxisol, the addition of 30–40 mg kg−1 carbon-humic acid increased root proliferation by 76–89%, while Brachiaria biomass produced in all soils increased by approximately 30%. Levels of carbon in solution were high (>580 mg L−1) and varied depending on the investigated soil type. Though solution carbon contents did not appear to be a driving factor controlling the positive effects of humic acid concentrations on Brachiaria dry matter, there was a direct relationship between other properties and nutrient content in the soil solution, and Brachiaria dry matter production.

A Dynamic Process-Based Method for Screening Salt-Tolerant and High-Yielding Crop Varieties

Maize, the most important cereal crop worldwide, is moderately sensitive to salt stress. Given the challenges of soil salinization, developing methods to screen and cultivate salt-tolerant maize varieties is vital for enhancing food security. Among the options, process model-based assisted screening is an effective method for faster and more thorough screening of salt-tolerant varieties. In this study, a method for quickly screening salt-tolerant and high-yielding crop varieties is proposed by combining a coupled model of crop growth and water–salt response with fitness function. Then, this method was applied to the saline areas of the Hetao Plain in China to demonstrate its applicability. This study includes three parts. Firstly, field trial data from 10 commonly grown maize varieties in Hetao Plain (i.e., Xianyu 335, Yinyu 238, Jindan 73, Deke 622, DK-815, Heyu 157, Xianyu 1321, Jinrun 919, Tianci 19, and Xianyu 1225) were used to calibrate the model for different maize varieties. Moreover, model accuracy was evaluated using four indexes including the regression coefficient (b), coefficient of determination (R²), root mean square error (RMSE), and Nash–Sutcliffe efficiency coefficient (NSE). Secondly, scenario simulations were conducted using the calibrated model by setting nine initial salinity scenarios to simulate daily dynamic crop growth and soil water–salt changes for the 10 maize varieties. Finally, salt-tolerant and high-yielding maize varieties were screened based on the fitness function method during crop growth periods. The results showed that the simulation model was applicable and functioned effectively for all 10 maize varieties in the region, with the determination coefficient (R2) and Nash–Sutcliffe efficiency coefficient (NSE) of simulated plant height and leaf area index being above 0.90. Furthermore, the R2 of soil water content, soil electrical conductivity, and groundwater depth are 0.51, 0.52, and 0.60, respectively. Afterward, the fitness function values were calculated to bridge the linkage between simulated indicators and scenarios to screen varieties step by step according to the predetermined percentage of screening. Jindan 73, Xianyu 1225, and DK-815 were eventually determined as the most suitable salt-tolerant and high-yielding maize varieties. Therefore, the above results show that the proposed method is suitable for saline crop variety screening with flexibility and applicability.

Effect of Different Fertigation Scheduling Methods on the Yields and Photosynthetic Parameters of Drip-Fertigated Chinese Chive (Allium tuberosum) Grown in a Horticultural Greenhouse

This study investigated the performance of four different fertigation scheduling methods in greenhouse-grown, drip-fertigated Chinese chive (Allium tuberosum) cultivation. These methods were based on (1) the use of a timer (control), (2) accumulated radiation (AR), (3) estimated evapotranspiration (ET), and (4) measured soil moisture (SM), with fertilizer application proportional to the supplied water. These methods caused considerable variations in the amount of fertigation water (I), soil volumetric water content (θ), and bulk soil electrical conductivity, leading to variations in the harvested fresh weight (FW). The SM-based method maintained the target θ and achieved the highest irrigation water productivity (WP; the ratio of FW to ΣI), while the ET-based method led to insufficient I and FW loss. The AR-based method over-fertigated, but no FW loss was observed. Compared to the WP of the control, those of the SM-, ET-, and AR-based methods varied by +1%, −14%, and −57%, respectively. Different fertigation methods did not significantly affect leaf photosynthetic capacity, but under-fertigation caused a significant decline in stomatal conductance. Compared to the ET- and AR-based methods, the SM-based method seemed to have a lower risk of under-/over-fertigation because I in the SM-based method could be adjusted according to θ.

Complementarity of Sentinel-1 and Sentinel-2 Data for Soil Salinity Monitoring to Support Sustainable Agriculture Practices in the Central Bolivian Altiplano

Soil salinization will affect 50% of global cropland areas by 2050 and represents a major threat to agricultural production and food sovereignty. As soil salinity monitoring is costly and time consuming, many regions of the world undertake very limited soil salinity observation (in space and time), preventing the accurate assessment of soil salinity hazards. In this context, this study assesses the relative performance of Sentinel-1 radar and Sentinel-2 optical images, and the combination of the two, for monitoring changes in soil salinity at high spatial and temporal resolution, which is essential to evaluate the mitigation measures required for the sustainable adaptation of agriculture practices. For this purpose, an improved learning database made of 863 soil electrical conductivity (i.e., soil salinity) observations is considered for the training/validation step of a Random Forest (RF) model. The RF model is successively trained with (1) only Sentinel-1, (2) only Sentinel-2 and (3) both Sentinel-1 and -2 features using the Genetic Algorithm (GA) to reduce multi-collinearity in the independent variables. Using k-fold cross validation (3-fold), overall accuracy (OA) values of 0.83, 0.88 and 0.95 are obtained when considering only Sentinel-2, only Sentinel-1 and both Sentinel-1 and -2 features as independent variables. Therefore, these results highlight the clear complementarity of radar (i.e., Sentinel-1) and optical (i.e., Sentinel-2) images to improve soil salinity mapping, with OA increases of approximately 10% and 7% when compared to Sentinel-2 and Sentinel-1 alone. Finally, pre-sowing soil salinity maps over a five-year period (2019–2023) are presented to highlight the benefit of the proposed procedure to support the sustainable management of agricultural lands in the context of soil salinization on a regional scale.

The Impact of Rice Milling Activities on the Quality of Soil

Rice is a very popular commodity amongst Nigerian families, however the demand for rice is on the rise daily, hence an increase in rice milling activities across the country. This study is aimed at determining the impact of rice milling activities on soil quality. The samples were gotten from Auchi, Anambra and Kogi State. The samples were digested and analysed using a varian 220 atomic absorption spectrometer (AAS). Physicochemical properties showed the ph of the soil, ranging from 6.7 -9.84, temperature 29.1oC – 30oC and electrical conductivity of soil ranged from 1.3(μS/cm )- 88.2(μS/cm). The available nutrients in the soil revealed the highest values for nitrogen to be 52.2779 (mg/kg), and phosphorus to be 296.421 (mg/kg), while the highest value for potassium was 188.315 (mg/kg). Conclusively, The rice mill operations was seen to affect the soil quality parameters, due to the release of effluents on the soil, resulting in an increase in the heavy metal concentrations in the soil and decrease in the available nutrients. Accumulative geo-index revealed that Auchi is moderately polluted with cadmium and Anambra is highly polluted with zinc.

Study on the EC prediction of cracked soda saline-alkali soil based on texture analysis of high-resolution images from ground-based observation and machine learning methods

The rapid and accurate measurement of soil salinity is essential for assessing the level of soil salinization. In natural conditions, the surface of cohesive soda saline-alkali soil experiences shrinkage and cracking phenomena during water evaporation. The propagation and development of these desiccation cracks can be effectively described using texture features due to their statistical randomness. This study aims to establish a relationship between electrical conductivity (EC) values and texture features derived from both gray-level co-occurrence matrix (GLCM) and wavelet decomposition, and to develop a prediction model for EC accordingly. To achieve these objectives, crack images on the surface of 200 soil samples with varying levels of salinity were obtained in the Songnen Plain field. GLCM was computed and wavelet decomposition was performed to extract texture features in different directions and scales. The results demonstrate a significant correlation between texture features and soil EC values. Among the various texture features, 12 GLCM texture features with a grayscale level of 2 and a step size of 1 pixel, and wavelet texture features derived from a 4th level orthogonal decomposition based on the coiflet-1 function were selected as the optimal parameters for establishing and comparing the predictive effects of two machine learning models on soil EC values. In comparison to the testing results of the BP neural network model (R2=0.83, RPD=1.64, RMSE=0.32 dS/m, MAE=0.18 dS/m), the random forest model exhibited higher accuracy and stability (R2=0.95, RPD=3.48, RMSE=0.21 dS/m, MAE=0.07 dS/m), indicating that although both machine learning models demonstrated rapid and nondestructive capabilities, the random forest method was better suited for EC prediction in soda saline-alkali soil due to its superior accuracy.

Leafiness-LiDAR index and NDVI for identification of temporal patterns in super-intensive almond orchards as response to different management strategies

The use of super-intensive orchards is a growing trend in fruit production. The present study aims to improve management of these cropping systems by focusing on how agronomic decisions impact orchard dynamics in the short to medium term and by providing a decision-support approach based on stable temporal patterns from previous seasons. A multitemporal study using remote sensing and LiDAR was conducted in a commercial almond orchard over four growing seasons (2019–2022) to determine the optimal timing of image acquisition for variable pre-harvest treatments. A model-based clustering (mclust) was applied to optimal Sentinel-2 NDVI maps and apparent soil electrical conductivity (ECa) data, interpolated to the pixel centroids of Sentinel-2 image grids, to delineate potential management zones (PMZs). The leafiness-LiDAR index (LLI), a leaf area index (LAI) estimator, was obtained as ground truth after summer pruning and before harvesting, showing a significant influence of fertigation and pruning on the LAI, with summer pruning particularly influencing orchard dynamics. The optimal time for NDVI mapping was found to be two months after summer pruning in productive years and two weeks after in unproductive years. The delineated PMZs were consistent across seasons and corresponded to significant LAI differences. This method could contribute to improving resource management and sustainability in super-intensive commercial orchards.

Biochar effects on salt-affected soil properties and plant productivity: A global meta-analysis

Biochar has been recognized as a promising practice for ameliorating degraded soils, yet the consensus on its effects remains largely unknown due to the variability among biochar, soil and plant. This study therefore presents a meta-analysis synthesizing 92 publications containing 987 paired data to scrutinize biochar effects on salt-affected soil properties and plant productivity. Additionally, a random meta-forest approach was employed to identify the key factors of biochar on salt-affected soil and plant productivity. Results showed that biochar led to significant reductions in electrical conductivity (EC), bulk density (BD) and pH by 7.4%, 4.7% and 1.2% compared to the unamended soil, respectively. Soil organic carbon (by 55.1%) and total nitrogen (by 31.3%) increased significantly with biochar addition. Moreover, biochar overall enhanced plant productivity by 31.5%, and more pronounced increases in forage/medicinal with higher salt tolerance than others. The results also identified that the soil salinity and biochar application rate were the most important co-regulators for EC and PP changes. The structural equation model further showed that soil salinity (P < 0.001), biochar pH (P < 0.001) and biochar specific surface area (P < 0.01) had a significant negative effect on soil EC, but it was positively impacted by biochar pyrolysis temperature (P < 0.05). Furthermore, plant productivity was positively affected by biochar pH (P < 0.001) and biochar feedstock (P < 0.01), while negatively influenced by biochar pyrolysis temperature (P < 0.01). This study highlights that woody biochar with 7.6 < pH < 9.0 and pyrolyzed at 400–600 °C under 30–70 t ha−1 application rate in moderately saline coarse soils is a recommendable pattern to enhance forage/medicinal productivity while reducing soil salinity. In conclusion, biochar offers promising avenues for ameliorating degradable soils, but it is imperative to explore largescale applications and field performance across different biochar, soil, and plant types.

Particle morphology and soil properties affect the retention of copper oxide nanoparticles in agricultural soils.

The interaction between nanoscale copper oxides (nano-CuOs) and soil matrix significantly affects their fate and transport in soils. This study investigates the retention of nano-CuOs and Cu2+ ions in ten typical agricultural soils by employing the Freundlich adsorption model. Retention of nano-CuOs and Cu2+ in soils was well fitted by the Freundlich model. The retention parameters (KD, KF, and N) followed an order of CuO NTs > CuO NPs > Cu2+, highlighting significant impact of nano-CuOs morphology. The KF and N values of CuO NPs/Cu2+ were positively correlated with soil pH and electrical conductivity (EC), but exhibited a weaker correlation for CuO NTs. Soil pH and/or EC could be used to predict KF and N values of CuO NPs or CuO NTs, with additional clay content should be included for Cu2+.The different relationship between retention parameters and soil properties may suggest that CuO NTs retention mainly caused by agglomeration, whereas adsorption and agglomeration were of equal importance to CuO NPs. The amendment of Ca2+ at low and medium concentration promoted retention of nano-CuOs in alkaline soils, but reduced at high concentration. These findings provided critical insights into the fate of nano-CuOs in soil environments, with significant implications for environmental risk assessment and soil remediation strategies.

Response of Soil Fungal Community in Coastal Saline Soil to Short-Term Water Management Combined with Bio-Organic Fertilizer

This study aimed to elucidate the response of soil microbial communities to saline soil amelioration via biological organic fertilizer. A year-long experiment was conducted on coastal saline soil, employing water and fertilizer strategies. Three treatments were compared: dry field (control, CK), paddy field (W), and combined dry and irrigated fields with biological organic fertilizer (BW). Soil DNA was extracted and sequenced using high-throughput methods, revealing significant reductions in soil electrical conductivity (EC) and pH with W and BW treatments. Moreover, the BW treatment notably increased soil organic carbon content by 17.2%, as well as soil urease and alkaline phosphatase activity. Fungal community richness increased, with the BW treatment showing a 36% rise in the ACE index and a 24% increase in the Shannon index, while the Simpson index decreased by 59%. Dominant fungal phyla were Ascomycota, Mortierellomycota, and Basidiomycota, with Basidiomycota prevailing at the genus level. Redundancy analysis (RDA) indicated that soil pH, EC, and organic carbon were key determinants of fungal community distribution, with the BW treatment correlating negatively with pH and salt and positively with soil organic carbon (SOC). Fungal functional groups varied among treatments, with saprophytic fungi predominating, but the BW treatment showed a higher relative abundance of animal pathogenic fungi. In summary, the integration of biological organic fertilizer with flooding ameliorates soil properties and influences the changes in soil fungal community structure and function in the short term. These results could enhance the scientific basis for the efficient utilization and development of saline soil resources in coastal areas.

Soil Microbial Community Structure and Its Contribution to Carbon Cycling in the Yalu River Estuary Wetland

Wetland microbial communities play a vital role in ecosystem functioning, particularly in the intricate processes of carbon cycling. This study employed metagenomic sequencing to investigate the diversity, composition, structural differences, carbon cycling functional gene, and microbial species of soil microbial communities in five distinct soil types of the Yalu River estuary wetland, including shoal soil, bog soil, paddy soil, meadow soil, and brown forest soil. We further explored the influence of environmental factors on both the microbial community structure and carbon cycling functional genes. Our results revealed a bacterial-dominated soil microbial community, constituting about 97.6%. Archaea and fungi represented relatively minor fractions, at 1.9% and 0.4%, respectively. While no significant differences were observed in Chao1 indices between bacterial and fungal communities, the Shannon index revealed notable differences. Both Chao1 and Shannon indices exhibited significant variations within the archaeal communities. The dominant bacterial phyla were Proteobacteria, Actinobacteria, Acidobacteria, Bacteroidetes, and Nitrospirae. Thaumarchaeota, Crenarchaeota, and Euryarchaeota formed the major archaeal phyla, while Ascomycota, Mucoromycota, and Basidiomycota were the dominant fungal phyla. Non-metric multidimensional scaling (NMDS) analysis based on Bray-Curtis distance revealed notable differences in the bacterial, archaeal, and fungal community structures across the samples. Redundancy analysis (RDA) identified key environmental factors for the major phyla. Soil pH, soil organic carbon (SOC), electrical conductivity (EC), and total phosphorus (TP) were the main influencing factors for bacteria, while soil TP, EC, total sulfur (TS), and SOC were the primary drivers for archaeal phyla. Soil total nitrogen (TN) and EC were the main influencing factors for fungal phyla. Analysis of key carbon cycling pathway genes utilizing the Kyoto Encyclopedia of Genes and Genomes (KEGG) database and clustering heatmap revealed some variations in functional gene composition across different soil types. Mantel test indicated that pH, TN, and SOC were the primary environmental factors influencing microbial functional genes associated with soil carbon cycling. Stratified bar chart analysis further demonstrated that the major contributors to carbon cycling originated from corresponding dominatnt phyla and genera of Proteobacteria, Thaumarchaeota, Actinomycetota, Euryarchaeota, and Bacteroidota. The species and relative abundance of microorganisms associated with carbon cycling pathways varied among the samples. These findings provide a crucial reference for informing the conservation and sustainable management of wetland ecosystems in the Yalu River estuary.

Role of malic acid in enhancing the efficiency of barley (Hordeum vulgare L.) and alfalfa (Medicago sativa L.) plants for phytoremediation of salt affected soil

Soil salinization is a growing global problem that influences plant growth and crop productivity. Most of the reclamation efforts in the past have focused on the installation of surface drainage systems. Other management approaches, such as excessive leaching and chemical amendments, have also been used on a limited scale to enhance the productivity of these soils. Phytoremediation can be cost-effective and environmentally sound technology.A laboratory experiment was carried out to study the role of malic acid which is low molecular weight organic acid (LMWOA) in enhancing the efficiency of barley and alfalfa plants for the phytoremediation of salt-affected soil. Seeds of barley and alfalfa were cultured in pots and irrigated with full strength Hoagland nutrient solution with three concentrations of seawater (SW) (10%, 20% and 30%) and a mixture of seawater with malic acid (MA) at 2, 4 and 6 mM l-1 (MA+SW), Hoagland solution was used as control. After twelve weeks, plants were harvested, and three types of soils (barley soil, alfalfa soil, and plant-free soil) were subjected to physical and chemical analysis for EC (electrical conductivity), TOC (total organic carbon), pH, potassium, sodium, and chloride ions. Results indicated a significant decrease was recorded in soil EC, pH, potassium, sodium, and chloride ions and a significant increase in soil TOC in barley and alfalfa soil compared with plant-free soil. Treatments with (MA+SW), especially at (2+10%) resulted in a significant increase in ions availability and phytoremediation activity in barley and alfalfa soils comparing with plant-free soil.

ECWS: Soil Salinity Measurement Method Based on Electrical Conductivity and Moisture Content

A novel method, ECWS, is proposed for measuring soil initial salinity content (b), based on the soil electrical conductivity EC and soil moisture content WS. This pioneering model rigorously establishes and incorporates the inherent potential correlation among soil bulk conductivity (ECa), soil solution conductivity (ECw), volume water content (θc), and soil salinity content (SSC). First of all, in order to delve the deeper relationship between ECa, ECw, θc and SSC, the soil salinity conductivity conversion coefficient ρa and soil leaching solution salinity conductivity conversion coefficient ρw were employed based on the formula of parallel conducting channels of the soil–water system, and a new measurement model of salinity content was constructed. After that, a mathematical analysis method was used to transform the coefficients of multiple sets of regression equations into matrices to solve ρa, ρw and b. Finally, to validate the accuracy of the proposed ECWS method, verification tests were conducted by utilizing TDR and PWMER sensors. The results with different salinity contents showed that the b size obtained by ECWS model were K2SO4 (1.84 g/kg), NaCl (1.91 g/kg), and KCl (1.92 g/kg). The maximum deviation was less than 0.08 g/kg (relative error less than 5%). The results showed that the influence of different anions and cations on the measurement of salinity content Cl− is greater than that of SO42−, and K+ is greater than that of Na+. This study revealed the relationship between soil electrical conductivity and soil salinity content to a certain extent, and realized the transformation between them, which provided a new method for the measurement of soil salinity content, and also provided a reference for related research on the measurement of soil salinization.

Evaluation of slow-release fertilizers derived from hydrogel beads: Sodium alginate-poly (acrylic acid) and humic acid-encapsulated struvite for soil salinity amelioration

Soil salinity, a severe environmental factor, significantly reduces the productivity of crop plants by increasing salt and mineral fertilizer concentrations in the soil. As a result, the development of sustainable slow-release mineral fertilizers (SRFs) is critical for addressing salt-affected soils. This study aimed to synthesize struvite (MgNH4PO4·6H2O) into hydrogel beads made from sodium alginate-poly (acrylic acid) in the absence (Sa@S) and presence (Sa@SHa) of humic acid (HA). The optimal conditions for struvite formation were at pH 9.0, resulting in a remarkable 73.21 %, 98.74 %, and 99.20 % for Mg, NH4-N and P removal, respectively. The SRFs study demonstrated that struvite had a significant release of Mg, P, and NH4-N, notably higher (P ≤ 0.05) than Sa@S and Sa@SHa. Experiments on swelling and soil water loss demonstrated that Sa@S yielded higher results in comparison to Sa@SHa. Furthermore, an experiment was conducted to study the impact of Sa@S and Sa@SHa on saline soil parameters over 20 days of incubation. The results showed both encapsulated struvite hydrogel beads reduced soil salinity, as indicated by the sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP). Additionally, a significant reduction (P ≤ 0.05) in soil electrical conductivity (EC) and sodium (Na) was observed for both hydrogel bead encapsulation treatments compared to the control soil. However, no apparent variance was observed in pH and soil organic carbon (SOC). Moreover, the levels of available phosphorus (P), ammonium-nitrogen (NH4-N), nitrate-nitrogen (NO3-N), cation exchange capacity (CEC), and exchangeable cations (Ca, Mg, K) in the soil were observed to be increased (P ≤ 0.05).

Strengthen sunflowers resilience to cadmium in saline-alkali soil by PGPR-augmented biochar

In the center of the Nile Delta in Egypt, the Kitchener drain as the primary drainage discharges about 1.9 billion m3 per year of water, which comprises agricultural drainage (75 %), domestic water (23 %), and industrial water (2 %), to the Mediterranean Sea. Cadmium (Cd) stands out as a significant contaminant in this drain; therefore, this study aimed to assess the integration of biochar (0, 5, and 10 ton ha−1) and three PGPRs (PGPR-1, PGPR-2, and PGPR-3) to alleviate the negative impacts of Cd on sunflowers (Helianthus annuus L.) in saline-alkali soil. The treatment of biochar (10 ton ha−1) and PGPR-3 enhanced the soil respiration, dehydrogenase, nitrogenase, and phosphatase activities by 137 %, 129 %, 326 %, and 127 %, while it declined soil electrical conductivity and available Cd content by 31.7 % and 61.3 %. Also, it decreased Cd content in root, shoot, and seed by 55.3 %, 50.7 %, and 92.5 %, and biological concentration and translocation factors by 55 % and 5 %. It also declined the proline, lipid peroxidation, H2O2, and electrolyte leakage contents by 48 %, 94 %, 80 %, and 76 %, whereas increased the catalase, peroxidase, superoxide dismutase, and polyphenol oxidase activities by 80 %, 79 %, 61 %, and 116 %. Same treatment increased seed and oil yields increased by 76.1 % and 76.2 %. The unique aspect of this research is its investigation into the utilization of biochar in saline-alkali soil conditions, coupled with the combined application of biochar and PGPR to mitigate the adverse effects of Cd contamination on sunflower cultivation in saline-alkali soil.

Deep vertical rotary tillage reduced soil salinity and improved seed cotton yield and water productivity under limited irrigation in saline-alkaline fields

Water scarcity and soil salinization severely limit cotton production in arid areas on the globe. A two-season (2020 and 2021) field experiment was performed on cotton under film-mulched drip irrigation in south Xinjiang of China to explore the responses of soil moisture, soil salinity, root growth, seed cotton yield and water productivity to deep vertical rotary tillage (DVRT) depth (T20: 20 cm, T40: 40 cm, T60: 60 cm, Tck: 20 cm, traditional rotary tillage) in saline-alkaline fields under two irrigation amounts (W1:360 mm, W2: 480 mm, local irrigation amount). It was found that the soil moisture storage (0–120 cm) increased with as irrigation amount increased and decreased with increasing DVRT depth. Soil electrical conductivity in the root zone (0–60 cm) and 0–120 cm soil layer declined as irrigation amount and DVRT depth increased. Irrigation amount and DVRT depth had significant effects on root length density, root mass density, root/shoot ratio, and seed cotton yield, all of which increased with increasing irrigation amount and DVRT depth. Under W2, T20, T40 and T60 increased seed cotton yield by 23.3 %, 45.3 %, 65.6 % in 2020, and by 38.9 %, 62.0 % and 84.1 % in 2021 compared with TCK, respectively. Both water productivity and irrigation water productivity increased with increasing DVRT depth. There were significant positive correlations among seed cotton yield and leaf area index, dry matter accumulation, harvest index, root length density, root mass density, root/shoot ratio, water productivity and irrigation water productivity. W1T60 was suggested for cotton production in the saline regions of southern Xinjiang. The DVRT offset the decrease in seed cotton yield under limited irrigation, which indicates that DVRT is promising to reduce soil salinity and improve seed cotton yield and water productivity in saline-alkaline fields for coping with water scarcity and soil salinization.

Can Biochar Made from Rice Husk Affect Savanna Soils’ pH, Electrical Conductivity, and Soil Respiration?

Biochar is now gaining awareness as a sustainable tool for soil health improvement, boosting carbon (C) storage and the enhancement of nutrient cycling in agricultural soils. This study assesses the effects of biochar on soil respiration, pH, and electrical conductivity (EC) in savanna soils over a 45-day incubation trail in the laboratory. Four different biochar treatments (0, 2, 4, and 6 t/ha) were used in the study. The treatments were established at 26°C, and after 2, 5, and 10 days, the CO2 levels were recorded. After incubation for 0, 5, 10, and 45 days, the EC and pH were assessed. As the rate of application of biochar increased, the rate of CO2 evolution increased as well. During the first two days of incubation, the CO2 evolution rate rose by a value of 129 at 2 t/ha biochar, 146 at 4 t/ha biochar, and 168 ug CO2/g soil/d at 6 t/ha biochar above the 0 t/ha biochar. Following five days of incubation, the amounts of CO2 evolution that were higher than the control were 99 with 2 t/ha, 116 with 4 t/ha, and 120 ug CO2/g soil/d with 6 t/ha of biochar. The increase in CO2 evolution above the control treatment at 10 days of incubation was 61 with 2 t/ha, 79 with 4 t/ha, and 87 ug CO2/g soil/d with 6 t/ha of biochar. Analogously, rising patterns in CO2 emissions were noted. Throughout the whole incubation period, the biochar treatments' soil EC and pH were greater than those of the control treatment. After applying biochar, there were increases in the evolution of CO2, however after 10 days of incubation, the percentage of C evolved from the addition of biochar decreased as the rates of biochar increased. At two t/ha, four t/ha, and six t/ha, the percentage C developed was 1.74 %, 1.66%, and 0.82% of the applied biochar C, respectively. Although the CO2 evolved ratio to the total amount of biochar C typically reduced with increasing biochar rates, this study shows that the addition of biochar increases soil respiration, EC, and pH.

Valorization of agricultural byproducts – The use of mustard seed meal for pest control

Mustard seed (Brassica juncea) meals from biodiesel production can be utilized as a feedstock for sourcing pesticidal compounds that can control ubiquitous soil pests such as wireworms. In the present study, we evaluated the pesticidal activity of B. juncea seed meal on wireworms (Limonius infuscatus) to promote the valorization of B. juncea seed meal with the end goal of increasing the overall sustainability of crop production. In the laboratory soil column study, B. juncea seed meal were applied to typical agricultural soil infested with wireworms. After application, the release of the primary biopesticidal compound was monitored and correlated with the motility, mortality, and metabolomic changes of wireworms. The pesticidal effect of B. juncea seed meal on wireworms was evident by the mass change and metabolomic response consistent with the stress response. Mortality of up to 100 % of wireworms was observed when soils was treated with B. juncea seed meal and tarped. Based on the statistical analysis, the release of the primary biopesticidal compound from B. juncea seed meal correlated well with soil electrical conductivity making it a potential proxy method for field monitoring.