Soil Electrical Conductivity Research Articles

Soil properties and microbial functional attributes drive the response of soil multifunctionality to long-term fertilization management

Fertilization is a vital management practice to improve soil fertility and promote agricultural production. However, there is limited knowledge about the interactive effects between soil abiotic and biotic factors and soil multifunctionality after long-term fertilization. There has been little research on determining whether the application of organic fertilizers can improve the functional potential of microorganisms to maintain multifunctional stability. In this study, we integrated soil physicochemical properties, extracellular enzyme activities, bacterial community characteristics, and the abundance of functional genes related to carbon (C) and nitrogen (N) cycling to evaluate the mechanism of soil functional potential response to 13 years of fertilization management. Four treatments were compared, including no fertilizer (CK), conventional fertilization (CF), formulated fertilization by soil testing (SF), SF with organic fertilizer (SFO). The addition of organic fertilizer enhanced the soil electrical conductivity, N-cycling enzyme activities, contents of macroaggregate and associated C, and soil nutrients, while decreasing the content of microaggregates compared with other treatments. The co-application of chemical and organic fertilizer led to significant increases in soil multifunctionality and the bacterial Shannon index compared with the CK and CF treatments. Soil abiotic factors are the key predictors for shaping soil multifunctionality. The addition of organic fertilizer could increase the abundance of functional genes related to C- and N-cycling mediated by the contents of nutrients and the aggregates associated with nutrients. Additionally, treatment with organic fertilizer can mitigate the decrease in genes for C-cycling function caused by the long-term application of chemical fertilizer (SF). In addition, the structural equation models revealed that the fertilization positively affected soil multifunctionality indirectly by changing the bacterial diversity and community composition, as well as the functional potential related to N-cycling. Overall, soil properties and microbial functional attributes jointly drive the response of soil multifunctionality to long-term fertilization management. These results suggest that the combination of organic and chemical fertilizer is worth popularizing to improve multifunctionality and its stability to maintain agricultural sustainability.

Mechanism of microbial regulation on methane metabolism in saline–alkali soils based on metagenomics analysis

Saline–alkali soils constitute a globally important carbon pool that plays a critical role in soil carbon dioxide (CO2) and methane (CH4) fluxes. However, the relative importance of microorganisms in the regulation of CH4 emissions under elevated salinity remains unclear. Here, we report the composition of CH4 production and oxidation microbial communities under five different salinity levels in the Yellow River Delta, China. This study also obtained the gene number of microbial CH4 metabolism via testing the soil metagenomes, and further investigated the key soil factors to determine the regulation mechanism. Spearman correlation analysis showed that the soil electrical conductivity, salt content, and Na+, and SO42− concentrations showed significantly negative correlations with the CO2 and CH4 emission rates, while the NO2−-N concentration and NO2−/NO3− ratio showed significantly positive correlations with the CO2 and CH4 emission rates. Metabolic pathway analysis showed that the mcrA gene for CH4 production was highest in low–salinity soils. By contrast, the relative abundances of the fwdA, ftr, mch, and mer genes related to the CO2 pathway increased significantly with rising salinity. Regarding CH4 oxidation processes, the relative abundances of the pmoA, mmoB, and mdh1 genes transferred from CH4 to formaldehyde decreased significantly from the control to the extreme–salinity plot. The greater abundance and rapid increase of methanotrophic bacteria compared with the lower abundance and slow increase in methanogenic archaea communities in saline–alkali soils may have increased CH4 oxidation and reduced CH4 production in this study. Only CO2 emissions positively affected CH4 emissions from low– to medium–salinity soils, while the diversities of CH4 production and oxidation jointly influenced CH4 emissions from medium– to extreme–salinity plots. Hence, future investigations will also explore more metabolic pathways for CH4 emissions from different types of saline–alkali lands and combine the key soil enzymes and regulated biotic or abiotic factors to enrich the CH4 metabolism pathway in saline–alkali soils.

Combined Application of Organic Fertilizer with Microbial Inoculum Improved Aggregate Formation and Salt Leaching in a Secondary Salinized Soil.

Greenhouse vegetable production provides significant quantities of vegetables throughout the year and improves farmers' income. However, over-fertilization with mineral fertilizer causes soil secondary salinization and decreases the stability of the soil structure. To improve aggregate formation and decrease salt accumulation in the soil profile, bio-organic fertilizers (Protaetia brevitarsis larvae frass with Bacillus amyloliticus and/or Trichoderma harziensis) were applied to partially substitute mineral fertilizer in a salinized vegetable soil. Soil nutrient condition, aggregate stability, and salt movement in the soil profile were measured in a greenhouse double-cucumber system. The results showed that soil organic matter (SOM), total nitrogen (TN), and available phosphorus (AP) increased significantly under bio-organic fertilizer treatments compared with control. Soil electrical conductivity (EC) and total salt content (TSC) decreased by 15.74-24.20% and 19.15-29.05%, respectively, with bio-organic fertilizers (p < 0.05). Cl-, NO3-, and SO42- content under double inoculation with B. amyloliticus and T. harziensis reduced by 31.19%, 26.30%, and 53.11%, respectively, compared to CK (p < 0.05). In addition, double inoculation was more efficient in reducing nitrate content in the soil profile than single inoculation. Soil microaggregates of 0.25-0.053 mm increased by 75.87-78.51% with bio-fertilizers compared with control, and double inoculation was the best for aggregate formation. In conclusion, the inoculation of plant-growth-promoting and salt-tolerant microorganisms with high humic acid larvae frass can alleviate salinization in vegetable soil, enhance soil nutrient content, and improve the soil structure.

Application of Fe3[KG-*2/5]O4/Mulberry Stem Biochar Effects on Soil Arsenic Species and Rice Arsenic Content

The passivation effect of Fe3O4/mulberry pole biochar (Fe-MBC) prepared at different carbonization temperatures on soil available arsenic content was studied through soil culture experiments, and Fe-MBC-800 (prepared by carbonization at 800℃) with good passivation effect was selected and characterized. The effects of 1%-7% (mass fraction of biochar to soil) Fe-MBC-800, MBC-800, and Fe3O4 on soil pH value, soil electrical conductivity, soil arsenic form, rice biomass, and total arsenic (As) content in rice were studied using a pot experiment. The results showed that:①Fe-MBC-800 successfully loaded Fe3O4, and its main functional groups were C=O double bond, O-H bond, C-O bond, and Fe-O bond. The specific surface areas of Fe-MBC-800, MBC-800, and Fe3O4 were 209.659 m2·g-1, 517.714 m2·g-1, and 68.025 m2·g-1, respectively. ②The addition of Fe-MBC-800 could increase the soil pH value, decrease the soil EC value, increase the content of residual arsenic in soil, and reduce the content of water-soluble arsenic and available arsenic in the soil. Under the treatment using 7% Fe-MBC-800 (ω) amendments, the content of water-soluble arsenic and available arsenic in the soil decreased by 81.6% and 56.33%, respectively. ③When the addition ratio of Fe-MBC-800 in the soil was 5%-7%, it could promote the growth of rice plants, increase rice biomass, and reduce the bioaccumulation of arsenic by between 62.5% and 68.75%.

Driving factors of community-level leaf stoichiometry patterns in a typical temperate mountain meadow ecosystem of northern China.

In ecological stoichiometry, the stoichiometry and spatial distribution of leaf carbon, nitrogen, and phosphorus are important research topics. Various studies have assessed leaf stoichiometry and its relationships with environmental factors at different scales. However, how the leaf carbon, nitrogen and phosphorus stoichiometric characteristics of the same vegetation type at the community level vary with environmental factors along a continuous altitudinal gradient remains poorly understood. In this paper, 13 sampling sites along an altitudinal gradient of 1,800-3,011 m in a typical temperate mountain meadow ecosystem on the southern slope of the Wutai Mountain in North China were sampled to explore the response of leaf carbon, nitrogen and phosphorus stoichiometric characteristics to altitude change using correlation analysis, and then quantified the contribution of driving factors using canonical correspondence analysis (CCA) and variation partitioning. We found that the community-level leaf stoichiometry of mountain meadows differed significantly at different altitudes, and an increase in altitude significantly decreased community-level leaf total nitrogen (LTN) and leaf total phosphorus (LTP); however, the leaf total carbon (LTC), C∶N, C∶P, and N∶P increased with an increase in altitude. Additionally, with increasing altitude, soil properties showed significant trends. Soil organic carbon (SOC), soil total nitrogen (STN), soil total phosphorus (STP), soil water content and soil electrical conductivity increased significantly, but soil temperature, soil bulk density and soil pH exhibited the opposite trend. Our results suggested that altitude, soil electrical conductivity and soil bulk density significantly influenced the changes in the leaf stoichiometric characteristics, explaining 75.5% of the total variation, and altitude had the greatest influence (36.6%). In the temperate mountains, altitude played a decisive role in affecting patterns of meadow plant nutrients and stoichiometry and was more important than soil in explaining leaf C∶N∶P stoichiometry variations. Our findings provide important references to understand the responses of plant stoichiometry to altitudinal gradients.

Characterizing of Sandy Loam Soil Electrical Conductivity and Cone Index Relationship at Varying Depths in Punjab Region

Soil constitutes a fundamental resource for the production of food and fiber, thereby meeting diverse human needs and sustaining global ecosystems. Soil compaction and electrical conductivity are key soil properties that can significantly impact soil health and contribute to environmental challenges. The findings of the study shed light on the severity of soil compaction, with the highest cone index 4495 kPa value recorded at a depth of 225 mm in sandy loam soil. This highlights the potential limitations on root growth and nutrient uptake, which can have implications for plant productivity and the overall ecosystem. Furthermore, the study examined the electrical conductivity of the soil, which serves as an indicator of soil salinity. Elevated electrical conductivity levels can lead to adverse effects such as reduced crop yields and environmental stress. Bulk density was increased (1.4 to 1.73 Mg/m3) as well as the moisture content of the soil was decreased (7.6 to 4.3 %). Understanding the range of electrical conductivity values observed in the study (11 to 29 mS/m) helps to assess the extent of salinity-related challenges in the studied region. By establishing regression equations between cone index and soil properties like bulk density and moisture content, the study provides valuable insights into the underlying relationships that contribute to soil compaction and its environmental implications. The coefficient of determination (R2) between the bulk density with moisture content and cone index was 0.99 and 0.95, respectively. These findings can assist in the development of strategies to mitigate soil degradation, promote sustainable land management practices, and address environmental concerns related to soil health.

Effect of Subsurface Drainage Combined with Biochar on the Bacterial Community Composition of Coastal Saline Soil

Waterlogging and salinization are considered to be the main threats to agricultural productivity and land resources in coastal areas of China. Thus far, drainage and field soil improvement programs have been ineffective. In this article, we investigated the effect of subsurface drainage combined with biochar (B–S) on soil physicochemical properties and soil bacterial community structure in coastal saline soil. In this study, B–S significantly reduced soil electrical conductivity (EC) and soil water content (W) by 35% and 10.65% compared to no drainage (CK). Compared to CK and drainage alone (S), B–S significantly increased soil total nitrogen (TN) by 24.78% and 39.62%, soil available phosphorus (AP) by 28.29% and 69.82%, soil nitrate (NO3−-N) by 64.65% and 35.45%, and significantly increased soil organic matter (SOM) by 74.69% and 66.10%, respectively. It also significantly increased alkaline phosphatase (ALP) and urease activities. The results of redundancy analysis (RDA) showed that CAT and urease made the greatest response to changes in environmental factors, indicating that CAT is more sensitive to changes in environmental alterations than ALP. AP was the dominant factor in the change in enzyme activity (R2 = 53.0%, p &lt; 0.05), followed by NO3−-N (R2 = 14.8%). SOM was the dominant factor in the variation in microbial abundance content (R2 = 38.5%, p &lt; 0.05), followed by ALP (R2 = 20.0%, p &lt; 0.05). The results of the study can provide guidance for effective land use and sustainable development of agricultural soil ecology in coastal areas.

Different soil textures can interfere with phosphorus availability and acid phosphatase activity in soybean

To achieve sustainable agricultural activity, phosphatase determination is an important practice for improving the efficiency of phosphorus (P) management in tropical agriculture. The objective of this study was to evaluate acid phosphatase activity in different soil textures and P stress levels affecting the nutritional, chemical, biochemical, and agronomic aspects of soybean. Treatments resulted from factorial combination in a 3 × 3 factorial scheme, consisting of three soil textures (clay, medium, and sandy) and three P stress levels (severe, moderate, and control) with four replications. Three different soil textures were used in the research: Latossolo Vermelho Distrófico (LVd) with clay texture, collected in the native forest, equivalent Oxisol (Soil Taxonomy); Cambissolo Háplico Tb Distrófico (CXbd) with medium texture collected in the natural field equivalent Inceptisols (Soil Taxonomy); and Latossolo Amarelo Distrófico (LAd) with sandy texture collected in the natural field equivalent Oxisol (Soil Taxonomy). Soil electrical conductivity, P available (method Mehlich-1), and acid phosphatase activity (ρ-nitrophenol released) (μg h−1 g−1 soil) were analyzed and the samples were collected at a depth of 0–20 cm. Also evaluated were the height of plants, number of leave and branches, dry mass (root, leave, and stem), P total concentration in leaf, and P translocation (transport from root to shoot) of soybean plants 45 days after sowing. Results showed the clayey textured soil provided the best results for plant growth, root, stem, and leaf dry matter content, P total concentration of P in leaf, P translocation (transport from root to shoot), P available in the soil, and higher acid phosphatase activity of under P stress. Results showed that the Latossolo Vermelho Distrófico (LVd) provided the best results in managing P in different soil textures. However, based on growth and development results, a reduction in phosphate fertilization (P stress moderate) may favor acid phosphatase activity. Acid phosphatase activity can be used as an option in the management of P soluble activity in different soil textures. However, in front of the complexity of soil–plant–P–environment interactions, further research needs to be conducted to investigate better these effects of the da acid phosphatase on different soil textures.

Fly Bioash Ameliorates Acid Luvisol and Increases Sunflower (Helianthus annuus L.) Yield in Field Conditions without Compromising the Risk of Radioactive Contamination

Fly bioash (FBA) as a by-product of biomass-fuelled facilities exhibits alkaline properties and is enriched with phytonutrients, thereby offering the potential to effectively ameliorate acidic and nutrient-deficient soils. However, concerns about health risks due to a potential FBA radioactive contamination are still not well studied, notably under field conditions. This study examined pH changes and concentrations of natural (238U, 232Th, 226Ra, 40K) and anthropogenic (137Cs) radionuclides after application of very alkaline (pH &gt; 12) FBA in: (i) highly acid (pHKCl = 4.1) Luvisol and (ii) sunflower (Helianthus annuus L.) seeds, grown in organic farming and rain-fed conditions. FBA (originated from a modern cogeneration, fuelled on certified deciduous forest wood chips) was applied at increasing doses; 0, 4.5, 8.6, 13, and 17.2 t/ha. After 54 months of application, FBA significantly increased soil pHKCl by up to 1.8 unit and the seed yield by 15%, compared with no amended Control, without compromising soil electrical conductivity (salinity). The activity concentrations (Ac) of all observed radionuclides, measured using high-resolution gamma-ray spectrometry, were not altered under FBA application, neither in the surface (0–30 cm) Luvisol horizon nor in the sunflower seed. Moreover, the Ac of 238U, 232Th, and 137Cs in the seed were below detection limit, whereas the Ac of 40K and 226Ra were lower by up to 2.6 and 61 times, respectively, than their corresponding Ac in the soil treatments. The radiological footprint of FBA exhibited lower Ac for most of the observed radionuclides compared with both (i) Croatian non-arable topsoils (with reductions of 238U 3.6 times, 232Th 1.8 times, 226Ra 1.7 times, and 137Cs 1.5 times) and (ii) widely used mineral N/P/K fertilisers in conventional agroecosystems (with reductions of 238U 12.5 times; 226Ra 1.3 times, and 40K 2.4 times). Our findings provide evidence that the application of FBA as a soil conditioner does not pose radiological health or environmental risks, contributing to more sustainable agri-food production and circular bioeconomy. However, it is essential to conduct further studies to comprehensively investigate the effects of FBA application on soil and crop quality across diverse environmental conditions and extended spatiotemporal scales.

A Mobile Laboratory Robot for Various and Precise Measurements of Crops and Soil in Agricultural Fields: Development and Pilot Study

Localized management based on multipoint measurements of crops and soil is expected to improve agricultural productivity. The difficulties with this process are as follows: it is time-consuming due to the many measurement points; it requires various sensors for various measurements; it can lead to unstable measurements due to sunlight and wind. To solve the above issues, the system we propose has the advantages of efficient measurements performed by a robot, various measurements performed through exchangeable sensor units, and stable measurements through protecting the crop from sunlight and wind. As a pilot study for the system, we conducted an experiment to simultaneously measure the crops and soil in a cabbage field. The robot achieved mobility in the field, &gt;4 h of operation time, and the ability to obtain soil electrical conductivity measurements and crop imaging at 100 points. Furthermore, the stability of the measurement conditions within the sensor unit during the experiment was evaluated. Compared to the case without the covering, the illuminance became 280-fold stabler (standard deviation = 0.4 lx), and the wind-induced crop shaking became 20-fold lower (root mean square error of the image pixels = 0.5%). The potential impacts of this research include high reproducibility because of the shareable sensor unit and the expectation of new discoveries using precise indoor sensors.

Effect of Grazing Management on Predator Soil Mite Communities (Acari: Mesotigmata) in Some Subalpine Grasslands from the Făgăraş Mountains-Romania.

For the first time in Romania, a complex study was conducted on soil mite communities from two types of managed grasslands: ungrazed and intensively grazed. The study was accomplished in August 2018, in the Făgăraş Mountains. Within the soil mite communities (Mesostigmata), 30 species were identified, from 80 soil samples. The following population parameters were investigated: species richness, numerical abundance, dominance, Shannon index of diversity, evenness and equitability. Eight environmental variables were also measured: soil and air humidity; soil and air temperature; soil pH; resistance of soil to penetration; soil electrical conductivity; and vegetation coverage. The results revealed that species richness, Shannon index of diversity, evenness and equitability indices had higher values in ungrazed grasslands, whereas in intensively grazed areas, the numerical abundance and dominance index had significantly higher values. The species Alliphis halleri was dominant in the ungrazed grasslands. Each type of managed grassland was characterised by specific environmental conditions, which had an important influence, even at the species level.

Determination of Some Physical Properties and Electrical Conductivity of Loamy Soil with Additives

In this study, the electrical conductivity and physical properties of loamy soil samples with various additives is determined. The electrical conductivity meter was used to obtain the electrical conductivity and some standard methods have been adopted to obtain other properties. It is observed that the soil combined with NPK had the highest electrical conductivity with the least coming from the soil (control). It is concluded that NPK raises the electrical conductivity of the soil. This goes forth to show a measure of the amount of salts in soil (salinity of soil), which is an important indicator of soil health. It affects crop yields, crop suitability, plant nutrient availability, and activity of soil microorganisms which in turn influences key soil processes including the emission of greenhouse gases such as nitrogen oxides, methane, and carbon dioxide. It is recommended that soil with organic manure should be used in order to maintain low salinity and good soil health.

Differences in Aroma Profile of Cabernet Sauvignon Grapes and Wines from Four Plots in Jieshi Mountain Region of Eastern China.

The Bohai Bay region is a famous wine-growing area in China, where the rainfall is concentrated in the summer due to the influence of the temperate semi-humid monsoon climate. As such, the vineyard terrain has a significant impact on the flavor quality of the grapes and the resulting wines. To explore the relationship between the 'Cabernet Sauvignon' wine style and terrain, this study takes four different plots in the Jieshi Mountain region to investigate the differences in the aroma profile of Cabernet Sauvignon grapes and wines of two consecutive vintages. Based on two-way ANOVA, there were 25 free and 8 glycosylated aroma compounds in the grapes and 21 and 10 aroma compounds with an odor activity value greater than 0.1 in the wines at the end of alcohol fermentation (AF) and malolactic fermentation (MLF), respectively, that varied among the four plots. Wines from the four plots showed a significant difference in floral and fruity aroma attributes, which were mainly related to esters with high odor activity values. The difference in concentration of these compounds between plots was more pronounced in 2021 than in 2020, and a similar result was shown on the Shannon-Wiener index, which represents wine aroma diversity. It has been suggested that high rainfall makes the plot effect more pronounced. Pearson's correlation analysis indicated that concentrations of (E)-3-hexen-1-ol in grapes and ethyl 3-methylbutanoate, ethyl hexanoate, isoamyl acetate, isopentanoic acid, and phenethyl acetate in wines were strongly positively correlated with the concentrations of N, P, K, Fe, and electrical conductivity in soil but negatively correlated with soil pH. This study laid a theoretical foundation for further improving the level of vineyard management and grape and wine quality in the Jieshi Mountain region.

Growth and development of bamboo in the coastal inundated area of Bangladesh

Bamboo has been introduced to coastal raised land under the Sonneratia apetala plantation and grew barren land in inundated areas in the western coastal belt of Bangladesh. This study aimed to quantify the bamboo growth in inundated areas at minimound, plain land, and barren land and under the S. apetala plantation and characterize the impact of inundation, soil pH, and soil salinity. The experimental plantation was carried out by B. vulgaris and B. balcooa on a mini-mound on barren coastal raised land in 2018. Other experiments of B. vulgaris were carried out on mini-mound and plain land under the S. apetala plantation in 2019 and 2020. Seedlings were raised by branch cutting. Mini mounds were prepared with soil. The soil sample was collected at different depths in off-peak and peak periods to determine soil pH, electrical conductivity (dsm-1), and nitrogen%. The growth of B. vulgaris in survival (p-value 0.0004) and new culms initiation% (p-value 0.0068) were significantly higher than B. balcooa in the barren land. Soil electrical conductivity showed significantly higher in all soil depths at barren land than under S. apetala forest in off-peak (p-value 0.0000, 0.0000, 0.0016) and peak periods (p-value 0.0002, 0.0028, 0.0000). The higher soil salinity affects the growth of two bamboo species. The higher soil pH affected the growth of B. balcooa on barren land. The growth performance of B. vulgaris showed significantly better survival% (p-value 0.030), height (p-value 0.0010), girth (p-value 0.011), total culms per clump (p-value 0.0086), and new culms initiation% (p-value 0.022) on the mini mound than plain land under S. apetala forest in 2019 and 2020 except height growth. The present study observed an inundation impact on the growth of B. vulgaris in the plain land plantation. B. vulgaris performed better on mini-mound under the S. apetala forest in inundated coastal areas. J. Asiat. Soc. Bangladesh, Sci. 49(1): 55-69, June 2023

Reducing nitrogen fertilizer combined with biochar amendment improves soil quality and increases grain yield in the intensive rice cultivation system

Intensive rice cultivation for a long time resulted in increasing soil degradation and less yield. This study aimed to evaluate effects of the combining reducing nitrogen fertilizer (N) with biochar amendment on soil chemical properties, rice growth parameters, and grain yield in the rice cultivation system in the Mekong Delta region, Vietnam (VMD). Field experiment was designed in the split-plot design with two factors, including N fertilizer (main plot) and biochar (sub-plot). Two N fertilizer rates were: (N50)—50 kg N ha–1 and (N100)—100 kg N ha–1, which is the farmer's practice. Biochar was amended with three rates: no applied biochar (B0), 5 t ha–1 (B5), and 10 t ha–1 (B10). The results indicated that reducing N fertilizer by 50% combined 5–10 t biochar ha–1 resulted in maintaining soil pH, soil electrical conductivity, soil organic carbon, cation exchange capacity, and rice biomass. Applying biochar at a rate of 5–10 t ha–1 significantly increased the available N, available P, and rice height compared to the treatment with no applied biochar (B0). Rice yield in the treatments applied with 5–10 t ha–1 was significantly higher than the treatment without the use of biochar by 11.6–14.7%. The findings of this study confirmed that reducing 50% N fertilizer combined with 5 t ha–1 or 10 t ha–1 of biochar could improve soil available N, available P, rice growth, and grain yield in intensive rice cultivation systems in the VMD region.

Soil Salinity Estimation in Cotton Fields in Arid Regions Based on Multi-Granularity Spectral Segmentation (MGSS)

Soil salinization seriously threatens agricultural production and ecological environments in arid areas. The accurate and rapid monitoring of soil salinity and its spatial variability is of great significance for the amelioration of saline soils. In this study, 191 soil samples were collected from cotton fields in southern Xinjiang, China, to obtain spectral reflectance and electrical conductivity (EC) indoors. Then, multi-granularity spectral segmentation (MGSS) and seven conventional spectral preprocessing methods were employed to preprocess the spectral data, followed by the construction of partial least squares regression (PLSR) models for soil EC estimation. Finally, the performance of the models was compared. The results showed that compared with conventional spectral preprocessing methods, MGSS could greatly improve the correlation between spectrum and soil EC, extract the weak spectral information of soil EC, and expand the spectral utilization range. The model validation results showed that the PLSR model based on the second-order derivative (2nd-der-PLSR) had the highest estimation accuracy among the models constructed by conventional methods. However, the PLSR model based on MGSS (MGSS-PLSR) had the highest estimation accuracy among all models, with Rp2 (0.901) and RPD (3.080) being 0.151 and 1.302 higher than those of the 2nd-der-PLSR model, respectively, and nRMSEP (5.857%) being 4.29% lower than that of the 2nd-der-PLSR model. The reason for the high accuracy of the MGSS-PLSR model is as follows: In the continuous segmentation of the raw spectrum by MGSS, the bands with strong and weak correlations with respect to soil EC were concentrated during low granularity segmentation. With the increase in granularity level, the spectral features decreased and were distributed discretely. In addition, the locations of spectral features were also different at different granularity levels. Therefore, the spectral features of soil EC can be effectively extracted by the MGSS, which significantly improves the spectral estimation accuracy of soil salinity. This study provides a new technical means for soil salinity estimation in arid areas.

Short-Scale Soil Spatial Variability of a Salt-Affected Land Allotment in &lt;em&gt;Maha-Illuppallama&lt;/em&gt;, Sri Lanka

The development of salt-affected soils is a serious limitation for sustainable agricultural crop production in Sri Lanka. This study was conducted to explore the short-scale spatial variability of a salt-affected land allotment at Maha-Illupallama in dry zone, Sri Lanka. Seventy soil samples from a depth of 0 - 30 cm were randomly collected within the study site. Soil Electrical Conductivity (EC), pH, Cation Exchange Capacity (CEC), Exchangeable (Ex.) cations; Ex.K, Ex.Na, Ex.Mg and Ex.Ca were measured using established techniques. Sodium Adsorption Ratio (SAR), Exchangeable Na percentage (ESP), K (EPP), Mg (EMP), and Ca (ECP) were estimated based on the relevant measured soil properties. Exploratory data analysis found considerable spatial variability in EC, ESP, SAR, and EPP while CEC, EMP, and ECP showed moderate spatial variability. The soil pH and BS exhibited lesser spatial variability within the study field. Variogram analyses revealed the presence of strong structured spatial variability for each analyzed soil parameter within the study site. Four Potential Management Zones (PMZs) i.e., PMZ1, PMZ2, PMZ3, and PMZ4 were demarcated using Fuzzy k means classification. Highest EC (1.19 ± 0.70 dS m-1) and SAR (19.05 ± 13.09) mean values were observed in PMZ2. Higher EMP mean values were observed in PMZ 1 and 3 in comparison to PMZ 2 and 4. Other evaluated soil properties varied among the designated PMZs. Soils in several places revealed pH &gt; 8.5, EC &lt; 4.5 dS m-1, ESP &gt; 15%, and SAR &gt; 13 values indicating an occurrence of sodic soil. The results underline the considerable potential for the use of Site-Specific Soil Management (SSSM) practices based on the PMZs in the examined salt-affected soil to boost productivity.

Effect of biochar and bioorganic fertilizer on the microbial diversity in the rhizosphere soil of Sesbania cannabina in saline-alkaline soil.

Biochar and bioorganic fertilizer (BOF) application in agriculture has garnered increasing interest recently. However, the effects of biochar and BOF on rhizosphere soil microecology, especially in a region with saline-alkaline soil, remain largely unexplored. In this study, we performed Illumina-based 16S rRNA sequencing to investigate the effects of biochar with or without BOF addition, as well as at different addition rates and particles sizes, on the microecology of saline-alkaline rhizosphere soil. In the field experiment, biochar and BOF application altered the rhizosphere soil microecology. Actinobacteriota, Proteobacteria, and Chloroflexi accounted for >60% of the total bacterial population in each treatment. In the different treatments, Actinobacteria and Alphaproteobacteria were the predominant classes; Micromonosporales and Vicinamibacterales were the dominant orders; norank_f__Geminicoccaceae and Micromonosporaceae were the most abundant families; and Micromonospora and norank_f_Geminicoccaceae were the predominant genera. Application of biochar with or without BOF decreased soil electrical conductivity (EC) by 7% -11.58% only at the depth of 10 cm below the surface, again, soil EC can be significantly reduced by an average of 4% at 10 cm depth soil after planting Sesbania cannabina. Soil organic carbon, organic matter, available potassium, and available phosphorus contents had significant effects on the soil bacterial community structure. Co-application of biochar and BOF resulted in the greatest improvement of rhizosphere soil microecology, either by promoting plant growth or improving the nutrition and physicochemical properties of soil, followed by BOF alone and biochar alone. Additionally, higher application rate of biochar was better than lower application rate, and fine biochar had a stronger effect than coarse biochar. These results provide guidance for the development of new saline-alkaline soil remediation strategies.

Response of tomato root endophytic bacterial communities to water-oxygen coupling under micro/nanoaerated drip irrigation in slightly saline soils

The aims of this study were to explore the effects of micro/nanoaerated drip irrigation on the root endophytic bacterial communities of crops in saline soils and to offer new insights into how to increase the productivity of such soils by regulating these communities using water-oxygen coupling. A tomato cultivation experiment was conducted in mildly saline soil to evaluate the responses of the root endophytic bacterial community to the soil microenvironment created by micro/nanoaerated drip irrigation. The results revealed that the total relative abundance of phyla, which accounted for 54.80–80.31% of the root endophytic bacterial communities, differed significantly among treatments. The tomato root volume, soil available nitrogen (N) and soil electrical conductivity (EC) were the top three factors that had the greatest influence on the composition and functions of the root endophytic bacterial communities. The ability of these factors to explain the composition differences in the root endophytic bacterial communities reached 0.169, 0.158 and 0.154, respectively. The top three factors were significantly correlated with 10, 13 and 10 functional groups, respectively, of the root endophytic bacterial communities. Furthermore, the structural equation model (SEM) suggested that root endophytic bacterial community functions were significantly correlated with tomato yield (r = 0.71). The combination of the high dissolved oxygen concentration with sufficient and excessive irrigation (A30W1 and A30W1.2) significantly reduced the soil EC and increased the soil available N and root volume, thereby significantly improving the metabolic functions of the root endophytic bacterial communities and the tomato yields. The combination of moderate dissolved oxygen concentration with sufficient and excessive irrigation (A15W1 and A15W1.2) had moderate effects on the metabolic functions of the root endophytic bacterial communities, leading to medium tomato yields. In conclusion, different water-oxygen coupling treatments significantly affected the environmental factors in the root zone and then regulated the metabolic functions of the root endophytic bacterial communities, thus affecting the tomato yields.

How to remediate sulfate-nitrate salinized greenhouse soil? An optimal combination of organic amendment, fertilizer and irrigation

Greenhouse soil secondary salinization is a widespread problem along the lower-middle reaches of the Yangtze River basin, which seriously deteriorates the yield and quality of vegetables. High multiple-cropping index of the greenhouse management needs intensive application of agrochemicals and frequent irrigation which led to significant soil salinization in this area. In this study, we investigated how to remediate the salinized plastic shed soils and improve the yield and quality of vegetables using various measures, including two types of irrigation (intermittent irrigation and 80% water-holding capacity), four types of organic matter (cow manure, mushroom residue, fermented sawdust, and half-fermented sawdust) with two application rates (2 g C kg−1 soil and 8 g C kg−1 soil), and two types of inorganic fertilizers (compound fertilizer with and without sulfate). Results showed that intermittent irrigation decreased either soil electrical conductivity from 1.55 to 0.36 mS cm−1 or the concentrations of soil nitrate from 507 mg kg−1 to 31 mg kg−1 and sulfate from 664 mg kg−1 to 114 mg kg−1 in the incubation period. This effect continued to the next two periods (before seed sowing and after the first harvest). After the second harvest, all these parameters had a recover trend but remained lower than those of the original soil. Half-fermented sawdust had the best effect for soil amelioration among the four organic amendments whilst the effects were not enhanced at higher application rate. Across the two continuous growing seasons (pak choi (Brassica rapa subsp. chinensis) in first season, cherry radish (Raphanus sativus L.) in second season), especially the second harvest season, the compound fertilizer without sulfates ameliorated soil degradation and maintained greater yield compared with sulfate-containing fertilizer. Therefore, application of 2 g C kg−1 half-fermented sawdust with intermittent irrigation and use fertilizer without sulfate was optimum for the degraded greenhouse soil remediation and vegetable yield improvement. This treatment could either decreased soil EC from 1.55 to 0.325 mS cm−1 or the concentration of soil nitrate from 507 to 89 mg kg−1 and sulfate from 664 to 266 mg kg−1 after continuous two growing seasons while the radish yield in second growing season was 71% higher than CK. These findings provided an economical and practical method to remediate sulfate-nitrate salinized greenhouse soil in a short period and designed a field management mode to maintain the efficacy.