Soil Samples Research Articles

Disperse reinforcement of artificial base with glass waste

The article presents the results of laboratory stamp tests of sandy soils, the dispersed reinforcement of which was made with cullet waste in the form of crumbs. The tested soil samples had different densities and, accordingly, for each density, several options were made for the percentage of glass in the mass of the total volume. The purpose of the laboratory research was to obtain such a mechanical characteristic of the soil as the deformation modulus, which was subsequently compared with the same deformation modulus, but not of reinforced soil. The research results obtained showed the effectiveness of using glass chips as dispersed reinforcement of loose soils, which makes it possible to improve its strength properties and significantly save on the installation of artificial foundations for buildings or structures, as well as solve the issue of recycling glass waste and, accordingly, improve the environmental performance of the environment.

Cropping history allows tracking of C4 cover crop residues by δ13C natural abundance

Given potato farm cropping history, the recent introduction of C4 cover crops may provide an in situ opportunity to track their residues by δ13C techniques. From 2019 to 2022 soil (0-15cm) samples were collected on PEI potato farms from 15 paired strips of sorghum sudangrass (SS) and C3 crops. Under C3 crops, soil δ13C was remarkably uniform at -27.7‰ +/- 0.26‰, while SS cover cropping (above ground biomass -12.8‰) significantly enriched soil δ13C values to -27.4‰ +/- 0.38‰. This study demonstrates proof of concept that δ13C techniques can quantify the dynamics of C4 cover crop residues in potato farm soils.

Geochemical assessments and human health risk evaluations of selected farm soils within the Abuja metropolis, North-central, Nigeria

Toxin accumulations in agricultural soils decreases the crop quality and productivity, and threatens the safety of foods, which could cause adverse human health effects. This study assessed the risks associated with potential toxins in the agricultural soils obtained from Lugbe and Jikwoyi in Abuja, Nigeria. An analytical technique for absorption spectrophotometry was adopted, and human health risks were evaluated. Twenty soil samples were collected from two farmlands, and two control samples were taken on unpolluted sites at depths 5-20 cm from the surface at the average suspension of plant roots where the soil holds most plant nutrients and water at a space interval of 5 m. The soils generally had low mean concentrations of Ca, Cu, Zn, Mn, Fe, and Co and moderately high mean concentrations of F, Ni, Pb, Cr, and Mo. The pattern of the pollutants reflected that the pollutants were majorly from anthropogenic activities, such as long-term fertilizer applications and other agrochemicals. The contamination indices revealed reassuringly low to moderate pollution risks to humans. The overall pollution loads suggested that the samples were largely unpolluted. The non-carcinogenic and carcinogenic health risks were within the safety limits for inhalation, dermal, and ingestion, which pose no significant risk to children and adults living in the vicinities of the farmlands. The cancer risks for inhalation were higher than dermal and ingestion, with Cr showing the highest values. The samples were slightly contaminated with potentially toxic metals, which could lead to increased phyto-accumulations, soil pollution, and groundwater contamination.

An investigation on the effect of soil erosion on the properties of soil adjacent to a road right of way (ROW)

ABSTRACT Recently, soil erosion has been a significant and common issue along road right of way (ROW). This study was designed to identify the effect of soil erosion on the physical and chemical properties of soil across a ROW. Land use land cover (LULC) map, soil map, and field observation were adopted to ensure proper sampling. Moisture content, grain size analysis, soil texture, consistency test, organic content and matter, pH, and cation exchange capacity (CEC) were conducted on 10 representative soil samples collected from 14 km ROW. The laboratory results from moisture content, pH, and CEC revealed samples taken from the erosion fields (20.79% to 26.41%), (8.48 to 8.66), and (18.02 to 24.03) appeared to be higher than those taken from non-eroded fields (16.79% to 18.51%), (8.18 to 8.3), and (14.5 to 16.15), respectively. The organic content of the soil in the non-eroded areas was higher than that in the eroded areas. This variation in soil properties is primarily attributed to differences in LULC and soil composition. With regard to consistency properties, the soil was marked as highly erodible. Treatment of drainage structures, demarcating ROW, ROW stabilization, and awareness creation were proposed as feasible remedial measures. Finally, the soil along Sawla to Bulki ROW was identified as erodible soil as per experimental results and analysis.

DEVELOPMENT AND OPTIMIZATION OF HPLC METHODS FOR THE CHIRAL SEPARATION OF ARYLPYRAZOLE, CHLOROACETANILIDE AND ORGANOCHLORINE PESTICIDES: CASE STUDIES OF BENZOBICYCLON, ACETOCHLOR AND CHLORDANE.

This work is centered on the development and optimization of High-Performance Liquid Chromatographic methods for the separation of chiral pesticides, particularly benzobicyclon, chlordane and acetochlor employing Agilent Technologies Infinity II chiral HPLC system equipped with a UV – 2000 detector. The stereoisomers were successively separated using a standard analytical column of dimensions 250 mm X 4.6 mm. The Cis– stereoisomers of chlordane exhibited partial baseline separation while the Trans – enantiomers were fully separated. Benzobicyclon and acetochlor enantiomers attained full baseline separation under optimized conditions. Chlordane and benzobicyclon were analyzed using normal phase chromatography [NP]c with a mobile phase of 90% Normal hexane and 10% Isopropanol, while acetochlor was analyzed by reverse phase chromatography [RP] c using 70% methanol and 30% water. Benzobicyclon was later spiked into soil sample and subsequently extracted using Environmental Protection Agency (EPA) methods and the extracts were further analyzed with a shorter analytical column of dimensions 75 mm X 4.6 mm. The HPLC separation revealed that the longer column provided more efficient separation for the benzobicyclon stereoisomers than the shorter column as reflected by high separation factors (?). The high recovery rate of the stereoisomers of benzobicyclon and the internal standard from the soil extracts confirmed the effectiveness of the method of extraction and the HPLC system employed.

Multiple Phytophthora species associated with declining wild olive trees in Sardinia, Italy

AbstractWild olive represents one of the most iconic woody plants in the Mediterranean Basin. This slow‐growing evergreen tree is characteristic of sclerophyll vegetation, extremely tolerant to drought, salinity and diseases, thus is commonly used as rootstock for grafting cultivated olive varieties. Since 2022, extensive dieback and mortality of wild olive trees have been observed in Sardinia, Italy. Affected plants showed leaf chlorosis, wilting, defoliation, shoot blight and epicormic shoots, often associated with root rot and necroses on the feeder roots, initially associated with Phytophthora bilorbang and P. pseudocryptogea. A 2‐year study was thereafter conducted to clarify the aetiology of this unusual disease. Using a baiting technique, 10 Phytophthora taxa from three phylogenetic clades (2, 6, 8) were isolated from 53 of 87 rhizosphere soil samples collected, including P. asparagi, P. bilorbang, P. crassamura, P. inundata, P. kelmanii, P. oleae, P. pseudocryptogea, P. sansomeana and P. syringae. Additionally, some isolates that showed several polymorphisms in rDNA internal transcribed spacer (ITS) sequences compared with closely related known species are reported here as P. taxon paulensis. Pathogenicity tests on 1‐year‐old wild olive seedlings showed that nine out of 10 Phytophthora taxa significantly reduced root length of inoculated seedlings compared to controls. P. inundata and P. oleae caused the greatest reduction, while root length of seedlings inoculated with P. kelmanii did not differ from the controls. This study provides insights into the role of Phytophthora taxa in the wild olive decline in Sardinia, indicating the urgent need to expand monitoring and implement effective management strategies to mitigate the disease.

Effects of Fresh and Composted Azolla on Soil Chemical Properties

The rise in chemical fertilizer use in Malaysia raises concerns about soil degradation and potential long-term yield reductions, highlighting the importance of using organic matter for soil restoration. Azolla has been extensively studied as an alternative soil amendment due to its high nitrogen and nutrient content, as well as its rapid growth. However, the effects of fresh and composted Azolla amendments on soil chemical properties are not yet fully understood. A soil incubation study was thus conducted to determine the effects of fresh and composted Azolla on soil chemical properties over a 3-month incubation period. The soil treatments consisted of non-amended soil (control); fresh Azolla at 3, 6, and 9% w/w; and composted Azolla at 1, 2, and 3% w/w, with soil water holding capacity maintained at 55% throughout the incubation period. The collected soil samples were analyzed for soil pH and electrical conductivity (EC), total carbon (C) and nitrogen (N), available phosphorus, exchangeable bases—potassium (K), calcium, and magnesium, using inductively coupled plasma optical emission spectrometry, and cation exchange capacity (CEC). All data were subjected to variance analysis for statistical analysis. The study revealed significant effects of interaction between soil treatments and incubation periods for all soil parameters. At the end of the incubation period, the soil treated with 3% composted Azolla exhibited higher soil EC, total C and N, exchangeable K, and CEC compared to other soil treatments. The 3% fresh Azolla treatments were also observed to improve the soil’s exchangeable calcium by the end of the incubation period. In conclusion, 3% composted Azolla is best to help restore soil nutrient levels for crop uptake.

Isolation and characterization of phosphate solubilizing bacteria from the rhizosphere of lentil (Lens culinaris M.) collected from Hagere Mariam district, Central Ethiopia.

Phosphorus plays a crucial role in regulating many of the plant's metabolic activities by enhancing physiological functions and stimulating biological activities such as nodulation, nitrogen fixation, and nutrient uptake in the soil rhizosphere environment. Inoculants of phosphorus solubilizing bacteria serve as an eco-friendly alternative technology that positively influences both soil sustainability and plant growth. The majority of North Shewa highland areas are characterized by low available phosphorus, primarily acidic, and exhibit strong phosphorus absorption. The objective of this study was to isolate and identify phosphorus solubilizing bacteria from the rhizosphere of lentils and characterize their phosphate solubilizing activity. The cultural, biochemical, physiological microbial analysis was conducted in the microbiology laboratory, department of biology. Pikovskaya's medium was utilized for the isolation, screening, and maintenance of phosphate solubilizing bacteria. Phosphate Solubilizing Bacteria were isolated using tri-calcium phosphate as the sole source of phosphorus in indicator plates. Fifteen phosphate solubilizing bacteria were isolated from lentil rhizosphere soil samples, among which six were the most efficient phosphate solubilizers designated as PSBYE, PSBYR, PSBYM, PSBYL, PSBW, and PSBSW. All isolates notably solubilized tri-calcium phosphate compared to the uninoculated control. The highest phosphorous solubilization was observed from the isolate PSBYL, with a value of 10.61mg/50ml, followed by PSBW with a value of 9.08 mg/50ml. The decrease in pH value correlated with the levels of tri-phosphate solubilization in the PVK broth by the PSB isolates. The pH dropped to 4.64 from the initial pH of 7.2 when grown in the broth, which suggests that the production of organic acids is likely the primary mechanism for phosphate solubilization.

Impact of Agricultural Activities on Soil Particle Size, pH, and Organic Matter in the Dimonika Biosphere Reserve, Mayombe (Republic of Congo)

Land-use change disrupts several soil physico-chemical parameters. This study aimed to analyze the influence of agricultural activities, topography, and localities on soil texture, pH, and organic matter in the Dimonika Biosphere Reserve. To achieve this, 90 soil samples were collected using an auger based on land use types, topography, and localities. Analyses of soil texture, pH, total organic carbon (TOC), and total nitrogen (TN) were conducted at the IRSEN laboratory in Pointe-Noire. The results showed that clay texture predominates in the studied area, which is related to the nature of the soils. The Kruskal-Wallis ANOVA test highlighted a significant effect of agricultural activities on soil acidity, with an acidic pH ranging from 4.2 to 5 in cultivated areas, compared to a very acidic pH (3.5 to 4.2) in mature forests. However, neither topography nor localities affected pH. Total organic carbon significantly decreased in old plantations (1.3±0.3%) and fallows (1.5±0.5%) compared to mature forests (1.9±0.5%) and savannahs (2.3±0.6%), while total nitrogen showed no notable variations. Topography also had no influence on organic status (TOC, TN). However, at the local level, the Makaba area stood out with significantly higher TOC (2±0.5%) and TN (0.2±0.03%) compared to Les Saras (0.14±0.03%) and Kayes (0.16±0.2%). The C/N ratio, influenced only by agricultural activities, was below 15, indicating rapid organic matter mineralization and a low TOC content. Several potential solutions were proposed for sustainable soil management.

Research on heavy metal enrichment and transportation in tea plant-soil systems of different varieties.

This study aimed to investigate heavy metal enrichment in different tea plant varieties and their distribution within different plant parts and to clarify the behavioral characteristics of heavy metals in the tea tree-soil system and their influencing factors. In this study, soil samples were collected from the root zones of 13 tea tree varieties in Guizhou, which had been planted for 10years. The aim was to compare the physicochemical properties of tea plantation soils under soil-forming matrixes and consistent management. Additionally, the study investigated the enrichment and transportation patterns of Cd, Cr, Cu, Pb, Zn, and Ni in the tea tree-soil systems of different tea tree varieties. The results showed that the planting of tea trees decreased the soil pH by 0.5; soil nutrients decreased; soil Pb, Cr, Ni, Cu, and Zn contents in the root zone increased; and Cd content decreased. Heavy metals were mainly enriched in the roots, and Zn, Cu, Ni, and other elements related to the protein and enzyme synthesis of tea trees could be mostly transported to the stems and leaves. There were significant differences in the enrichment and transportation of heavy metals among the different tea tree varieties. Under consistent soil-forming parent material, soil pH, organic matter, nutrients, and other indices only had a significant effect on heavy metal enrichment in the tea tree roots. Therefore, in areas with high background soil heavy metal contents, the construction of tea plantations should be based on regional soil environmental conditions to choose tea tree varieties with low heavy metal enrichment capacities to avoid the risk of high background soil heavy metals on the safe production of tea for consumers.

Impact of hydrochar in stabilization/solidification of heavy metal-contaminated soil with Portland cement.

Stabilization/Solidification (S/S) using Portland cement is a common soil remediation technique for heavy metal-contaminated sites. However, due to the hindrance of cement hydration by heavy metals (HMs) and the high CO2 emissions from cement production, efforts have been made to reduce cement consumption. Supplementary cementitious materials (SCMs) present an efficient alternative for this purpose. This study investigates the impact of hydrochar and modified hydrochar as SCMs for remediating soils contaminated with Zn, Pb, and Cd. Forty treated soil samples were evaluated using unconfined compressive strength (UCS), pH, Toxicity characteristic leaching procedure (TCLP), and sequential extraction procedure (SEP) tests, and statistical analysis was conducted to assess the effects of binder content, hydrochar dosage, and hydrochar type. Results show that substituting cement with hydrochar or modified hydrochar reduces UCS by 10-40%, with hydrochar having a greater negative impact than modified hydrochar. pH values ranged from 6.98 to 12.64, facilitating HMs precipitation. In heavily contaminated samples, hydrochar or modified hydrochars significantly decreased the Zn, Pb, and Cd TCLP values by 55%, 63%, and 50%, respectively. In moderately contaminated samples, the reduction was slight for Zn and Pb, with no significant change for Cd. SEP test results indicated that hydrochar or modified hydrochar in cement improves the transformation of the acid-soluble fraction to the residual fraction of Zn and Pb, but not for Cd-contaminated soil samples. Overall, these findings suggest that incorporating hydrochar or modified hydrochar as SCMs in cement contributes to reducing cement usage and CO2 emissions while enhancing the stabilization efficiency of certain heavy metals in contaminated soils.

Complete genome sequences of mycobacteriophages Ashwin from cluster O and Chanagan from cluster A1.

Ashwin and Chanagan are double-stranded siphoviral mycobacteriophages isolated from a single soil sample from a lavender flowerpot in Johannesburg, South Africa. Both are capable of infecting and lyzing Mycobacterium smegmatis and are predicted to contain 122 and 91 open reading frames, respectively, most without known function.

Validation of Double Constant and Falling Head Permeameter for Determination of Hydraulic Conductivity of Soils in the Laboratory

The objective of this research was to validate alternative equipment for determining the hydraulic conductivity of saturated soil (Ksat) in laboratory settings. The aim was to develop a single piece of equipment that could be used to carry out tests using both the constant-head permeameter (CHP) and the falling-head permeameter (FHP) methods with minimal disturbance to the samples. To this end, undisturbed soil samples were collected (in volumetric cylinders with 100 and 250 cm3) from three soil profiles with different textures to evaluate the sensitivity of the double permeameter (DP) in determining Ksat, considering the method, the sample size, and the textural class of the soils. To assess the efficacy of the DP in estimating Ksat, the coefficient of variation (CV) was determined for the two methods (CHP and FHP), the sample size (100 and 250 cm3), and the applied hydraulic head (cwc) (constant: 1.5 and 2.5 cwc; falling: Δhi, upper limit, h1 = 67.6 and h2 = 57.6 cwc; Δhii, medium limit, h1 = 49.3 and h2 = 39.3 cwc; and Δhiii, lower limit, h1 = 31.3 and h2 = 21.3 cwc). The results indicate that the DP may be employed as an alternative permeameter for Ksat tests employing the CHP and FHP methods. The most favorable statistical coefficients were observed in tests conducted with samples of a sandy texture (Profile 3, Ap horizon), particularly those with a larger volume (250 cm3), for both the CHP and FHP methods, irrespective of the applied hydraulic head. The equipment can be utilized within the full range of methodological limits employed in this study, and the appropriate limit must be selected according to the physical properties of the soil to be employed in the tests.

Prediction and pathway models for assessing soil properties influencing soil selenium enrichment and bioavailability in Aksu Prefecture, northwest China.

Selenium (Se) in soil is the primary source of human Se intake, and its content and bioavailability are influenced by soil physicochemical properties. However, the influence of soil physicochemical properties on Se enrichment and bioavailability in soil remains uncertain. Therefore, this study investigated 536 soil samples and their corresponding wheat grain samples collected from the oasis zone of Aksu Prefecture, located in northwest China. The Se content, spatial distribution, and bioaccumulation factor (BCF) in soil and wheat grains as well as soil Se fractions were examined, and the effects of soil physicochemical properties on Se enrichment and bioavailability were assessed. The results indicated that the mean Se content of soil (0.32 mg/kg) surpassed the national Se background level for Chinese soil by a factor of 1.10. The average Se content (0.13 mg/kg) in wheat grains met the national standard for Se-rich cereal products. The prediction model established using multiple linear regression showed that soil calcium carbonate (CaCO3), organic matter (OM), cation exchange capacity (CEC), and electrical conductivity (EC) were the main physicochemical factors influencing Se enrichment in soil, accounting for 29 % of the variation. The main physicochemical factors affecting Se bioavailability were CaCO3, OM, and iron, and the main Se fractions were the exchangeable and humic acid-bound Se fractions, which together explain 12 % of the variance. Additionally, a structural equation model was employed to analyze the pathways and interactions of soil factors on soil Se enrichment and bioavailability. The results indicated that soil CaCO3 and OM were the most critical factors affecting Se enrichment and bioavailability in soil. These findings can provide technical guidance for the cultivation and layout of Se-rich wheat in local and other similar regions around the world.

Prediction of soil organic carbon and total nitrogen affected by mine using Vis-NIR spectroscopy coupled with machine learning algorithms in calcareous soils.

The utilization of visible-near infrared (Vis-NIR) spectroscopy presents a nondestructive, fast, reliable and cost-effective approach to predicting total nitrogen (TN) and organic carbon (OC) levels. This study employed a combination of Vis-NIR spectroscopy, partial least-squares regression (PLSR), and support vector machine (SVM) models to investigate the effects of mining on TN and OC stocks in both the topsoil (0-10 cm) and subsoil (10-40 cm). 105 soil samples were collected from agricultural areas near an iron mine, polluted, moderately-polluted, and non-polluted sites. Results indicated that soils at the non-polluted site had the highest of soil OC stocks (7.5 kg m-2) and total nitrogen (2.5 kg m-2), followed by the moderately-polluted site. Furthermore, it was observed that soils from the polluted site displayed the highest spectral reflectance. The spectral bands in the range of 500-700 nm showed the strongest correlation with soil organic carbon content. Notably, the SVM method utilizing Vis-NIR spectroscopy provided superior predictions for both subsoil and topsoil organic carbon and total nitrogen compared to the PLSR methods. Additionally, SVM demonstrated better performance in predicting topsoil soil organic carbon (R2 = 0.87, RMSE = 0.13%, and RPD = 2.8) and total nitrogen (R2 = 0.91, RMSE = 0.13%, and RPD = 2.4) compared to the subsoil, owing to the larger OM content in the topsoils.

Investigation on possibility of mangrove regeneration: a case study from Indian Sundarbans.

Mangroves serve as biotic fences of estuarine belts consisting of salt-tolerant plants that grow in intertidal zones and can be regenerated naturally as well as artificially. Mangrove regeneration refers to the process of restoring or rebuilding mangrove ecosystems that have been already degraded, damaged, or lost from their native place through the monitoring of geomorphological, taxonomical, pedological, and ecological aspects. The primary objective of this study was based on the remote sensing application through several important health monitoring indices over the minute part of Indian Sundarbans to prove the possibility of mangrove regeneration. Change detection analysis in the indices proves that there was possible growth and development in mangrove colonization over the same. The secondary objective is to comprehend the association of field-related study with the remotely sensed data on species diversity assessment over the same where the native species are Avicennia marina (Peyara Bain), Avicennia officinalis (Jat Bain), Avicennia alba (Kalo Bain), Aegialitis rotundifolia (Tora), Acanthus ilicifolius (Horgoj Kanta), Bruguiera gymnorrhiza (Kankra), Ceriops tagal (Goran), and Aegiceras corniculatum (Khalisi). The latter objective is associated with the tertiary one that unveils the correlation between several physico-chemical properties of soil samples taken from the field with the species accommodation.Textural classes are grouped between clay and silty clay that helps to get the foundation of hard wood-basedspecies (Avicennia type) specifically with the salinity ranges between 200 ppt (Site 2) and 633 ppt (Site 1)approximately which presents that the zone is highly saline zone as specifically Avicennia species can sustain highsalinity. Importance Value Index (IVI) and species diversity indices have been run to support whether the zone is diversified or not.Equilibrium between deforestation and regeneration through mangrove plantation has to be attained in the nearfuture as deforestation for the livelihood purposes exists, so this newly born island locally named Dorabagdamangrove patch, upper part (Gopalganj) of Kaikhali village, would be the best experimental study site on mangroveregeneration.

Temporal Trends in Soil Health and Productivity on Reclaimed Natural Gas Pipeline Rights‐of‐Way on Cropland

ABSTRACTThe construction of underground pipelines negatively impacts soil productivity in various ecosystems. However, the temporal progression in the recovery of soil productivity following the reclamation of cropland impacted by natural gas pipeline rights‐of‐way (ROWs) construction remains unclear. This study examined temporal, post‐reclamation changes in selected soil health indicators and productivity on reclaimed underground natural gas pipeline ROWs on cropland. Soil and crop samples were collected from ROWs ranging in time elapsed since reclamation (TSR) from 6 to 12 years and from adjacent undisturbed locations (off‐ROW) in the same field. The soil samples were analyzed for soil health indicators (permanganate‐oxidizable carbon (POXC), soil respiration, and autoclaved citrate‐extractable (ACE) protein) and selected chemical properties. Crop samples were assessed for grain and total biomass yields as well as grain protein content. Compared to the off‐ROW, soil organic C on the ROWs was 29% (6‐year ROW) and 33% (9‐year ROW) lower than on the off‐ROWs. Soil respiration recovered within 6 years of ROW reclamation, whereas it took 12 years for POXC and ACE protein to recover to off‐ROW levels. Grain and biomass yields 12 years post‐reclamation were still 42% and 36%, respectively, lower on the ROWs than on the off‐ROWs. However, measured soil attributes recovered faster than crop variables, indicating that pipeline construction on cropland has longer‐term impacts on crop yields than on soil attributes. These results indicate that, although underground pipeline construction has detrimental impacts on soil and crop attributes, these attributes would slowly recover to pre‐construction levels with increasing TSR.

Changes in 129I concentration of soil samples after thermal drying.

To precisely evaluate the concentration of iodine-129 (129I) in soil samples, changes in this concentration after thermal drying under several temperature conditions were investigated. The soil sample used in this study was collected from a site located near a nuclear fuel reprocessing plant, which atmospherically released 129I in a test operation in 2006-2008, resulting in the soil sample containing higher 129I concentrations than their natural levels. Thermal drying was conducted from 60°C to 110°C and compared with lyophilization result, showing that the 129I concentration in the soil sample was statistically comparable among all the drying treatments.

Impact of continuous cropping on tobacco growth, stress resistance, and soil microecological structure

Tobacco fields have been continuously cropped for several years because of the high demand for tobacco leaves and limited land resources. To explore the effects of continuous cropping on tobacco growth and soil microecological community structure, this study compared the agronomic traits and physiological resistance characteristics of tobacco plants grown in noncontinuous cropping soil and soil with different continuous cropping years. High-throughput sequencing technology was used to analyze and predict the microbial community structure and functional gene variation patterns of tobacco soil. The results demonstrated that continuous cropping significantly impacted the average height, leaf area, and stem diameter of tobacco plants, as well as the contents of malondialdehyde, hydrogen peroxide, and glutathione in tobacco leaves that were continuously cropped. The relative abundances of Proteobacteria, Bacteroidetes, and Gemmatimonadetes in tobacco soil decreased with an increase in continuous cropping years, while relative abundance of Acidobacteria increased. The biodiversity index of tobacco soil samples showed a decreasing trend with an increase in continuous cropping years, with the sample with the longest continuous cropping year (33 years) having the lowest biodiversity index. Prediction of the potential functions of soil samples with different continuous cropping years revealed that the Z-scores of each pathway in noncontinuous cropping soil samples ranged from 1.12 to 0.078, while those in 33-year continuous cropping samples decreased from −0.10 to −1.41. Our findings indicate that continuous cropping has negative impacts on soil health and microecology, leading to a reduction in beneficial microbial population and microbial diversity.

Sustainable Nitrogen Management in Rice Farming: Spatial Patterns of Nitrogen Availability and Implications for Community-Level Practices

Sustainable nitrogen management is crucial for long-term food security and environmental protection in rice farming systems. However, the spatial patterns of nitrogen availability at the community level remain poorly understood, hindering the development of effective sustainable management strategies. This study introduces a novel application of spatial autoregressive analysis to investigate available nitrogen distribution in paddy soils across a rice farming community in Kyoto, Japan. Soil samples from 61 plots, including organically farmed ones, were analyzed for available nitrogen and various physicochemical properties. Contrary to the hypothesis of high variability between adjacent plots, significant positive spatial autocorrelation in available nitrogen was observed, revealing previously unrecognized community-level patterns. The spatial Durbin model outperformed traditional regression approaches and revealed complex spatial interactions in soil properties. Water-soluble organic carbon and humus content showed strong but opposing effects, with a positive direct impact but negative spatial interaction, suggesting topography-driven accumulation processes. Water-soluble nitrogen exhibited reverse patterns with negative direct effects but positive spatial interaction, indicating potential nutrient transport through water movement. These findings highlight the importance of considering both direct and indirect spatial effects in understanding soil fertility patterns, challenging the conventional plot-by-plot management approach. This methodological advancement provides new perspectives for more effective, community-scale soil management strategies in rice farming systems. Moreover, it demonstrates an innovative approach to maximizing the value of outsourced soil analysis data, providing a model for more comprehensive utilization of such data in agricultural research. By enabling more targeted and efficient nitrogen management practices that consider both plot-level processes and landscape-scale interactions, this study potentially contributes to the development of more sustainable and resilient rice production systems.