Soil & Tillage Research最新文献

{"title":"Spatiotemporal variations and driving factors of farmland soil organic carbon in various landforms of a complex topography","authors":"","doi":"10.1016/j.still.2024.106248","DOIUrl":"10.1016/j.still.2024.106248","url":null,"abstract":"<div><p>Estimating the spatiotemporal variations and driving factors of farmland soil organic carbon density (SOCD) is of great significance for enhancing soil carbon sequestration capacity. Herein, a large region of complex topography was targeted, which includes hill–mountain, valley–basin, and plain–platform. Based on the massive amounts of sampling data (57,254 measured values) and a large-scale soil map of 1:10,000 (371,976 polygonal patches), the gravity center migration model and gray correlation model were used to quantify the spatiotemporal variations and driving factors of farmland SOCD. The results indicated that the farmland soils in the study area had dual functions of carbon source and sink during 1982–2018, of which 45.50 % and 54.50 % were identified as carbon source and sink, respectively. Specifically, the SOCD for the entire study area, its hill–mountain, and valley–basin increased from 2.79 kg m⁻², 2.97 kg m⁻², and 3.06 kg m⁻² to 2.87 kg m⁻², 3.06 kg m⁻², and 3.14 kg m⁻², respectively, with 0.08 kg m⁻² carbon sequestrations and a northeast migration direction for the SOCD gravity center (angle: 21.94°, 23.56°, and 18.82°; distance: 1.56 km, 2.73 km, and 3.20 km). There was a smaller increase of 0.07 kg m⁻² in SOCD for the plain–platform from 2.38 kg m⁻² (1982) to 2.45 kg m⁻² (2018), and the SOCD gravity center migrated to the southwest with an angle of −172.46° and a distance of 1.84 km. Thus, the spatiotemporal variations of farmland SOCD in various landforms varied greatly. Over the past 36 years, SOCD variations were driven by a combination of intrinsic soil factors and external factors such as human disturbance. However, the driving effects of these factors on the landforms of hill–mountain, valley–basin, and plain–platform were quite different in size and order. Therefore, we suggest that topography must be considered when formulating policies to improve soil carbon sequestration, and priority should be given to landform-specific SOCD variation and the factors contributing to them.</p></div>","PeriodicalId":49503,"journal":{"name":"Soil & Tillage Research","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141769206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Adoption of no-tillage alters the pools of SOM with various thermal stability and their chemical composition by changing their sources in Northeast China","authors":"","doi":"10.1016/j.still.2024.106242","DOIUrl":"10.1016/j.still.2024.106242","url":null,"abstract":"<div><p>The stability and chemical composition of SOM are related to the changes of the proportions of old and young SOM. However, there are few studies that investigated the effects of no-tillage (NT) on the stability, chemical composition, and sources of SOM. In this study, the effects of 9-years of NT on the contents of total, thermally labile and stable SOM, their chemical composition and the contributions from C₃ and C₄ plants were determined. Before application of NT, the field has been used for C₄ maize cultivation under conventional tillage (CT) management about 80 years after initial C₃ grassland reclamation. Soil samples were collected in the 0–20 cm soil profile. Under NT treatment, the contents of total SOC, thermally labile and stable SOC, and C₄-SOC decreased with soil depths. However, they were greater in the 0–10 cm layers than that in the 10–20 cm layer under CT. The contents of C₃-SOC showed no change with depths under both of tillage treatments. NT had greater contents of total SOC, C₄-SOC, thermal-labile SOC, and C₄-SOC_{thermal-labile} than CT in the 0–5 cm layer, but lower in the subsoil layers. The contents of C₃-SOC_{thermal-labile} decreased in the 0–5 cm layer under NT. The alkyl-C and O-alkyl-C were the main fractions of thermal-labile SOM and aromatic-C was the dominant fraction of thermal-stable SOM. C₄-SOC (young SOC) was significantly positively correlated with alkyl-C and O-alkyl-C and negatively correlated with aromatic-C. Our results indicated that: (1) compared with continuously CT, applying NT resulted in SOC accumulation in the surface layer, (2) more maize residue input increased the new thermally labile and stable SOM yet lead to decrease the C₃-SOC_{thermal-labile} under NT, (3) the contributions of C₃ and C₄-direved SOM determined the chemical compositions of various SOM pools.</p></div>","PeriodicalId":49503,"journal":{"name":"Soil & Tillage Research","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141769207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Amended soils with weathered coal exhibited greater resistance to aggregate breakdown than those with biochar: From the viewpoint of soil internal forces","authors":"","doi":"10.1016/j.still.2024.106244","DOIUrl":"10.1016/j.still.2024.106244","url":null,"abstract":"<div><p>Soil erosion is the first threat to soil functions. Reducing the soil aggregate breakdown strength is a key step to improve the soil’s ability to resist rainfall splash erosion. Soil internal forces have been found to be the initial and important forces driving aggregate turnover. The application of exogenous organic materials can effectively improve soil aggregate stability and the resistance to rainfall erosion of agricultural soils. However, from the perspective of soil internal forces, information about the reduction effects of the exogenous organic materials application on soil aggregate breakdown is scarce, especially in comparing the effects of different materials. In this study, weathered coal and biochar were individually applied to loamy clay soil at rates of 0 %, 1 %, 2 %, and 3 % (w/w). Soil internal forces, aggregate breakdown strength, and splash erosion rate of different amended soils were then examined after four years. The results showed that compared with unamended soils (0 %), both weathered coal and biochar applications clearly increased the van der Waals attractive pressure and thus decreased the positive net pressure between soil particles. Additionally, these materials reduced soil aggregate breakdown strength and splash erosion rate. The application effects of the two materials were increased with their application rates. Under a lower electrolyte concentration in soil solution (0.0001 mol L⁻¹), the aggregate breakdown strength in the soils amended with weathered coal was lower than that with biochar by 9.6 %, 23.2 %, and 17.7 % (when the diameter of broken aggregate was &lt; 10 μm) and by 10.3 %, 20.8 %, and 17.5 % (when the diameter of broken aggregate was &lt; 20 μm) at the 1 %, 2 %, and 3 % application rates, respectively (<em>P</em> &lt; 0.05). Additionally, soils amended with weathered coal exhibited lower splash erosion rates compared to those amended with biochar, particularly at the higher application rate of 3 %. From the viewpoint of soil internal forces, weathered coal appears to be a suitable exogenous organic material for improving soil aggregate stability and anti-erosion ability during rainfall events. Our findings provide valuable insights into utilizing exogenous materials to improve soil resistance to rainfall splash erosion, assisting agricultural soil management in areas frequently affected by rainfall erosion.</p></div>","PeriodicalId":49503,"journal":{"name":"Soil & Tillage Research","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141769209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Does spontaneous cover crop increase the stocks of soil organic carbon and nitrogen in commercial olive orchard?","authors":"","doi":"10.1016/j.still.2024.106237","DOIUrl":"10.1016/j.still.2024.106237","url":null,"abstract":"<div><p>Management practices in the inter-row area of olive orchards are undergoing significant transformations. Current regulations and recommendations are increasingly advocating the implementation of temporary spontaneous cover crops (TSCV) mainly to reduce erosion. Existing research has predominantly focused on evaluating the effectiveness of TSCV in mitigating soil erosion in olive orchards, with limited attention given to carbon (C) cycling, despite the potential of TSCV for contributing to the removal of atmospheric CO₂ and in the reduction of eroded carbon. Moreover, the limited number of studies on the effects of TSCV on C cycling have been confined to a few experimental sites and at the short term. This study aimed to assess the potential of TSCV to enhance carbon sequestration and nitrogen retention in rainfed commercial olive orchards under semi-arid conditions. To achieve this, we evaluated the annual aboveground organic carbon input due to TSCV, as well as the stocks of soil organic (SOC) and inorganic (SIC) carbon and total N (STN) in 24 commercial olive groves with calcareous Regosols and calcium Cambisols as the predominant soil types that have implemented TSCV for at least the last 8 years. These were compared with 24 comparable groves with bare soil (BS). Net aboveground annual carbon and CO₂ fixation of the TSCV averaged 125.7 kg C ha⁻¹ y⁻¹ and 460 kg CO₂ ha⁻¹ y⁻¹, respectively, which are figures relatively low mainly due to the low area covered by the TSCV. After eight years of implementing TSCV, the SOC stocks increased by an average of 2.03 Mg C ha⁻¹ (in the top 30 cm of soil) compared to BS olive orchards. Moreover, SOC content of unprotected (&gt;250 µm) and physically protected (53–250 µm) fractions were 82 and 38 % higher in the TSCV olive farms. Although there was a tendency of lower SIC content in TSCV olive orchards, differences were not significant. The STN content and the potentially mineralizable nitrogen in TSCV farms were on average 26 % and 77 % higher than in BS olive orchards. These findings underscore the potential of TSCV for organic carbon accumulation and nitrogen retention in the soil, contributing to climate change mitigation and soil fertility enhancement. Increasing vegetation coverage and productivity can enhance their effectiveness.</p></div>","PeriodicalId":49503,"journal":{"name":"Soil & Tillage Research","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0167198724002381/pdfft?md5=d28f98c2df738159c7e5b4d78b92d142&pid=1-s2.0-S0167198724002381-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141769210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of nutrient fertilization and soil tillage on soil CO2 emissions in a long-term grassland experiment","authors":"","doi":"10.1016/j.still.2024.106232","DOIUrl":"10.1016/j.still.2024.106232","url":null,"abstract":"<div><p>A better understanding of how land management might affect soil respiration can greatly help enhancing the long-term sustainability of agricultural soils. This study investigated the effects of two key management practices, nutrient fertilization and soil tillage, on soil respiration in an intensive grassland system. Data were collected from a long-term grassland experiment established in 1970 in Northern Ireland, UK. The experiment commenced with eight nutrient treatments: an unfertilised control, inorganic fertiliser (NPK), two types of slurry: cattle and pig slurry at three application rates. In September 2019 half of the experimental plots were tilled and reseeded with a multi-species sward mixture. Static automated chambers were used to measure the fluxes of CO₂ between 2018 and 2021. Surprisingly, we did not find any significant nutrient treatment effects on mean hourly or cumulative CO₂ emissions. Likewise, there were no significant differences in CO₂ emissions between the type of slurry, slurry application rate or the interaction of these treatment factors. However, seasonal changes in CO₂ emissions were highly significant while ploughing had a significant decreasing effect on the cumulative daily CO₂ emissions but only during the establishment period (first nine weeks). Significant relationships with CO₂ flux were found for soil temperature and soil water content. We also found no relationship between short-term soil CO₂ emissions and long-term soil organic carbon storage data, which highlights the complexity of soil C source-sink dynamics and C balance. Our study brings evidence that regarding CO₂ emissions the impact of soil tillage is short-lived, and the direct effect of nutrient additions is small.</p></div>","PeriodicalId":49503,"journal":{"name":"Soil & Tillage Research","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0167198724002332/pdfft?md5=f33a66a46b0674625c437d7c981a0914&pid=1-s2.0-S0167198724002332-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141769211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Soil aggregate stability and erosion resistance in response to integration of cover crops and poultry litter in a no-till rainfed soybean cropping system","authors":"","doi":"10.1016/j.still.2024.106245","DOIUrl":"10.1016/j.still.2024.106245","url":null,"abstract":"<div><p>Soil aggregate stability plays a crucial role in influencing erodibility and soil health. This study explored the integration of cover crops and poultry litter effects on soil aggregate stability and erosion resistance in a no-till rainfed agriculture system. A five-year field experiment was conducted in an Atwood silt loam soil near Pontotoc, Mississippi in which no-till soybean was grown every year following five winter cover crops and three fertilization treatments. The cover crop treatments included native vegetation (control), cereal rye, winter wheat, hairy vetch, and a mix of mustard plus cereal rye and the fertilizer treatments included no fertilizer (control), recommended inorganic fertilizers, and poultry litter in a split-plot design. Soil aggregate stability indicators were measured at the conclusion of the study. The results showed that aggregates in the 0.25–0.053 mm fraction were the most prevalent among all treatments while the 2–1 mm fraction represented the smallest proportion. The highest soil aggregate stability index of 60.2 % was observed under cereal rye and the highest mean weight diameter of 1.6 mm was observed under mustard plus cereal rye. The mustard plus cereal rye also displayed the lowest soil erodibility factor K. Among the fertilizer sources, poultry litter resulted in the highest values of soil aggregate stability index, mean weight diameter, mean weight specific surface area, and fractal dimension. Random forest modeling and path analysis identified mean weight specific surface area, fractal dimension, and mean weight diameter as the dominant predictors of soil erodibility factor K. The results overall highlight that integrating cereal rye with or without mustard along with poultry litter can enhance soil aggregate stability and this enhancement may contribute to increased soil erosion resistance in rainfed cropping systems.</p></div>","PeriodicalId":49503,"journal":{"name":"Soil & Tillage Research","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141769208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Manure application influences microbial stoichiometry and alters microbial life strategies to regulate phosphorus bioavailability in low-P paddy soil","authors":"","doi":"10.1016/j.still.2024.106241","DOIUrl":"10.1016/j.still.2024.106241","url":null,"abstract":"<div><p>Microbial stoichiometry is pivotal in the soil elements cycle within terrestrial ecosystems. However, the impact of microbial stoichiometry on the phosphorus (P) pool transformation in low-P paddy soil, especially with manure addition, remains poorly understood. This study aimed to elucidate the response mechanism of microbial stoichiometry in regulating P pool transformation in two low-P paddy soils during a 60-day flooding-drought incubation. The results demonstrated that pig manure and vermicompost application significantly increased soil Olsen-P by 202–309 %, and microbial biomass P (MBP) by 54.4–79.3 % compared to no fertilization. Additionally, vermicompost treatment increased moderately labile organic P (MLP_o) by 133–257 % and decreased fulvic acidassociated organic P (FAP_o) by 10.5–25.4 % in Acrisol-flooding, Acrisol-drought, and Ultisol-drought, indicating that manure application improved the transformation of FAP_o to MLP_o. The microbial biomass carbon (MBC)/MBP ratio was lowest under Acrisol-flooding and highest under Ultisol-drought, suggesting that microorganisms adjust high ratios for stoichiometric stability and enhanced MBP utilization under deficient resource conditions. Manure treatments increased alkaline phosphatase (ALP) by 5.33–12.9 % under flooding conditions, indicating microorganisms facilitate the mineralization of soil organic P (P_o). Compared to Acrisol-flooding, both ALP and β-1,4-glucosidase (BG) significantly increased by 103 % and 259 %, respectively, under Ultisol-drought, along with a positive correlation between BG and MLP_o, implying that microorganisms enhance soil organic matter mineralization in resource-limited conditions by increasing C-acquiring enzymes and releasing P_o. Additionally, the microbial community composition shifted from <em>r</em>-strategists to <em>K</em>-strategists, primarily by decreasing Proteobacteria and increasing Acidobacteria under resource deficiency and drought. The <em>r</em>-strategists directly mineralize P_o by maintaining a low MBC/MBP and high ALP, while <em>K</em>-strategists indirectly mineralize P_o by maintaining a high MBC/MBP and high BG. The findings suggest that manure application altered the resource status of low-P paddy soils, changed microbial stoichiometry, and influenced soil P availability through adjustments in microbial activity and extracellular enzyme production.</p></div>","PeriodicalId":49503,"journal":{"name":"Soil & Tillage Research","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141729698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New insights into organic carbon mineralization: Combining soil organic carbon fractions, soil bacterial composition, microbial metabolic potential, and soil metabolites","authors":"","doi":"10.1016/j.still.2024.106243","DOIUrl":"10.1016/j.still.2024.106243","url":null,"abstract":"<div><p>Cover crops are an important component of sustainable agriculture, and additional carbon (C) source inputs can accelerate the soil C cycle. However, the specific processes and factors that control cover crop impact on soil organic carbon (SOC) mineralization are still uncertain. In this study, the ecological associations among SOC fractions, soil bacterial composition, microbial metabolic potential, and soil metabolites and their combination with SOC mineralization based on an eight-year cover crop field experiment (summer fallow–winter wheat (Fallow), buckwheat–winter wheat (Buckwheat), black bean–winter wheat (Black bean) and sorghum sudangrass–winter wheat (Grass)) were analyzed. The results showed that cover crops increased SOC mineralization, which was 10.61 mg CO₂-C kg⁻¹ soil d⁻¹ for Fallow and 1.17, 1.20 and 1.34 times greater for Buckwheat, Black bean and Grass, respectively, and that the SOC fractions and microbial metabolic potential showed similar trends to those of SOC mineralization. Cover crops increased the labile C content and amino acid and carboxylic acid metabolic activity, altered the soil bacterial composition and increased the amount of differentially abundant metabolites (DAMs). Hierarchical analyses revealed that soil bacteria and metabolites explained the majority of the variation in SOC mineralization, and partial least squares path modeling (PLS-PM) further revealed that soil bacteria increase microbial metabolic activity by regulating metabolites to promote SOC mineralization. Thus, cover crops alter the soil bacterial composition and stimulate microbial catabolic activity to influence the SOC cycle, a process in which soil metabolites play a key role.</p></div>","PeriodicalId":49503,"journal":{"name":"Soil & Tillage Research","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141729697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Improving soil quality and wheat yield through diversified crop rotations in the North China Plain","authors":"","doi":"10.1016/j.still.2024.106231","DOIUrl":"10.1016/j.still.2024.106231","url":null,"abstract":"<div><p>Continuous wheat-maize rotation (WM) has caused soil degradation and yield reduction in the North China Plain (NCP). To explore sustainable crop systems, four diversified rotations were conducted over three 2-year cycles from 2015 to 2021: (ⅰ) Maize → WM, spring maize-WM; (ⅱ) Millet → WM, spring millet-WM; (ⅲ) Peanut → WM, spring peanut-WM; and (ⅳ) Soybean → WM, spring soybean-WM. During the third rotation cycle (2019–2021), we investigated variations in soil nutrients and enzyme activities in the 0–40 cm layer throughout wheat growth stages (sowing, regreening, jointing, anthesis, and maturity stage) among different rotations and assessed their impacts on wheat production and soil quality. Results indicate that diversified 2-year rotations reduced nitrogen loss by lowering soil mineral nitrogen during wheat growth stages compared to WM. The heightened activities of nutrient-acquisition (carbon, nitrogen, and phosphorus) enzymes in diversified 2-year rotations contributed to an improvement in soil quality index (SQI) by 4.1 %-8.7 % (<em>P</em> &lt; 0.05) and 9.8 %-18.9 % in the 0–20 cm and 20–40 cm soil layers, respectively, compared to WM. However, the SQI in the 0–20 cm was significantly lower in Peanut → WM compared to Soybean → WM. Diversified 2-year rotations also increased wheat yield by 45.7 %-66.4 % (<em>P</em> &lt; 0.05) compared to WM. The stoichiometry of enzymes revealed that diversified 2-year rotations exacerbated soil microbial carbon limitation during wheat growth stages. This issue, however, was effectively addressed by increasing dissolved organic carbon to fulfill the crop's carbon requirements. The findings highlight the potential of incorporating diverse spring crop species, whether leguminous or non-leguminous, into wheat-maize rotation as a promising crop pattern to enhance soil quality and increase wheat yield in the NCP.</p></div>","PeriodicalId":49503,"journal":{"name":"Soil & Tillage Research","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141639292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transport and deposition of bacteria in undisturbed calcareous soils under saturated and unsaturated conditions","authors":"","doi":"10.1016/j.still.2024.106229","DOIUrl":"10.1016/j.still.2024.106229","url":null,"abstract":"<div><p>The unsaturated zone plays a significant role in protecting groundwater resources from microbial contaminants. The mechanisms governing bacteria transport and retention in aggregated soils are still not fully understood and quantified. This study aims to investigate <em>Pseudomonas fluorescens</em> transport and retention in undisturbed calcareous soils under both saturated and unsaturated conditions. Series of transport experiments with well-controlled suctions and flow rates were performed. The breakthrough curves of bacteria and a nonreactive tracer (Cl^-) were obtained. The bacteria were then quantified in different layers of soil. HYDRUS-1D two-site depth-dependent deposition model was employed to simulate transport and retention of bacteria. HYDRUS-1D two-site depth-dependent deposition model fit the observed data well (R²=0.99). Results revealed that the average ratio of detachment to attachment rate was 0.028 and 0.016 under saturated and unsaturated flow conditions, respectively, demonstrating nearly irreversible attachment of cells. Increasing depth dependent-deposition coefficient (<em>k</em>₂) in unsaturated soils was attributed to straining and film straining. The majority of bacteria were deposited nearby the inlet of soil columns, and the rate of retention diminished with depth. Bacterial removal rate was 2.5 times higher under unsaturated than under saturated condition. High removal rate of bacteria under unsaturated flow was attributed to retention of bacteria to film straining, air-water interface, and also attachment to CaCO₃ minerals that contained preferred sites for negatively charged cells.</p></div>","PeriodicalId":49503,"journal":{"name":"Soil & Tillage Research","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141639290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}