Proceedings - Soil Science Society of America最新文献

{"title":"Soil organic carbon fractionation in sandy soils in the semiarid grasslands and forested areas of Nebraska Sandhills","authors":"Lidong Li,&nbsp;Britt Fossum,&nbsp;Mahmoud Sleem,&nbsp;Tala Awada,&nbsp;Jeremy Hiller,&nbsp;Michael Kaiser","doi":"10.1002/saj2.70084","DOIUrl":"10.1002/saj2.70084","url":null,"abstract":"<p>Soil organic carbon (OC) fractionation enhances our mechanistic understanding of the processes that govern OC storage. However, research on OC fractionation in sandy soils remains limited. Here, we sampled the sandy soils under three vegetation types: native grass, eastern redcedar (<i>Juniperus virginiana</i>), and ponderosa pine (<i>Pinus ponderosa</i>). We fractionated soils into free particulate organic matter (fPOM), occluded particulate organic matter (oPOM), mineral-associated organic matter (MAOM), and water-extractable organic matter (WEOM) at three soil depths (0–10, 10–30, and 30–100 cm). At the 0- to 10-cm depth, the grassland had lower bulk soil OC compared to the cedar and pine forests (7.09 ± 0.88 vs. 12.84 ± 1.65 and 17.90 ± 2.53 g kg⁻¹, <i>p</i> &lt; 0.05). At 10–30 cm, grassland had higher bulk soil OC than pine forest (4.24 ± 0.49 vs. 2.68 ± 0.32 g kg⁻¹, <i>p</i> &lt; 0.05) but did not differ from cedar forest (4.51 ± 0.55 g kg⁻¹, <i>p</i> &gt; 0.05). At 30–100 cm, vegetation cover did not have significant effects (<i>p</i> &gt; 0.05). The proportion of protected (MAOM or oPOM) to unprotected (fPOM) OC increased with soil depth, highlighting the increasing OC persistence with soil depth. The MAOM shows a finite capacity for OC. The POM rather than MAOM dominated soil OC because of limited mineral surface area and microbial transformation in these sandy soils. Our study enhances the mechanistic understanding of OC dynamics within fractions of sandy soils, an important component of terrestrial OC sequestration.</p>","PeriodicalId":101043,"journal":{"name":"Proceedings - Soil Science Society of America","volume":"89 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/saj2.70084","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144245058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparing dry and wet sieving with laser diffraction to the hydrometer method for particle size analysis of sandy bioretention soil media","authors":"Joseph S. Smith,&nbsp;R. Andrew Tirpak,&nbsp;William R. Osterholz,&nbsp;Ryan J. Winston","doi":"10.1002/saj2.70079","DOIUrl":"10.1002/saj2.70079","url":null,"abstract":"<p>Standardization of particle size analysis (PSA) is crucial to ensure the proper blending of stormwater filter media such as bioretention soil media (BSM). BSM typically contains &gt;80% sand and is amended with organic matter and fines (silt and clay) to support pollutant removal. However, there is currently no standardized PSA method to verify whether BSM meets design specifications. This study compares three PSA methods—hydrometer, dry sieving with laser diffraction (DS + LD), and wet sieving with laser diffraction (WS + LD)—to evaluate their accuracy and repeatability for analyzing sandy BSM. Twenty-seven BSM samples were collected from three bioretention cells in Ohio. Substantial variability in results was observed depending on the BSM sample mass used in the hydrometer method. Triplicate BSM analyses by both DS + LD (83.9 ± 1.7% sand, 9.6 ± 3.0% silt, 6.5 ± 2.7% clay) and WS + LD (84.1 ± 1.7% sand, 10.6 ± 2.2% silt, 5.3 ± 1.7% clay) demonstrated high intra- and inter-method agreement, especially for sand content. The hydrometer and WS + LD methods were the most consistent for measuring clay content. We recommend measuring the sand and fines fractions separately after appropriate dispersion when conducting PSA on sandy soils like BSM. Although PSA requires additional time and cost, ensuring the proper delivery of well-characterized BSM outweighs the costs of potential bioretention cell clogging and reconstruction. The method used for BSM textural analysis should be reported by laboratories and on delivery of BSM. Future research should focus on BSM pretreatment methods prior to analysis of the mineral fraction to establish a standardized method for BSM PSA.</p>","PeriodicalId":101043,"journal":{"name":"Proceedings - Soil Science Society of America","volume":"89 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/saj2.70079","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144237294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Precipitation influences pre-sidedress soil nitrate thresholds for corn production","authors":"Emerson F. C. Souza,&nbsp;Fabián G. Fernández,&nbsp;Karina P. Fabrizzi,&nbsp;Jeffrey A. Coulter,&nbsp;Rodney T. Venterea,&nbsp;Daniel E. Kaiser,&nbsp;Carl J. Rosen,&nbsp;Jeffrey A. Vetsch,&nbsp;Paulo H. Pagliari,&nbsp;Melissa L. Wilson,&nbsp;Yuxin Miao,&nbsp;Katsutoshi Mizuta,&nbsp;Renzo Negrini,&nbsp;Jeppe Kjaersgaard,&nbsp;Dawn Bernau,&nbsp;Vasudha Sharma","doi":"10.1002/saj2.70085","DOIUrl":"10.1002/saj2.70085","url":null,"abstract":"<p>Minnesota is a leading corn (<i>Zea mays</i> L.) producer in the United States, requiring substantial nitrogen (N) inputs for optimal yields. Using an in-season critical soil nitrate (NO₃⁻-N) concentration threshold to adjust fertilization rates can improve N management and reduce environmental impacts. This study assessed corn grain yield response to in-season (i.e., V4–V6 corn development stage) soil NO₃⁻-N concentration to establish a critical pre-sidedress soil NO₃⁻-N test (PSNT) under Minnesota conditions. Data included were obtained from 34 field experiments conducted from 2012 to 2019 across the major corn production regions of Minnesota. Relationships between PSNT and relative corn grain yield were analyzed using a quadratic-plateau regression model. Across the entire dataset, a PSNT of 20 ± 2.5 mg NO₃⁻-N kg⁻¹ soil was the critical level to reach 97% of maximum corn grain yield. To increase suboptimum PSNT concentrations up to the critical threshold, application of 13.8 ± 2.4 kg N ha⁻¹ is needed per 1 mg kg⁻¹ increase in soil NO₃⁻-N concentration based on pre-/at planting N application, but validation is needed for actual sidedress applications. When precipitation was lower or greater than the 30-year mean, the critical PSNT value was 21.5 or 17.4 mg kg⁻¹, respectively. Nonetheless, the 20 ± 2.5 mg NO₃⁻-N kg⁻¹ PSNT critical value is applicable across the state as limited model improvements were achieved when the data were segregated according to soil characteristics, location, corn material, and/or previous crop.</p>","PeriodicalId":101043,"journal":{"name":"Proceedings - Soil Science Society of America","volume":"89 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/saj2.70085","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144220265","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Forest management practices can increase the soil organic carbon sequestration potential of Robinia pseudoacacia plantations in the Loess Plateau","authors":"Zhiyong Li,&nbsp;Baojiang Guo,&nbsp;Yechen Zhou,&nbsp;Tongchuan Li,&nbsp;Ming'an Shao","doi":"10.1002/saj2.70082","DOIUrl":"10.1002/saj2.70082","url":null,"abstract":"<p>Forest management practices such as thinning and understory removal can directly or indirectly affect soil organic carbon (SOC) content in plantations. However, the effects of plantation management practices in semiarid regions are unclear. The following management practices were used in <i>Robinia pseudoacacia</i> plantations in the Loess Plateau: control treatment (CK), understory removal (UR), thinning, and thinning–understory removal (TUR). This study aimed to determine the effects of different management practices on SOC fractions and stability in plantations. After a 3-year period, we measured soil physicochemical properties and SOC fractions. The results showed that the thinning and understory removal did not significantly change SOC content but did change soil easily oxidized organic carbon (EOC) storage and non-oxidizable organic carbon (NOC) storage, and their proportions in aggregates. Thinning and TUR significantly (<i>p</i> &lt; 0.05) increased EOC in macroaggregates and microaggregates and decreased EOC in silt–clay fractions compared to CK. Soil total nitrogen was the most important factor, explaining 56.9% of the variation in SOC fractions. Soil temperature explained most of the variation in SOC stability (61.6%). Different management practices have a major indirect impact on EOC storage, NOC storage, and the carbon pool management index by affecting soil temperature, soil total nitrogen, and soil water content. Understory removal increased the carbon pool management index without increasing the carbon lability index. As an effective forest management practice, understory removal can increase the potential for SOC sequestration in <i>R. pseudoacacia</i> plantations. Our findings can serve as a reference for the management of plantation forests in the Loess Plateau and for promoting high-quality development.</p>","PeriodicalId":101043,"journal":{"name":"Proceedings - Soil Science Society of America","volume":"89 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144213809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mid-infrared spectroscopy and machine learning improve accessibility of Hawaiʻi soil health assessment","authors":"Tanner B. Beckstrom,&nbsp;Arianna Bunnell,&nbsp;Tai M. Maaz,&nbsp;Michael B. Kantar,&nbsp;Jonathan L. Deenik,&nbsp;Christine Tallamy Glazer,&nbsp;Peter Sadowski,&nbsp;Susan E. Crow","doi":"10.1002/saj2.70081","DOIUrl":"10.1002/saj2.70081","url":null,"abstract":"<p>Monitoring soil health is important for sustaining agricultural productivity and ecological integrity around the world. However, current assessment approaches relying on conventional laboratory methods are resource intensive. Mid-infrared (MIR) soil spectroscopy offers an opportunity to increase assessment throughput and reduce user costs, potentially improving accessibility for land managers and producers. This study aims to develop a high-throughput, hybridized model for soil health assessment tailored to the diverse agricultural and ecological landscapes of Hawaiʻi, with potential applicability to other subtropical and tropical areas. Leveraging a newly developed spectral dataset (<i>n</i> = 634) and machine learning methods, we predicted inherent mineralogy and intensive land use legacy with 94.5% and 91.4% accuracy, respectively, validated with threefold cross-validation. Additionally, we predicted four key soil health indicators: total organic carbon (CCC = 0.97), CO₂ burst (CCC = 0.93), potentially mineralizable nitrogen (CCC = 0.89), and water-stable mega-aggregates (CCC = 0.79). These predicted soil features were then used to predict the Hawaiʻi soil health score. Our results demonstrate the potential for MIR spectroscopy to reshape soil health assessment in Hawaiʻi by offering a rapid, cost-effective alternative to traditional methods. Finally, we discuss the importance of adopting a soil health testing framework to report results that are intuitive for diverse stakeholders, including local producers and land managers.</p>","PeriodicalId":101043,"journal":{"name":"Proceedings - Soil Science Society of America","volume":"89 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/saj2.70081","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144190648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Applications of biochar in the remediation of soil microplastic pollution: A review","authors":"Hengying Ji,&nbsp;Canrong Zhou,&nbsp;Pan Li","doi":"10.1002/saj2.70078","DOIUrl":"10.1002/saj2.70078","url":null,"abstract":"<p>Microplastics (MPs), recognized as an emerging pollutant, represent a significant threat to terrestrial ecosystems worldwide by compromising soil structure, inhibiting plant growth and the reproduction of soil fauna, and disrupting biogeochemical cycles. The remediation of MP-contaminated soils is essential for sustaining healthy soil, ensuring global food security, and mitigating climate change. This review provides a comprehensive analysis of the current research advancements regarding biochar (BC) as a sustainable approach for the remediation of MP-contaminated soils. BC, an environmentally benign material with multifunctional properties, has been shown to enhance soil characteristics in MP-affected environments by stabilizing soil aggregates, improving porosity and moisture retention, and regulating pH and nutrient levels. The review illustrates that BC promote microbial diversity, increases populations of beneficial bacteria, and creates a favorable environment for the growth and reproduction of plants and soil animals in MP-contaminated soils. The efficacy of BC remediation is influenced by its physicochemical properties (such as surface area, porosity, and functional groups) as well as the specific conditions of the soil (including texture, organic matter content, and pH). This comprehensive evaluation underscores BC as a promising, cost-effective, and environmentally sustainable strategy for the remediation of MP-contaminated soils, bearing significant implications for agricultural sustainability and ecosystem health. However, knowledge gaps persist in the understanding of microscopic interactions between BC and MPs, as well as in the application of BC at the field scale. These gaps should inform and direct future research endeavors.</p>","PeriodicalId":101043,"journal":{"name":"Proceedings - Soil Science Society of America","volume":"89 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144140742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Long-term cropping system and manure effects on soil health parameters and associated soil-borne pathogens","authors":"Joyce Mutai,&nbsp;Beth Medvecky,&nbsp;Steven J. Vanek,&nbsp;John Ojiem,&nbsp;Peter Bolo,&nbsp;Job Kihara,&nbsp;Steven J. Fonte","doi":"10.1002/saj2.70076","DOIUrl":"10.1002/saj2.70076","url":null,"abstract":"<p>Soil-borne pathogens reduce the performance of key food crops in sub-Saharan Africa. Diversified cropping and nutrient management can enhance soil and plant health, limiting pathogen damage. To examine how management and soil health changes influence soil-borne pathogens, we leveraged an 18-year field trial in western Kenya, evaluating cropping systems typical of smallholder farms. We considered three cropping systems and two organic matter management strategies: continuous maize monocrop (M–M), <i>Tephrosia</i> in rotation with maize (T–M), maize intercropped with soybean (M–S), application or not of farmyard manure, and retention or removal of crop residues. We assessed soil physical and chemical properties and major soil-borne pathogens—<i>Fusarium</i>, <i>Pythium</i>, root knot nematodes (RKN), and lesion nematodes. T–M rotation significantly improved permanganate oxidizable C (POXC), particulate organic matter (POM), aggregation, and available P, while reducing pH and bulk density, compared to other systems. M–S did not significantly improve soil health relative to M–M. Manure reduced RKN by 92% but increased <i>Fusarium</i> by 54%. Soil pH and POXC were negatively correlated with <i>Pythium</i> and RKN, while <i>Fusarium</i> correlated positively with POXC, total C, and aggregation. Overall, continuous nutrient mining and minimal organic inputs led to declines in key soil properties (pH, POXC, POM, aggregation, and total C), with implications for pathogen dynamics. Our findings highlight the importance of organic inputs in enhancing soil health and managing pathogens but caution against using <i>Tephrosia</i> in nematode-infested soils, as it appears to be a suitable host and may not suppress their populations.</p>","PeriodicalId":101043,"journal":{"name":"Proceedings - Soil Science Society of America","volume":"89 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/saj2.70076","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144131608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Water quality and soil nutrient availability trade-offs associated with timing and duration of managed flooding for migratory waterbird habitat","authors":"A. Chatterjee,&nbsp;J. M. Taylor,&nbsp;Q. D. Read,&nbsp;M. T. Moore,&nbsp;M. A. Locke,&nbsp;J. D. Hoeksema","doi":"10.1002/saj2.70077","DOIUrl":"10.1002/saj2.70077","url":null,"abstract":"<p>Controlled fall and winter flooding of cropland for migratory shorebird and waterfowl habitat may reduce nutrients in runoff, but the impact of anoxic conditions under corn (<i>Zea mays</i> L.)–soybean (<i>Glycine max</i>) rotation due to flooding is not well studied. Influences of fall and/or winter flooding on total soil carbon (C), total and inorganic soil nitrogen (N), Mehlich 3-extractable soil nutrients, including phosphorus (P), and soil exoenzyme activities, including aryl sulfatase and β-N-acetyl-glucosaminidase (NAG), were compared before (September) and after (February) flooding. Five flood treatments were distributed across three farms under corn–soybean rotation. Treatments included control or no flooding, passive rainfall capture, fall flood, winter flood, and fall through winter (FW) flooding. Flooding decreased suspended solids (SS), total and dissolved P, and inorganic N concentrations in runoff water during storm events. Soil pH, total soil C and N, and inorganic N increased between pre- and post-flooding time in all treatments. Soil available-P decreased in FW treatments, but remaining P availability was still not limiting for crop production. The magnitude of increased NAG activity was lower in fields experiencing winter flooding. While fall-winter flooding decreased available P, fall or winter only flooding did not induce significant changes in soil nutrient availability, and all three management options provided significant reductions in runoff nutrient concentrations across three different farms in the Mississippi Alluvial Plain.</p>","PeriodicalId":101043,"journal":{"name":"Proceedings - Soil Science Society of America","volume":"89 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144131597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluating routine agronomic soil tests for coastal soil salinity detection in the mid-Atlantic","authors":"Sapana Pokhrel,&nbsp;Willow Blew,&nbsp;Jarrod O. Miller,&nbsp;Amy L. Shober","doi":"10.1002/saj2.70075","DOIUrl":"10.1002/saj2.70075","url":null,"abstract":"<p>Coastal salinity is a growing concern for managing agricultural soils in the eastern United States, including the Delmarva Peninsula. The saturated paste (SP) extraction, which is the standard method for measuring soil salinity in arid climates, is not widely available in the eastern United States and its effectiveness in humid coastal soils is unknown. We evaluated the Mehlich-3 (M3) routine agronomic soil test as an alternative to SP and ammonium acetate (AA) extractions on samples from 13 Delmarva agricultural fields with known salinity issues. Soils were analyzed for electrical conductivity (EC) by SP extract (EC_e) or deionized water (1:2 and 1:5 soil-to-water ratios; EC_1:2 and EC_1:5). Extractable cations (Na, Ca, Mg, and K by SP, M3, and AA) were used to calculate exchangeable sodium percentage (ESP), sodium cation ratio (SCR), and sodium adsorption ratio (SAR). We noted significant positive relationships between SP-extractable Na and both M3-extractable and AA-extractable Na (<i>r</i>² = 0.81 and 0.77, respectively). Soil SCR values calculated from M3 and AA exhibited significant linear relationships (<i>r</i>² = 0.82–0.88) with ESP_SAR and SAR. Strong positive linear relationships were also noted between M3-extractable Na and EC_e (<i>r</i>² = 0.81). Reclassification of salinity using predicted EC_e from M3-Na and SCR_M3 were similar to standard classification methods. We suggest M3 as a cost-effective and accessible option for salinity assessment in coastal soils of the Eastern United States. Further field studies linking soil salinity to crop health and yields are needed to validate soil salinity interpretations prior to widespread adoption of M3-based salinity assessments.</p>","PeriodicalId":101043,"journal":{"name":"Proceedings - Soil Science Society of America","volume":"89 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/saj2.70075","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144125998","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Acid–base properties of humic acid from soils amended with different organic amendments over 17 years in a long-term soil experiment","authors":"Ibrahim Mohammed,&nbsp;Busayo Kodaolu,&nbsp;Yuki Audette,&nbsp;D. Scott Smith,&nbsp;James Longstaffe","doi":"10.1002/saj2.70074","DOIUrl":"10.1002/saj2.70074","url":null,"abstract":"<p>The acid–base properties of soil organic matter are crucial in regulating plant nutrient availability in agricultural soils. This study examined the effect of long-term application of different forms of manure: liquid swine manure (LSM), solid swine manure (SSM), and swine manure compost (SMC), applied biennially over 17 years, on the intrinsic charge characteristics of humic acid (HA) extracted from soils. Potentiometric titration and a continuous distribution p<i>Ka</i> model assessed buffer intensity, surface charge excess, p<i>Ka</i> distribution, and proton binding site capacities. The HA formed in soils amended with SMC (SMC-HA) showed higher proton neutralization, particularly in the pH range critical for plant nutrient availability, correlating with phenol content. Variations in p<i>Ka</i> distribution highlighted stronger acidic sites in SMC-HA, attributed to phenols and sulfur content, while LSM-HA (HA formed in soils amended with LSM) and SSM-HA (HA formed in soils amended with SSM) displayed weaker acid strength due to lower phenol content and molecular configurations. Acidic/basic site ratios revealed dominance of acidic functional groups in LSM-HA and SSM-HA, whereas SMC-HA exhibited relatively higher basic site content and a lower acid/basic ratio. These findings underscore the heterogeneity of binding sites and differences in binding strengths among HA samples from various manure forms. The enhanced buffering capacity and distinct charge characteristics of SMC-HA suggest a greater potential to improve nutrient availability and overall soil health. SMC amendment produces HAs with properties conducive to improved nutrient management in agricultural soils.</p>","PeriodicalId":101043,"journal":{"name":"Proceedings - Soil Science Society of America","volume":"89 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/saj2.70074","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144100738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}