Proceedings - Soil Science Society of America最新文献

Information on water absorption from the air by urea fertilizers and on NH₃ loss when applied to grasslands is limited. Urea application to grassland is typically broadcast (Bcast), whereas urea-ammonium nitrate (UAN) is applied either Bcast or in bands (dribble). This work was conducted to (1) evaluate water absorption from the air by Bcast granular urea, Bcast UAN, and dribble UAN under laboratory conditions, and (2) compare NH₃ losses from Bcast urea, Bcast UAN, and dribble UAN when applied to a grassland. Six field studies were conducted from 2017 to 2019. In the laboratory, Bcast UAN exposed to 100% relative humidity absorbed water from air at a faster rate than dribble UAN and Bcast urea. In the field, all three fertilizers lost similar amounts of NH₃ when applied to relatively wet soil (> −0.1 MPa). In contrast, when the fertilizers were applied to dry soil (≤ −1.2 MPa), Bcast UAN lost the most NH₃ (17.3% and 19.8%) likely because of its capacity to absorb water from the air. Also, at −1.2 MPa, dribble UAN lost more NH₃ than Bcast urea (15.3 vs. 10.7%, p < 0.05), probably because the low osmotic potential of UAN (−55 MPa) allowed it to absorb water from the soil at a faster rate than urea could absorb water from the air. In contrast, when the soil water potential was −5.7 MPa, dribble UAN lost less NH₃ than Bcast urea (4.4 vs. 17.3%, p < 0.05), likely because the low soil water potential reduced its water absorption.

This study investigates the utility of plant δ¹³C natural labeling in predicting the impacts of environmental shifts on carbon cycling within ecosystems, particularly focusing on paddy fields treated with maize (Zea mays L.) residues and biochar. Specifically, it examines how soil δ¹³C and the sources of soil organic carbon (SOC), respond in paddy fields (which cultivate C₃ plants like rice) when amended with maize residues, maize biochar, and silica-enriched biochar (derived from C₄ plants). Conducted in the Fuzhou paddy fields, the experiment included control groups and treatment groups with maize residue (4 t ha⁻¹), maize biochar (4 t ha⁻¹), and silicon-modified maize biochar (4 t ha⁻¹) during both the early and late rice growth periods. The results indicate that all soil treatments increased soil δ¹³C. The application of maize residues notably affected the δ¹³C of the upper soil profile (0–15 cm) differently from the deeper layers (15–30 cm), and it increased soil organic C more than biochar or silicon-modified maize biochar. Soil available P (AP) and pH emerged as significant factors linking δ¹³C, influencing rice yield through changes in soil physicochemical properties. Unlike maize residues, which reduced rice yields, applications of biochar and silicon-modified maize biochar increased rice yields. The latter, which was particularly effective in lowering SOC decomposition rates and addressing rice's silica needs, emerged as the preferred option. The study highlights maize biochar and silicon-modified maize biochar as sustainable alternatives to maize residues for rice cultivation, enhancing soil fertility, carbon pool stability, and yields.

Researchers in urban environments sample where people live and work. However, there is limited extant guidance available to scientists engaging with community stakeholders to sample soils in urban settings. Leveraging our cumulative experiences, insights gained from community collaborations, and interdisciplinary literature, we present a community-engaged framework for urban soils research. Community-engaged research frameworks emerged over the past two decades to foster trust and respect between communities and researchers as a response to historical exploitation of communities by the academy. Today, these frameworks have become standard for social and public health researchers investigating the physical well-being of communities. However, there is no equivalent framework for scientists studying the soils that underpin the physical and ecological well-being of the same communities. Here, we present the first such framework for soil scientists that incorporates nuanced aspects that are often overlooked. Our proposed framework recognizes the iterative nature of collaboration with community stakeholders and highlights the significance of ethical considerations throughout the research process by emphasizing protection of community stakeholders from harm, involvement of all parties in decision-making processes, maintaining informed consent, and fostering mutual accountability among researchers throughout the research and sampling process.

The TEROS 10 and TEROS 12 are widely used capacitance-based sensors for measuring volumetric water content ($�{\theta }_v$), but few systematic studies of the measurement volume and accuracy of these sensors have been published. The objectives of this study were to (1) calibrate and validate these sensors in mineral soils, (2) determine the sensing volume of each sensor, and (3) evaluate the temperature sensitivity of the sensors. Both sensors were calibrated in the laboratory using columns of packed soil at multiple moisture levels from air-dry to near saturation. Sensors were validated using additional laboratory and field measurements. The sensing volume was determined by quantifying the response of raw sensor outputs while increasing the level of oven-dry sand, moist sand (0.100 cm³ cm⁻³), or water around the sensor in the radial and axial directions. Temperature sensitivity was tested in controlled conditions over a range of temperatures from 2°C to 40°C using encapsulated sensors in packed soil columns at constant $�{\theta }_v$. Linear calibration models resulted in mean absolute error ≤0.030 cm³ cm⁻³ for both sensors during laboratory and field validations. In moist sand, the sensing volume contributing 95% of the maximum sensor response was 439 cm³ for the TEROS 10 and 423 cm³ for the TEROS 12. Both sensors exhibited changes in $�{\theta }_v$ of ≤0.02 cm³ cm⁻³ when subjected to a temperature change from 2°C to 40°C. For the soils considered here, both sensors demonstrated accuracy that is likely sufficient for a variety of agricultural and hydrological applications.

Increased environmental nitrogen (N) losses have prompted the use of enhanced efficiency nitrogen fertilizers, including nitrification inhibitors. However, the comparative effects of nitrification inhibitors with conventional nitrogen fertilizers and herbicides on soil nitrification and nitrogen losses remain poorly understood. This study evaluated the impact of a nitrification inhibitor (Instinct NXTGEN), two nitrogen sources (broadcast urea vs. injected aqueous ammonia), and a preemergence herbicide (Acuron) on (1) soil nitrification through a 25-day soil incubation experiment and (2) NH₃ volatilization, NO₃-N leaching, and N₂O-N emissions through a 31-day soil column study in loamy sand soil. In both experiments, treatments included combinations of nitrification inhibitor versus no inhibitor, two nitrogen sources, and preemergence herbicide versus no herbicide. Results revealed that nitrogen source significantly influenced nitrification, with injected aqueous ammonia reducing nitrification by 33% compared to surface broadcast urea. Nitrification inhibitors and herbicide had no effect on soil nitrification. Injected aqueous ammonia reduced NH₃ volatilization by 87% compared to surface broadcast urea, but the effect of the nitrification inhibitor on NH₃ volatilization was inconsistent across both nitrogen sources. Injected aqueous ammonia led to 39% higher cumulative nitrogen (NO₃-N + NH₄-N) leaching than urea, while the nitrification inhibitor had an inconsistent effect on NO₃-N leaching across both nitrogen sources. No significant differences in N₂O-N emissions were observed among treatments, and the herbicide had no effect on any measured parameters. These findings suggest that nitrogen source plays a more critical role in regulating soil nitrogen losses than nitrification inhibitors or herbicides.

Plant-available soil-water and adequate soil aeration within the root zone are essential corequisites for successful plant growth. Characterization of these two requirements for plant growth is generally done by independent measurements of water and air phase properties and functions in soil, with limited emphasis on their combined effect. This study investigated soil-water characteristic (SWC) measurements in vadose soil profiles (up to 117-cm depth) in six pasture soils to examine the combined behavior of soil-water and diffusion-controlled aeration within the root zone. The soil moisture measurements were made over matric potentials ranging from −1 to −1500 kPa using tension table and pressure plate apparatus. The van Genuchten model was used to parameterize the measured SWC curve, while the Millington–Quick model was used to derive soil-gas diffusivity from measured soil physical properties. Based on two simple indices, derived to represent plant-available soil-water and soil aeration status at a given moisture content, we propose an assessment matrix, which illustrates how a soil satisfies the corequisites for successful plant growth, as it drains to different matric potentials upon irrigation. Results show a pronounced effect of soil texture and, to a lesser extent, soil structure on satisfying these corequisites. With the aid of the assessment matrix, we observed that loam, sandy loam textures exhibited a good overall performance, while sand, clay loam, and clay soils struggled to meet these corequisites during drainage.

Efficient and harmless treatment of microplastics in soil is the current focus of microplastic pollution management. In this study, the pyrolysis effect of soil microplastics at different temperatures and holding times was analyzed. The results showed that temperature and holding time significantly affected the morphology and compositional structure of soil. Pure microplastics and product adhesion after pyrolysis at low temperature (400°C) were not easy to remove. Interestingly, compared with pure polyethylene (PE), direct pyrolysis of microplastics in soil could obtain better results, and the content of organic matter and polycyclic aromatic hydrocarbons (PAH) could be significantly reduced. However, the pyrolysis performance was very unsatisfactory even if the action time was prolonged at 400°C. Prolonged high-temperature treatment accelerated the fragmentation of the alkane main chain of PE, thus generating more PAH, and the temperature was not high enough (400°C) for further effective degradation of PAH into carbon dioxide and water. Therefore, higher temperature and longer holding time need to be selected to ensure the pyrolysis performance. This study revealed the role and mechanism of pyrolysis in soil microplastic mixed systems, aiming to provide a basis for the treatment of microplastics in terrestrial ecosystems.

Soil structure is a standard component of pedon descriptions collected to characterize the nature and function of soils as a natural body. Soil structure is an important indicator of soil development and a predictor of water, air, and root movement throughout the profile. However, inconsistencies exist within the current standardized methodologies used to describe soil structure in the field, making soil structure data difficult to use and often confusing to students encountering these concepts for the first time. Therefore, we propose an updated method of soil structure description to add an interpretive component that clearly distinguishes geogenic, pedogenic, and human-induced structures. This method employs terminology that communicates both observable morphology and the mechanism of formation. The updated method herein differentiates three classes of structure: (a) geogenic structural formation (GS), (b) natural pedological structural formation (current nomenclature), and (c) significant human-induced structure changes from natural pedological structure. This updated approach improves the documentation of scientifically relevant soil morphology and communicates the processes involved in the formation of all forms of soil structure. As a result, this change eases description challenges around soil structure and interpretations common in soil science classes, including soil judging.

We used mid-infrared (MIR) spectra (4000–600 cm⁻¹) to identify and classify soil orders and soil horizons from 102 pedons across five soil orders (Alfisols, Entisols, Mollisols, Spodosols, and Histosols). The soils were analyzed for texture, total carbon, pH, and elemental properties. Random forest models were used to group the spectra of master horizons (O, A, E, B, and C), B horizons (Bs, Bt, and Bw), and the five soil orders. The prediction accuracies for the master horizons and B horizons were 0.81 and 0.89, respectively. The Kappa coefficient was 0.71 for the prediction of master horizons and 0.73 for the prediction of B horizons. The soil orders had an overall accuracy of 0.73 and a Kappa coefficient of 0.64. Histosols exhibited unique absorption characteristics at 2930 and 2860 cm⁻¹ that differed distinctly from mineral soils. The MIR spectra accurately distinguished the O horizons. The spectral curve of topsoil of Spodosols was comparable to the O horizons. Spodosols under forest had A horizons with high organic matter and were classified accurately. Entisols (Psamments) displayed absorption peaks associated with sand, facilitating their differentiation from the other soil orders. The model struggled to discern subtle differences among some soil orders, and identification is hampered if soils undergo irreversible changes upon drying. However, our results showed that MIR spectra can be used for effectively identifying and classifying soil orders as well as soil horizons.

Plant growth-promoting rhizobacteria (e.g., Bacillus) confer health benefits to the host. Bacillus siamensis has been used to control plant disease in fruits and vegetables, but its potential effects on crop performance remain unclear. This study investigated changes in the growth, root transcriptomic profile, and rhizosp here microbiome of maize plants (Zea may L.) following inoculation with B. siamensis 33. All inoculated plants grew better than non-inoculated controls in pots, as exemplified by 24.0% and 6.8% increase in plant height and stem diameter, respectively (p < 0.01). Shoot dry weight also increased by 20.6% upon inoculation, accompanied by 46.9% increase in root dry weight (p < 0.01). Transcriptomic analysis revealed that inoculation induced (2.16- to 5.53-fold) upregulated expression of genes related to auxin signal transduction in maize. The expression of genes involved in phenylpropanoid biosynthesis, glutathione metabolism, and plant defense-related signal (e.g., jasmonic acid and salicylic acid) transduction was (2.06- to 11.30-fold) upregulated in inoculated plants. Upon inoculation, bacterial α-diversity trended higher and potentially beneficial taxa (e.g., Sphingobium, Flavihumibacter, and Parasegetibacter) were enriched in the rhizosphere, likely a result of enhanced root exudation of specific metabolites (e.g., flavonoids) and subsequent recruitment of beneficial microbial taxa. Potential microbial functions associated with nitrogen cycling and pollutant degradation were stimulated by inoculation. These findings indicate that B. siamensis 33 mediates the reprogramming of plant gene expression and reshaping of rhizosphere microbiome structure to bolster maize crop performance.