Proceedings - Soil Science Society of America最新文献

Mountain hay meadows are a high-elevation forage-producing agroecosystem dependent on flood irrigation and nitrogen (N) fertilization to maintain yields, meaning management has great potential to influence greenhouse gas (GHG) emissions. To assess GHG fluxes and inorganic N dynamics in meadows, field monitoring was established at four ranches in Wyoming and Colorado for 24 months from October 2021 through September 2023. At each ranch, three long-term management systems were compared: unirrigated rangeland, irrigated-unfertilized meadow, and irrigated-fertilized meadow. Soil carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) fluxes were measured along with soil samples (0- to 10-cm depth) analyzed for water content, nitrate (NO₃⁻), and ammonium (NH₄⁺). Flood irrigation resulted in 41%–91% increase in annual CO₂ emissions compared to rangelands. Flood irrigation combined with fertilization increased CO₂ emissions by another 19% in 2023. Both irrigated-fertilized and irrigated-unfertilized meadows emitted CH₄ during flooding, while rangeland soils assimilated CH₄ throughout the study. Unexpectedly, N₂O emissions were highest in rangelands and not influenced by irrigation or fertilization in meadows. Soil NO₃⁻ and NH₄⁺ concentrations were low during the growing season and no correlation between inorganic N and N₂O emissions was observed. Calculated global warming potential in meadows revealed GHG emissions were driven mainly by CO₂, indicating that maintaining photosynthetic carbon (C) sequestration in meadows through optimum agronomic management may be an important strategy to balance GHG emissions.

Soil water retention curves (SWRCs) are traditionally determined in the laboratory, but modern sensors enable their measurement under field conditions. This study compared SWRCs obtained from laboratory and field instrumentation within the same soil volume. A well-aggregated tallgrass prairie soil was instrumented with co-located sensors that measured volumetric water content and matric potential at 3.5-cm depth inside collars that prevented root intrusion, minimized lateral flow, and ensured consistent sensor placement. The field experiment was conducted from June 1 to August 11, 2023, capturing multiple wetting and drying cycles. Afterward, the collars were excavated and analyzed in the laboratory using precision mini-tensiometers and a dewpoint water potential meter. Laboratory-derived SWRCs consistently showed greater water contents near saturation compared to field-derived SWRCs, which were consistent across three drydown periods and collars. The two methods produced nonequivalent SWRCs, likely due to sensor responsiveness, air entrapment, and rapid macropore drainage that limited in situ measurement of near-saturation conditions.

Basic indicators of soil health that influence water infiltration, root growth, gaseous exchange, and overall agronomic productivity are soil physical properties such as bulk density (BD), total porosity (TP), particle density (PD), and penetration resistance (PR). Agricultural practices, particularly tillage and land use, are known to alter soil physical properties by disrupting soil structure and altering soil organic matter content. Therefore, this study aimed to assess the effects of conservation agriculture practices, meadows, and woodlands on above-mentioned soil properties. This on-farm study was conducted at 41 sites located within five counties that covered five soil series (Blount, Eldean, Pewamo, Spinks, and Warsaw) in Central Ohio. From November 2023 to July 2024, soils (0- to 10-cm depth) were sampled from cropland under conventional tillage, minimum tillage (MT), and no-tillage (NT), as well as from meadows and woodlands, to evaluate BD, PD, and TP. PR was measured in the field. All land management practices had been in place for at least 15 years prior to sampling. Data were analyzed using a linear fixed-effects model to test the effects of land use within each soil series. Soil TP, BD, and PR varied significantly (p < 0.05) across land management practices and soil series, with woodland soils consistently showing lower BD and PR, and higher TP compared to those under cropland independent of tillage practice and those under meadow, whereas PD did not differ among practices. Soil TP, BD, and PR were significantly related (R² ≥ 0.33, p < 0.001) to soil organic carbon (SOC) content, reflecting a moderate influence of SOC on reducing soil compaction. Overall, these findings highlight the lasting positive impact of relatively undisturbed land use (woodlands) on soil physical health, while also suggesting that NT and MT may require longer timeframes (>15 years) to induce improvements in soil structure and compaction.

Microwave (MW) soil treatment has proven to have the potential to reduce weeds and enhance soil nutrient availability and crop yields. This study hypothesized similar benefits in newly established pastures. Four treatments (Lucerne and Phalaris, with and without pre-sowing MW soil treatment for 120 s) were tested with four replicate plots (1.5 m² each). Three 700 W MW magnetrons, with a frequency of 2.45 GHz, were attached and remotely connected to the controller circuitry of three domestic MW ovens. Soil physio-chemical properties were analyzed, and plots were harvested via mowing three times during the experiment. Pasture samples were assessed for nutritive value. MW treatment increased nitrate, ammonium nitrogen, and potassium in both species plot soil but decreased soil phosphorus. Germination counts significantly increased in MW-treated Lucerne (p = 0.018) and Phalaris (p = 0.002), while weed counts decreased (p = 0.091 and p < 0.001, respectively). MW-treated Phalaris plots had 30% and 26% higher crude protein and metabolizable energy yields compared to controls (p < 0.05). However, MW treatment did not affect Lucerne's nutrient yields (p > 0.05). The findings suggest MW soil treatment can enhance nutrient yields in Phalaris but not Lucerne, while also aiding weed control. Further research is needed to explore the interactions between pasture species and MW treatment. This technology has potential as a sustainable tool for improving pasture productivity and weed management.

This paper establishes standardized terminology and field documentation protocols for cryostructures and cryogenic soil structures in permafrost-affected soils and provides brief guidance on descriptions of ground ice morphology and ice volume estimates. We consolidate permafrost terminology from Russian and North American literature, clarify long-standing ambiguities, and provide explicit guidelines that align with US Department of Agriculture-Natural Resources Conservation Service soil description standards. Our scheme makes critical distinctions between cryostructure, the distribution of ice within soil, and cryogenic soil structure, the morphological structure of soil resulting from ice formation. The scheme organizes cryostructures into three main categories: non-segregated ice, visible segregated ice, and ice matrices. We introduce standardized codes and parameters for field descriptions of ice and soil that enable machine-readable data collection compatible with existing soil information systems. This standardization will significantly enhance the integration of field observations into landscape-scale assessments of permafrost stability, infrastructure vulnerability, and ecosystem response to permafrost thaw, addressing an urgent need for quantitative data to inform modeling and decision-making in rapidly changing Arctic and subarctic environments.

Enhanced efficiency fertilizers, including urease inhibitors (UIs), nitrification inhibitors (NIs), and dual inhibitors (DIs [UI + NI]), are widely used to reduce nitrogen (N) losses and improve crop nitrogen use efficiency (NUE). However, their relative effectiveness across multiple nitrogen loss pathways remains unclear. This study aimed to address that gap through a 31-day soil column experiment and a 25-day soil incubation study using loamy sand soil. Here we assessed the impact of single and DIs on nitrate (NO₃-N) and ammonium (NH₄-N) leaching, ammonia (NH₃) volatilization, nitrous oxide (N₂O) emissions, and residual soil nitrogen. Treatments included UAN alone and UAN with established (Agrotain, Instinct NXTGEN, and Nitrolock) and novel (VLS-UI, VLS-NI, and VLS-UI + NI) inhibitors. The NIs reduced potential NO₃⁻-N leaching by up to 20% compared to UAN and outperformed DIs by 10%. In contrast, UIs and DIs did not reduce NO₃⁻-N leaching. UI treatments increased NH₄⁺-N leaching, while NIs and DIs had no significant effect. DIs were most effective in reducing NH₃ volatilization (82%–89% reduction), surpassing UIs and NIs (68%–75%). N₂O emissions did not differ significantly among treatments. NIs significantly reduced nitrification potential, with VLS-NI showing the greatest reduction (22%). Soil pH decline correlated with increased NO₃⁻-N leaching and nitrification. Total mineral N leaching accounted for 31% of applied N, and gaseous losses (NH₃ + N₂O) accounted for up to 9%. Overall, NIs were more effective in reducing NO₃⁻-N leaching and nitrification, while DIs were best for controlling NH₃ volatilization. These findings highlight the importance of selecting nitrogen stabilizers based on dominant loss pathways and site-specific conditions to optimize NUE and reduce environmental impacts.

Biochar consistently improves soil physicochemical properties and lowers the bioavailability of Cd and Pb, yet the exact mechanisms controlling metal mobility under field-relevant flow conditions remain unresolved. We therefore conducted a leaching column experiment to quantify the vertical migration of Cd and Pb in a sandy-loam paddy soil. The soil was amended with wheat straw biochar and shrub branch and leave-biochar and leached with two concentrations (5 and 10 mM) of citric acid or sodium humate. The results revealed distinct patterns for Cd and Pb in response to biochar treatments. Biochar accelerated the migration of surface layer Cd but simultaneously reduced exchangeable Cd content by 4.5%–10.7% compared to control treatment. In contrast, Pb migration was retarded, and breakthrough was delayed even though the proportion of bioavailable (reducible + oxidizable) Pb increased by 3.1%–4.7%, reflecting ligand-enhanced dissolution that was later re-immobilized along the profile. Organic acid concentration governed the extent of transport. At 5 mM, neither citric acid nor sodium humate appreciably moved Cd or Pb beyond 4 cm. At 10 mM, however, sodium humate doubled leachate velocity and transported both metals to 8–12 cm, enhancing subsoil concentrations and increasing groundwater risk. However, biochar also increased the proportion of residual fractions of both Cd and Pb in the 4- to 8-cm layer, indicating its role in transforming bioavailable forms into stable and non-bioavailable forms. Collectively, the data show that Cd mobility is controlled primarily by leachate ionic strength, whereas Pb transport is driven by the concentration of water-soluble organic ligands. Thus, biochar can be an effective long-term immobilization agent only if coupled with management practices that limit the buildup of strong organic acid solutions in the profile.

Lettuce (Lactuca sativa) is a widely consumed leafy vegetable with high nutritional value. Enhancing its yield and quality through sustainable practices is crucial. This study aimed to investigate the combined effects of arbuscular mycorrhizal fungi (AMF) and phosphorus nanofertilizer (PNPs) on lettuce growth, productivity, and nutritional traits. A total of eight treatment combinations were established and replicated three times under greenhouse conditions, including the control (no AMF, no PNPs), AMF inoculation at 20 g plant⁻¹, foliar application of PNPs at 250, 500, and 750 mg L⁻¹, and their respective combinations with AMF, using a randomized complete block design. Results indicated that both AMF and PNPs, particularly when combined at 500 mg L⁻¹, significantly enhanced plant growth (plant height and root dry weight), folded leaf number, plant weight (fresh weight), and total biomass (root and shoot system), nutritional value (ascorbic acid, chlorophyll a and b, carotenoids, and total phenolic content), and mineral content (phosphorus and potassium) compared to the control, the individual applications, and the other combination treatments. The next most effective treatments were AMF with 750 mg L⁻¹ PNPs and 500 mg L⁻¹ PNPs alone. This combined approach enhanced physiological performance and increased the levels of bioactive compounds. These results suggest that combining bio- and nano-fertilizers can synergistically improve lettuce productivity and nutrition, providing a promising method for sustainable crop production. Future studies should explore the long-term and field-scale impacts of these treatments.

Aluminum (Al) is one of the most abundant elements in soils. As poorly crystalline Al hydroxides are reactive toward soil organic matter (SOM), they are thought to be involved in SOM stabilization. This is also inferred from correlations between soil organic carbon contents and those of Al extracted by acid oxalate in darkness (AOD), although it is known that several species release Al by this extraction. We tested the completeness of dissolution by AOD of synthesized poorly crystalline Al hydroxides and models of Al in organic association, which included dissolved organic matter flocculated by Al ions and Al adsorbed on peat. While Al was almost completely extracted from the organic models, all hydroxides were completely dissolved by AOD extraction. A review of the literature revealed frequent misinterpretation of data on the extraction of Al from hydroxides. An approximation of the detection limit of a combination of extractions, X-ray diffractometry, and X-ray fluorescence spectroscopy revealed that unambiguous quantification of oxidic Al in soils of temperate latitudes is not possible because of the low contents. Therefore, we consider statements about the importance of Al hydroxides for stabilizing SOM in these soils to be questionable as long as adequate analytical technology is unavailable to identify and selectively quantify Al in poorly crystalline phases.

Applied Zn undergoes multiple biogeochemical reactions that determine the available Zn concentration in soil. The choice of Zn fertilizer should depend on the chemical reactions it undergoes, namely, adsorption-desorption, precipitation-dissolution, and complexation-dissociation. The treatments included four different Zn fertilizers: ZnO, ZnSO₄.7H₂O (ZnSO₄), ZnEDTA, and Zn mix (a new Zn product with 60% ZnO, 36% ZnSO₄·7H₂O, and 4% ZnEDTA by weight). The treatments also included a control (No-Zn) and an ethylenediamine tetraacetic acid (EDTA) treatment (No-Zn + EDTA). The overall objective of this study was to compare the above treatments based on relative Zn diffusion, water extractability, plant biomass, and plant Zn uptake using incubation (soil only) and greenhouse (soil + plant) studies. The X-ray absorption near-edge structure (XANES) spectroscopy was used to evaluate the Zn reaction products in soil. Zinc sulfate and ZnEDTA showed greater diffusion, water extractability, plant concentration, and diethylenetriaminepentaacetic acid extractability of Zn in soil than ZnO and Zn mix treatments. The XANES analysis showed that Zn mainly existed as Zn aluminum nitrate double-layered hydroxide (ZnALDHnitrate)-like species in all treatments except ZnEDTA, complementing our understanding from the incubation and greenhouse studies that Zn gets sorbed quickly to metal oxides or soil surfaces. Plant uptake, Zn concentration, and biomass were comparable between ZnSO₄ and ZnEDTA, indicating that both can serve as effective Zn sources under neutral soil conditions. Given its comparable performance and lower cost, ZnSO₄ represents a practical alternative to chelated Zn sources such as ZnEDTA.