Proceedings - Soil Science Society of America最新文献

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.

Woody perennial polycultures (WPPs) can contribute to sequestration of soil organic carbon (SOC). We studied how WPP diversity and density, and landscape features influence SOC change. We quantified SOC, particulate organic matter-carbon and -nitrogen (POM-C and POM-N), potentially mineralizable nitrogen (PMN), and inherent properties in soil collected in 2015 and 2022 using plot- and grid-based sampling approaches. The SOC stocks increased in the top 60 cm in 3- and 4-species (3-Sp and 4-Sp) treatments, double density 3-Sp (3-SpX2), and corn (Zea mays L.)-soybean (Glycine max (L.) Merr.) control (CS). Gains ranked 3-Sp > CS > 3-SpX2 > 4-Sp and ranged from 0.6 to 3.5 Mg C ha⁻¹ year⁻¹. Only differences between 3-Sp and 4-Sp were statistically significant. Gains in the CS are attributable to their relatively small plot size (one-fifth that of WPP plots) that reduced erosion and increased deposition. Gains in POM found in the pastured inter-rows drove SOC stock change in the 0- to 30-cm depth. Comparatively, small POM gains in the WPP rows suggest WPP diversity and density were not important drivers of SOC change. Multiple linear regression of grid-based data revealed that SOC gains in the surface were positively related to PMN and negatively related to elevation, and SOC change was less than that seen at the 30–60 cm that was positively related to available P. Net SOC change is the result of plant productivity in the surface and of erosion, deposition, and leaching at depth. The use of both treatment- and spatial-based sampling was needed to understand where and how vegetative inputs and landscape features determined SOC change.

A multi-probe heat pulse (HP) sensor measures in-depth variations of water evaporation rates (E) in subsurface soil layers. A multi-probe HP sensor requires an input source of heating power, a high-frequency data logging system, and computer software for data analysis, which may hinder its adoption for wide use in field applications. This study aims to optimize the measurement configurations via systematic evaluations of vertical probe distributions, heater probe requirements, and thermal property sampling intervals. Field data obtained with an 11-probe HP sensor revealed that 87% of evaporation occurred within the 0- to 23-mm soil layer during drying cycles, requiring the use of only seven temperature probes and two heater probes (root mean square error < 0.02 mm h⁻¹ vs. full configuration). Thermal property measurement intervals could be extended from 4 to 8 h when timed to capture critical daytime transitions in soil thermal conductivity, maintaining accuracy while reducing the data collection requirement by 38%. Soil thermal gradients accounted for >90% of sensible heat flux values, necessitating ±0.3 mm spacing precision for the uppermost probes. These quantified operational thresholds provide sensor manufacturers and field researchers with evidence-based design criteria that balance measurement integrity and system efficiency.

In the karst region of southwestern China, limited land resources and intense human-land conflict pose challenges to sugarcane (Saccharum officinarum L.) cultivation, a key economic crop. Sloping farmland is particularly vulnerable to water erosion, causing soil, water, and nutrient losses that hinder sustainable agriculture. Results show that runoff and sediment production vary significantly (p < 0.05) with rainfall intensity and sugarcane growth stages. Compared to conventional downslope tillage, contour tillage combined with straw mulching and trenching reduced runoff and sediment yield by 39.90% and 88.32%, respectively. Nutrient loss was mainly driven by sediment transport, with nutrient retention varying among tillage methods. Contour tillage with straw mulching and trenching effectively retained soil organic carbon, total phosphorus, alkali-hydrolyzable nitrogen, available phosphorus, and available potassium, while contour deep tillage with biochar was more effective in preserving total nitrogen and total potassium. Path analysis revealed that sediment yield had stronger correlations and path coefficients with nutrient losses than with runoff. These findings provide a scientific basis for soil and water conservation strategies and the selection of sustainable tillage practices for sloping farmland in karst regions.

Tropical peatlands are globally significant carbon (C) pools, and effective monitoring of their condition is crucial to preserving these stores and preventing further carbon loss. Spectroscopic techniques provide valuable insights into the specific carbon functional groups within organic matter, offering a rapid and cost-effective alternative to conventional soil analyses. Despite increasing recognition of their potential, no attempt has been made to evaluate the existing scientific literature on the application of spectroscopy on tropical peat soils. This paper reports on the results of a quantitative systematic review of 32 peer-reviewed English-language scientific literature that have applied spectroscopy to whole tropical peat soils. Most of these studies were undertaken in Malaysia (12) and Indonesia (10), areas experiencing the most rapid land use conversion of tropical peatlands. However, there is a notable scarcity of studies from other areas where large areas of tropical peatland occur, including Africa and South America. Infrared spectroscopy in the mid-infrared range and ¹³C nuclear magnetic resonance spectroscopy were the most reported spectroscopic techniques. Most studies using Fourier transform infrared spectroscopy employed attenuated total reflectance mode (nine), while two studies used diffuse reflectance infrared Fourier-transform mode, and seven studies used the classic KBr pellet transmission method. One study utilized Raman spectroscopy, one used visible near-infrared, and none applied photoacoustic spectroscopy, the latter being theoretically promising for highly absorbing organic samples especially where pyrogenic carbon is present. This review identifies key research gaps, including assessing the potential application of spectroscopy combined with chemometric techniques to predict a wide range of tropical peat soil properties. The importance of international collaboration and the development of standard sample preparation methods to enable comparison between studies is highlighted. Implementation of these recommendations could help to fast track the development of rapid and cost-effective spectroscopic approaches to monitor peatland condition.

The efficacy of empty oil palm fruit bunch (EFB) on crop productivity was evaluated by examining the effect of a one-time application of EFB biochar and compost on soil properties, okra (Abelmoschus esculentus L.) nitrogen and phosphorus use efficiency, and yields across two cropping cycles. Treatments involved EFB biochar at 10 and 20 t ha⁻¹ (B10 and B20), EFB compost at 20 t ha⁻¹ (CP20), combinations of biochar and compost (B10CP20 and B20CP20), an unamended control (B0), and an inorganic fertilizer treatment (NPK). Soil chemical properties, okra yield, and microbial biomass were assessed using the whole-cell fatty acid (WCFA) profiling method. The results showed that both single and combined applications of EFB biochar and compost significantly improved okra pod yields, with increases up to 283% in the first cropping cycle. CP20 and B20CP20 treatments increased yield by 58% and 100%, respectively, compared to the mineral fertilizer treatment. These treatments also enhanced phosphorus uptake and recovery efficiency, primarily due to increased soil pH and improved nutrient availability. B20CP20 was especially effective in boosting cation exchange capacity (CEC) and micronutrient content. The presence of arbuscular mycorrhizal fungi in the CP20 treatment was associated with improved phosphorus uptake and recovery in the second cycle. However, an overall decline in soil CEC and total organic carbon by an average of 16% and 25%, respectively, resulted in a threefold yield reduction in the second cycle. Importantly, only the B20CP20 treatment sustained yield increases into the second cycle. The study demonstrates that a one-time co-application of EFB biochar and compost can enhance soil fertility and soil microbial properties and increase nitrogen and phosphorus use efficiencies, resulting in increased okra yields.

de Lima, R. P., Tormena, C.A., Menillo, R. B., La Scala Júnior, N., da Silva, A.R., Souza, Z. M., Cerri, C. E. P., & Cherubin, M. R. (2025). Correlation of total organic C, particulate and mineral-associated C fractions with strength indicators in Oxisols. Soil Science Society of America Journal, 89, e70141. https://doi.org/10.1002/saj2.70141

A funding source was inadvertently left out of the Funding Information and Acknowledgments. The Center for Carbon Research in Tropical Agriculture (CCARBON) – São Paulo Research Foundation (FAPESP, grant 21/10573-4) has now been added to the Funding Information on the title page. The Acknowledgments section has also been updated to add the following sentence “We gratefully acknowledge support from the Center for Carbon Research in Tropical Agriculture (CCARBON) – São Paulo Research Foundation (FAPESP, grant 21/10573-4).”

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