117 reads in the past 30 days
Soil landscapes of the United States (SOLUS): Developing predictive soil property maps of the conterminous United States using hybrid training setsOctober 2024
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311 Reads
Published by Wiley and American Society of Agronomy; Crop Science Society of America; Soil Science Society of America
Online ISSN: 1435-0661
Disciplines: Agriculture
117 reads in the past 30 days
Soil landscapes of the United States (SOLUS): Developing predictive soil property maps of the conterminous United States using hybrid training setsOctober 2024
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311 Reads
79 reads in the past 30 days
Soil organic carbon and total nitrogen after 34 years under conventional and organic management practices at the Rodale Institute Farming Systems TrialJanuary 2025
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81 Reads
Long‐term agricultural experiments are uniquely positioned to capture the spatiotemporal dynamics of farming system effects on soil profile properties, which typically require decades for measurable changes to become apparent. Soil organic carbon (SOC) and total nitrogen (TN) concentrations and stocks were determined at a depth of 0–30 cm in the 34th year of the Rodale Institute Farming Systems Trial (FST), Kutztown, Pennsylvania, USA. Only the organic agriculture (OA) with manure (OA‐MNR) system plots had higher SOC concentrations and stocks than the plots of the other systems but only at depths of 0–10 and 10–20 cm, and not on equivalent soil mass (ESM) basis to 30‐cm depth. The ESM SOC stocks to 30‐cm depth at the tilled plots were 53.3, 56.2, and 61.9 Mg C ha⁻¹ for conventional (CONV), OA‐legume (OA‐LEG), and OA‐MNR systems, respectively. The concentrations and stocks of TN, as well as ESM TN stocks to 30‐cm depth at the tilled plots, were higher for both OA systems compared to CONV. However, observations at the recently established reduced tillage (RT) subplots were inconsistent, as at least 10 years may be needed to ensure that differences in tillage treatment effects on SOC can be detected. The results are consistent with many other long‐term field experiments that have reported differences in SOC and TN concentrations and stocks only in the topsoil. Overall, the OA‐MNR system was advantageous in 2015 in increasing SOC and TN compared to the CONV and OA‐LEG systems. Thus, OA practices when combined with composted manure addition can result in increases in the SOC stock in the long term. However, subsequent studies should assess the implications for input of manure sourced from outside the OA‐MNR system. Further, soil samples should be taken several times over multiple years to more comprehensively assess management‐induced changes in soil properties.
55 reads in the past 30 days
Comparison of laser diffractometry and pipetting methods for particle size determination: A pilot study on the implications of result discrepancies on soil classificationDecember 2024
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101 Reads
42 reads in the past 30 days
Biodegradability of dissolved organic carbon in boreal peatland forest is affected by water table, labile carbon, and nitrogen availability but not forest harvesting aloneJanuary 2025
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42 Reads
41 reads in the past 30 days
A portable low‐cost incubation chamber for real‐time characterization of soil respirationDecember 2024
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90 Reads
Soil Science Society of America Journal publishes basic and applied soil research covering all areas of soil science in agricultural, forest, wetlands, and urban settings. Soil Science Society of America Journal is an international, comprehensive venue for interdisciplinary soil scientists, biogeochemists, and agronomists. It is the flagship journal of Soil Science Society of America.
February 2025
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3 Reads
Tiantian Ma
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Tingli Liu
Bentonite, commonly used for geological disposal of high‐level radioactive waste and landfill liners, can experience increased permeability under high groundwater salinity, compromising its effectiveness. This article presents a novel approach to enhance the anti‐seepage performance of hydraulic barriers, particularly in hypersaline environments. The proposed design incorporates a gradient distribution of fixed net negative charges, based on the principles of the Donnan equilibrium and generalized Darcy's law. The Donnan equilibrium, caused by fixed net charges on clay particles, alters the salt concentration of pore water that seeps through the soil. This creates a semipermeable membrane effect on the clay, leading to a concentration difference of salts between the flowing water in the soil and the external water supply. The concentration difference is dependent on the density of fixed net negative charges on the clay surfaces. By artificially controlling the distribution of fixed net negative charges, a salinity gradient is induced in the pore water. Based on the generalized Darcy's law, the salinity gradient can counteract seepage driven by pressure gradients and effectively reduce the seepage velocity. The study discusses key factors affecting the gradient distribution of fixed net charges in the designed hydraulic barrier, including void ratio, external solution concentration, and cation exchange capacity. The new hydraulic barrier is compared with existing methods (traditional bentonite and polymer–bentonite mixtures), demonstrating the effectiveness of the proposed method in enhancing anti‐seepage performance, especially in hypersaline environments.
February 2025
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8 Reads
Accurate estimation of sediment transport capacity is crucial for effective soil erosion modeling and management. While empirical methods offer a practical approach for calculating sediment transport capacity using limited data, existing equations often lack reliability and applicability across a broad range of scenarios. This study addresses this gap by developing an empirical equation based on extensive datasets encompassing a wide spectrum of hydraulic and physical conditions ranging from slopes (1%–45%), unit flow discharges (0–15 × 10⁻² m² s⁻¹), and median particle sizes from (0.021–10.5 mm). The proposed equation integrates slope, discharge, and particle size to predict sediment transport capacity, leveraging advanced machine learning techniques. It was rigorously tested against other empirical equations, demonstrating superior performance with a coefficient of determination (R²) of 0.99 and a Nash‐Sutcliffe efficiency of 0.99. The equation's strong alignment with physical sediment transport principles, particularly its similarity to stream power equations, underscores its theoretical robustness and practical relevance. Findings indicate that sediment transport capacity increases with discharge and slope while decreasing with particle size. Notably, rainfall intensity and flow depth did not significantly impact sediment transport capacity, emphasizing the equation's focus on the most influential variables. This research presents a significant advancement in sediment transport modeling, providing a reliable and accurate tool for a wide range of conditions and contributing valuable insights for soil erosion and sediment management. Future work should involve further validation with additional datasets to enhance the equation's applicability and robustness.
February 2025
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15 Reads
Astropedology is the study of soils on other planetary bodies and stretches the definition of soil to materials on the surface of a planetary body altered in place by physical, chemical, or biological processes. This new disciplinary name was coined by Roy E. Cameron in 1966 from studies of desert soils and their microbes in Arizona and Antarctica as analogs for Martian soils to be investigated by NASA Viking missions. Astropedology now has documented numerous actual soil profiles exposed in cliff faces, natural cracks, or cores studied by robotic missions to the Moon, Venus, and Mars, with increasingly advanced and precise chemical and other analyses. Specimens are also available for study from Lunar and Martian meteorites, and from sample return from the Moon, also planned from Mars. Life has yet to be found beyond Earth, but Mars has surprisingly Earth‐like soils, which can be identified as Gypsids in US taxonomy. Soil formation by micrometeoroid bombardment on the Moon and by melting and glazing on Venus are truly out of this world.
January 2025
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23 Reads
Phosphorus (P) fixation in soil following fertilizer application is a major issue that may be mitigated through a number of methods. Our main objective was to utilize an innovative unsaturated flow system to directly image the mobility of P in soil material as affected by AVAIL, a commercial copolymer phosphate fertilizer enhancer. Air‐dried clayey soil material, passed through a 0.25‐mm sieve and adjusted to pH 6, was packed in three side‐by‐side 1.4‐cm wide, 20‐cm long, and 0.6‐cm deep tracks. Water was applied to the tracks under approximately 1 cm tension and moved downstream by sorptivity. Five microliters of aqueous solutions containing 400 mmol P/L and varying levels of AVAIL were applied at a point near the upstream end of each track. Once water passed approximately 6 cm from the point of P application, each track was sectioned into small blocks and air‐dried. Synchrotron micro X‐ray fluorescence (μ‐XRF) images of P, silicon (Si), and aluminum (Al) were collected on block samples to measure relative movement of phosphorus along the soil tracks. Our results show that, despite the high affinity of soil minerals for P, it was relatively mobile with no enhancer under unsaturated flow conditions. Images showed diminished rate of P movement and enhanced clay dispersion with increasing proportion of AVAIL. We postulate that clay dispersion, corroborated by X‐ray computed tomography imaging, affected P transport due to interactions with Si and Al minerals. Our results demonstrate the potential utility of our unsaturated flow system combined with μ‐XRF imaging to measure convective mobility of plant nutrients or contaminants through soils.
January 2025
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4 Reads
Industrial‐scale coffee ground waste has the potential to serve as a nutrient‐rich soil amendment, which would offer growers an opportunity to reduce applications of traditional fertilizers. Composted spent coffee grounds (CSCGs) and noncomposted spent coffee grounds (NCSCGs) were evaluated for their potential as organic N fertilizers. Nitrogen mineralization of NCSCGs and CSCGs was compared to commonly used synthetic and organic N fertilizers: urea and Milorganite. Net N mineralization and microbial activity were measured in a fine sandy loam field soil at 25°C and 60% water holding capacity weekly for 100 days. Despite a C:N of 13:1, the CSCGs appeared to have slow mineralization. Total inorganic N was lower in both CSCGs and NCSCGs than the control throughout the 100‐day incubation with no additional N to the system. Greater CO2─C respiration was recorded with SCGs, suggesting microbial activity is required for the breakdown of SCGs relative to other treatments. CSCGs may serve as a long‐term fertilizer due to the time it takes to mineralize; however, over a shorter period, it may increase the nutrient‐ and water‐holding capacity of soil, which can improve plant growth.
January 2025
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16 Reads
The use of ¹⁵N‐labeled dinitrogen (¹⁵N2) affords the only direct means of measuring free‐living nitrogen fixation (FLNF); however, progress in utilizing this approach has been impeded by methodological limitations arising from the presence of nitrogenous contaminants, a lack of atmospheric uniformity, and incomplete description of procedural details. Such constraints are eliminated with an ex situ technique comprehensively described herein, which involves circulating ¹⁵N2 generated by hypobromite oxidation through a closed system that includes chemical (sulfuric acid–potassium permanganate) and cryogenic (isopentane–liquid N2) traps for atmospheric purification and an incubation chamber consisting of a desiccator equipped with a pressure gauge. Studies to evaluate the circulation system described showed that a uniform atmosphere was readily achieved with a 10‐L desiccator by pumping for 30 min, and that both chemical and cryogenic traps were necessary to ensure complete (98.8%–99.6%) removal of gaseous contaminants subject to physicochemical retention by sterilized soil samples. The method proposed was successfully demonstrated in detecting the stimulatory effect of organic carbon (C) on FLNF in active soils, and can be further utilized to improve the reliability of ex situ assessment of FLNF in relation to soil processing and storage, climatic conditions, microbial dynamics, and land management practices.
January 2025
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18 Reads
The conversion of forest into coffee plantation through deforestation has become one of the main land use changes in tropical region, yet its impact on soil organic carbon (SOC) and methane (CH4) uptake remains unclear, leading to uncertainties in estimating carbon fluxes in tropical area. The main coffee planting areas in China and the adjacent forests were selected to explore the effects of forest‐to‐coffee conversion and coffee stand ages on SOC and CH4 uptake. We conducted our study by comparing coffee plantations of varying ages to the nearby forests within the same area. We treated the different‐aged coffee plantations as our experimental groups and used the forests as our control groups. This paired comparison allowed us to exclude external factors such as climate, soil type, and vegetation differences, ensuring that our analysis focused on the effects of stand age alone. The 25‐year, 43‐year, and 55‐year coffee plantations reduced SOC by 51%, 66%, and 65% compared to nearby forests, while soil microbial biomass carbon decreased by approximately 60%. Coffee stand age influenced ambient CH4 uptake significantly: soils in 43‐ and 55‐year‐old coffee plantations and natural forests acted as CH4 sinks, while the 25‐year‐old stand showed weak CH4 emission. In 25‐year, 43‐year, and 55‐year coffee plantations, the CH4 uptake rates were 87%, 54%, and 65% lower, respectively, compared to the CH4 uptake rates in the natural forests nearby. Soil moisture, inorganic nitrogen content, and CH4 monooxygenase (MMO) activity were the main factors affecting CH4 uptake rates across land uses in the ambient CH4 background. Further CH4 metabolism indicated a close relationship between ambient CH4 uptake, CH4 oxidation, and methanogenesis pathways. Our study highlights the reduction of SOC pools in coffee plantations in China is accompanied with the reduction of CH4 uptake and changed metabolism of CH4‐oxidizing microorganisms.
January 2025
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41 Reads
Phosphorus (P) is one of the most limiting essential nutrients for agricultural production and its availability to crops is assessed by various methods. Mehlich‐3, however, remains the most used method worldwide. For decades, the colorimetric method by blue ascorbic acid‐molybdate reaction has been used to determine soil P concentration following Mehlich‐3 extraction. Since early 1990s, the use of automated methods to quantify soil nutrients including P has expanded rapidly, and the inductively coupled plasma (ICP) emission spectroscopy is becoming one of the most popular instruments in routine soil testing. The main objective of this study was to compare ICP (where M3P is Mehlich‐3 P, M3P‐ICP) with colorimetric (M3P‐Col) methods to estimate soil P using data from soil samples (3020) collected between 2005 and 2021 from 16 experiments conducted under different agroecosystems in Canada and Europe. Five case studies were assessed: (1) laboratory incubation, (2) native lowbush blueberry, (3) soil depth, (4) soil tillage, and (5) annual field crops versus perennial forage. In each study, a regression equation was established between soil M3P‐ICP and M3P‐Col. Results indicated that the two methods were strongly related in all studies (0.82 < r² < 0.99; p < 0.001), where soil P measured by ICP (2.1–352 mg kg⁻¹) was higher than that measured by colorimetry (0.6–339 mg kg⁻¹) except for the incubation study. Most important P differences were observed with forage and blueberry. Further analysis revealed that large differences between M3P‐ICP and M3P‐Col occurred primarily due to soil total C content. Soil pH, clay and Fe content, and previous crops also affected the relationship.
January 2025
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30 Reads
The application of compost increases soil organic matter (SOM) content; however, there is a lack of information on the short‐ and long‐term effects of compost application on the dynamics of labile SOM pools in compost‐amended soils in semiarid region. The goal of this study is to distinguish between parameters that can be used for investigating the accumulative effects of compost application and parameters that are sensitive for short‐term changes but diminish with time. To address this goal, we focused on (1) the effects of compost application rates on short‐term dynamics of soil contents of microbial biomass carbon (MBC), cold water‐extractable organic carbon (WEOC), and hot water‐extractable organic carbon (HWEOC), respectively, and (2) composition of WEOC and HWEOC characterized using (i) absorbance at 254 nm (Abs254) representing the presence of aromatic components and (ii) fluorescence spectroscopy of excitation–emission matrices coupled with parallel factor analysis. Soil samples were taken from a long‐term field experiment in semiarid region, which investigated the effects of the annual load of a cattle manure‐based compost (at rates of 0, 20, 40, or 60 m³ ha⁻¹ year⁻¹) on soil properties and crop performance. C concentrations in soil water extracts were found to be sensitive indicators of compost‐load effect on soil organic carbon content. Compost dose had a strong short‐term (2 weeks) impact on MBC, but no long‐term (over months and years) effect was observed. Of the variables examined in the short term, the MBC, WEOC, and Abs254 values of the extracts were found to be the most responsive to compost load. The proportion of the fluorescent constituents out of the WEOC and HWEOC decreased with compost dose. UV‐ and fluorescence‐spectroscopy were found to be useful means to characterize the influence of compost load on the composition of water‐extractable organic matter and hot water‐extractable organic matter in semiarid region.
January 2025
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22 Reads
Water content of the soil has a significant role to play in the hydrological cycle and environmental processes. This study includes two phases: (1) approximation of soil moisture at the farm level based on optical‐thermal images of Landsat‐8 satellite and (2) retrieval of soil moisture by the dual‐polarized basis decomposition model with the help of approximate soil moisture that is obtained by the optical‐thermal model. In this research, two mechanisms, volume scattering and surface scattering, are considered. Furthermore, in order to model surface scattering, Bragg matrix has been used. The proposed radar model estimates soil moisture without using ground data, although few ground measurements have been used in the optical‐thermal model. The Carlson triangular model has been used to approximate soil moisture using optical‐thermal images. Three indices, normalized difference vegetation index (NDVI), normalized difference moisture index (NDMI), and moisture stress index (MSI), have been used in the optical‐thermal model. Two ground soil moisture datasets are used in this study: (1) Cook Agronomy Farm (CAF) soil moisture data located in the United States and (2) real‐time in situ soil monitoring for agriculture (RISMA) soil moisture data located in Canada. The radar model (base decomposition model) achieved a lowest root mean square error (RMSE) of 3.33% and a highest of 11.21%, showing strong accuracy in soil moisture retrieval. The optical‐thermal model had a slightly higher minimum RMSE of 4.04% and a maximum of 9.68%. These results suggest that the radar model generally outperforms the optical‐thermal model, making it more reliable for accurate soil moisture estimation in agricultural applications, which is crucial for optimizing irrigation and managing resources.
January 2025
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42 Reads
Potassium fertilizer recommendations for optimal crop production may be improved by considering the ratio between expanding 2:1 layer silicates (smectite) with non‐expanding 2:1 layer silicates (illite). However, the interactive effects between clay mineralogy and various soil tests are not well understood. This study evaluated the relationships among soil test K (STK), water‐soluble K, HNO3‐extractable K, pH, apparent cation exchange capacity (CECa), soil organic matter, clay content, and smectite:illite ratios. Soil samples (0–15 cm) were collected from 41 locations in central and eastern South Dakota, with textures ranging from sandy loam to clay. Data were partitioned into soils with smectite:illite ratios < 1 (illitic), ≥1 but ≤4.5 (smectitic), and > 4.5 (highly smectitic). Mean pH and CECa were lowest in illitic soils, higher in smectitic soils, and highest in highly smectitic soils, whereas STK and water‐soluble K were lowest in highly smectitic soils relative to illitic and smectitic. Correlation analysis also showed that STK decreased with increasing smectite:illite ratio. These results suggest that exchangeable and water‐soluble K forms are reduced when the proportion of smectite increases. There was a strong, positive relationship between STK and HNO3‐extractable K across all three smectite:illite ratio groups. For soil pH, however, the relationship with STK was positive for illitic and smectitic soil groups, but negative for highly smectitic soils. Overall, these results suggest that the smectite:illite ratio influences the relationship among soil parameters and STK. This improves our understanding of the influence of clay mineralogy on plant‐available K and the implications for K fertilizer recommendations.
January 2025
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32 Reads
Plain Language Summary Soils can be hard or soft, wet or dry, so it is difficult to compare soil from 1 month to the next because even a carefully measured cube of soil will contain different amounts of soil. I studied different ways to measure soil to find an accurate and practical way to get the same amount of soil no matter the soil conditions on a particular day. As others have found, the key is to dry the soil and then weigh it, but this seems impossible when you are out in the field wondering if your sample should be deeper or less deep to get the right dry weight. A solution is to take a column of soil with a hollow tube, wrap it in paper, and take it to an oven to dry it. When dry, take soil from the top of the sample until you have your target weight. No matter how compacted or how wet, your dry sample can be exactly the same weight. We will need accurate and unbiased accounting for soil carbon markets to help us avoid mistakes in evaluating changes in soil quality.
January 2025
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81 Reads
Long‐term agricultural experiments are uniquely positioned to capture the spatiotemporal dynamics of farming system effects on soil profile properties, which typically require decades for measurable changes to become apparent. Soil organic carbon (SOC) and total nitrogen (TN) concentrations and stocks were determined at a depth of 0–30 cm in the 34th year of the Rodale Institute Farming Systems Trial (FST), Kutztown, Pennsylvania, USA. Only the organic agriculture (OA) with manure (OA‐MNR) system plots had higher SOC concentrations and stocks than the plots of the other systems but only at depths of 0–10 and 10–20 cm, and not on equivalent soil mass (ESM) basis to 30‐cm depth. The ESM SOC stocks to 30‐cm depth at the tilled plots were 53.3, 56.2, and 61.9 Mg C ha⁻¹ for conventional (CONV), OA‐legume (OA‐LEG), and OA‐MNR systems, respectively. The concentrations and stocks of TN, as well as ESM TN stocks to 30‐cm depth at the tilled plots, were higher for both OA systems compared to CONV. However, observations at the recently established reduced tillage (RT) subplots were inconsistent, as at least 10 years may be needed to ensure that differences in tillage treatment effects on SOC can be detected. The results are consistent with many other long‐term field experiments that have reported differences in SOC and TN concentrations and stocks only in the topsoil. Overall, the OA‐MNR system was advantageous in 2015 in increasing SOC and TN compared to the CONV and OA‐LEG systems. Thus, OA practices when combined with composted manure addition can result in increases in the SOC stock in the long term. However, subsequent studies should assess the implications for input of manure sourced from outside the OA‐MNR system. Further, soil samples should be taken several times over multiple years to more comprehensively assess management‐induced changes in soil properties.
January 2025
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42 Reads
Around 30% of peatland in Nordic and Baltic countries has been drained for forestry. Drained peatlands are major sources of dissolved organic carbon (DOC) and nutrients to surface waters, contributing to global warming, eutrophication, and brownification. However, the effects of forest clearcutting and changes in the water table on the biodegradation of DOC to CO2 are poorly known. We collected peat columns from drained, uncut, and clearcut forests for a common garden experiment and exposed them to high and low water tables to study the effects of clearcutting and water table levels on DOC production and biodegradation. ¹³C‐labeled glucose was added to half of the columns to study the effects of labile carbon (C) addition on DOC dynamics. We measured the concentration, quality, and biodegradation rate of DOC monthly by incubating the column porewater at 15°C. Nitrogen (N) limitation of DOC biodegradation was studied by adding ¹⁵N‐labeled glycine to half of the incubated water samples. DOC concentrations decreased in the columns with both low water table and glucose addition, while clearcutting had no clear effects. The biodegradation rate of recalcitrant DOC in the later stages of the incubation increased with glycine addition but was not affected by glucose or water table. The results suggest that the biodegradation of recalcitrant DOC in these drained peatland forests is N‐limited and dependent on the quality of DOC, which can be seasonally variable.
January 2025
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44 Reads
Arid regions in Northwest China were characterized by water scarcity and soil salinization problems. Understanding water evaporation behavior in salinized soils is crucial to quantify land water loss and control soil secondary salinization. This study aims to explore how specific components in irrigation water influence soil evaporation, focusing on soil pore‐water composition, sodium adsorption ratio (SAR) in particular, and their concentrations. Soil columns saturated with different levels of salt concentration (C1, C2, and C3), SAR (S1, S2, and S3), and salt type (NaCl and CaCl2) were placed in a Climate‐Controlled Chamber and underwent evaporation for 20 days. The salt areal ratio, salt crust thickness, crust composition, and their mutual interactions with soil evaporation were investigated. Results show that CaCl2 tends to precipitate as subflorescence, while NaCl as efflorescence. Subflorescence for the CaCl2 treatment (1.192 mmol L⁻¹) inhibits evaporation, but takes no effect on evaporation for a C3 treatment (0.392 mmol L⁻¹), indicating that the evaporation rate will not be reduced if a lower salt concentration prevents internal precipitation from reaching the threshold for soil pore clogging. Under varying salt concentrations, SAR affects salt areal ratio (rsalt) differently, while increased salt concentration consistently accelerates rsalt regardless of SAR levels. Initially, the salt crust enhances evaporation (days 1–3), then suppresses it (days 3–10), and finally evaporation is primarily influenced by soil moisture content (after day 10).
January 2025
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13 Reads
Plain Language Summary In Appalachia and many other parts of the world, forest soils are acidic and becoming more so because of acid deposition. Liming can reduce these negative acid impacts, which can improve forest health. The effects of applying 10 Mg ha⁻¹ of coarse‐textured limestone by helicopter to 323 ha in the Monongahela National Forest, West Virginia, were evaluated. Five limed and five unlimed sites were selected, and soil samples were extracted from the O, A, and B horizons and analyzed for soil pH, acidity, and calcium and aluminum concentrations. Liming increased soil pH and calcium concentrations in O horizons and decreased acidity and aluminum concentrations. The positive effects of liming these acid forest soils persisted for 5 years after liming.
January 2025
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10 Reads
Digestion of animal manures with crop residues to produce methane (CH4) gas is a promising technique to generate “green” energy from agricultural wastes while producing biofertilizers. This study was conducted to understand nitrogen (N) release by biofertilizers from the products of solid‐state anaerobic digestion of untreated corn stover and stover treated with aqueous ammonia (NH4OH), calcium hydroxide (Ca(OH)2), or Ca(OH)2 plus Fe3O4 nanoparticles blended with dairy manure. Eight biofertilizer materials (feedstocks and digestates) from anaerobic digestion were incubated in the lab for 28 days and the NH4–N and NO3–N data obtained were used to predict N release for seasonal plant availability. Of the untreated and alkaline pretreated biofertilizer materials examined, only calcium hydroxide‐pretreated digestate (CaD) had greater N release (220 mg kg⁻¹) than the untreated soil control (155 mg kg⁻¹) after 28 days of incubation time. In addition, CaD had the most rapid N release rate (0.16 mg kg⁻¹ day⁻¹) and shortest lag phase time (41 days) with a predicted mineral N release of 777 mg kg⁻¹ at 120 days. However, including Fe3O4 nanoparticles slightly suppressed N release. Thus, applying calcium hydroxide‐pretreated digestate to soil could complement N supply for crop cultivation as facilitated by the initial carbon to nitrogen (C/N) ratio, despite slight N immobilization when iron nanoparticles were added.
January 2025
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22 Reads
Soil organic matter concentrations are associated with soil texture in some but not in all studies. Why there are variable responses to soil texture can have logical reasons, the most obvious of which are inconsistent historical land uses, interactions with climatic and landscape settings, and management variations within a land use. In an evaluation of surface soils (0‐ to 10‐cm depth) under consistently undisturbed land use from 648 sites across relatively narrow climatic variations in North Carolina, large soil texture variations were assembled into structured populations (n = 27) of sand and clay categories (n = 24). Sand concentration varied from 220 to 881 g kg⁻¹, silt concentration varied from 67 to 517 g kg⁻¹, and clay concentration varied from 47 to 360 g kg⁻¹ (5%–95% limits). Overwhelmingly, total, particulate, and non‐particulate organic C and N fractions were more statistically associated with sand concentration than with clay concentration alone. Sand concentration is the inverse of clay + silt summation and is a necessary feature when determining particulate organic C and N. Soil bulk density and sieved soil density were also more closely associated with sand concentration than with clay concentration alone. This study confirmed there was no saturation limit for the accumulation of non‐particulate organic C and N (sometimes labeled mineral‐associated organic matter). Therefore, sand concentration should be considered the best indicator of soil textural influence on soil organic matter properties and a key contextual feature necessary for soil health assessments.
January 2025
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54 Reads
Soil carbon (C) sequestration by restoring degraded grasslands with adequate management practices offers significant opportunities for climate change mitigation while remaining highly uncertain. In this study, a combination of a biogeochemical model DayCent‐CABBI and eddy covariance (EC) flux towers was applied to evaluate soil C sequestration potential (at a depth of 0–0.3 m) of management strategies in subtropical grasslands. DayCent‐CABBI was calibrated for grasslands in northeast Australia using biomass and soil organic carbon (SOC) data from a long‐term trial and then fine‐tuned using EC flux tower data from seven sites in the region. The model was then validated with cumulative net ecosystem exchange, biomass, and SOC, resulting in root mean square errors of 1.16, 0.88, and 2.81 Mg C ha⁻¹, respectively. The model was used to project long‐term changes in SOC stocks under innovative management practices (time‐controlled grazing and pasture legume incorporation), estimating soil C sequestration by 0.37–0.48 and 0.15–0.26 Mg C ha⁻¹ year⁻¹ toward 2050 with the respective practices. This study confirms the validity of the Measure, Model, and Verification (MMV) approach to estimate and project soil C sequestration for evaluating SOC methodologies by grassland management within a shorter period than soil sampling—measuring the baseline SOC, modeling the C dynamics with the calibrated DayCent‐CABBI, and verifying the projected soil C sequestration with EC flux tower data.
January 2025
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6 Reads
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1 Citation
To mitigate water shortages, mulched drip irrigation disrupts soil‐air gas exchange, disturbing the balance between gas production and diffusion in the soil. This study explored the effects of nitrogen (N) application and aerated irrigation on the soil microenvironment, greenhouse gas emissions in the root zone, and processing tomato yields. The objective was to offer a theoretical framework and scientific evidence to guide fertilization practices, improve the soil microenvironment, and enhance crop productivity, especially under aerated irrigation. Two irrigation methods (non‐aerated [A0] and aerated [A1]) and two N rates (150 kg·hm⁻² [N1] and 270 kg·hm⁻² [N2]) were tested. Results showed that aerated irrigation increased soil organic carbon (SOC), dissolved organic carbon (DOC), total nitrogen (TN), and ammonium nitrogen (NH₄⁺‐N), while N application enriched soil nitrogen content. Both aeration and N application elevated N₂O and CH₄ emissions. Path analysis revealed that fertilization‐coupled drip irrigation indirectly influences carbon‐nitrogen cycling genes by altering soil nutrient levels, affecting greenhouse gas emissions. Soil nutrients and functional gene abundance directly impacted yield, with nitrate nitrogen (NO₃⁻‐N) showing the most substantial direct effect on processing tomato yield (direct path coefficient = −1.047***). Under A1N2 (aerated irrigation with 270 kg hm⁻² N), soil nutrient levels improved (total carbon: 25.19 g·kg⁻¹, SOC: 18.25 g·kg⁻¹, DOC: 93.65 mg·kg⁻¹, TN: 0.97 g·kg⁻¹, NH₄⁺‐N: 2.64 mg·kg⁻¹, and NO₃⁻‐N: 1.18 mg·kg⁻¹), resulting in a yield of 32.05 t hm⁻², a 23.69% increase over increase over A0N1. Aerated irrigation combined with moderate nitrogen application is recommended for sustainable production to enhance soil fertility and crop yields. However, mitigation strategies such as nitrification inhibitors or optimized irrigation schedules should be employed to minimize greenhouse gas emissions.
January 2025
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24 Reads
Soil organic matter (SOM) influences a wide range of ecosystem processes, including nutrient cycling, water movement, plant productivity, and biodiversity. In agricultural landscapes, adjacent land uses often differ in SOM contents and related soil properties, such as soil organic carbon (SOC) stocks, but the direction and magnitude of these effects are inconsistent across studies. We assessed how land uses differed in SOM and related properties in a representative US Midwest agricultural–forest landscape to support land‐use and management decisions by local landowners and producers. We measured SOM, bulk density (Db), root biomass, and pH, and estimated SOC stocks, in a Typic Hapludalf under four adjacent land uses (permanent forest, pasture, restored prairie on former pasture, and spruce plantation on former pasture). Surface SOM concentrations and stocks were higher under permanent forest (89 g kg⁻¹ and 85 Mg ha⁻¹, respectively) and pasture (63 g kg⁻¹ and 81 Mg ha⁻¹, respectively) than under restored prairie (49 g kg⁻¹ and 58 Mg ha⁻¹, respectively) and spruce plantation (46 g kg⁻¹ and 46 Mg ha⁻¹, respectively). Land uses also differed in Db, root biomass, and pH, with permanent forest and spruce plantation soils having generally lower Db, more root biomass, and more acidic pH than pasture and restored prairie soils. Specific statistically significant differences depended upon depth in the soil profile. Overall, our results suggest that each land use differentially impacts a unique set of soil properties, precluding any single explanation or management recommendation aimed at improving soil health as a whole.
December 2024
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57 Reads
Soil apparent electrical conductivity (ECa) measurements, although more suitable for soil salinity quantification, are often used to determine volumetric soil water content, θv, in site‐specific crop management. Generally, the approach is to develop a field‐specific calibration function between ECa and measured θv, θv(m). Such a calibration function is possible when soil water dominates ECa at a field. When this is not the case, θv(m) data taken over time may be helpful to develop a function. Data regarding θv(m) can be costly and time‐consuming as soil samples are needed to measure bulk density and gravimetric soil water. We postulate that capacitance probes, which measure scaled frequency (SF) as an indicator of the dielectric constant to estimate θv, can be used to establish ECa‐θv calibration functions. Capacitance probes that simultaneously provide temperature readings allow for ECa to be temperature‐corrected to 25°C, enabling development of ECa25‐θv calibration functions. A field experiment was set up to establish whether SF readings can be used to estimate θv, θv(SF), in structured high montmorillonite clay soils accurately and determine if ECa25‐θv(SF) calibration functions are possible. Our results revealed that a single SF‐θv(m) calibration function representing 12 probes, or a specific soil form, is impossible. Each capacitance probe should be calibrated separately. The parameters for ECa25‐θv(m) calibration functions were like ECa25‐θv(SF) functions. The R² for ECa25‐θv(m) calibration functions was higher compared to the ECa25‐θv(SF) functions. Further investigation of using capacitance probes to estimate θv for developing ECa‐θv functions is needed before this approach can be applied confidently.
December 2024
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41 Reads
Organic cropping systems may potentially improve soil and environmental health relative to simplified conventional systems due to the use of extended crop rotations, perennial crops, and animal manure. However, few studies have evaluated the impacts of organic row crop systems on a suite of soil health indicators relative to conventional systems across time. Thus, our objective was to assess how cropping system (conventional corn [Zea mays L.]–soybean [Glycine max L.] vs. organic corn–soybean–oat [Avena sativa L.]/alfalfa [Medicago sativa L.]–alfalfa vs. organic perennial pasture) and duration of management affect surface soil health indicators (soil biological, chemical, and physical properties) after 1–9 years of management in a Central Iowa Mollisol. Overall, the organic rotation improved six of 14 soil health indicators compared with the conventional system and the organic pasture improved eight indicators. The improved indicators included soil biological indicators, labile C and N pools, and wet‐aggregate stability, but not organic C or total N concentrations. Organic systems had fewer effects on most soil chemical properties. The conventional system reduced soil C by 0.35 g kg⁻¹ year⁻¹ (r = −0.84, n = 9, p = 0.005), unlike the organic systems in which soil C levels were generally maintained. The changes in soil health indicators were attributed to use of perennials, reductions in tillage frequency (during perennial phases), manure, and differing plant residue amounts among the three systems. In conclusion, organic cropping systems can enhance soil biological and related indicators in the medium term, but have fewer effects on soil fertility indicators under the conditions of this study.
December 2024
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90 Reads
Monitoring CO2 or O2 concentrations within a closed, volume‐defined chamber is widely used to quantify soil respiration during laboratory soil incubation experiments. The standard method of using periodic manual gas sampling is costly, labor‐intensive, and frequently fails to capture the aerobic respiration process. Thus, tools that allow continuous, real‐time tracking of CO2 and O2 concentration changes are needed for soil respiration research. This study presents a new, portable, low‐cost (∼$700), open‐source sensor system to measure CO2 and O2 concentrations in four closed chambers. We provided non‐engineering end‐users with step‐by‐step instructions on how to build the system, enabling replication and customization. System performance was tested by comparing two respiration rates using the same soil—soil with and without glucose added for 1 week. Consistent CO2 production and O2 consumption rates were measured at 1‐min intervals, and the reliability of the system was validated by a trace gas analyzer. Two distinctive continuous apparent respiratory quotient time series between two soil treatments were observed, with higher values of CO2 in glucose soil, demonstrating the ability of the system to capture ongoing respiration processes and sufficient sensitivity to distinguish differences among respiration substrates (i.e., glucose). The tested performance of the system highlights its capabilities for soil respiration research and the potential for further adoption in real‐time gas monitoring applications.
December 2024
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58 Reads
In the coming decades, humanity will be faced with the challenge of feeding 10 billion people and managing large quantities of solid waste. These issues can be mitigated through the development of sustainable fertilizers derived from electrochemically treated waste activated sludge (EWAS) while promoting a nitrogen circular economy. This study investigates the chemistry of novel fertilizers to determine their soil chemistry dynamics. Untreated waste activated sludge (WAS) and EWAS were applied to agricultural soil and potting mix, and the resulting aqueous samples were analyzed to determine nitrogen, phosphorous, and carbon adsorption and release behaviors. Commercial inorganic and natural fertilizers were utilized for comparison. X‐ray absorption near‐edge structure (XANES) spectroscopy was performed to characterize phosphorus speciation in the solid phases of the novel fertilizers. Results indicated that EWAS and WAS samples released less total nitrogen into solution than other treatments due to organoclay complexation of biomolecules and differences in the solubility of the nitrogen species. Samples containing EWAS released a higher percentage of organic and total carbon into solution due to the deformation of the structure of the organic matter by the alkaline electrolysis process. The solubility of nitrogen and carbon in the sludge was increased by the electrochemical process. Solid‐phase phosphorus in EWAS and WAS was characterized by XANES analysis as struvite, which is a novel finding with important implications for P management from waste‐based fertilizers. These experimental findings suggest that fertilizing with EWAS could result in reduced runoff and improved soil health while facilitating domestic fertilizer production.
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University of California Davis, United States