Search Results (227)

Invasive plant species pose an increasing threat to mangroves globally. This study assessed the impact of Paspalum vaginatum invasion on carbon loss and early recovery following four years of restoration in a mangrove forest with Rhizophora racemosa in Benin. Organic carbon was quantified in the total biomass, including both aboveground and belowground components, as well as in the soil to a depth of −50 cm. In addition, soil gas fluxes of CO₂, CH₄, and N₂O were measured. Three sites were evaluated: a conserved mangrove, a site degraded by P. vaginatum, and the same site post-restoration via hydrological rehabilitation and reforestation. Invasion significantly reduced carbon storage, especially in soil, due to lower biomass, incorporation of low C/N ratio organic residues, and compaction. Restoration recovered 7.8% of the total biomass carbon compared to the conserved mangrove site, although soil organic carbon did not rise significantly in the short term. However, improvements in deep soil C/N ratios (15–30 and 30–50 cm) suggest enhanced soil organic matter recalcitrance linked to R. racemosa reforestation. Soil CO₂ emissions dropped by 60% at the restored site, underscoring restoration’s potential to mitigate early carbon loss. These results highlight the need to control invasive species and suggest that restoration can generate additional social benefits. Full article

Perennial ryegrass (Lolium perenne), an important forage and turfgrass species, can establish a mutualistic symbiosis with the fungal endophyte Epichloë festucae var. lolii. Although the physiological and ecological impacts of endophyte infection on ryegrass have been extensively investigated, the response of the soil microbial community and nitrogen-cycling gene to this relationship has received much less attention. The present study emphasized abundance and diversity variation in the AOB-amoA, nirK and nosZ functional genes in the rhizosphere soil of the endophyte–ryegrass symbiosis following litter addition. We sampled four times: at T₀ (prior to first litter addition), T₁ (post 120 d of 1st litter addition), T₂ (post 120 d of 2nd litter addition) and T₃ (post 120 d of 3rd litter addition) times. Real-time fluorescence quantitative PCR (qPCR) and PCR amplification and sequencing were used to characterize the abundance and diversity of the AOB-amoA, nirK and nosZ genes in rhizosphere soils of endophyte-infected (E+) plants and endophyte-free (E−) plants. A significant enhancement of total Phosphorus (P), Soil Organic Carbon (SOC), Ammonium ion (NH₄⁺) and Nitrate ion (NO₃⁻) contents in the rhizosphere soil was recorded in endophyte-infected plants at different sampling times compared to endophyte-free plants (p ≤ 0.05). The absolute abundance of the AOB-amoA gene at T₀ and T₁ times was higher, as was the absolute abundance of the nosZ gene at T₀, T₁ and T₃ times in the E+ plant rhizophere soils relative to E− plant rhizosphere soils. A significant change in relative abundance of the AOB-amoA and nosZ genes in the host rhizophere soils of endophyte-infected plants at T₁ and T₃ times was observed. The experiment failed to show any significant alteration in abundance and diversity of the nirK gene, and diversity of the AOB-amoA and nosZ genes. Analysis of the abundance and diversity of the nirK gene indicated that changes in soil properties accounted for approximately 70.38% of the variation along the first axis and 16.69% along the second axis, and soil NH₄⁺ (p = 0.002, 50.4%) and soil C/P ratio (p = 0.012, 15.8%) had a strong effect. The changes in community abundance and diversity of the AOB-amoA and nosZ genes were mainly related to soil pH, N/P ratio and NH₄⁺ content. The results demonstrate that the existence of tripartite interactions among the foliar endophyte E. festucae var. Lolii, L. perenne and soil nitrogen-cycling gene has important implications for reducing soil losses on N. Full article

Management of livestock manure is a major concern due to its environmental impacts; consequently, laboratory-based incubations aim to quantify the C and N mineralization of organic matter (OM) to assess its potential to supply OM to soils. However, they can be limited by methodological constraints, notably the drying process of organic products. While litterbag experiments allow in situ decomposition of OM to be monitored, they often focus only on mass loss on a dry matter basis, which may overestimate biodegradation rates. To address these limitations, we designed an experiment that combined the measurement of material fluxes with the characterization of OM using transmission electron microscopy. Raw and dried farmyard cattle manure were incorporated into the soil and incubated in litterbags (200 µm mesh) for 301 days. The results demonstrated that drying significantly altered the biochemical composition of the cattle manure and influenced its microbial dynamics at the beginning of the incubation. However, this alteration did not influence the C mineralization rate at the end of incubation. Biodegradation alone could not explain C losses from litterbags after day 112 of incubation, which supports the assertion that physical and biological processes transferred large amounts of matter from the litterbags to the soil. These results highlight the importance of conditioning samples before laboratory incubations. Full article

Film mulching and gravel mulching are effective methods for increasing crop yields in Northwest China but exacerbate soil organic carbon (SOC) mineralisation. Manure amendment is a viable method for offsetting carbon (C) losses from mulching. SOC stability is a key factor in determining the nutrient supply capacity of soils, as it affects the C sources available to microorganisms. However, the synergistic effects of film mulching and manure amendment on SOC stability and crop nutrient uptake are still unclear. Therefore, four treatments—no mulching (CK), gravel mulching (GM), film mulching (FM), and film mulching with manure amendment (FCM)—were established on the Loess Plateau. Experiments were conducted to measure plant and grain nitrogen (N), phosphorus (P), potassium (K) uptake, SOC, labile organic C fractions (LOCFs), stability-based organic C fractions (SOCFs), and the C management index (CMI) in 2019 and 2020. The results showed that the FM and FCM treatments significantly improved crop dry matter accumulation in both years compared to the control. The FCM treatment significantly increased the two-year NPK averages of plants to 44.9%, 50.7%, and 54.5% and significantly increased those of grains to 46.7%, 58.2%, and 30.4%. The FCM treatment significantly increased all LOCFs, water solution C (WSC), hot-water-extractable C (HWC), permanganate oxidisable C (POXC), and particulate organic C (POC) in the topsoil (0–20 cm) in both years. The fractions of the active C pool (AP) in the SOCFs, namely, very labile C (C_VL) and labile C (C_L), were significantly increased, suggesting that the FCM treatment significantly decreased C stability in the topsoil. The sensitivity index showed that, among all SOC fractions, POC (21.5–72.9%) and less labile C (C_LL) (20.8–483.8%) were the most sensitive fractions of LOCFs and SOCFs compared to SOC (1.93–35.8%). A random forest analysis showed that most labile C fractions and the CMI significantly contributed to crop N, P, and K uptake, especially POXC to crop N uptake, the CMI to crop P uptake, and the AP to crop K uptake. It was concluded that the FCM treatment synergistically enhanced SOC lability, crop NPK uptake, and labile C fractions, especially POXC, the AP, and the CMI, which serve as robust indicators for guiding precision nutrient management in semi-arid croplands. Full article

This review assesses biochar’s potential to mitigate nitrogen (N) losses when co-applied with N fertilizers, emphasizing mechanisms linked to its measurable physicochemical properties. The mitigation of ammonia (NH₃) volatilization shows variable effects from its cation exchange capacity (−21.7% to 20.4%) and specific surface area (SSA; −23.8% to 39.1%). However, the biochar pH (influencing mitigation from −45.0% to −9.0%) and application rate are key factors, with clayey soils exhibiting the greatest mitigation (−52.2%), potentially due to their high bulk density. High SSA biochar, often from high pyrolysis temperatures, reduces nitrate-N (NO₃⁻-N) leaching (up to −26.6%) by improving the soil’s water-holding capacity. A co-application with organic fertilizers shows a pronounced mitigation (up to −39.0%) due to a slower N release coupled with biochar adsorption. A high SSA also plays an important role in mitigating nitrous oxide (N₂O) emissions (up to −25.9%). A higher biochar C/N ratio promotes microbial N immobilization, contributing to N₂O reductions (+1.5% to −34.2%). Mitigation is greater in sandy/loamy soils (−18.7% to −7.9%) than in clayey soils, where emissions might increase (+18.0%). Overall, biochar applications demonstrate significant potential to mitigate N losses and improve N use efficiency, thereby supporting sustainable agriculture; however, its effectiveness is optimized when biochar properties (e.g., high SSA and appropriate C/N ratio) and application strategies are tailored to specific soil types and N sources. Full article

3,4-dimethylpyrazole (DMPZ), when used as a nitrification inhibitor, exhibits volatility, poor thermal stability, high production costs, and limited functionality restricted to nitrogen fixation. To address these limitations and introduce novel phosphorus-solubilizing and soil-loosening abilities, herein, a poly (acrylamide-co-acrylic acid)-encapsulated NI (P(AA-co-AM)-e-NI) is synthesized by incorporating linear P(AM-co-AA) macromolecular structures into NI systems. The P(AA-co-AM)-e-NI demonstrates an obvious phase transition from a glassy state to a rubbery state, with a glass transition temperature of ~150 °C. Only 5 wt% of the weight loss occurs at 220 °C, meeting the temperature requirements of the high-tower melt granulation process (≥165 °C). The DMPZ content in P(AA-co-AM)-e-NI is 1.067 wt%, representing a 120% increase compared to our previous products (0.484 wt%). P(AA-co-AM)-e-NI can effectively reduce the abundance of ammonia-oxidizing bacteria and prolong the duration during which nitrogen fertilizers exist in the form of ammonium nitrogen. It can also cooperatively enhance the conversion of insoluble phosphorus into soluble phosphorus in the presence of ammonium nitrogen (NH₄⁺-N). In addition, upon adding P(AA-co-AM)-e-NI into soils, soil bulk density and hardness decrease by 9.2% and 10.5%, respectively, and soil permeability increases by 10.5%, showing that it has a good soil-loosening ability and capacity to regulate the soil environment. Full article

The high-input production mode of rice monoculture (RM) has caused severe soil degradation and biodiversity loss, necessitating a transition toward more sustainable practices. The traditional rice-fish co-culture (RF) may provide valuable insights for this situation. However, it remains elusive how long-term RF system influences soil microbial community structure, enzyme activities, and carbon (C) sequestration. Here, a study was conducted at two representative RF areas in Lianshan Zhuang and Yao Autonomous County. At Shatian (P1), three treatments included rice monoculture (RM1) and 2-year and 5-year RF (RF2, RF5). At Gaoliao (P2), the experimental treatments included rice monoculture (RM2) and 15 and 30 years of RF (RF15, RF30). We collected the surface layer (0–20 cm) soils. Then, we analyzed the chemical properties, phospholipid fatty acids (PLFA), and enzyme activities to investigate the effects of their variation on soil C sequestration. The results showed that RF treatments significantly increased soil organic C (SOC) content. Specifically, RF2 and RF5 treatments promoted the SOC content by 4.82% and 13.60% compared with RM1 treatment at P1, respectively; RF15 and RF30 treatments increased the SOC content by 23.41% and 31.93% compared with RM2 treatment at P2, respectively. Additionally, RF5 treatment significantly increased the biomass of the soil microbial community in comparison with RM1 treatment, as did RF15 treatment and RF30 treatment compared with RM2 treatment, including the contents of total PLFA and the PLFA of gram-positive bacteria (G+), gram-negative bacteria (G−), actinomycetes, fungi, and bacteria. Activities of β-glucosidase, cellobiohydrolase, β-1,4-N-acetylglucosaminidase, and urease significantly increased in RF5 and RF30 treatments. The piecewise SEM results indicated that the changes of total PLFA content and the PLFA content ratio of fungi to bacteria were related to contents of dissolved organic C (DOC) and total N (TN) under different RF durations, which are key indicators affecting SOC content. Overall, SOC storage increases with the RF durations, and soil microbial community structure may drive soil C sequestration under long-term RF, which provides a scientific significance and practical value in promoting the sustainability of agricultural ecosystems, enhancing the potential of soil as a carbon sink, and addressing global climate change. Full article

Corn is a globally important crop, requiring extensive soils and intensive practices to meet the growing human and animal consumption demand. However, intensive agriculture has caused soil deterioration and fertility loss. In response, the Mexican government established the National Soil Strategy for Sustainable Agriculture (ENASAS, acronym in Spanish) to ensure food security and maintain soil fertility. This study develops “Soil Quality Indexes” ($SQI$) to monitor soil quality under corn cultivation using four methodologies (additive ($SQ{I}_a$), weighted ($SQ{I}_w$), unified weighted ($SQ{I}_u$), and Nemoro ($SQ{I}_n$)) in the Bajio region of Guanajuato, Mexico. Twenty-four physicochemical indicators were analyzed, with four (CLY, WHC, Na, and C/N) identified as key indicators of soil quality and fertility through principal component analysis. Among these, $SQ{I}_a$ was the most sensitive and efficient (SI = 2.32, ER = 50) in assessing soil quality, showing values from very low to low ($SQ{I}_a=0.13$ and $SQ{I}_a=0.39$ respectively). Aligned with the ENASAS program, $SQ{I}_a$ can help monitor and improve soil quality under corn cultivation, supporting food security through soil conservation. Moreover, $SQ{I}_a$ performed similarly to the globally recognized Soil Management Assessment Framework (SMAF), making it a valuable tool for managing and improving agricultural soil quality under similar conditions in both Mexico and worldwide. Full article

The construction of sports spaces such as ski resorts leads to deforestation, soil degradation and carbon (C) loss. However, the impact of ski pistes on soil C and nutrients remains unclear. The impact of an 18-year-old ski piste operation on the stock and stoichiometry of soil C, nitrogen (N), phosphorus (P), bulk density, and water content across a 0–100 cm profile in a forest area in Northeast China was quantitatively assessed using the equivalent soil mass method and fixed depth method. The fixed depth method overestimated soil C, N and P stocks of the SP by 5% to 8% of 0–100 cm stocks of soil C and nutrients relative to the equivalent soil mass method used as a reference. The equivalent soil mass method demonstrated that the ski piste soil C, N, and P stocks were significantly reduced by 27.4%, 21.3%, and 27.5%, respectively, in comparison to the undisturbed forest. Surface layers (0–10 cm) exhibited the highest C and N losses, while deep soil (>50 cm) showed significant C, N and P depletion. The ski piste significantly reduced surface C:N (15.8%) and C:P (38.0%) ratios, indicating decoupled nutrient constraints on C loss. Soil compaction increased bulk density in surface layers (0–10 cm) but reduced it in deeper strata, correlating with altered C physical interdependencies. The findings highlight the vertical stratification of disturbance effects, emphasizing the critical role of stoichiometric controls and methodological considerations in assessing anthropogenic impacts on soil ecosystems. These insights are vital for the sustainable management of ski resorts to mitigate soil degradation. Full article

The soybean is an important source of protein and is gaining popularity in Ghana due to a rising demand for its use in the poultry industry. However, the grain yield of soybeans is relatively low in the Upper West Region due to infertile soil and climate change. This study evaluated root nodulation and symbiotic effectiveness in 31 rhizobial isolates obtained from the nodules of soybeans planted at Da in the Upper West Region, Ghana, as well as measured photosynthetic activity of the soybean plants grown under glasshouse conditions. This study further assessed the tolerance of the rhizobial isolates to different levels of temperature, drought, salinity, and pH in the laboratory and also measured the ability of the isolates to produce indole-3-acetic acid. An infrared gas analyser and the ¹⁵N and ¹³C natural abundance techniques were used to assess the photosynthetic activity, N₂ fixation, and water-use efficiency, respectively. The results showed that the test isolates that induced greater photosynthetic rates from higher stomatal conductance also stimulated increased water loss via leaf transpiration in soybean plants. Isolates TUTGMGH9 and TUTGMGH19 elicited much higher shoot δ¹³C in the soybean host plant and induced higher shoot biomass, C accumulation, percent relative symbiotic effectiveness, and N₂ fixation relative to Bradyrhizobium strain WB74 and 5 mM of nitrate, which were used as positive controls. Although isolate TUTGMGH9 did not grow at 40 °C, it showed growth at 5% of PEG-6000, NaCl, and a low pH while also producing moderate IAA. However, for better utilisation of these rhizobial isolates as bioinoculants, their growth performance needs to be assessed under field conditions to ascertain their competitiveness and symbiotic efficacy. Full article

Agricultural land abandonment is a widespread phenomenon found in many regions of the world. There are many studies on post-agricultural changes in temperate, arid, semi-arid regions, etc., but studies of such soils in boreal or Arctic conditions are rare. Our study aims to fill the gaps in research on the processes of post-agricultural soil transformation, with a focus on the harsh climatic conditions of the Arctic and Subarctic regions. Parameters of soil organic matter (SOM) are largely reflected in the quality of soil, and this study investigates the dynamics of SOM properties in Subarctic agricultural soils in process of post-agrogenic transformation and long-term fertilization. Using a chronosequence approach (0–25 years of abandonment) and a reference site with over 90 years of fertilization, we performed elemental (CHN-O) analysis, solid-state ¹³C NMR spectroscopy of SOM, PXRD of soil and parent material, and multivariate statistical analysis to identify the connections between SOM composition and other soil properties. The results revealed transient increases in soil organic carbon (SOC) during early abandonment (5–10 years; 3.75–4.03%), followed by significant declines after 25 years (2.15–2.27%), driven by mineralization in quartz-dominated soils lacking reactive minerals for organo-mineral stabilization. The reference site (the Yamal Agricultural Station) maintained stable SOC (3.58–3.83%) through long-term organic inputs, compensating for poor mineralogical protection. ¹³C NMR spectroscopy highlighted shifts from labile alkyl-C (40.88% in active fields) to oxidized O-alkyl-C (21.6% in late abandonment) and lignin-derived aryl-C (15.88% at middle abandonment), reflecting microbial processing and humification. Freeze–thaw cycles and quartz dominance mineralogy exacerbated SOM vulnerability, while fertilization sustained alkyl-C (39.61%) and balanced C:N (19–20) ratios. Principal Component Analysis linked SOC loss to declining nutrient retention and showed SOM to be reliant on physical occlusion and biochemical recalcitrance, both vulnerable to Subarctic freeze–thaw cycles that disrupt aggregates. These findings underscore the fragility of SOM in Subarctic agroecosystems, emphasizing the necessity of organic amendments to counteract limitations of poor mineralogical composition and climatic stress. Full article

The need for renewable and biodegradable materials for packaging applications has grown significantly in recent years. Growing environmental worries over the widespread use of synthetic and non-biodegradable polymeric packaging, particularly polyethylene, are linked to this increase in demand. This study investigated the degradation properties of low-density polyethylene (LDPE), a material commonly used in packaging, after incorporating various natural fillers that are sustainable, compatible, and biodegradable. The LDPE was mixed with 2.5, 5, and 10 wt.% of sawdust, cellulose powder, and Nanocrystalline cellulose (CNC). The composites were melted and mixed using a twin-screw extruder machine with a screw speed of 50 rpm at 190 °C to produce sheets using a specific die. These sheets were used to prepare samples for rheological tests that measured the viscosity curve, the flow curve, and a non-Newtonian mathematical model using a capillary rheometer at 170, 190, and 210 °C. X-ray diffraction analysis was carried out on the 5 wt.% samples, and a short-term degradation test was conducted in soil with a pH of 6.5, 50% humidity, and a temperature of 27 °C. The results revealed that the composite melts exhibited non-Newtonian behavior, with shear thinning being the dominant characteristic in the viscosity curves. The shear viscosity increased as the different cellulose additives increased. The 5% ratio had a higher viscosity for all composite melts, and the LDPE/CNC melts showed higher viscosities at different temperatures. The curve fitting results confirmed that the power-law model best described the flow behavior of all composite melts. The LDPE/sawdust and cellulose powder melts showed higher flow index (n) and lower viscosity consistency (k) values compared with LDPE/CNC melted at different temperatures. The sawdust and powder composites had greater weight loss compared with the LD vbbPE/CNC composites; digital images supported these results after 30 days. The degradation test and weight loss illustrated stronger relations with the viscosity values at low shear rates. The higher the shear viscosity, the lower the degradation and vice versa. Full article

Acid rain and understory vegetation removal are critical drivers altering soil ecosystem alterations. However, the mechanisms by which these factors influence soil moisture dynamics, nutrient availability, and microbially mediated enzyme activities remain insufficiently elucidated. This study investigated the impacts of simulated acid rain and understory vegetation removal on soil properties, enzyme activities, and microbial community in a subtropical Cinnamomum camphor (Linn) Presl plantation. The results indicated that acid rain and understory vegetation removal significantly decreased the soil organic carbon (SOC) while concurrently elevating the C-acquiring enzyme activities and microbial C limitation. Understory vegetation removal markedly reduced the soil moisture, nutrient availability, and N- and P-acquiring enzyme activities. Additionally, acid rain increased the bacterial diversity, but the understory vegetation removal increased the fungal diversity. Moreover, both acid rain and understory vegetation removal enhanced the bacterial community deterministic processes and destabilized the community by shifting generalists toward specialists, but had no significant effect on the fungal community structure. Partial least squares path modeling revealed that the bacterial stability loss intensified the C limitation, while the fungal stability regulated the P limitation. Collectively, the findings highlighted the critical role of understory vegetation in buffering the soil microclimate and nutrient cycling, and demonstrated that bacterial communities are more responsive to acid rain and understory vegetation removal than fungal communities. This study provides insights into the mechanisms by which anthropogenic disturbances alter soil ecological functions in subtropical plantations, emphasizing the need for integrated forest management strategies to conserve and manage soil ecosystems in subtropical plantations. Full article

Peanut yield and quality are often threatened by soil degradation under continuous cropping. Biochar has been known to improve the soil microbial community and plant resistance. However, studies on its functions to reduce soil degradation losses and improve the peanut yield are limited. A field peanut experiment was conducted in an Alfisol soil and biochar was applied at a rate of 20 t ha⁻¹ in 2022. The biochar was prepared from woodchip (WB) and maize straw (MB) feedstocks alone, as well as with co-composted biochar of the same feedstocks with pig manure labeled as WBSC and MBSC amendment, respectively. The conventional organic manure was applied as a control treatment (OM). All plots were base-fertilized with a mineral compound fertilizer of N-P₂O₅-K₂O (16-16-16, %) at 600 kg ha⁻¹. Topsoil (20 cm) and plant samples were collected at the time of peanut harvest. Soil quality, enzyme function, peanut growth traits, microbial abundance, and community composition were analyzed. Compared to OM, peanut yields increased by 22%, 23%, and 18% under WB, WBSC, and MBSC, respectively. The content of oleic acid increased by 4–5%, while the content of linoleic acid decreased by 7–9%, respectively, under biochar–compost treatments. However, biochar amendment alone showed non-significant changes in these fatty acids. The soil extracellular enzyme activity increased by 3.7–5.5% with biochar amendments and 6.4–10.1% with biochar–compost application. The enzyme activity ratio of hydrolase to non-hydrolase, of C cycling to N cycling, and of P cycling increased by 11.4–15.9%, 20.9–33.8%, and 14.7–23.5% under biochar amendments and by 20.5–25.0%, 17.4–39.0%, and 23.5–32.3% under biochar–compost, respectively. Overall, crop residue biochar enhanced peanut yield and quality by improving soil aggregation, enzyme functionality, and fungal community in line with the soil nutrient supply. Full article

European grasslands are vital carbon (C) sinks, contributing to climate change mitigation. Grazing intensity significantly influences soil C and nitrogen (N) cycles through effects on soil conditions and microbial communities. While heavy grazing is linked to soil C loss and altered N processes, existing studies show conflicting outcomes. This study examines the impact of cattle grazing on soil C and N cycles in a historical alpine pasture in the eastern Italian Alps (1868 m a.s.l.). The following three grazing intensities were analyzed: heavy (8.19 LU ha⁻¹), moderate (0.59 LU ha⁻¹), and light (0.06 LU ha⁻¹). Soil was sampled from two depth layers (0–5 cm, 5–10 cm) and analyzed for bulk density, C and N content, C/N ratio, exchangeable N, δ¹⁵N, and microbial genes targeting general abundance (16S), N fixation (nifH), nitrification (amoA), and denitrification (nirK, nosZ) using real-time PCR. The results revealed decreased C and N concentrations with increasing grazing intensity, exclusively in the 0–5 cm soil layer. Higher δ¹⁵N and enhanced nitrification and denitrification suggest a more open N cycle under heavy grazing. These findings highlight the potential of microbial gene markers and δ¹⁵N isotopic ratios to monitor N cycle dynamics in alpine pastures, informing sustainable grazing management. Full article