Organic Matter Research Articles

Seasonal and Spatial Variability of Absorption Properties in Cartagena Bay’s Complex Waters

Characterizing inherent optical properties (IOPs) of water constituents is crucial for remote sensing applications. Remote sensing in Cartagena Bay is particularly challenging due to significant variations in constituent concentrations caused by the seasonal and annual variability of discharges from the Canal del Dique. This article presents the variability in absorption coefficients of phytoplankton, chromophoric dissolved organic matter (aCDOM), and non-algal particles (aNAP) in Cartagena Bay. Absorption coefficients were measured in the laboratory across multiple monitoring campaigns, with seasonal analyses conducted to establish relationships between absorption properties and biogeochemical parameters such as chlorophyll-a, salinity, and turbidity. Results indicate that at 440 nm, aCDOM and aNAP primarily dominate absorption during the rainy season, while aNAP dominates during the dry season. This variation is influenced by inflows from the Canal del Dique. Lower CDOM absorption in 440 nm (aCDOM440), and higher CDOM absorption slope (SCDOM275–295) and higher salinity values were observed during the dry season, which is consistent with the reduced fluvial influx. Spatial variability shows that higher CDOM values prevail in the river plume area during both seasons, with particularly higher values in the rainy season. Median values of aNAP were similar in both seasons, with a strong relationship found between all aNAP data and turbidity (rp = 0.785). Compared to other estuaries, Cartagena Bay exhibits optical characteristics typical of a coastal water body subjected to river discharges, including the elevated turbidity and the high dissolved organic matter influenced by significant inflow from the Canal del Dique. These features highlight the bay’s dynamic interactions with terrestrial inputs. This study provides invaluable information on the optical characteristics of Cartagena Bay, which is crucial for improving the accuracy and effectiveness of remote sensing models for optically active parameters such as turbidity, suspended solids, CDOM, and chlorophyll-a.

A closed-loop sustainable method for the fabrication of electrospun nanofiber using food waste for filtration of particulate matters (PMs) and volatile organic matter (VOCs) from air

Indoor air pollution significantly impacts human health and the environment. Humans suffer the greatest health burden due to inefficient combustion technologies and polluted fuels. Therefore, air filtration is essential for a healthy and prosperous household. This study aims to develop a sustainable approach for the fabrication of biodegradable electrospun nanofibers (ENs) as air filters from food waste materials and offer a closed-loop circular solution and potential replacement for non-biodegradable HEPA air filters. We have tested banana peel extract (BPE), eggshell membrane, chitosan, and starch blended with polyvinyl alcohol (PVA) for fabricating ENs. Among the nanofibers investigated for air filtration application, BPE/PVA nanofiber shows the best performance in terms of maximum particulate matter (PM) removal efficiency and minimum pressure drop while incorporating > 50 % of the food waste into the electrospinning solution. Adding BPE into a 10 % PVA solution leads to a reduction in the hydrophilic behavior of the BPE/PVA nanofiber as compared to neat 10 % PVA ENs. The BPE/PVA nanofiber shows minimum pressure drop (156–160 Pa) and highest quality factor (Qf) in comparison with other waste-derived nanofibers with > 98 % filtration efficiency of PM2.5. Further, BPE/PVA nanofiber shows the highest adsorption of xylene vapor among other food waste derived nanofibers studied. Based on the above results, it can be concluded that BPE based nanofiber shows the best performance as air filter media among all other food waste-based ENs. The study demonstrates a successful regeneration and reuse of the BPE/PVA filter up to 3 cycles. The leftover material from banana peels after BPE extraction was utilized as a soil ameliorant. It showed 55 % soil water retention (SWR) capacity, making it possible to apply in arid regions or crops with high water requirements.

Microplastics and their interaction with microorganisms in Bosten Lake water

Microplastic pollution in inland freshwater lakes, formed from melting ice, atmospheric precipitation, and groundwater, remains under-researched. This study examines microplastic (MPS) presence and distribution in Bosten Lake and their interaction with microorganisms. We employed a Confocal Raman spectrometer to identify MPS types and 16S rRNA high-throughput sequencing to analyze microbial diversity and composition. In May, the lake's average microplastic concentration was 108.20 particles per liter (PCS/L), decreasing to 21.67 PCS/L by October. Transparent and yellow fibrous microplastics, predominantly 0.2–0.5 mm in size, were most common. Key microplastics in May included PEEK (27%), PMMA (25%), and PET (9%), while October saw a prevalence of PET (35%), PS (13%), and PA (9%). Higher microplastic concentrations correlated with reduced microbial diversity. In May, the high microplastic concentration group (MH) showed increased Planctomycetota, while in October, Patescibacteria and Bacteroidota rose significantly in the high plastic group (OH), known for microplastic degradation. MH also had a higher abundance of Cryptomycota compared to OH. Functional analysis indicated that MH had more genes related to bisphenol, benzene, and chlorine compounds, whereas OH had genes linked to methane, nitrogen, and organic matter degradation. Microplastic concentrations peaked near the lake inlet and tourist areas, affecting microbial quantity, diversity, structure, and function. This research enhances our understanding of MPS distribution and environmental microbial shifts in similar settings, providing essential data for environmental management strategies at Bosten Lake.

Performance of a pilot-scale microbial electrolysis cell coupled with biofilm-based reactor for household wastewater treatment: simultaneous pollutant removal and hydrogen production.

The septic tank is the most commonly used decentralized wastewater treatment systems for household wastewater treatment in on-site applications. The removal rate of various pollutants is lower in different septic tank configurations. The integration of a microbial electrolysis cells (MEC) into septic tank or biofilm-based reactors can be a green and sustainable technology for household wastewater treatment and energy production. In this study, a 50-L septic tank was converted into a 50-L MEC coupled with biofilm-based reactor for simultaneous household wastewater treatment and hydrogen production. The biofilm-based reactor was integrated by an anaerobic packed-bed biofilm reactor (APBBR) and an aerobic moving bed biofilm reactor (aeMBBR). The MEC/APBBR/aeMBBR was evaluated at different organic loading rates (OLRs) by applying voltage of 0.7 and 1.0V. Result showed that the increase of OLRs from 0.2 to 0.44kg COD/m3 d did not affect organic matter removals. Nutrient and solids removal decreased with increasing OLR up to 0.44kg COD/m3 d. Global removal of chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen (TN), ammoniacal nitrogen (NH4+), total phosphorus (TP) and total suspended solids (TSS) removal ranged from 81 to 84%, 84 to 85%, 53 to 68%, 88 to 98%, 11 to 30% and 76 to 88% respectively, was obtained in this study. The current density generated in the MEC from 0 to 0.41 A/m2 contributed to an increase in hydrogen production and pollutants removal. The maximum volumetric hydrogen production rate obtained in the MEC was 0.007 L/L.d (0.072 L/d). The integration of the MEC into biofilm-based reactors applying a voltage of 1.0V generated different bioelectrochemical nitrogen and phosphorus transformations within the MEC, allowing a simultaneous denitrification-nitrification process with phosphorus removal.

Unveiling the impact of low-molecular-weight organic acids on enrofloxacin sorption in North China agricultural soil: Insights and implications

Low-molecular-weight organic acids (LMWOAs) play a crucial role as components of dissolved organic matter in soil, influencing the sorption/desorption, degradation, and plant uptake of diverse pollutants within the agricultural soil ecosystem. This study delves into the sorption behavior and mechanism of the fluoroquinolone antibiotic enrofloxacin (ENR) on agricultural soil in North China, focusing on the impact of LMWOAs. Through batch equilibrium experiments, we explored the sorption/desorption kinetics of ENR under varying conditions such as temperature, pH, ion strength, and ion type, with the addition of acetic acid, oxalic acid, and citric acid individually. Our findings reveal that the sorption and desorption kinetics of ENR—whether with or without LMWOAs—conformed well to the pseudo-second-order kinetic model (R2 ≥ 0.997). The presence of LMWOAs notably enhanced ENR sorption while impeding desorption in soil, with oxalic acid demonstrating the highest promotion effect followed by acetic acid and citric acid. Moreover, the sorption capacity and affinity of ENR decreased with rising solution pH, dropping from 96.8%-98.5% to 30.9%–34.4%. Acidic conditions favored ENR retention in soil, with inhibition of sorption escalating alongside increasing ionic strength. LMWOAs, soil solution pH, and coexisting ions emerge as pivotal factors shaping ENR sorption behavior. Furthermore, LMWOA presence intensified desorption hysteresis of ENR on soil, with a desorption hysteresis coefficient (HI) ≤ 0.124. These results suggest that LMWOAs restrict ENR mobility in the local soil environment, heightening the risk of its accumulation in soil and crops. This study offers valuable insights into the intricate interplay among LMWOAs, ENR sorption dynamics, and environmental outcomes, underscoring the importance of understanding such complexities in agricultural soil management.

Method Development and Comprehensive Study of Matrix Effects for the Determination of Trace Organic Contaminants in Lake Sediments

The presence of trace organic contaminants (TrOCs), such as pharmaceuticals, personal care products, additives, and polar pesticides in sediments of rivers and lakes highly impacted by anthropogenic activities makes sediments a secondary source of contamination for aquatic ecosystems. Considering this, a method for analyzing 44 TrOCs of diverse nature (including five transformation products, 13 pharmaceuticals, five personal care products, 14 pesticides, and seven additives) was developed and validated. It is based on extraction by pressurized liquid extraction (PLE), followed by purification and pre-concentration by solid phase extraction (SPE) and quantification by liquid chromatography coupled to a triple quadrupole mass spectrometer (LC-QqQMS). The method was optimized according to dispersant type, temperature, and extraction solvent. The influence of organic matter in sediments on quantitative analysis was also investigated in detail. Matrix effects were highly and significantly correlated (r=-0.9146, p < 0.0001) with retention time. Using internal standards showed the best results for effectively correcting matrix effects without affecting method sensitivity. The method was then validated according to key figures of merit: linearity (R2 > 0.990), extraction recoveries (> 60% for 34 compounds), trueness (bias % < 15%), precision (relative standard deviation < 20%) and matrix effects (between -13.3% and 17.8%). This method can be applied for routine analysis of TrOCs in different sediment matrices. The method was applied to ten lake sediment samples collected in Québec, Canada. Results demonstrated the presence of 17 compounds in at least one lake at concentrations between 0.07 to 1531 ng g-1. The reported concentrations provide a first picture of the occurrence of chemical stressors in sediments of small lake highly anthropized ecosystems in Eastern Canada.

Variations in the level of available phosphorus with changes in the status of water-soluble organic matter derived from different organic materials in soil

The combined application of organic material and phosphorus fertilizer is an effective method to enhance phosphorus use efficiency for plant growth. This is partly because the presence of water-soluble organic matter (WSOM) derived from different organic materials can enhance the level of available phosphorus in the soil; however, it is poorly understood how this level varies with changes in the WSOM status (i.e., decomposed, dissolved, and retained) in the soil depending on WSOM types. This study aimed to (i) understand how changes in the WSOM status enhances the available phosphorus level in the soil, and (ii) determine the WSOM type that contributes to such enhancement. The incubation test showed that fractions of 73%–92% and 8%–27% of WSOM-derived organic carbon were retained and dissolved, respectively, at the beginning of incubation, while 31%–45% was decomposed during the incubation period. The WSOM derived from cattle manure compost (CM) and sewage sludge compost (SSC) that was initially retained was maintained until the late stage of the incubation test, whereas that derived from hydrothermal decomposed liquid fertilizer (HDLF) was rapidly desorbed during the first 14 days of the incubation period. The available phosphorus level was higher under the combined application of CM- and SSC-derived WSOM than under the single phosphorus application throughout the incubation period, while it was high only during the first 3 days of incubation under the application of HDLF-derived WSOM. The amounts of retained organic carbon at each sampling point during the incubation period compared to those at the beginning were positively and linearly correlated to the available phosphorus levels that were enhanced by the WSOM present in the soil. This study for the first time provides quantitative experimental evidence that 1) the longer the WSOM continues to be retained, the higher the amount of available phosphorus remaining in the soil, and 2) the available phosphorus level decreases with WSOM sorption or decomposition. Furthermore, it was shown that highly humified WSOM has a great potential for the maintenance of higher available phosphorus levels. This study provides the insight that a combined application of highly humified organic materials with a chemical fertilizer is necessary for not only cost effective but also sustainable fertilization design.

Water and carbon fluxes from a supra-permafrost aquifer to a stream across hydrologic states

Supra-permafrost aquifers within the active layer are present in the Arctic during summer. Permafrost thawing due to Arctic warming can liberate previously frozen particulate organic matter (POM) in soils to leach into groundwater as dissolved organic carbon (DOC). DOC transport from groundwater to surface water is poorly understood because of the unquantified variability in subsurface properties and hydrological environments. These dynamics must be better characterized because DOC transport to surface waters is critical to predict the long-term fate of recently thawed carbon in permafrost environments. Here, we used distributed Darcy’s Law calculations to quantify groundwater and DOC fluxes into Imnavait Creek, Alaska, a representative headwater stream in a continuous permafrost watershed. We developed a statistical ensemble approach to model the parameter variability and range of potential contributions of steady-state groundwater flow to the creek. We quantified the model prediction uncertainty using statistical sampling of in-situ, active-layer soil hydro-stratigraphy (water table, ice table, and soil stratigraphy), high-resolution topography data, and DOC data. Moreover, the predicted groundwater discharge values representing all possible hydrologic conditions towards the end of the thawing season were also considered given the potential variability in saturation. The model predictions were similar to and span most of the observed range of Imnavait Creek streamflow, especially during recession periods, and also during saturation excess overland flow. As the Arctic warms and supra-permafrost aquifers deepen, groundwater flow is expected to increase. This increase is expected to impact stream, river, and lake biogeochemical processes by dissolving and mobilizing more soil constituents in continuous permafrost regions. This study highlights how quantifying the uncertainty of hydro-stratigraphical input parameters helps understand and predict supra-permafrost aquifer dynamics and connectivity to aquatic systems using a simple, but scalable, modeling approach.

Revealing the catalytic behavior of different types ZVI (powder Fe0, sponge Fe1, foam Fe2) in US/Fex/PDS and its effect on the dewaterability of waste activated sludge

The ultrasound (US) irradiation-coupled zero-valent iron (ZVI) activated persulfate system could improve dewatering performance, reduce WAS volume, decrease transport and final disposal costs. However, there are huge differences between various types of ZVI on activation efficiency, reaction mechanism, and application potential in WAS conditioning process. In this study, three ZVI (Fex) catalysts (Fe0 powder iron, Fe1 sponge iron and Fe2 foam iron) were used in the US/PDS system, whose catalytic performance and the fundamentals of the WAS conditioning were explored and compared. The results showed that the capillary suction time (CST) reduction rates were 89 %, 85 %, and 87 % in US/Fe0/PDS, US/Fe1/PDS, and US/Fe2/PDS, respectively, which indicated that the US/Fex/PDS system had an outstanding conditioning performance. The WAS reduction rate was US/Fe1/PDS > US/Fe2/PDS > US/Fe0/PDS attributed to Fe1 surface activate sites. Similarly, the organic matters characterization showed soluble protein content (PN), polysaccharide content (PS), and microbial by-products were significantly reduced in the US/Fe1/PDS system. Further examination of the thermodynamic parameters revealed that the WAS cohesive interfacial energy (ΔGslscoh) was minimally reduced to promote release of bound water in the system due to the effective regulation of intermolecular forces. In addition, examination of the trivalent iron/divalent iron ratio (Fe3+/Fe2+) to assess the efficacy of ferric ion recycling showed a significant advantage for US/Fe1/PDS system. On the basis of improving catalyst utilization, PDS produced SO4·- that dominated free radicals to condition WAS, improve dewaterability and achieve WAS reduction. Finally, evaluating laboratory WAS conditioning results and costs, US/Fe1/PDS system has potential applications value.

Effects of DOM and cations on the diffusion migration of PPCPs through ion exchange membranes

The transportation of pharmaceuticals and personal care products (PPCPs) in ion-exchange membranes was worrying, especially in complex substrates. Dissolved organic matter (DOM), the complexation of PPCPs and the membrane pollution formed by DOM were often confused in the existing studies. This paper investigated the diffusive migration patterns of three kinds of (PPCPs) through ion exchange membranes (IEMs) in complex substrates. Triclosan (TCS) exhibited the most probability of migration. Without considering the interference of environmental factors, more than 90 % of TCS was adsorbed by IEMs. The migration of sulfadiazine sodium (SD) and carbamazepine (CBZ) was less than 5 %. The DOM and cations altered the interaction of PPCPs and IEMs. DOM fouling on IEMs converted the direct strong binding of TCS to IEMs to indirect weak binding, and increased the transmembrane migration of TCS consequently. The presence of cations (Ca2+ and Mg2+) increased the inorganic binding of TCS to IEMs, and also promoted the transmembrane migration of TCS. However, coexisting of Mg2+ and humic acid (HA) decreased TCS migration through anion exchange membrane (AM), but increased TCS migration through cation exchange membrane (CM) due to the increasing of solution potential. The research provided a theoretical basis for exploring the safety of product solutions in IEMs systems.

New insights into aqueous Hg(II) photoreduction from paddy field system to natural water: Gear effect of straw returning and soil tillage

Soil dissolved organic matter (SDOM) has a strong complex with divalent mercury (Hg(II)) and can affect the fate of aqueous Hg(II) photoreduction. However, little is known about the influence of straw returning and soil tillage on the composition of SDOM in paddy soil and Hg(II) photoreduction in paddy water. Here, we demonstrate that the combined drivers of long-term straw returning and tillage can result in higher degrees of aromatization, and the enrichment of oxygen-containing functional groups in surface SDOM. Hg(II) photoreduction under low Hg/DOC conditions is mainly constrained by the composition of SDOM, whereas solar radiation emerged as a dominant controlling factor associated with high ratio of Hg/DOC. By increasing the release of SDOM and mobility of Hg(II), reducing the stability of Hg(II)-SDOM complexes, and potentially enhancing generation of reactive intermediates, gear effect of straw returning and soil tillage significantly enhanced Hg(II) photoreduction in the presence of surface SDOM from 0-40cm (maximum photoreduction percentage can reach 44.76 ± 2.24%). Previous inventories of Hg(0) emissions from paddy field system may have overlooked or underestimated this critical process. Future modeling work should be carried out to evaluate the role of straw returning and soil tillage on global Hg cycle.

Characterization and mitigation measures for carbon dioxide, methane, and ammonia emissions in dairy barns

The agricultural sector is a major contributor to global greenhouse gas emissions, with dairy production being a significant source. In this context, the study aims to characterize CO₂, CH₄, and NH₃ emissions—key greenhouse gases in dairy barns—and to evaluate strategies for mitigating these emissions. Inside dairy barns, the primary sources of CO₂, CH₄, and NH₃ emissions are linked to the enteric processes of the animals and the waste deposited within the dairy barns. CO₂ mainly originates from animal respiration and the decomposition of organic matter. CH₄ is generated through enteric fermentation in the rumen and the anaerobic decomposition of manure. Additionally, NH₃ is released from the enzymatic breakdown of urea in urine. Mitigation efforts have shown promise within dairy barns through various approaches. Optimizing animal diets by incorporating supplements and controlling protein intake helps reduce methane production from enteric fermentation. Enhanced manure management practices, including separating feces and urine, adjusting manure pH, and increasing cleaning frequency, are effective in minimizing ammonia and methane emissions within dairy barns. Nevertheless, achieving significant emission reductions also requires effective waste management beyond the facilities. This study contributes to the ongoing dialogue on sustainable livestock production by addressing both emission sources and potential solutions in dairy farming.

N-doped hierarchically porous carbon from lignite-derived residue for high-performance supercapacitor

Lignite-derived residue with cross-linked aromatic structure and heteroatom groups is an alternative and low-cost precursor for porous carbon. Herein, N-doped hierarchically porous carbon (NDHPC) was prepared by KOH activation from lignite-derived residue using ZnO as the template and dicyandiamide as the nitrogen source. The optimal NDHPC presents hierarchically porous stacked layered structure with high specific surface area (2648.18 m2/g) and contains abundant O/N functional groups, making it promising candidate as the electrode material. Introducing nitrogen can provide more pseudocapacitors and meanwhile improve the wettability of the NDHPC, thus enhancing electrochemical performance. The optimal NDHPC exhibits a high specific capacitance of 336 F g−1 at the current density of 0.5 A g−1 with good rate performance. Additionally, the assembled NDHPC symmetrical supercapacitor presents outstanding cycle stability with 96.2 % capacitance retention and possesses energy density of 7.85 Wh kg−1 at power density of 250 W kg−1. This study offers an effective and low-cost approach to fully utilize the organic matter in coal-derived residue for preparing supercapacitor electrode materials.

Content and quality of soil organic matter in topsoils under different tundra vegetation in central Spitsbergen (High Arctic)

Permafrost-affected soils contain a large amount of soil organic matter (SOM) which may become easily available to microbial decomposition due to climate warming. Despite numerous studies conducted on SOM in permafrost-affected soils, our knowledge about its quantity and chemistry requires further enhancement in the central part of Spitsbergen, due to a lack of detailed studies in this area. Especially, very little is known about the link between soil and vegetation in the High Arctic region. The main aim of this study was to determine the quantity and chemistry of SOM in the topsoil horizons of permafrost-affected soils covered with different tundra vegetation types in the vicinity of Longyearbyen (central Spitsbergen). Four types of tundra (pioneer tundra, arctic meadow, wet moss tundra, and heath tundra) were selected for this study. The obtained results indicate that the highest mean content of total organic carbon (TOC, 24.22 %) and total nitrogen (TN, 0.79 %) occurred in topsoils covered with heath tundra, while clearly lower mean contents of TOC and TN were noted in topsoils under wet moss tundra (5.96 %, 0.37 %, respectively), arctic meadow (3.40 %, 0.19 %, respectively), and pioneer vegetation (2.56 %, 0.21 %, respectively). The obtained FTIR-ATR spectroscopy results indicated significant differences in the chemical composition of SOM under different types of tundra. The highest mean value of the aromatic C/aliphatic C ratio (1632/2928 ratio) was noted for topsoils covered with arctic meadow (2.82). On the other hand, the lowest mean value of aromatic C/aliphatic C ratio for SOM was obtained for topsoils covered with heath tundra (0.81). This indicated that SOM in topsoils under heath tundra vegetation is characterized by a higher content of aliphatic compounds in relation to aromatic compounds. Moreover, both soil texture and soil pH significantly affected the content and quality of SOM in the studied topsoils.

Moderate grazing intensity and pika disturbance can enhance plant diversity and soil nutrient cycling in the alpine grasslands of the Qinghai-Xizang Plateau

Grazing livestock and pikas, as the primary herbivores in grasslands, influence the health of grassland ecosystems through activities such as feeding, burrowing, and trampling. This study reviews 86 articles and examines the effects of varying grazing levels and pika activity on alpine grassland vegetation and soil in the Qinghai-Xizang Plateau, providing scientific insights to guide grassland conservation efforts. The research shows that: 1) Both grazing and pika disturbance significantly reduce aboveground biomass (AGB) in alpine grasslands (p < 0.05). Moderate grazing increases diversity indices, while pika disturbance has the opposite effect. 2) As grazing intensity increases, there is a significant decrease in total nitrogen (TN), total phosphorus (TP), and soil organic matter (SOM) content (p < 0.05). However, moderate pika disturbance leads to a significant increase in TP and TN content (p < 0.05). 3) In grazing trials, bulk density (BD) and the Shannon-Wiener index are significant positive drivers. Conversely, during pika disturbance, the Shannon-Wiener index and total nitrogen (TN) act as significant positive drivers, while BD is a significant negative driver. The study's findings indicate that moderate grazing intensity and pika disturbance can enhance plant diversity indices in grasslands, as well as improve soil structure and nutrient levels. Therefore, establishing a reasonable grazing system and controlling the pika population are effective methods for managing alpine grasslands.

Integration of biogas and liquid recirculation enhance methane production in high-solid anaerobic digestion of pig manure and rice husks

High-solid anaerobic digestion (HSAD) is a promising technology for treating livestock manure and agricultural waste; however, the wide application has been limited due to homogenization problems. This study established a novel HSAD system by integrating liquid and biogas recirculation (RBL), aiming to enhance the biogas conversion efficiency of high-solid substrates at low costs. Results showed that the highest methane yield was 357 mL/gVSadded in the novel HSAD system (RBL), 30.7 % and 251.7 % higher than those with only liquid recirculation (RL) or with no recirculation (RNo). Biogas recirculation helped enhance dissolution and degradation of organic matter, and prevented the VFAs accumulation, contributing to the enhanced methane production in the novel HSAD system. The net electric energy benefit of RBL was 301.2 kWh for treating 1-ton raw materials, suggesting the high economic feasibility of the novel HSAD system for the sustainable treatment of high-solid organic wastes.

What is the impact of neutral detergent fibre digestibility on productive performance of beef cattle fed tropical forages?

Our objective was to quantify the relationship between total neutral detergent fibre (NDF) digestibility and nutritional and productive characteristics in cattle fed tropical forages using a meta-analytical approach. The dataset used to develop this work was compiled from 24 experiments carried out with beef cattle in Brazil, published between 2005 and 2020, and totalising 115 treatment means. All the experiments were carried out using change-over designs and included a control treatment (i.e., only forage). There was a linear and positive relationship (P<0.01) between total NDF digestibility and voluntary forage intake. We estimated a 0.17 g/kg body weight increase in forage intake for each percentage point (i.e., 0.01 g/g) of improvement in NDF digestibility. On average, increasing total NDF digestibility caused a linear improvement (P<0.01) in rumen microbial nitrogen production (NMIC) and in dietary digested organic matter (DOM). The total NDF digestibility was linear and positively associated with nitrogen balance (NB, P<0.01). However, the increment in NB as a response to total NDF digestibility was more prominent as dietary NDF decreased (P<0.01). In summary, we concluded that increasing NDF digestibility in cattle fed tropical forage-based diets improves the voluntary forage intake and the supply of energy and metabolisable protein. This simultaneous effect causes an increase in the animal's nitrogen accretion and weight gain, but this effect will be more prominent as the dietary content of neutral detergent fibre decreases.

Effect of biochar on the co-conversion of carbon-nitrogen and humification of kitchen waste composting process

Composting was an effective technique to treat kitchen waste into high-quality fertilizer or soil amendment. During the composting process of kitchen waste, different degradation rates of carbon and nitrogen resulted in carbon loss, nitrogen emission and low product quality. Consequently, the aim of this study was to investigate the mechanisms and effects of biochar (5%, 10% and 15%) on synergistic conversion of nitrogen and carbon and humification processes in kitchen waste composting. The findings revealed that the addition of 10% and 15% biochar prolonged the thermophilic phase (>55°C) by a minimum of three days compared to CK. Additionally, the final NH4+-N concentration in the 10% and 15% treatment groups exhibited a 66.7% reduction in comparison to the control. Besides, the 15% addition proved more efficacious in reducing the NH4+-N content. The increase in biochar facilitates the adsorption of ammonia nitrogen and influences the structure of the microbial community, especially Bacteroides and Pseudoxanthomonas, thus promoting nitrogen mineralisation and humification, which provides energy and carbon for the survival and metabolism of more microorganisms. The compost with 15% biochar exhibited higher levels of SBR1031, resulting in a 73.8% increase in the conversion of nitrogen to NO3--N compared to the control. The aforementioned behaviour facilitates a synergistic conversion of nitrogen and carbon. Therefore, the addition of biochar promotes synergistic carbon and nitrogen transformations in terms of nitrogen conservation, organic matter decomposition, microbial species and their interactions, which is essential for the production of value-added compost fertilizers.

Impacts of shifting from single-species pine forests to distinct agroforestry models on soil fertility, exchangeable cations, and microbial functions

The transition from monoculture to mixed-species agroforestry systems affects soil organic matter and microbial activity. However, the specific dynamics of these changes, particularly within medicinal plant-based agroforestry, remain underexplored. This study investigates the impact of monoculture Pine (Pinus massoniana) forests and four agroforestry models: (M1) Pinus massoniana and Alpina oxyphylla, (M2) Pinus massoniana and Ficus simplicissima, (M3) Pinus massoniana and Amomum villosum, and (M4) Pinus massoniana and Curcuma longa on soil properties and microbial activity in rhizosphere and non-rhizosphere environments. Our results showed significantly higher pH (4.80) and total nitrogen (N) content (1.77 g kg−1) in the rhizosphere of model (M4) compared to (CK). Total organic carbon (TOC) and carbon fractions (POC, DOC, and MBC) also differed significantly across monoculture and agroforestry models, with highest TOC concentrations (31.70 g kg⁻1) in rhizosphere of CK. Exchangeable cations, including Ca2⁺, and Mg2⁺ were significantly higher in the rhizosphere of agroforestry models compared to CK, particularly in M4, where Ca2⁺ was recorded at 12.03 cmol kg−1 with the highest percent base saturation (PBS) at 90.17%. Enzymes leucine aminopeptidase and polyphenol oxidase varied significantly, with higher activity in the rhizosphere of agroforestry models and greater activity in non-rhizosphere of monoculture. Soil microbial respiration (MRes) revealed substantial differences, with an average 17% decrease in rhizosphere soil for models M2 and M4 and a 20.83% reduction in non-rhizosphere soil for model M1 compared to CK. Generalized Linear Model (GLM) demonstrated a significant positive correlation between TOC and MRes (R2 = 0.885, p < 0.01), indicating that higher TOC levels are linked with increased MRes. In conclusion, model M4 most effectively enhanced soil fertility and nutrient availability followed by the other agroforestry models tested. This suggests that integrating medicinal plants into agroforestry systems is a viable strategy for improving ecosystem functioning compared to monoculture practices.

Plant-Parasitic and Free-Living Nematode Community Associated with Oak Tree of Magoebaskloof Mountains, Limpopo Province, South Africa

A study was conducted in the mountains of Magoebaskloof, Limpopo Province, where oak trees grow along the banks of the Broederstroom River. This study revealed that 22 nematode genera were associated with oak trees (Quercus robur). The most frequently occurring nematodes were Aphelenchus sp. (100%) and Plectus sp. (100%), followed by Helicotylenchus sp. (90%). This study examined the relationship between nematodes and the physicochemical properties of the soil using Pearson correlation. It uncovered that the organic matter content (OMC) had a negative correlation with the number of Panagrolaimus sp. (r = −0.770) and Hemicycliophora sp. (r = −0.674). Conversely, the sand percentage positively correlated (r = 0.695) with the number of Hemicycliophora sp. The clay content of the soil showed a positive correlation (r = 0.617) with the number of Ditylenchus. Soil pH demonstrated a significant negative correlation with Acrobeloides sp. (r = −0.877). The canonical correspondence analysis (CCA) explained 63.3% of the relationship between nematodes and soil physicochemical properties. The CCA results indicated that Ditylenchus exhibited a positive correlation with OMC, while the Panagrolaimus and Hemicycliophora species showed a negative correlation with OMC. The results indicated that none of the soil sample sites were under stress. The soil food web analysis revealed that most soil samples were nutrient-enriched with a low C/N ratio. In conclusion, this study revealed that oak trees harbor a high diversity of plant-parasitic and free-living nematodes. The results suggest that soil nematodes, particularly free-living bacterivores, such as Panagrolaimus, can indicate organic matter content in the soil.