Application of nitrogen-rich sunflower husks biochar promotes methane oxidation and increases abundance of Methylobacter in nitrogen-poor soil.

The area of sunflower crops is steadily increasing. A beneficial way of managing sunflower waste biomass could be its use as a feedstock for biochar production. Biochar is currently being considered as an additive for improving soil parameters, including the ability to oxidise methane (CH4) - one of the key greenhouse gases (GHG). Despite the high production of sunflower husk, there is still insufficient information on the impact of sunflower husk biochar on the soil environment, especially on the methanotrophy process. To fill this knowledge gap, an experiment was designed to evaluate the effects of addition of sunflower husk biochar (produced at 450-550 °C) at a wide range of doses (1-100 Mg ha-1) to Haplic Luvisol. In the presented study, the CH4 oxidation potential of soil with and without sunflower husk biochar was investigated at 60 and 100% water holding capacity (WHC), and with the addition of 1% CH4 (v/v). The comprehensive study included GHG exchange (CH4 and CO2), physicochemical properties of soil (pH, soil organic carbon (SOC), dissolved organic carbon (DOC), nitrate nitrogen (NO3--N), WHC), and the structure of soil microbial communities. That study showed that even low biochar doses (5 and 10 Mg ha-1) were sufficient to enhance pH, SOC, DOC and NO3--N content. Importantly, sunflower husk biochar was significant source of NO3--N, which soil concentration increased from 9.40 ± 0.09 mg NO3--N kg-1 for the control to even 19.40 ± 0.26 mg NO3--N kg-1 (for 100 Mg ha-1). Significant improvement of WHC (by 11.0-12.4%) was observed after biochar addition at doses of 60 Mg ha-1 and higher. At 60% WHC, application of biochar at a dose of 40 Mg ha-1 brought significant improvements in CH4 oxidation rate, which was 4.89 ± 0.37 mg CH4-C kg-1 d-1. Higher biochar doses were correlated with further improvement of CH4 oxidation rates, which at 100 Mg ha-1 was seventeen-fold higher (8.36 ± 0.84 mg CH4-C kg-1 d-1) than in the biochar-free control (0.48 ± 0.28 mg CH4-C kg-1 d-1). CO2 emissions were not proportional to biochar doses and only grew circa (ca.) twofold from 3.16 to 6.90 mg CO2-C kg-1 d-1 at 100 Mg ha-1. Above 60 Mg ha-1, the diversity of methanotrophic communities increased, with Methylobacter becoming the most abundant genus, which was as high as 7.45%. This is the first, such advanced and multifaceted study of the wide range of sunflower husk biochar doses on Haplic Luvisol. The positive correlation between soil conditions, methanotroph abundance and CH4 oxidation confirmed the multifaceted, positive effect of sunflower husk biochar on Haplic Luvisol. Sunflower husk biochar can be successfully used for Haplic Luvisol supplementation. This additive facilitates soil protection against degradation and has the potential to mitigate GHG emissions.

Responses of Nitrous Oxide Emissions and Bacterial Communities to Experimental Freeze-Thaw Cycles in Contrasting Soil Types.

Nitrous oxide (N2O) pulse emissions are detected in soils subjected to freeze-thaw cycles in both laboratory and field experiments. However, the mechanisms underlying this phenomenon are poorly understood. In this study, a laboratory incubation experiment that included freeze-thaw cycles (FTC), freezing (F) and control (CK) treatments was performed on three typical Chinese upland soils, namely, fluvo-aquic soil (FS), black soil (BS) and loess soil (LS). A higher similarity in soil properties and bacterial community structure was discovered between FS and LS than between FS and BS or LS and BS, and the bacterial diversity of FS and LS was higher than that of BS. FTC significantly increased the denitrification potential and the proportion of N2O in the denitrification gas products in FS and LS but decreased the denitrification potential in BS. Accordingly, with the increasing number of freeze-thaw cycles, the bacterial community composition in the FTC treatments in FS and LS diverged from that in CK but changed little in BS. Taxa that responded to FTC or correlated with denitrification potential were identified. Taken together, our results demonstrated that the effects of FTC on N2O emissions are soil-type-dependent and that the shift in the microbial community structure may contribute to the elevated N2O emissions.

Variation in methane uptake by grassland soils in the context of climate change - A review of effects and mechanisms.

Grassland soils are climate-dependent ecosystems that have a significant greenhouse gas mitigating function through their ability to store large amounts of carbon (C). However, what is often not recognized is that they can also exhibit a high methane (CH4) uptake capacity that could be influenced by future increases in atmospheric carbon dioxide (CO2) concentration and variations in temperature and water availability. While there is a wealth of information on C sequestration in grasslands there is less consensus on how climate change impacts on CH4 uptake or the underlying mechanisms involved. To address this, we assessed existing knowledge on the impact of climate change components on CH4 uptake by grassland soils. Increases in precipitation associated with soils with a high background soil moisture content generally resulted in a reduction in CH4 uptake or even net emissions, while the effect was opposite in soils with a relatively low background moisture content. Initially wet grasslands subject to the combined effects of warming and water deficits may absorb more CH4, mainly due to increased gas diffusivity. However, in the longer-term heat and drought stress may reduce the activity of methanotrophs when the mean soil moisture content is below the optimum for their survival. Enhanced plant productivity and growth under elevated CO2, increased soil moisture and changed nutrient concentrations, can differentially affect methanotrophic activity, which is often reduced by increasing N deposition. Our estimations showed that CH4 uptake in grassland soils can change from -57.7 % to +6.1 % by increased precipitation, from -37.3 % to +85.3 % by elevated temperatures, from +0.87 % to +92.4 % by decreased precipitation, and from -66.7 % to +27.3 % by elevated CO2. In conclusion, the analysis suggests that grasslands under the influence of warming and drought may absorb even more CH4, mainly because of reduced soil water contents and increased gas diffusivity.

Feasibility of Biochar Derived from Sewage Sludge to Promote Sustainable Agriculture and Mitigate GHG Emissions-A Review.

Sewage sludge (SS) has been connected to a variety of global environmental problems. Assessing the risk of various disposal techniques can be quite useful in recommending appropriate management. The preparation of sewage sludge biochar (SSB) and its impacts on soil characteristics, plant health, nutrient leaching, and greenhouse gas emissions (GHGs) are critically reviewed in this study. Comparing the features of SSB obtained at various pyrolysis temperatures revealed changes in its elemental content. Lower hydrogen/carbon ratios in SSB generated at higher pyrolysis temperatures point to the existence of more aromatic carbon molecules. Additionally, the preparation of SSB has an increased ash content, a lower yield, and a higher surface area as a result of the rise in pyrolysis temperature. The worldwide potential of SS output and CO2-equivalent emissions in 2050 were predicted as factors of global population and common disposal management in order to create a futuristic strategy and cope with the quantity of abundant global SS. According to estimations, the worldwide SS output and associated CO2-eq emissions were around 115 million tons dry solid (Mt DS) and 14,139 teragrams (Tg), respectively, in 2020. This quantity will rise to about 138 Mt DS sewage sludge and 16985 Tg CO2-eq emissions in 2050, a 20% increase. In this regard, developing and populous countries may support economic growth by utilizing low-cost methods for producing biochar and employing it in local agriculture. To completely comprehend the benefits and drawbacks of SSB as a soil supplement, further study on long-term field applications of SSB is required.

Biochar dose determines methane uptake and methanotroph abundance in Haplic Luvisol.

Biochar promotes C sequestration and improvement of soil properties. Nevertheless, the effects of biochar addition on soil condition are poorly understood, especially with respect to greenhouse gas (GHG) emissions. A large proportion of GHG emissions derive from agriculture and, thus, recognition of the effect of biochar addition to soil on GHG emissions from terrestrial ecosystems is an important issue. The purpose of our study was to evaluate the short- and long-term effects of biochar application on soil in aspects of: GHG exchange (CH4 and CO2), basic physicochemical soil properties and structure of microbial communities in Haplic Luvisol. Soil was collected from fallow fields enriched with three doses of wood offcuts biochar (10, 20 and 30 Mg ha-1) and incubated at two moisture levels (60 and 100% WHC) with the addition of 1% CH4. To evaluate the influence of biochar aging in soil, the samples were analysed directly (short-term response) and five years (long-term response) after amendment. Generally, biochar addition increased soil pH, redox potential (Eh), organic carbon (SOC) and dissolved organic carbon (DOC) contents. Under 60% WHC, direct biochar application to the soil resulted in a clear improvement in the CH4 uptake rate. In contrast to that (at 100% WHC) methane uptake rates were twofold decreased. The positive effect was reduced due to biochar aging in the soil, but five years after application, at 60% WHC and the highest biochar dose (30 Mg ha-1) still significantly enhanced CH4 oxidation. From a short-term perspective, biochar application increased CO2 emissions, but after five years this effect was not observed. Microbial tests confirmed that the improvement in CH4 oxidation was correlated with methanotroph abundance in the soil. Moreover, an increase of Methylocystis abundance in the soil enriched with biochar along with enhanced CH4 uptake rates confirm the positive biochar influence on methanotrophic communities.

Contrasting Effects of Forest Type and Stand Age on Soil Microbial Activities: An Analysis of Local Scale Variability.

Understanding the functioning of different forest ecosystems is important due to their key role in strategies for climate change mitigation, especially through soil C sequestration. In controlled laboratory conditions, we conducted a preliminary study on six different forest soils (two coniferous, two deciduous, and two mixed sites comprising trees of different ages) collected from the same region. The aim was to explore any differences and assess seasonal changes in soil microbial parameters (basal respiration BR, microbial biomass Cmic, metabolic quotient qCO2, dehydrogenase activity DHA, and Cmic:Corg ratio). Indicator- and forest-specific seasonality was assessed. In addition to litter input, soil parameters (pH, nutrient content, texture and moisture) strongly regulated the analyzed microbial indicators. PCA analysis indicated similarity between mature mixed and deciduous forests. Among annual mean values, high Cmic and DHA with simultaneously low qCO2 suggest that the mature deciduous stand was the most sustainable in microbial activities among the investigated forest soils. Research on the interrelationship between soil parameters and forest types with different tree ages needs to be continued and extended to analyze a greater number of forest and soil types.

The effects of humic substances on DNA isolation from soils.

BACKGROUND: Humic substances (HS) are compounds with a complicated structure, present in the humus soil layer, water, lake sediments, peat, brown coal and shales. Due to their similar physicochemical properties to DNA, they may have an adverse effect on the subsequent use of the isolated material. The main aim of this research was to examine the effect of HS on DNA isolation depending on the soil type and land use, taking into account the spectroscopic full characteristics of HS fractions. METHODS: The research was conducted on eight types of soil sample. Soils represented the most important Soil Reference Groups for temperate climates: Fluvisols, Regosols, Cambisols, Arenosols, Histosols and Luvisols. Soil samples were also collected from areas diversified in terms of use: arable land, grassland and forest. The extraction of HS fractions was performed using the procedure recommended by the International HS Society. The fractional composition of HS was characterized by UV-Vis and fluorescence methods. Soil DNA is extracted by direct cell lysis in the using a CTAB-based method with a commonly-used commercial soil DNA isolation kit. The basis for assessing the quantity and quality of extracted DNA was the Polymerase chain reaction (PCR) reaction since the analysis of soil DNA often relies on the use of PCR to study soil microorganisms. RESULTS: Based on the results, it can be concluded that in the presence of a high concentration of HS, the isolated DNA was low quality and the additional purification procedure was necessary. Despite the differentiation of the internal structure of HS fractions, the decisive factor in the efficiency of DNA isolation from soil samples was the total carbon content in HS. Reduced DNA yields can significantly constrain PCR detection limits to levels inadequate for metagenomic analysis, especially from humus-rich soils.

Biochar addition reinforces microbial interspecies cooperation in methanation of sugar beet waste (pulp).

Biogas production and microbial community structure were analyzed as an effect of biochar addition to a fermentation sludge containing sugar beet pulp. Positive effects of the treatment including an increase in process efficiency and better biogas quality were noted. The effect of biochar on AD (anaerobic digestion process) microbial communities was investigated after total DNA extraction from biochar-amended fermentation mixtures by PCR amplification of bacterial 16S rRNA gene fragments and Illumina amplicon sequencing. A combination of microbiological and physico-chemical analyses was used to study the mechanism by which biochar influences the process of anaerobic digestion of sugar beep pulp. It was found that the main reason of the changes in biogas production was the reshaping of the microbial communities, in particular enrichment of Bacteroidales and Clostridiales. It was proposed that biochar, in addition to being a conductor for mediating interspecies electron transfer, serves also as a habitat for hydrolytic bacteria. It was elucidated that the main driving force for the preferential colonization of biochar surfaces is its hydrophobicity. The presented research indicates the high potential of biochar to stimulate the methane fermentation process.

Evaluation of Nanocomposite Made of Polylactic Acid and Nanocellulose from Carrot Pomace Modified with Silver Nanoparticles.

In this research, it was proposed to use carrot cellulose nanofibrils (CCNF) isolated from carrot pomace modified with silver nanoparticles (AgNPs) as a filler of polylactic acid (PLA) composites matrix. The new procedure was based on two steps: first, the preparation of nanocellulose modified with metal nanoparticles, and then the combination with PLA. Two concentrations-0.25 mM and 2 mM-of AgNO3 were used to modify CCNF. Then, PLA was mixed with the filler (CCNF/AgNPs) in two proportions 99:1 and 96:4. The influence of CCNF/AgNPs on mechanical, hydrophilic, thermal, and antibacterial properties of obtained nanocomposites was evaluated. The greatest improvement of mechanical properties was observed for composite containing CCNF with 2 mM of AgNPs, which obtained the lowest Young modulus and highest strain at break. The degradation temperature was lower for PLA with CCNF/AgNPs, but crystallization temperature wasn't influenced. The addition of CCNF/AgNPs also increased hydrophilicity. The transmission rates of oxygen, nitrogen, and carbon dioxide also increased after the addition of CCNF/AgNPs to PLA. The antibacterial function against Escherichia coli and Bacillus cereus was obtained after the addition of AgNPs but only at the contact surface with the material made, suggesting the lack of migration of nanoparticles from the composite.

Electromagnetic field pretreatment of Sinapis alba seeds improved cadmium phytoextraction.

It was hypothesized that electromagnetic field (EMF) pretreatment of white mustard (Sinapis alba L.) seeds could increase the accumulation of non-essential, pollutant heavy metals such as cadmium (Cd) in shoots. Seeds of white mustard were treated with either 60 or 120 mT of alternating EMF (50 Hz) for 1 minute and then grown in a Petri dish in the presence of Cd, in comparison to the control (seeds grown without EMF pretreatment). Biomass production and content of calcium (Ca) and Cd in seedling shoots were measured. The Cd content in shoots from the EMF-treated seeds was higher in both variants than in the control (by 73% and 78%, respectively; p < 0.05). In plants treated with 60 mT, the Ca content was slightly, but significantly, lower (3%) than in the control. EMF stimulation did not affect the biomass production. The results have shown potential benefits of this physical seed pretreatment method in the context of cadmium phytoextraction, but more research is needed.

Methane oxidation in lead-contaminated mineral soils under different moisture levels.

Methane (CH4) oxidation in soil reduces the concentration of this greenhouse gas due to the activity of methanotrophic bacteria. This process is influenced by chemical and physical parameters of soil. We tested the methanotrophic activity of selected mineral soils (Mollic Gleysol, Haplic Podzol, Eutric Cambisol) contaminated with lead (Pb) under different soil water potentials (pF 0; 2.2; 3.2). The heavy metal was added as PbCl2 in two doses. Together with the initial content of Pb in soils, the final contents of heavy metal in different soils were 11.6 and 30.8 mg kg-1 in Eutric Cambisol, 7.1 and 26.3 mg kg-1 in Haplic Podzol, and 12.2 and 31.4 mg kg-1 in Mollic Gleysol (dry mass of the soil is specified in all cases). The results showed relatively low sensitivity of methane oxidation to the addition of the heavy metal. The major factor controlling this process was soil water content, which in most cases turned out to be the most optimal at pF = 2.2.

Effect of substrate stiffness on differentiation of umbilical cord stem cells.

Tissue formation and maintenance is regulated by various factors, including biological, physiological and physical signals transmitted between cells as well as originating from cell-substrate interactions. In our study, the osteogenic potential of mesenchymal stromal/stem cells isolated from umbilical cord Wharton's jelly (UC-MSCs) was investigated in relation to the substrate rigidity on polyacrylamide hydrogel (PAAM). Osteogenic differentiation of UC-MSCs was enhanced on stiff substrate compared to soft substrates, illustrating that the mechanical environment can play a role in differentiation of this type of cells. These results show that substrate stiffness can regulate UC-MSCs differentiation, and hence may have significant implications for design of biomaterials with appropriate mechanical properties for regenerative medicine.