Biochar-amended Soils Research Articles

Biochar inoculated with Pseudomonas putida alleviates its inhibitory effect on biodegradation pathways in phenanthrene-contaminated soil

Controversial results are reported whereby biodegradation of polycyclic aromatic hydrocarbons (PAHs) can be promoted or inhibited by biochar amendment of soil. Metabolomics was applied to analyze the metabolic profiles of amendment with biochar (BB) and biochar inoculated with functional bacteria (Pseudomonas putida) (BP) involved in phenanthrene (PHE) degradation. Additionally, metagenomic analysis was utilized to assess the impact of different treatments on PHE degradation by soil microorganisms. Results indicated that BB treatment decreased the PHE biodegradation of the soil indigenous bacterial consortium, but BP treatment alleviated this inhibitory effect. Metabolomics revealed the differential metabolite 9-phenanthrol was absent in the BB treatment, but was found in the control group (CK), and in the treatment inoculated with the Pseudomonas putida (Ps) and the BP treatment. Metagenomic analysis showed that biochar decreased the abundance of the cytochrome P450 monooxygenase (CYP116), which was detected in the Pseudomonas putida, thus alleviating the inhibitory effect of biochar on PHE degradation. Moreover, a noticeable delayed increase of functional gene abundance and enzymes abundance in the BB treatment was observed in the PHE degradation pathway. Our findings elucidate the mechanism of inhibition with biochar amendment and the alleviating effect of biochar inoculated with degrading bacteria.

Decreasing the urban carbon footprint with woody biomass biochar in the united states of america

Urban centers are places with a high human population concentration, and they can pose social, economic, and environmental challenges. These challenges are accentuated by the increased use of available open space for housing and industrial expansion, leading to elevated energy consumption, increased pollution, higher carbon emissions, and, consequently, adverse effects on human health. Many of these issues also contribute to the acceleration of climate change. There are several ways to decrease these problems through the expansion of greenspaces that conserve biodiversity, decrease air pollution, improve human well-being, and reduce human health risks, while also allowing people to enjoy the benefits of ecosystem services. This review is aimed at professionals who can manage urban landscapes - including adjacent forests, urban parks, tree beds, or home gardens that produce biomass that, together with other non-chemically treated wood waste, could be used to produce and use biochar. Biochar-amended soils provide the benefits of increased carbon sequestration, water retention, and soil productivity and can also decrease stormwater runoff. In addition, a small number of cities around the world have adopted biochar as a nature-based solution to decrease the impacts of climate change. We point out the opportunities and benefits of converting urban wood waste into biochar, how cities can improve their green environments, and, at the same time, produce energy from waste that would otherwise end in landfills with no use or value. Finally, based on previous assessments of wood waste in the United States of America, we estimate the biochar potential to sequester CO2.

Effects of acid modified biochar on potassium uptake, leaching and balance in an alternate wetting and drying paddy ecosystem

Straw biochar amended soils reduce fertilizer losses and alleviate soil K-exhaustion, while decrease grain yield due to its high pH. H2SO4-modified biochar has been studied as a means to enhance the advantages of biochar and address yield decrease. However, little information is available on its effects on aboveground K uptake, soil K fixation, K leaching, and utilization in paddy rice systems, especially under water stress. A 3-year field experiment was conducted with two irrigation regimes (continuously flooded irrigation, ICF and alternate wetting and drying irrigation, IAWD) as main plots and 0 (control), 20 t ha−1 biochar (B20), and 20 t ha−1 acid-modified biochar (B20A-M) as subplots. The results showed that IAWD significantly decreased water percolation by 9.26 %–14.74 % but increased K leaching by 10.84 %–15.66 %. Compared to B0, B20 and B20A-M significantly increased K leaching by 32.40 % and 30.42 % in 2019, while decreased it by 11.60 %–14.01 % in 2020 and 2021. Both B20 and B20A-M significantly improved aboveground K uptake by 3.45 %–6.71 % throughout the three years. B20 reduced grain yield in 2019 and increased it in 2020 and 2021, while B20A-M increased grain yield throughout the three years. Apparent K balance (AKB) from pre-transplanting to post-harvest over the three years suggested that IAWD significantly increased the risk of soil K depletion but B20 and B20A-M significantly increased AKB, thereby addressing the depletion of it. IAWDB20A-M have a comparable AKB with ICFB20A-M, but had up to 18.3 % and 21.61 % higher AKB than IAWDB20 and ICFB20. Therefore, the use of H2SO4 modified biochar could produce higher grain yield with lower K leaching for addition in IAWD paddy systems, which is beneficial to mitigate soil K depletion and ensure a sustainable agricultural production.

Effects of biochar, compost, and composted biochar soil amendments on okra plant growth

Soil fertility can be improved by incorporating organic matter such as biochar and compost. The combined addition of biochar and compost effectively restores soil degradation by enhancing nutrient availability, soil aggregation, and porosity. Nonetheless, many studies mainly concentrated on a single application of biochar and compost as a soil amendment. In this work, the biochar samples were prepared from oil palm empty fruit bunch (OPEFB) material at the desired microwave power (450 W) under 1 L/min of N2 flow for 10 min. Then, sandy soil was amended with 5 g of sole biochar and compost, as well as a biochar-compost mixture at a ratio of 1:1 for 8-weeks polybag experiment of okra plants. At 4 weeks of the plantation, the physical and chemical soil properties were analyzed. The okra plant's growths were also measured weekly for 8 weeks of the plantation. The application of biochar and composts alone, and in combination significantly improved soil physicochemical properties and plant growth compared to control soil. The synergetic positive effect of biochar and compost combination resulting lowered soil bulk density with higher soil porosity, moisture content, and nutrients availability. The study showed that a biochar-compost mixture is more effective to enhance soil quality over individual treatments and unamended soil.

Interactive effect of biochar and urea addition increases plant growth and rhizosphere microbial activity and decreases N2O emissions

Simultaneous addition of biochar with applied N fertilizer was proposed as useful way how to improve soil fertility and reduce negative effects of nitrogen fertilization. A hypothesis that added N decreases root growth and soil microbial activity and increases N2O emissions while addition of biochar has opposite effect was tested. We further hypothesized that increased microbial activity in biochar-amended soil stimulates growth of subsequently cultivated plants.The supposed interactive effect of biochar and N-fertilizer was studied in pot experiment with cultivation of lettuce in soil amended with urea, biochar and their combination. In each pot, yield of plant biomass was determined and basal respiration, substrate-induced respiration and content of mineral N were determined in soil samples. Soil with roots decomposing after lettuce harvest was also analyzed and subsequently used for the cultivation of wheat plants.Emissions of N2O were measured following N application and measurement continued after harvest. Contrary to the hypothesis, N fertilization stimulated the growth of not only aboveground but also belowground plant biomass. Biochar increased growth of roots in agreement with the hypothesis. The effect of treatments on microbial biomass and respiration was relatively weak in the rhizosphere of growing plants. However, when roots were decomposed, lower Nmin and higher microbial biomass were observed in biochar amended soils. Biochar amendment significantly stimulated the yield of subsequently cultivated wheat. At the beginning of the experiment, N2O emissions were higher in biochar-amended soil. However, at the later phase of the experiment, cumulative emissions were lower in biochar-amended soils. Results suggest that biochar supports more efficient N utilization by plants and increases soil fertility. Biochar also decreases N losses through N2O emissions, even with simultaneous N fertilization.

Influence of biochar-triggered bottom-up effects on soil enzymes, soybean defenses, and the fitness of Spodoptera litura and its parasitoid

Bottom-up effects are major ecological forces in plant–herbivore–parasitoid multitrophic interactions. Biochar amendment in the field alters the bottom-up effects, as it can directly affect the soil environment and plant nutrient uptake, which in turn, indirectly affects herbivores and their natural enemies. However, such effects are poorly documented. We examined the influence of biochar on soil enzyme activity, soybean defense chemicals, and fitness of Spodoptera litura and its parasitoid Meteorus pulchricornis. As the biochar application rate increased, soil urease and sucrase activities, soybean trypsin protease inhibitor content, and polyphenol oxidase activity gradually increased. However, S. litura survival rate and adult body weight showed an initial increase, followed by a decrease, and then remained steady. Soil phosphatase activity initially increased and then stabilized, while M. pulchricornis cocoon emergence rate and fecundity showed an initial increase, followed by a decrease. Spodoptera litura adults preferred to oviposit on soybean at the 10 g/kg biochar level, whereas the parasitoids preferred the hosts at the 20 g/kg biochar level. Our results indicate that the biochar amendment of soils increased soil enzymes activity and soybean defenses, which had a positive effect on S. litura and M. pulchricornis at low levels, but became detrimental at high levels. The bottom-up effects triggered by biochar seemingly affected the second and third trophic levels, resulting in increased defense potential against herbivorous insects. Thus, biochar showed potential to enhance direct plant defenses against pests and indirectly influenced defenses mediated by natural enemies.

Biochar ageing improves soil properties, growth and yield of red radish (Raphanus sativus) in a Haplic Cambisol.

The use of biochar as a soil ameliorant has recently gained momentum. However, its application has been reported to have some adverse effects soon after the pyrolysis process. This study aimed to determine the effect of different biochar ageing methods and fertiliser applications on selected soil properties, growth, and yield of red radish (Raphanus sativus L.). A 2 x 3 factorial arrangement was used in a complete randomised design (CRD) with three replications. The factors were (1) biochar ageing at three levels, i.e., naturally aged biochar (NB), artificially aged biochar (AB), and fresh biochar (FB), and (2) fertiliser at two levels viz fertilised (F) and non-fertilised (NF). A control treatment (without biochar) was also included. Irrespective of the ageing method used, biochar application significantly increased soil pH, while fertiliser application significantly reduced soil pH throughout the experiment. Similarly, biochar application significantly increased soil hydraulic conductivity compared to the control. However, after ten weeks, significantly higher soil hydraulic conductivity was reported in treatments with AB biochar compared to both NB and FB. The application of fertiliser in biochar-amended soils improves the soil's hydraulic properties and increases radish growth. The study concludes that AB biochar + fertiliser application improves soil properties and growth of radish.

Influence of grass root density on gas permeability and water retention in water hyacinth‐based biochar amended soil

AbstractThe present study focuses on the effect of root density on gas permeability and water retention in biochar‐amended soil used as a cover material in landfills. Biochar amendment of soil is important measurement in landfill cover, while vegetation is an important for ecological restoration. Despite its importance, little attention has been given to the adaptation of vegetated biochar‐amended soil in landfill cover. The interactions between the biochar, vegetation, and soil concerning the gas permeability remain unknown, which may lead to unexpectedly increased waste gas emissions in landfill covers. To enhance the utilization efficiency of biochar amendment and vegetation techniques in landfill covers, further investigation of their coupled effects on gas permeability and water retention is necessary. Four different treatments were applied to manufacture series of soil columns: bare soil (BS), biochar‐soil composite (BSC), vegetated biochar‐soil composite with low planting density (VBSCL) and high planting density (VBSCH). The soil water characteristic curve and gas permeability were observed under natural wetting and drying cycles. The results showed that VBSCL increased gas permeability by 142% as compared to BSC. VBSCH enhanced gas permeability by 168% as compared to BSC. This was due to the spreading and decaying root systems forming preferential pathways for gas transfer. Additionally, VBSCL and VBSCH made around a 10% increase in volume water content at the whole suction range, while BSC just enhanced around 20% water content at the low suction range (less than 10 kPa). The combination of roots and biochar have significantly enhanced water retention during entire suction range due to capillarity.

Investigating the Impacts of Biochar Amendment and Soil Compaction on Unsaturated Hydraulic Properties of Silty Sand

The application of biochar as an environmentally friendly additive for agricultural soils has recently gained significant attention. However, the influence of biochar addition on unsaturated hydraulic behavior at high suction ranges (i.e., exceeding 100 kPa) remains largely understudied. This study investigates the impact of biochar addition on the unsaturated hydraulic properties of biochar amended soil (BAS). The effects of biochar content, particle size, and soil compaction on the unsaturated hydraulic properties of BAS were also considered. Peanut shell biochar was utilized in this investigation and was amended into a compacted silty sand with distinct particle size groups. Soil water retention curves and unsaturated permeability were measured through a series of evaporation tests. Results demonstrate that the impact of soil compaction on the unsaturated hydraulic properties of BAS diminishes at high suction range, regardless of biochar particle size and content. A high degree of compaction reduces the saturated permeability of BAS by minimising soil macropores. On the other hand, incorporating high biochar contents with fine particles into the soil enhances the reduction of unsaturated permeability and the improvement of water holding capacity, thereby making biochar an effective application in soil for sustainability of the agroecological environment.

Increased humic materials explain aggregate-protected carbon and nitrogen accumulation in biochar-amended tropical soils

Humic materials make important contributions to soil organic carbon (SOC) and nitrogen (TN) accumulation. However, information on the correlation between humic substances and the accumulation of aggregate-protected C and N in response to biochar application to soils under tropical agroecosystems is limited. Therefore, a replicated field trial was conducted to elucidate the effects of biochar on soil aggregate properties and humic materials, and how these humic compounds affect aggregate-protected SOC and TN in a humid tropical agroecosystem. The treatments included no biochar/ control (CT), 15-Mg biochar ha-1 (BC-15), 30-Mg biochar ha–1 (BC-30), and 30-Mg biochar ha-1 + phosphate fertilizer (BC-30+P). The BC-30 and BC-30+P treatments significantly increased the contents of humic materials (humic and fulvic acids) as compared to the CT. There was a significant increase in the mean weight diameter of soil aggregates by 3- and 4-fold in the BC-30 and BC-30+P treated soils, respectively. Similarly, the application of the BC-30 and BC-30+P treatments yielded significant increases in the soil structural coefficient by 3- and 4-fold, respectively, relative to the CT. A 10% decline in soil bulk density was observed with biochar applied at 30-Mg ha-1. Significant increases in SOC and TN accumulation were observed in the macroaggregates of the biochar-amended soils. An inverse relationship between the degree of polymerization and aggregate-protected C and N was observed, implying that low molecular weight aliphatic compounds favor SOC and TN accumulation with biochar amendments. The important soil property that contributed to SOC and TN accumulation in aggregates was FA, which could be used as an early and sensitive indicator to notice early changes in aggregate-protected C and N accumulation in soils of the humid tropics.

Soil factors that contribute to the abundance and structure of the diazotrophic community and soybean growth, yield, and quality under biochar amendment

BackgroundA 2-year field trial was conducted to test the effect of biochar addition (0, 15, 30, and 45 t hm−2) on soil properties, nutrients, diazotrophic community diversity, abundance, and structure, and soybean growth, yield, and quality. Furthermore, we aimed to explore the responses of diazotrophs, grain yield, and quality to nine soil environmental factors. Rhizosphere soil and plant samples were collected after harvest.ResultsBiochar application resulted in a lower soil bulk density (γd) but higher total organic carbon (TOC), effective phosphorus (AP) and total nitrogen (TN). Compared with untreated soil, the diversity index of diazotrophic bacteria in biochar-amended soil decreased, but the abundance of diazotrophic bacteria increased. The microbial community remained stable when a small amount of biochar was applied but changed as biochar amount increased. Furthermore, biochar reduced the proportion of unique nitrogen-fixing bacteria, but did not affect that of common nitrogen-fixing bacteria between biochar-amended and untreated soils, and increased the relative abundance of Bradyrhizobium (B9 vs. B0) and Sinorhizobium (B18 or B21 vs. B0) involved in symbiotic nitrogen fixation. The main components and content of fatty acids (except for stearic acid) and the content of protein and soybean oil remained stable under biochar application. The low biochar treatment (15 t hm−2) promoted soybean growth and yield. Redundancy analysis suggested that TN greatly influenced the diazotrophic community structure at the phylum and genus levels, and that pH, TOC, and NO3−-N greatly influenced grain yield and quality.ConclusionsSoil diazotroph environment can be improved by targeted farmland implementation based on changes in soil physicochemical properties, which would benefit biological N fixation in agricultural soils and further increase economic benefit.Graphical

Dynamics of carbon dioxide emission during cracking in peanut shell biochar-amended soil

As a primary source of greenhouse gas emissions and a carbon sink, soil plays a key role in climate regulation. The development of cracks in soil strongly influences CO2 emissions, and soil amendment with biochar has been shown to reduce cracking. However, the impact of biochar on CO2 emissions during soil cracking is not well understood. This study investigates the release of CO2 flux during the cracking of peanut shell biochar-amended soil. The biochar-amended soil was incubated at a constant temperature of 35 °C for 160 h with periodic photography and analysis of CO2 concentration and soil moisture. To achieve continuous monitoring of incubation soil, a new coupled sensor was specially designed to measure CO2 concentration and soil moisture, based on the Arduino microcontroller. Measured results reveal that peanut shell biochar reduced the evaporation rate by 29 % compared to unamended soil, resulting in slower soil cracking caused by water loss. The biochar also decreased the shrinkage crack length by 20 % compared to unamended soil. In addition, the crack volume fraction was reduced by 16 % after the peanut shell biochar amendment. Due to the reduction of the soil crack channel openings during drying shrinkage when biochar was applied to the soil, cumulative CO2 fluxes were also reduced by 5 % compared to unamended soil. The presence of biochar induced more stable and larger compounds with the soil particles, which blocked the crack propagation path and inhibited further development of the crack.

Thallium release from biochar-amended soil to runoff in laboratory experiments

Biochar has been widely used for trace metal(loid) (TM) immobilisation in contaminated soils. However, studies on the physicochemical mobility of TMs related to biochar application are highly limited, hampering the evaluation of the immobilisation efficiency of biochar. Therefore, after confirming the ability of biochar to decrease soil Tl bioavailability, this study examined the release of Tl in dissolved and particulate forms in surface runoff and leachate from soil mixed with biochar at different dosages and grain sizes under artificially simulated rainfall and irrigation experiments. The rainfall experimental results showed that the dissolved Tl in the surface runoff decreased from 1.30 μg in the control group to 0.75 μg and 0.54 μg in the groups with 3% and 5% biochar application, respectively. With the same dosages (5%), the finer the biochar applied, the higher the immobilisation ability achieved in surface runoff and the lower the Tl amounts in the leachate, indicating that the grain size of biochar can impact Tl mobility in dissolved forms. Comparisons between rainfall and irrigation experiments indicated that raindrops disturb the soil-water surface and enhance Tl diffusion. The mass in particulate form accounted for more than 95% of lateral released Tl in surface runoff. However, biochar application did not decrease the enrichment ratio of Tl in the eroded sediments. Notably, the finest biochar group produced less mass of eroded Tl owing to the low flux of soil erosion, indicating that grain size would indirectly impact sediment-bound Tl lateral mobility. Colloidal particles should be highlighted as they carried a maximum TI of up to 38% in the rainfall leachate. Focusing on the effect of biochar application on Tl chemical- and physical mobility from the soil matrix to runoff, this study contributes the comprehensive understanding of the role of biochar in TM remediation.

Short-term impact of poultry biochar amendments to stimulate antioxidant enzyme activity of wheat (Triticum aestivum L. HD-2967) in response to greywater.

The present study was designed to test the hypothesis that poultry manure and biochar-amended soil alter the antioxidant enzyme activity of T. aestivum L. HD-2967. For this, a box experiment was conducted using poultry-amended soil (5 g and 10 g) irrigated with greywater (50% and 100%) which was analysed on 7 and 14 days of seed sowing. Antioxidant enzyme activity (catalase, ascorbate peroxidase, and guaiacol peroxidase ) was elucidated to be varied in response to soil biochar and manure amendments both for shoots and roots so as to counteract the reactive oxygen species generated by plants under stress. Also, it was observed to be decreased on a temporal basis. Moreover, soil-biochar amendments efficiently defend the irrigation stress, increase soil nutrition, and reduce waste quantity through sustainable reuse.

Characterization and Risk Assessment of Different-Origin Biochars Applied in Agricultural Experiments

This study aimed to assess the impacts of biochar amendments derived from different feedstocks (sewage sludge (SS), olive-mill waste (OMW), compost, and sawdust) in land applications. Tomatoes were used as a test crop in four experiments both under greenhouse and field conditions. SS, OMW, and compost biochar treatments presented 17% to 178.5% higher tomato productivity than control, verifying that biochar behaves as a plant-growth bio-stimulant. This impact is related to the raw material since sawdust biochar did not present results as positive as the other types of biochars. The physicochemical characterization of biochars and their comparison with international and European standards confirmed the safety of their use. A risk-assessment analysis of tomato consumption was conducted in order to explore unfavorable effects on human health. The estimation of cumulative non-carcinogenic risk, found to be between 8.25 × 10−3 and 4.23 × 10−2, and cancer risk for Cr(VI), found to be between 6.56 × 10−6 and 5.2 × 10−5, suggested no risk of potential chronic exposure due to tomato consumption cultivated in biochar-amended soils. This study may be used as a recommendation for farmers and agriculturists for maximizing the yield of agricultural crops in the Mediterranean region, improving soil health, and contributing to the sustainable management of agroecosystems.

Retention and loss pathways of soluble nutrients in biochar-treated slope land soil based on a rainfall simulator

Global food crisis makes intense agricultural activity necessary, which accelerates soil degradation and increases pollution risk to nearby catchments. Application of biochar can effectively retain plant-required nutrients in soils. However, the linkage between retention and loss pathways of nutrients is still unclear, particularly at slope lands. Therefore, a simulated rainfall experiment (rainfall intensity ​= ​50 ​mm ​h−1) was conducted in a sandy soil with 10° gradient slope (indoor experiment) to clarify loss pathways of soluble C, N, P and K in biochar-amended soils. Wood biochar pyrolized at 300 ​°C (LWB) or 600 ​°C (HWB) was applied at 1% (LWB1; HWB1) or 2% (LWB2; HWB2). Our results show that the pathways for C, N, P and K loss was percolation ​> ​surface runoff ​> ​soil erosion. Compared to control, HWB2 treatment had a 2–4 times higher infiltration amount but 5–6 times lower surface runoff and soil loss, indicating that this treatment alleviated nutrient loss via erosion and runoff in the sloped soil. Among all treatments, HWB2 treatment was the most effective for retaining organic C, dissolved organic C, total N, and exchangeable K through various pathways. However, a substantial amount of soluble P was lost through percolation. Therefore, the potential pollution of groundwater by P through percolation pathway should be considered during biochar application.

Dairy Manure-Derived Biochar in Soil Enhances Nutrient Metabolism and Soil Fertility, Altering the Soil Prokaryote Community

Although various studies have investigated biochar (BC) soil amendments for improving soil microbial abundance, functions, and community structure, a comparison of dairy manure biochar (MBC) to wood biochar (WBC) is warranted given the large volume of manure produced in high-intensity dairy production. Additionally, the synergistic effects of different BC sources and loading percentages on microbial functions and community composition using massively parallel 16S DNA sequencing in BC-amended soils with different types of crops are limited. In this study, the synergistic effects of BC type, BC loading percentage, and crop types on soil fertility, prokaryote community diversity, and functions were investigated in a greenhouse study. The MBC and WBC were used to amend sandy loam soils at increasing BC loading percentages (0, 5, and 10%) to grow the cool-season forages crimson clover (Trifolium incarnatum; an annual legume) and Italian ryegrass (Lolium multiflorum Lam.; an annual forage grass) for 120 days. High nutrient concentrations in MBC shifted microbial communities towards r-strategists and alkaliphiles, potentially increasing the rate of nutrient bioremediation from high nitrogen- and phosphorus-containing soil amendments. This study enables emerging biochar agronomic use recommendations with different crops.

Biochar enhancement of nitrification processes varies with soil conditions

Application of inorganic nitrogen (N) fertilizers in agriculture can increase emissions of nitrous oxide, a potent greenhouse gas, leaching of nitrate (NO3−), a groundwater contaminant hazardous to human health, and soil acidification. Soil amendment with biochar potentially mitigates these losses and undesirable outcomes. However, there have been considerable inconsistencies in reported impacts, likely owing to variable physiochemical characteristics of the biochar materials and/or the soil environment. This study methodically evaluated the impact of biochar soil incorporation on N transformation and underlying microbial processes using soils with varying biochar types, soil texture, soil moisture, and manure compost co- amendments. Laboratory incubations were conducted to monitor the fate of urea fertilizer N spiked in biochar amended and unamended soils by assaying soil ammonium (NH4+), nitrite (NO2−), and NO3− concentrations, pH, and abundances of soil nitrifiers; ammonia oxidizing bacteria and archaea (AOB and AOA) and Nitrospira with the capacity to perform complete ammonia oxidation (comammox). Soil moisture was a critical factor affecting N transformation processes, more so than biochar, but biochar did result in significantly different concentrations of N species in response to urea application. Biochar enhanced nitrification, more significantly in drier conditions and in sandy soil. Biochar offered some buffering potential in the neutral-alkaline, unsaturated soils, preventing >1 unit drop in pH compared to unamended soils. Co-application of biochar with manure composts enhanced nitrification slightly, which was evidenced by higher abundances of some soil nitrifiers at 4 weeks, although increases in nitrification rates were not statistically significant. Soil nitrifier populations tended to increase in response to a pinewood biochar, but trends differed for saturated soil, in soils of differing textures, or when different biochar materials were evaluated. Thus, when evaluating implications of biochar on the fate of mineral N fertilizer, soil moisture and other environment conditions should be considered.

Effects of biochar amendment on bacterial communities and their function predictions in a microplastic-contaminated Capsicum annuum L. soil

Microplastics (MPs) have been confirmed as a novel type of environmental pollutant. They have long-term existence in the soil environment and threaten the soil ecological environment system. Biochar soil amendment is capable of enhancing the water and nutrient holding capacity and improving the soil structure and quality of terrestrial ecosystems. However, the effect of biochar amendment on bacterial community in MPs-contaminated soil–plant system remain unclear, in particular the prediction of bacterial function of these systems. In this study, the effects of biochar amendment on the bacterial community structure of MPs-contaminated soil were investigated through different treatments at three pepper growth stages, and the bacterial function of MPs-contaminated soil was predicted. As indicated by the results of this study, biochar amendment led to the increased species evenness and richness of bacterial community in MPs-contaminated soil, the enhanced relative abundance of MPs-contaminated tolerant bacteria (e.g., Proteobacteria, Acidobacteria, Actinobacteria, and Bacteroidetes), as well as the improved relative abundance of Massilia, Lysobacter, and Terrimonas. Furthermore, soil total phosphorus (TP), soil organic carbon (SOC), NH4+-N, NO3−-N, and pH served as the main factors for the composition of soil bacterial community, as revealed by the result of Pearson correlation analysis and redundancy analysis. Bacterial genera Massilia, Lysobacter, and Terrimonas significantly affected the growth indicator of pepper. PICRUSt functional prediction suggested that the bacterial community of MPs-contaminated soil primarily comprised four level-1 functional layers and 16 level-2 functional layers, and the active soil bacterial community was identified in Metabolism, Genetic information processing, as well as Cellular processes. Biochar amendment enhanced the abundance of genes correlated with Amino acid metabolism and Carbohydrate metabolism of bacteria in MPs-contaminated soil, thus facilitating the nitrogen and phosphorus metabolism cycle of MPs-contaminated soil plants. Our results confirmed that biochar amendment increase the beneficial bacteria in MPs-contaminated soil, more significantly facilitate the nitrogen and phosphorus metabolism cycle within MPs-contaminated soil plants, while effectively expediting the growth of plants in MPs-contaminated soil. This study provides more insights into the correlation of plant and bacterial communities in response to biochar amendment in MPs-contaminated soil system.

Effect of Bamboo biochar on strength and water retention properties of low plastic clay and silty sand

Biochar is a carbon-rich stable product derived from the thermochemical decomposition of biomass. The properties of biochar vary with types of feedstock, heating rate, pyrolysis temperature, etc. Consequently, the mechanical and hydrological properties of biochar amended soil (BAS) also differ with types of biochar and soils. However, the effect of bamboo biochar (BB) amendment on soil strength and water retention properties is missing in the previous literature. Bamboo biomass was pyrolysed at 600 °C to produce biochar. BB and soils (low plastic clay (CL) and silty sand (SM)) were mixed to prepare BAS. The samples were prepared by mixing BB in five ratios, i.e., 0%, 1%, 2%, 3.5% and 5% of dry soil weight. The biochar application has increased optimum moisture content, alkalinity (pH) and Atterberg limits, whereas, reduced maximum dry density and specific gravity of both the soils (CL and SM). The unconfined compressive strength (UCS) of CL soil was noted to increase by 10.5% with 2% biochar content and decreased after that, whereas the UCS of SM soil was found to decrease continuously with the biochar content increment. Therefore, the unconfined compressive strength (UCS) result showed that biochar application has contrary effects on both soils. The measured gravimetric water content (GWC) of BAS was increased with biochar increment in both soils. However, GWC increased more in CL than in SM soil at the same biochar content. The microstructural analysis showed that the biochar amendment filled the pore space of the soil matrix, resulting in an increase in UCS and GWC values. The increased water retention capacity and strength (UCS) of biochar amended CL soil provides evidence that it could be used as a landfill cover material.