Biochar-amended Soils Research Articles

Impact of Biochar Aging on Soil Physicochemical Properties

Biochar undergoes significant transformations in soil as a result of chemical, physical, and biological processes. These alterations can impact its initial properties, influencing both its agronomic effectiveness and its capacity for carbon sequestration. Long-term observations of biochar-aging effects in soil are limited but highly relevant, as they provide a more realistic picture of the agronomic and societal benefits of biochar than short-term studies with relatively “fresh” biochar. This study aimed to describe the aging effects of biochar and their impact on a range of soil properties at a long-term biochar experiment in Bayreuth, Germany. For this purpose, soil and biochar samples were taken 13 years after application (two variants: 1. co-composted and 2. pristine biochar) and compared with a fresh variant in which the same unaged biochar was freshly mixed with the control soil. The soil quality parameters, pH and electrical conductivity, decreased significantly (p < 0.05) during biochar aging. Specifically, the pH dropped from 7.4 in freshly biochar-amended soil to 6.8 in the pristine aged biochar variant and 6.9 in the co-composted aged biochar variant. Electrical conductivity decreased from 217.0 µS cm−1 in the freshly amended soil to 81.1 µS cm−1 in the pristine aged variant and 87.6 µS cm−1 in the co-composted aged variant. Nitrogen retention was enhanced in the soil amended with co-composted aged biochar compared to the pristine aged biochar soil. Total nitrogen (TN) was higher at 1.94 g kg−1 versus 1.57 g kg−1 (p < 0.05), and ammonium-N (NH₄+-N) was slightly elevated at 35.7 mg kg−1 versus 33.0 mg kg−1, although the difference was not statistically significant. The nitrate-N (NO₃−-N) content was significantly lower in all biochar-amended soil variants compared to the control soil. Total carbon (TC) levels decreased during biochar aging in all soil variants. However, the reduction was significantly lower in the co-composted aged biochar soil (25.0 g kg−1) compared to the pristine aged biochar soil (20.5 g kg−1, p < 0.05). This study identified multiple aging effects on biochar following 13 years of exposure in loamy soil. Importantly, the results showed that compared to the amendment of pristine biochar, co-composting did not diminish the TC of the treated soil, and more N could be retained, 13 years after amendment. In fact, co-composting prior to soil application is recommended to fully realize the potential agronomic benefits.

Theoretical and Experimental Investigation of Thermal Conductivity of Unsaturated Soils Amended with a Sustainable Biochar

This study investigates the thermal conductivity of unsaturated kaolin soil amended with biochar to promote sustainable geotechnical engineering. Biochar from agricultural waste offers the dual benefits of carbon sequestration and sustainable waste management. Experimental measurements were conducted for kaolin soil with 0% (control) and 10% biochar under varying moisture contents. Peach pit biochar increased thermal conductivity by 2–3% at 30–40% saturation and 40–50% at higher saturation as compared to the bare soil. Reed biochar decreased thermal conductivity by 1–2% at lower saturation but increased it by 55–60% at higher saturation. Applewood biochar increased thermal conductivity by 35–50% at moderate saturation, decreased beyond 50% water content, and had minimal variation at lower saturation. Further, the existing empirical models (such as Kersten and the Johansen model, Wiener’s model, and Mickley’s model) for predicting the thermal conductivity of materials were validated using the measured results of biochar-amended soils. Adding 10% biochar reduces thermal conductivity by 34.8%, and the Haigh model (2012) fits best with high accuracy and lower RMSE values than models such as Kersten and Johansen, which appears to be less reliable in case of biochar-amended soils. With an addition of biochar, the R2 values of the models decreased from a range of 0.8 to 0.9 to a range of 0.4–0.6, indicating the need for better model adaptation. Wiener bounds accurately predicted thermal conductivity at low saturation levels but varied greatly at higher ones. The most variable sample was peach pit biochar, highlighting the need to refine predictive models for material-specific differences. These findings provide a foundation for developing improved predictive models and integrating biochar into sustainable geotechnical and geothermal systems.

Converting plastic-contaminated agricultural residues into fit-for-purpose biochar soil amendment: an initial study

Addressing agricultural plastic pollution is vital for ecosystem sustainability. Shifting from traditional waste treatments to a sustainable pathway presents both challenges and opportunities for global plastic management. This study investigated the properties and environmental applications of biochar derived from honeydew melon vines contaminated with plastic hanging ropes, pyrolyzed at temperatures of 300, 500, and 700 °C. The resulting biochars were evaluated for their ability to remove Pb and Cd from aqueous solutions. Additionally, a Chinese cabbage pot experiment was conducted to assess the impact of biochar on Pb and Cd immobilization and plant growth in contaminated soil. Results revealed that the properties of biochar varied with pyrolysis temperature. Specifically, incomplete carbonization of plastic ropes was observed at 300 °C, while biochar produced at 500 °C (BC500) showed a higher yield and contained higher levels of available P and K compared to the biochar produced at 700 °C (BC700). The presence of polycyclic aromatic hydrocarbons (PAHs) in biochars increased with temperature but remained within recommended limits. BC500 exhibited the highest adsorption capacities for Pb and Cd at 127 mg g−1 and 36 mg g−1, respectively. Soil amendment with BC500 and BC700 significantly improved soil pH, increased the availability of nutrients and microbial biomass, and effectively immobilized Pb and Cd in the soil. Consequently, the biomass yield of Chinese cabbage was enhanced by 119 % and 86 % under BC500 and BC700, respectively. Moreover, the Pb and Cd content in cabbage decreased by more than 80 % and 29 %, respectively. However, PAHs levels in cabbage leaves increased from 9.2 ng g−1 in the control to 20.8 ng g−1 and 30.4 ng g−1 under BC500 and BC700, respectively, remaining below China’s standard for benzo(a)pyrene. This study suggests pyrolyzing plastic-contaminated crop residues at 500 °C is a feasible strategy for waste recycling.Graphical

Enhancing clay soil reinforcement using MICP-BIN method with biochar-induced nucleation

The microbially induced carbonate precipitation (MICP) method has gained extensive use in the realm of soil stabilisation. This study presents a novel microbial solidification technique known as the biochar-induced nucleation (MICP-BIN) method for reinforcing clay soil. Corn stover biochar was employed as an auxiliary material, mixed with dry clay powder, and subsequently reinforced using the MICP technique. Direct shear tests, drying experiments, X-ray diffraction, and scanning electron microscopy were also conducted to investigate the efficacy of the MICP-BIN method. Compared with that of the remoulded soil, the shear strength of the treated soil exhibited a substantial increase of 22.4%, the CaCO3 content increased by 30%, and the shear strength improved by 389.5%. Similarly, the internal friction angle exhibited increases of 22.7% and 405.2%, while the cohesion showed improvements of 9.4% and 344.3%, respectively. The MICP-BIN method is found to increase suction for a given water content. Furthermore, biochar-amended soil possesses highest water-retention ability (especially at lower suction magnitude), followed by MICP-amended soil, MICP-BIN-amended soil, and untreated soil. This study demonstrated the promising results achieved by combining biochar and the MICP-BIN technique, providing a novel approach for reinforcing soft ground.

Biochar amendment affects the fate of phthalic acid esters in the soil-vegetable system

Phthalates, e.g., esters of phthalic acid (PAEs), when used as plasticizers due to weak physical bonding with polymer matrix favoring leaching, are widely noted in the environment. Their confirmed toxicity to plants and animals implies that their fate should be monitored in the environment, especially when considering the interaction between soil and vegetables. Removal of PAEs from the environment or limiting their bioavailability is a key point in reducing their harmful effects. In the present paper, the fate of six PAEs in the biochar-amended soil during the cultivation of two popular vegetables, lettuce, and radish, was estimated. High bioaccumulation in the soil was noted with the biochar obtained from residues from biogas production being up to 15% higher than in the case of the other biochar and up to 10 times higher than in plants due to increased basic character of biochar. This biochar reduced the bioavailability of DEP (diethyl phthalate), DBP (dibutyl phthalate), BBP (butyl benzyl phthalate), and DNOP (di-n-octyl phthalate) in radish roots and DBP in lettuce leaves. However, PAEs significantly increased the fresh mass of radish and slightly increased the mass of lettuce. All six tested PAEs in both plants reached higher concentrations in the leaves (up to two orders of magnitude) than in the roots. Additionally, PAEs were present in two times higher concentrations in the lettuce than in the radish. The biochar aromaticity, porosity, and the presence of organic carbon and inorganics (ash) affect the fate of tested pollutants depending on the tested plant and compound.

Global meta-analysis and machine learning reveal the critical role of soil properties in influencing biochar-pesticide interactions

Biochar application in soils is increasingly advocated globally for its dual benefits in enhancing agricultural productivity and sequestering carbon. However, lingering concerns persist regarding its environmental impact, particularly concerning its interactions with pesticide residues in soil. Previous research has fragmentarily indicated elevated pesticide residues and prolonged persistence in biochar-amended soil, suggesting a potential adverse consequence of biochar application on pesticide degradation. Yet, conclusive evidence and conditions for this phenomenon remain elusive. To address this gap, we conducted a comprehensive assessment using meta-analysis and machine learning techniques, synthesizing data from 58 studies comprising 386 observations worldwide. Contrary to initial concerns, our findings revealed no definitive increase in pesticide concentrations in soil following biochar application. Moreover, a significant reduction of 66 % in pesticide concentrations within soil organisms, such as plants and earthworms, was observed. The quantitative analysis identified soil organic matter content as a key factor influencing biochar-pesticide interactions, suggesting that applying biochar to soils rich in organic matter is less likely to increase pesticide persistence. This study provides a critical assessment of the environmental fate of pesticides under biochar application, offering valuable guidance for the optimal utilization of both pesticides and biochar in sustainable agricultural practices.

Evaluating the potential of different crop straw biochar to capture carbon dioxide and increase the growth of Zea mays L.

The roles of biochar in capturing CO2 and ensuring food security are intertwined. Thus, a comprehensive understanding of these roles is crucial for optimizing the environmental benefits of biochar. Six crop straws: non-legumes (rice straw-RS, maize straw-MS, and wheat straw-WS), and legumes (chickpea straw-CS, mustard straw-MTS, and peanut straw-PS), were used to prepare biochar (RB, MB, WB, CB, MTB, and PB, respectively) at 700 °C and their ability to capture CO2, improve soil fertility, and enhance maize plant growth was evaluated. Our results revealed that the CO2 reduction potential (CRP) differed significantly, with CB being more efficient in retaining CO2. The CRP showed a significant polynomic relationship with ΔpH (R2 = 0.9646) and Δexchangeable acidity (R2 = 0.6356) but not with Δsoil organic carbon (R2 = 0.4181). Due to the differences in their physicochemical properties, straws and biochar had significantly different effects on soil pH, exchangeable acidity, nutrient uptake, maize growth, and maize biomass accumulation. Also, the N uptake potential of maize plants grown in biochar-amended soils was significantly larger than that of the respective straw. This significant difference in nutrient uptake between biochar and straw treatments was also observed for K, Ca, and Mg, and corroborates the significant differences recorded in plant growth parameters. Thus, converting crop residues to biochar sequesters carbon through the storage of captured CO2 thereby mitigating climate change. Also, by incorporating biochar in soil, soil acidity decreases, soil fertility increases, and the growth of maize plants improves. Nevertheless, it is important to carefully select biochar feedstock so as to achieve the optimal effects of carbon sequestration and soil fertility improvement when applied to agricultural soils.Graphical

Interactions between nanobiochar and arsenic: Effects of biochar aging methods on arsenic binding capacity and mechanisms

Nano-biochar (nanoBC), produced from biochar aging, exhibits significant molecular heterogeneity that may affect the fate and toxicity of co-occurring pollutants. However, the interaction between nanoBC and arsenic (As) remains unclear. Herein, we simulated biochar aging through water erosion, photoaging, and thermal chemical decomposition to generate three types of nanoBC (nUBC, nPBC, and nHBC). We then investigated their distinct binding affinities and interaction mechanisms with arsenite (AsIII) and arsenate (AsV). Complementary analysis using optical spectrophotometer and high-resolution mass spectrometry revealed significant differences in properties and chemical compositions among the three nanoBCs at a size of 100 nm. Specifically, nHBC had higher yield, nPBC had higher aromaticity, and nUBC had more intricate molecular compositions and larger molecular weights. Binding experiments showed that nHBC and nUBC exhibited the highest conditional distribution coefficient (KD) for AsIII and AsV, respectively. In nHBC, a higher proportion of humic-like fluorescent component C3 enhanced its affinity for AsIII, attributed to lignin-like molecules with CHONS formulas where thiol acted as active binding sites. In contrast, the robust AsV binding capacity of nUBC stemmed from its richness in humic-like fluorescent component C1 and tryptophan-like fluorescent component C2. This is facilitated by lipid-like molecules and CHO formulas in C1 and aliphatic/peptide-like molecules and CHON formulas in C2, which provided oxygenic and nitrogen-containing groups for binding. All nanoBC had a significantly higher binding affinity for As than bulk BC. These findings provide a deeper understanding of As-nanoBC binding mechanisms at the molecular level, facilitating more accurate prediction of As fate in biochar-amended soil and associated ecosystem risks.

Heavy Metals Analysis of Breweries Effluent used in Soil Cultivated with Glycine Max (L.) Merr. Accessions with Biochar Augmentation

Beer production has promulgated the prevalence of heavy metal contamination in the environment (soil and water bodies). The magnitude of breweries wastewater-effluent effect discharged on soil and its effect on crop quality in terms of growth and physiology must therefore be investigated. This study aims to assess the level of seven heavy metals (HM) (lead (Pb), nickel (Ni), chromium (Cr), copper (Cu), cadmium (Cd), zinc (Zn) and iron (Fe)) in breweries wastewater-effluent and its effect on the growth of Glycine max accessions (TGM-3990, TGM-1348, TGM-1732, TGM-2175 and TGM-928) as well as the influence of biochar soil amendment in the induction of HM tolerance in G. max. Effluent properties were analyzed using the A1 portable TDS/EC meter. HM in the wastewater-effluent was determined using Atomic Absorption Spectrometer (AAS). The experiment was set up in a complete block design. 3 seeds G. max accessions were planted in 7kg of sterilized soil (control, effluent and biochar treatments). Growth parameters were taken using standard methods, while the total photosynthetic pigments (TPP) were determined using the atLeaf chlorophyll meter. The wastewater-effluent recorded an electrical conductivity (EC) of 928µS/cm, total dissolved solids (TDS) (464ppm), Temperature (31.9-32.6°C) and pH (5.37). Results for HM concentration showed; Pb (0.20mg/L), Ni (<0.001mg/L), Cr (0.03mg/L), Cu (<0.001mg/L), Cd (<0.001mg/L), Zn (<0.001mg/L) and Fe (8.74mg/L). The trend shows that Fe˃Pb˃Cr˃Cd˃Cu˃Ni˃Zn. Cr, Cd, Cu, Ni and Zn were significantly below the World Health Organization (WHO) and Waste Water Forum (WWF) permissible limit, while Fe and Pb significantly higher. G. max accessions TGM-928 (80%) and TGM-3990 (80%) had better germination percentage (GP), TGM-1348 (60%) had the lowest GP, while TGM-2175 recorded no germination in all treatments. At 6 weeks after planting (WAP), it was observed that irrigation of G. max accessions with breweries wastewater-effluent significantly (p=0.001) stimulated growth parameters such as shoot length for TGM-3990 which recorded; Treatment=19.53±0.94cm; Control=17.10±0.67cm; Biochar=40.83±1.01cm) while TGM-1732 had the highest shoot growth (T=38.57±1.53cm; C=25.00±0.00cm; B=82.33±5.70cm) when compared to their controls. TGM-3990 (T=32.20mg/kg, C=34.10mg/kg, 43.30mg/kg) recorded the least TPP contents, while TGM-928 (T=51.00mg/kg, C=45.60mg/kg, B=43.50mg/kg) recorded the highest TPP in all treatments. Amelioration of soil with biochar significantly (p=0.001) stimulated growth above the effluent treatment and control. Similar trend was observed for leaf area, petiole length, leaf number, stem girth and internode length. This study has shown that breweries effluent has the potential of growth enhancement in G. max cultivation and in combination biochar application reduces the need for additional fertilizer application.

Co‐Application of Wood Biochar and Nano‐Titanium Dioxide to Immobilize Vanadium in Alkaline Soils

ABSTRACTTitanium dioxide (TiO2) and biochar have been used as amendments to adsorb vanadium (V) in aqueous solutions; however, their simultaneous application in the remediation of V‐contaminated neutral‐alkaline soils is rare. TiO2 nanoparticles, biochar, and a blend of biochar+TiO2 were investigated as amendments for an alkaline V‐contaminated soil. Treatments involved mixing (weight basis) 1% TiO2 (T1), 5% biochar (T2), 1% TiO2 + 5% biochar (T3) with soil, and an unamended soil (T4). An adsorption edge study was performed from pH 4 to 10 at the V concentration of 200 mg L−1. A standard vanadium (V) solution was prepared using NaVO3. An incubation study was conducted over 3 months with V‐contaminated soil at a rate of 200 mg kg−1, at 80% field capacity. At the end of the incubation period, the treated soils were subjected to V fractionation. X‐ray diffraction (XRD) patterns and FTIR spectra of TiO2 nanoparticles, biochar, uncontaminated soil, and four treated soils were obtained. The adsorption edge of V was below pH 4.6, suggesting reduced retention of V in alkaline soils. In the combined treatment, the adsorption edge was elevated by one unit compared to the control. V adsorption increased in TiO2, biochar, and combined TiO2+biochar treatments at 7%, 4%, and 20%, respectively, compared with the unamended soil (control) at a pH of ~7.6. Functional groups revealed the possibility of inner‐sphere and outer‐sphere adsorption mechanisms between vanadate and the mix amendment of TiO2+biochar. The labile V fraction decreased, and the nonlabile V fraction increased, significantly in the TiO2+biochar amended soil compared to the unamended soil. Applying a blend of biochar+TiO2 reduced the mobility of V in a neutral‐alkaline soil, thereby preventing it from contaminating the nearby soil and water bodies.

Response of wheat to arbuscular mycorrhizal fungi inoculation and biochar application: Implications for soil carbon sequestration

The sequestration of atmospheric CO₂ in soil is suggested as an effective climate change mitigation strategy. Biochar application shows promise in this regard, while the role of fungi in soil carbon cycling and sequestration is also under investigation. Using a novel high-throughput plant phenomics approach, we explore the impact of arbuscular mycorrhizal fungi (AMF) inoculation and biochar application on wheat growth and soil carbon, guided by one of the leading global carbon credit schemes. Wheat was successfully colonised by AMF, achieving an average root length colonisation of 35.9%. We uncover an indirect fungal-mediated pathway to soil carbon sequestration, with mycorrhizal plants generating more biomass across all soil treatments without yield penalties, suggesting colonised plants deliver more plant derived carbon to the soil, potentially leading to long-term soil carbon gains. Conversely, fungal-driven carbon loss occurred, significantly reducing soil carbon accumulation in unamended soil, but not in biochar-amended soil, suggesting that biochar moderates fungal activity and positively impacts the soil carbon balance. While both biochar and AMF enhance plant growth, their direct effects on soil carbon are complex. Although biochar did not significantly increase soil carbon stocks beyond its own contribution, its ability to regulate fungal activity could play an important role in influencing soil carbon sequestration.

Effect of biochar application on physiochemical properties and nitrate degradation rate in a Siliciclastic Riverine Sandy soil

This study investigated the efficacy of biochar as a soil amendment for enhancing soil physicochemical properties and solute transport dynamics, with implications for agricultural sustainability and environmental stewardship. Batch laboratory experiments and column studies were conducted to assess the effects of biochar application on soil parameters and solute transport under saturated conditions. The saturation soil extraction approach was employed in batch leaching tests, while column experiments replicated subsurface conditions. Transport modeling using CXTFIT 2.1 elucidated solute dispersion dynamics in biochar-amended soils. Batch experiments revealed significant alterations in soil pH, electrical conductivity, and nutrient release following biochar addition. Biochar exhibited adsorption capacity for fluoride ions and released dissolved organic carbon, highlighting its potential for soil carbon sequestration and microbial activity. Column studies demonstrated enhanced solute dispersion and increased microbial activity in biochar-amended soils, as evidenced by changes in breakthrough curves and degradation rates of nitrate. Indeed, nitrate first-order degradation coefficients were 9.08E-06 for the column with only sandy soil, 3.09E-05 and 1.47E-04 for the columns with minimum and maximum doses of biochar respectively. Biochar application significantly influenced soil physicochemical properties and solute transport dynamics, with potential implications for nutrient management and contaminant attenuation in agricultural systems. Despite limitations in laboratory-scale experiments, this research provides valuable insights into biochar-soil interactions. It underscores the need for further investigation under field conditions to validate findings and optimize biochar management practices for sustainable soil and environmental management.

Biochar and Straw Amendments over a Decade Divergently Alter Soil Organic Carbon Accumulation Pathways

Exogenous organic carbon (C) inputs and their subsequent microbial and mineral transformation affect the accumulation process of soil organic C (SOC) pool. Nevertheless, knowledge gaps exist on how different long-term forms of crop straw incorporation (direct straw return or pyrolyzed to biochar) modifies SOC composition and stabilization. This study investigated, in a 13-year long-term field experiment, the functional fractions and composition of SOC and the protection of organic C by iron (Fe) oxide minerals in soils amended with straw or biochar. Under the equal C input, SOC accumulation was enhanced with both direct straw return (by 43%) and biochar incorporation (by 85%) compared to non-amended conventional fertilization, but by different pathways. Biochar had greater efficiency in increasing SOC through stable exogenous C inputs and inhibition of soil respiration. Moreover, biochar-amended soils contained 5.0-fold greater SOCs in particulate organic matter (POM) and 1.2-fold more in mineral-associated organic matter (MAOM) relative to conventionally fertilized soils. Comparatively, although the magnitude of the effect was smaller, straw-derived OC was preserved preferentially the most in the MAOM. Straw incorporation increased the soil nutrient content and stimulated the microbial activity, resulting in greater increases in microbial necromass C accumulation in POM and MAOM (by 117% and 43%, respectively) compared to biochar (by 72% and 18%). Moreover, straw incorporation promoted poorly crystalline (Feo) and organically complexed (Fep) Fe oxides accumulation, and both were significantly and positively correlated with MAOM and SOC. The results address the decadal-scale effects of biochar and straw application on the formation of the stable organic C pool in soil, and understanding the causal mechanisms can allow field practices to maximize SOC content. These results are of great implications for better predicting and accurately controlling the response of SOC pools in agroecosystems to future changes and disturbances and for maintaining regional C balance.

Long-term biochar and soil organic carbon stability – Evidence from field experiments in Germany

Organic soil amendments (OSA) with long residence times, such as biochar, have a high potential for soil organic carbon (SOC) sequestration. The highly aromatic structure of biochar reduces microbial decomposition and explains the slow turnover of biochar, indicating long persistence in soils and thus potential SOC sequestration. However, there is a lack of data on biochar-induced SOC sequestration in the long-term and under field conditions. We sampled two long-term field experiments in Germany, where biochar was applied 12 and 14 years ago. Both locations differ in soil characteristics and in the types and amounts of biochar and other OSA. Amendments containing compost and 31.5 Mg ha−1 of biochar on a loamy soil led to a SOC stock increase of 38 Mg ha−1 after OSA addition. The additional increase is due to non-biochar co-amendments such as compost or biogas digestate. After eleven years, this SOC stock increase was still stable. High biochar amount additions of 40 Mg ha−1 combined with biogas digestate, compost or synthetic fertilizer on a sandy soil led to an increase of SOC stocks of 61 Mg ha−1; 38 Mg ha−1 dissipated in the following four years most likely due to lacking physical protection of the coarse soil material, and after nine years the biochar-amended soils showed only slightly higher SOC stocks (+7 Mg ha−1) than the control. Black carbon stocks on the same soil increased in the short- and mid-term and decreased almost to the original stock levels after nine years. Our results indicate that in most cases the long-term effect on SOC and black carbon stocks is controlled by biochar quality and amount, while non-biochar co-amendments can be neglected. This study proves that SOC sequestration through the use of biochar is possible, especially in loamy soils, while non-biochar OSA cannot sequester SOC in the long term.

Drought Stress in Quinoa: Effects, Responsive Mechanisms, and Management through Biochar Amended Soil: A Review

Drought Stress in Quinoa: Effects, Responsive Mechanisms, and Management through Biochar Amended Soil: A Review

Mitigation of Drought Stress for Quinoa (Chenopodium quinoa Willd.) Varieties Using Woodchip Biochar-Amended Soil.

Drought stress deteriorates agro-ecosystems and poses a significant threat to crop productivity and food security. Soil amended with biochar has been suggested to mitigate water stress, but there is limited knowledge about how biochar affects the physiology and vegetative growth of quinoa plants under soil water deficits. We grew three quinoa (Chenopodium quinoa Willd.) varieties, Titicaca (V1), Quipu (V2), and UAFQ7 (V3) in sandy loam soil without (B0) and with 2% woodchip biochar (B2) under drought conditions. The drought resulted in significant growth differences between the varieties. V3 performed vegetatively better, producing 46% more leaves, 28% more branches, and 25% more leaf area than the other two varieties. Conversely, V2 displayed significantly higher yield-contributing traits, with 16% increment in panicle length and 50% more subpanicles compared to the other varieties. Woodchip biochar application significantly enhanced the root development (i.e., root biomass, length, surface, and projected area) and plant growth (i.e., plant height, leaf area, and absolute growth rate). Biochar significantly enhanced root growth, especially fresh and dry weights, by 122% and 127%, respectively. However, biochar application may lead to a trade-off between vegetative growth and panicle development under drought stress as shown for V3 grown in soil with woodchip biochar. However, V3B2 produced longer roots and more biomass. Collectively, we suggest exploring the effects of woodchip biochar addition to the soil on the varietal physiological responses such as stomatal regulations and mechanisms behind the increased quinoa yield under water stress conditions.

Short-term microbial community dynamics induced by 13C-labeled maize root, its derived biochar and NPK in long-term amended soil

Crop residues and their derived biochar are frequently used for their potential to improve grain yield, soil fertility and carbon (C) sequestration. However, the effects of root are often overlooked, and the effects of chemical fertilizer (NPK) combined with root or its biochar on microbial community structure need further study. This study used 13C-labeled maize root, its biochar and soil with different fertilization for 8 years as materials and substrates. A 112-day incubation experiment was conducted to explore the effects of microbial community on the C processing. During incubation, the root-C (54.9%) mineralized significantly more than biochar-C (12.8%), while NPK addition significantly increased the root-C mineralization. Adding biochar alone did not significantly change the microbial community. Compared to the biochar treatment (BC), the root treatment (R) notably increased the contents of total phospholipid fatty acids (PLFAs), 13C-PLFA and the proportion of fungi and Gram-negative bacteria, but reduced the proportion of actinomycetes. The root mineralization was significantly correlated with the relative content of 13C-Gram-positive bacteria and 13C-fungi, while biochar mineralization was significantly correlated with the relative content of 13C-Gram-positive bacteria and 13C-actinomycetes. Notably, NPK addition significantly increased the contribution of biochar-C to PLFA-C pool, while decreasing the contribution of root-C. In summary, due to microbial adaptation to the lack of bioavailable C in biochar-amended soil, biochar can act as a buffer against the significant disturbance caused by NPK to microbial communities and native soil organic carbon (SOC), which contributes to the steady enhancement in soil C storage.Graphical

Microbially Driven Iron Cycling Facilitates Organic Carbon Accrual in Decadal Biochar-Amended Soil.

Soil organic carbon (SOC) is pivotal for both agricultural activities and climate change mitigation, and biochar stands as a promising tool for bolstering SOC and curtailing soil carbon dioxide (CO2) emissions. However, the involvement of biochar in SOC dynamics and the underlying interactions among biochar, soil microbes, iron minerals, and fresh organic matter (FOM, such as plant debris) remain largely unknown, especially in agricultural soils after long-term biochar amendment. We therefore introduced FOM to soils with and without a decade-long history of biochar amendment, performed soil microcosm incubations, and evaluated carbon and iron dynamics as well as microbial properties. Biochar amendment resulted in 2-fold SOC accrual over a decade and attenuated FOM-induced CO2 emissions by approximately 11% during a 56-day incubation through diverse pathways. Notably, biochar facilitated microbially driven iron reduction and subsequent Fenton-like reactions, potentially having enhanced microbial extracellular electron transfer and the carbon use efficiency in the long run. Throughout iron cycling processes, physical protection by minerals could contribute to both microbial carbon accumulation and plant debris preservation, alongside direct adsorption and occlusion of SOC by biochar particles. Furthermore, soil slurry experiments, with sterilization and ferrous iron stimulation controls, confirmed the role of microbes in hydroxyl radical generation and biotic carbon sequestration in biochar-amended soils. Overall, our study sheds light on the intricate biotic and abiotic mechanisms governing carbon dynamics in long-term biochar-amended upland soils.

Spatial variation of methane oxidation and carbon dioxide sequestration in landfill biogeochemical cover

ABSTRACT The study investigated the spatial variation of potential methane (CH4) oxidation and residual carbon dioxide (CO2) sequestration in biogeochemical cover (BGCC) system designed to remove CH4, CO2, and hydrogen sulfide (H2S) from landfill gas (LFG) emissions. A 50 cm x 50 cm x 100 cm tank simulated BGCC system, comprising a biochar-amended soil (BAS) layer for CH4 oxidation, a basic oxygen furnace (BOF) slag layer for CO2 and H2S sequestration, and an upper topsoil layer. Synthetic LFG was flushed through the system in five phases, with each corresponding to different compositions and flow rates. Following monitoring, the system was dismantled, and samples were extracted from different depths and locations to analyze spatial variations, focusing on moisture content (MC), organic content (OC), pH, and electrical conductivity (EC). Additionally, batch tests on selected samples from BAS and BOF slag layers were performed to assess potential CH4 oxidation and residual carbonation capacity. The aim of study was to evaluate the BGCC's effectiveness in LFG mitigation, however this study focused on assessing spatial variations in physico-chemical properties, CH4 oxidation in the BAS layer, and residual carbonation in the BOF slag layer. Findings revealed CH4 oxidation in the BAS layer varied between 22.4 and 277.9 µg CH4/g-day, with higher rates in the upper part, and significant spatial variations at 50 cm below ground surface (bgs) compared to 85 cm bgs. The BOF slag layer showed a residual carbonation capacity of 40-49.3 g CO2/kg slag, indicating non-uniform carbonation. Overall, CH4 oxidation and CO2 sequestration capacities varied spatially and with depth in the BGCC system.

Effects of biochar addition on soil fauna communities—A meta‐analysis

AbstractSoil fauna is an important part of global biodiversity and plays a vital role in ecosystems. The microbial communities in soil fauna can have significant impacts on soil fertility, as microbial communities play a pivotal role in soil function by supporting ecological integrity and agricultural productivity. This study assesses the effect of biochar on soil fauna and response of microbial communities. Biochar is a highly porous organic carbon material, and the impact of biochar on microbial communities in soil fauna remains unclear. To date, no quantitative or comprehensive investigation has been undertaken to examine the effects of biochar on microbial communities in soil fauna. In this paper, we aim to quantify the effects of biochar on the abundance and diversity of soil fauna communities in various environments by conducting a meta‐analysis of 24 studies and analysing 459 observations. The impact of biochar on soil fauna communities was determined by analysing the responses of soil fauna that included differences in biochar feedstock, pH and pyrolysis, application rates and application times, as well as soil fauna with different physiological characteristics (body size, presence of exoskeletons). The results showed that biochar had a neutral (non‐significant) effect on the soil fauna community, with a total mean effect size (Hedge's g) = −0.04 (CI: −0.28; −0.20). Results Data validation using Egger regression showed no publication bias. Higher pH biochar and biochar from conventional pyrolysis were beneficial to soil fauna, but not significant (QM (df = 3) = 4.07, p = .25). In addition, body size of soil animals significantly reflected different sensitivities to biochar application, with Medium‐sized animals benefiting the most from biochar addition (0.35; CI: 0.05; 0.65; n = 6; 56). Animals with (n = 11; 125) and without exoskeletons (n = 17; 308) also showed favourable and unfavourable responses to biochar addition, respectively. This study can provide basic data for the evolutionary pattern of animal communities during biochar soil amendment, as well as information for the comprehensive evaluation of the environmental and biological effects of biochar.