Biochar Soil Research Articles

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.

Performance and mechanistic study of biochar and magnesium-enhanced phytoremediation in cadmium-contaminated soil by alfalfa

Recently, phytoremediation has been regarded as a green and environment friendly technique to treat metals contaminated soils. Thus, in this study, pot experiments were designed to investigate the combine effects of biochar and magnesium (MPs) to purify cadmium (Cd)-contaminated soils by Medicago sativa L. (alfalfa). The results showed that the combined use of biochar and Mg significantly increased the accumulation of Cd and promoted the transport of Cd from root to shoot in alfalfa, simultaneously. Importantly, the combined use of biochar and Mg could increase the accumulation of Cd in shoot and whole plant (shoot + root) of alfalfa up-to 59.1% and 23.1%, respectively. Moreover, the enhancement mechanism can be analyzed from several aspects. Firstly, the photosynthesis was enhanced, which was beneficial to plant growth. The product of photosynthesis provided energy for uptake and transport of Cd. Meanwhile, its transport in phloem could promote the transport of Cd. Secondly, the enhancement of antioxidant capacity of alfalfa effectively protected the membrane structure of alfalfa, which indicated that Cd could enter alfalfa from the channel on the cell membrane. Lastly, the chemical form of Cd and microbial community structure in soil were changed. Overall, these changes reduced the Cd toxicity in soil, enhanced the resistance capability of alfalfa, increased the Cd uptake by alfalfa and promoted the growth of alfalfa. Thus, the obtained results suggested that the combined use of biochar and Mg is an effective approach to enhance phytoremediation performance for purifying Cd-contaminated soils.

Optimal biochar selection for cadmium pollution remediation in Chinese agricultural soils via optimized machine learning

Biochar is effective in mitigating heavy metal pollution, and cadmium (Cd) is the primary pollutant in agricultural fields. However, traditional trial-and-error methods for determining the optimal biochar remediation efficiency are time-consuming and inefficient because of the varied soil, biochar, and Cd pollution conditions. This study employed the machine learning method to predict the Cd immobilization efficiency of biochar in soil. The predictive accuracy of the random forest (RF) model was superior to that of the other common linear and nonlinear models. Furthermore, to improve the reliability and accuracy of the RF model, it was optimized by employing a root-mean-squared-error-based trial-and-error approach. With the aid of the optimized model, the empirical categories for soil Cd immobilization efficiency were biochar properties (60.96 %) > experimental conditions (19.6 %) ≈ soil properties (19.44 %). Finally, this study identified the optimal biochar properties for enhancing agricultural soil Cd remediation in different regions of China, which was beneficial for decision-making regarding nationwide agricultural soil remediation using biochar. The immobilization effect of alkaline biochar was pronounced in acidic soils with relatively high organic matter. This study provides insights into the immobilization mechanism and an approach for biochar selection for Cd immobilization in agricultural soil.

Texture and Contamination-Level Dependent Effects of Calcium-Rich Deinking Paper Sludge Biochar on Soil Cd Availability, Enzymatic Activity, and Plant Stress Mitigation

The study evaluated calcium-rich deinking paper sludge (DPS) biochar's capability as a viable alternative method to mitigate soil cadmium (Cd) availability. Our analysis of 68 recent studies showed that 75% of the studies focused on contamination levels below 10 mg kg-1. However, mining and smelting areas exhibit higher levels of Cd contamination (mean value of 57.5 mg kg-1 with a CV of 128%), necessitating a contamination rate-dependent approach.Clay loam (CL) and sandy loam (SL) soils were artificially contaminated with Cd to mimic polluted areas (20, 40, 80 mg kg-1). Soils were aged for six months and then treated with DPS biochar doses of 0%, 1%, and 3% (w/w) for a month. Cd extractability and toxicity were gauged using diethylenetriaminepentaacetic acid extraction and plant physiology tests. Supplementarily, machine learning algorithms were tested to predict plant physiological parameters and biomass production, leveraging variables from principal component analysis and design parameters.Biochar application (3%, w/w) reduced soil Cd availability (20.1% in SL, 8.4% in CL; p < .05), attributed to increased soil pH, enhanced microbial activity, and expanded soil surface area. The plants grown in treated soils displayed increased dry matter content, chlorophyll, relative water content, and decreased malondialdehyde levels. The impact varied, being more pronounced in SL soils with high Cd contamination.This study presents the first report on the use of DPS biochar in Cd-contaminated soils and sets expectations for its outcomes regarding plant physiology and soil microbial activity in a diversified experimental design. DPS biochar appeared as a tool for mitigating soil Cd availability and alleviating plant stress particularly in SL soils. The biochar's efficiency was influenced by its dose, the level of contamination, and the soil type, highlighting the importance of tailored application strategies.

Ecological consequences of biochar and hydrochar amendments in soil: assessing environmental impacts and influences.

Anthropogenic activities have caused irreversible consequences on our planet, including climate change and environmental pollution. Nevertheless, reducing greenhouse gas (GHG) emissions and capturing carbon can mitigate global warming. Biochar and hydrochar are increasingly used for soil remediation due to their stable adsorption qualities. As soil amendments, these materials improve soil quality and reduce water loss, prevent cracking and shrinkage, and interact with microbial communities, resulting in a promising treatment method for reducing gas emissions from the top layer of soil. However, during long-term studies, contradictory results were found, suggesting that higher biochar application rates led to higher soil CO2 effluxes, biodiversity loss, an increase in invasive species, and changes in nutrient cycling. Hydrochar, generated through hydrothermal carbonization, might be less stable when introduced into the soil, which could lead to heightened GHG emissions due to quicker carbon breakdown and increased microbial activity. On the other hand, biochar, created via pyrolysis, demonstrates stability and can beneficially impact GHG emissions. Biochar could be the preferred red option for carbon sequestration purposes, while hydrochar might be more advantageous for use as a gas adsorbent. This review paper highlights the ecological impact of long-term applications of biochar and hydrochar in soil. In general, using these materials as soil amendments helps establish a sustainable pool of organic carbon, decreasing atmospheric GHG concentration and mitigating the impacts of climate change.

An integrated agroforestry-bioenergy system for enhanced energy and food security in rural sub-Saharan Africa

Most people in rural sub-Saharan Africa lack access to electricity and rely on traditional, inefficient, and polluting cooking solutions that have adverse impacts on both human health and the environment. Here, we propose a novel integrated agroforestry-bioenergy system that combines sustainable biomass production in sequential agroforestry systems with biomass-based cleaner cooking solutions and rural electricity production in small-scale combined heat and power plants and estimate the biophysical system outcomes. Despite conservative assumptions, we demonstrate that on-farm biomass production can cover the household’s fuelwood demand for cooking and still generate a surplus of woody biomass for electricity production via gasification. Agroforestry and biochar soil amendments should increase agricultural productivity and food security. In addition to enhanced energy security, the proposed system should also contribute to improving cooking conditions and health, enhancing soil fertility and food security, climate change mitigation, gender equality, and rural poverty reduction.

Biochar soil addition alters ant functional traits as exemplified with three species

The response of soil microorganisms and plants in soil ecosystems to biochar is well recognised. However, biochars’ impact on large soil animal, such as ants, is inadequately understood, with only limited studies focusing on the abundance and mortality rates of some specific ant species. In this study, soil physicochemical properties, and ant community diversity and functional characteristics were compared between experimental plots with and without biochar application. No significant differences in soil (soil physicochemical properties) or ants (ant community richness, species abundance, and morphological characteristics) were observed between the two plots before biochar application. However, the biochar-treated plot soil surface temperatures, pH, and soil water content were significantly higher after 48 weeks. Biochar application promoted Cardiocondyla nuda (by 426%) and Formica japonica abundance (by 93%), but decreased Solenopsis invicta invasive ant species richness (by 54%), consistent with the fact that changes in soil properties were more beneficial to the former two species. In addition, in biochar-treated plots, F. japonica and S. invicta generally showed larger body size (18% and 6.7%), larger eyes (2.7% and 4.0%), and longer femurs (6.3% and 7.9%), which enabled them to respond better to potential barriers, such as plants. Our results highlighted that, besides species abundance and community structure, certain ant functional morphological indicators were also informative in evaluating biochar ecological implications.Graphical abstract

Biochar is colonized by select arbuscular mycorrhizal fungi in agricultural soils

Arbuscular mycorrhizal fungi (AMF) colonize biochar in soils, yet the processes governing their colonization and growth in biochar are not well characterized. Biochar amendment improves soil health by increasing soil carbon, decreasing bulk density, and improving soil water retention, all of which can increase yield and alleviate environmental stress on crops. Biochar is often applied with nutrient addition, impacting mycorrhizal communities. To understand how mycorrhizas explore soils containing biochar, we buried packets of non-activated biochar in root exclusion mesh bags in contrasting agricultural soils. In this greenhouse experiment, with quinoa (Chenopodium quinoa) as the host plant, we tested impacts of mineral nutrient (as manure and fertilizer) and biochar addition on mycorrhizal colonization of biochar. Paraglomus appeared to dominate the biochar packets, and the community of AMF found in the biochar was a subset (12 of 18) of the virtual taxa detected in soil communities. We saw differences in AMF community composition between soils with different edaphic properties, and while nutrient addition shifted those communities, the shifts were inconsistent between soil types and did not significantly influence the observation that Paraglomus appeared to selectively colonize biochar. This observation may reflect differences in AMF traits, with Paraglomus previously identified only in soils (not in roots) pointing to predominately soil exploratory traits. Conversely, the absence of some AMF from the biochar implies either a reduced tendency to explore soils or an ability to avoid recalcitrant nutrient sources. Our results point to a selective colonization of biochar in agricultural soils.

Improved tomato development by biochar soil amendment and foliar application of potassium under different available soil water contents

The use of carbonaceous materials such as biochar has been considered an innovative solution in agriculture, especially to mitigate dry events caused by climate change. Biochar can improve water holding capacity, physical and chemical properties of soil, and increase the productivity of agricultural systems. However, underlying physiological mechanisms remain poorly understood. Mineral supplementation with potassium nitrate (KNO3) via foliar application is another promising strategy in agricultural management under irrigation deficit. Thus, we investigated the combined effects of biochar and foliar application of KNO3 on growth, yield, and physiology of tomato plants under different irrigation regimes. Results did not indicate a synergistic effect of biochar and foliar application of KNO3. Biochar application alleviated tomato plant stress under deficit irrigation, with plants showing better functioning of photosynthetic apparatus, higher yield, and better fruit quality, as well as increased water use efficiency. Coffee husk biochar (K-rich feedstock) fully met the tomato plant’s demand for K and partially met the demand for some other elements (P, Mg, Fe, Zn, Mn, and Cu). Although positive effects of KNO3 application was verified for some physiological and fruit quality components, overall, foliar application of KNO3 did not improve tomato yield. It is concluded that biochar soil amendment can be a promising practice to increase yield and quality of tomato fruits under deficit irrigation. Therefore, biochar-based fertilizer can be an alternative K source that also provides stable carbon to soil and helps to mitigate stress caused by prolonged drought.

Rock Phosphate and Biochar Effects on Greenhouse Gas Emissions and Soil Fertility in Southern Alberta Potato Field

The application of biochar soil amendment and rock phosphate fertilizer to the soil could lead to achieving net zero emissions and food security; however, the effectiveness of using biochar and rock phosphate in southern Alberta brown chernozemic soil is not yet assessed. In the first trial of this study, varying levels of urea (N), with varying levels of biochar (B) were applied. The same level of rock phosphate (RP) and triple super phosphate (TSP) were applied to compare efficiency of the two fertilizers. The second trial involved applying the same nutrients, but with higher levels than the first trial. The results indicated that the fertilizer application rates did not affect the growth and yield of potatoes because of the application rates of the fertilizer and fertility status of the soil, whereas in the second trial, TSP and RP treatments had the same growth and yield. Furthermore, the high application rate of nitrogen fertilizer and RP with or without biochar in the potato plot emitted high nitrous oxide gas emissions while the low application rate of nitrogen fertilizer and RP kept the carbon dioxide in the soil. Nevertheless, in the second experiment, the application of biochar and rock phosphate reduced nitrous oxide and carbon dioxide emissions. We observed high residual nitrogen and manganese nutrients after harvest in the plot treated to rock phosphate and biochar. Therefore, rock phosphate and biochar have the potential to increase food production and mitigate climate change.

Investigating the growth promotion potential of biochar on pea (Pisum sativum) plants under saline conditions

Pea, member of the plant family Leguminosae, play a pivotal role in global food security as essential legumes. However, their production faces challenges stemming from the detrimental impacts of abiotic stressors, leading to a concerning decline in output. Salinity stress is one of the major factors that limiting the growth and productivity of pea. However, biochar amendment in soil has a potential role in alleviating the oxidative damage caused by salinity stress. The purpose of the study was to evaluate the potential role of biochar amendment in soil that may mitigate the adverse effect of salinity stress on pea. The treatments of this study were, (a) Pea varieties; (i) V1 = Meteor and V2 = Green Grass, Salinity Stress, (b) Control (0 mM) and (ii) Salinity (80 mM) (c) Biochar applications; (i) Control, (ii) 8 g/kg soil (56 g) and (iii) 16 g/kg soil (112 g). Salinity stress demonstrated a considerable reduction in morphological parameters as Shoot and root length decreased by (29% and 47%), fresh weight and dry weight of shoot and root by (85, 63%) and (49, 68%), as well as area of leaf reduced by (71%) among both varieties. Photosynthetic pigments (chlorophyll a, b, and carotenoid contents decreased under 80 mM salinity up to (41, 63, 55 and 76%) in both varieties as compared to control. Exposure of pea plants to salinity stress increased the oxidative damage by enhancing hydrogen peroxide and malondialdehyde content by (79 and 89%), while amendment of biochar reduced their activities as, (56% and 59%) in both varieties. The activities of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) were increased by biochar applications under salinity stress as, (49, 59, and 86%) as well as non-enzymatic antioxidants as, anthocyanin and flavonoids improved by (112 and 67%). Organic osmolytes such as total soluble proteins, sugars, and glycine betaine were increased up to (57, 83, and 140%) by biochar amendment. Among uptake of mineral ions, shoot and root Na+ uptake was greater (144 and 73%) in saline-stressed plants as compared to control, while shoot and root Ca2+ and K+ were greater up to (175, 119%) and (77, 146%) in biochar-treated plants. Overall findings revealed that 16 g/kg soil (112 g) biochar was found to be effective in reducing salinity toxicity by causing reduction in reactive oxygen species and root and shoot Na+ ions uptake and improving growth, physiological and anti-oxidative activities in pea plants (Fig. 1).Figure 1A schematic diagram represents two different mechanisms of pea under salinity stress (control and 80 mM NaCl) with Biochar (8 and 16 g/kg soil).

Comparing combined application of biochar and nitrogen fertilizer in paddy and upland soils: Processes, enhancement strategies, and agricultural implications

Recently, biochar and N fertilizers have been used to tackle low N use efficiency (NUE) in crops across diverse environmental conditions. The coupling of biochar and N fertilizer may impact crop N utilization through different pathways in various soil types. However, there is currently a lack of comprehensive assessment of how coupling effects specifically influence N utilization in paddy and upland crops. We conducted a meta-analysis of 175 peer-reviewed studies to assess the responses of soil properties and crop traits in paddy and upland fields under coupling effects. The results indicate that NUE (+26.1 %) and N uptake (+15.0 %) in paddy fields increase more than in upland fields (+23.7 % and +8.0 %, respectively), with the coupling effect providing NH4+ predominantly for rice and NO3− for upland crops. NH4+ increases in paddy fields (+6.9 %) but decreases in upland fields (−0.7 %), while microbial biomass carbon (MBC) decreases in paddy fields (−2.9 %) and increases in upland fields (+36.0 %). These findings suggest that coupling effects supply soil inorganic nutrients in paddies and affect microbes in uplands, thereby positively affecting crop N utilization. Specifically, the greatest increase in paddy crop yield and N use efficiency occurs when the ratio of N fertilizer to biochar exceeds 1.5 %, and in uplands, it manifests when applying 10–20 t·ha−1 of biochar and <150 kg·ha−1 N fertilizer. In conclusion, this meta-analysis explores the differential effects of biochar and N fertilizer coupling in different arable land types, offering novel insights into the utilization strategies of biochar in agricultural fields.

Crucial roles of soil inherent Fe-bearing minerals in enhanced Cr(VI) reduction by biochar: The electronegativity neutralization and electron transfer mediation

Biochar has been used for soil Cr(VI) remediation in the last decade due to its enriched redox functional groups and good electrochemical properties. However, the role of soil inherent Fe-bearing minerals during the reduction of Cr(VI) has been largely overlooked. In this study, biochar with different electron-donating capacities (EDCs) was produced at 400 °C (BC400) and 700 °C (BC700), and their performance for Cr(VI) reduction in soils with varied properties (e.g., Fe content) was investigated. The addition of BC400 caused around 14.2–36.0 mg g−1 Cr(VI) reduction after two weeks of incubation in red soil, paddy soil, loess soil, and fluvo-aquic soil, while a less Cr(VI) was reduced by BC700 (2.57–16.7 mg g−1) with smaller EDCs. The Cr(VI) reduction by both biochars in different soils was closely related to Fe content (R2 = 0.93–0.98), so red soil with the richest Fe (14.8% > 1.79–3.49%) showed the best reduction capability, and the removal of soil free Fe oxides (e.g., hematite) resulted in 71.9% decrease of Cr(VI) reduction by BC400. On one hand, Fe-bearing minerals could increase the soil acidity, neutralize the surface negative charge of biochar, enhance the contact between Cr(VI) and biochar, and thus facilitate the direct Cr(VI) reduction by biochar in soils. On the other hand, Fe-bearing minerals could also facilitate the indirect Cr(VI) reduction by mediating the electron from biochar to Cr(VI) with the cyclic transformation of Fe(II)/Fe(III). This study demonstrates the key role of soil Fe-bearing minerals in Cr(VI) reduction by biochar, which advances our understanding on the biochar-based remediation mechanism of Cr(VI)-contaminated soils.

Insights into CO2 and N2O emissions driven by applying biochar and nitrogen fertilizers in upland soil

Biochar and soil carbon sequestration hold promise in mitigating global warming by storing carbon in the soil. However, the interaction between biochar properties, soil carbon-nitrogen cycling, and nitrogen fertilizer application's impact on soil carbon-nitrogen balance remained unclear. Herein, we conducted batch experiments to study the effects and mechanisms of rice straw biochar application (produced at 300, 500, and 700 °C) on net greenhouse gas emissions (CO2, N2O, CH4) in upland soils under different forms of nitrogen fertilizers. The findings revealed that (NH4)2SO4 and urea significantly elevated soil carbon dioxide equivalent emissions, ranging from 28 to 61.7 kg CO2e/ha and 8.2 to 37.7 kg CO2e/ha, respectively. Conversely, KNO3 reduced soil CO2e emissions, ranging from 2.2 to 13.6 kg CO2e/ha. However, none of these three nitrogen forms exhibited a significant effect on CH4 emissions. The pyrolysis temperature of biochar was found negatively correlated with soil CO2 and N2O emissions. The alkaline substances presented in biochar pyrolyzed at 500–700 °C raised soil pH, increased the ratio of Gram-negative to Gram-positive bacteria, and enhanced the relative abundance of Sphingomonadaceae. Moreover, the co-application of KNO3 based nitrogen fertilizer and biochar increased the total carbon/inorganic nitrogen ratio and reduces the relative abundance of Nitrospirae. This series of reactions led to a significant increase in soil DOC content, meanwhile reduced soil CO2 emissions, and inhibited the nitrification process and decreased the emission of soil N2O. This study provided a scientific basis for the rational application of biochar in soil.

Greenhouse gas emissions, carbon stocks and wheat productivity following biochar, compost and vermicompost amendments: comparison of non-saline and salt-affected soils

Understanding the impact of greenhouse gas (GHG) emissions and carbon stock is crucial for effective climate change assessment and agroecosystem management. However, little is known about the effects of organic amendments on GHG emissions and dynamic changes in carbon stocks in salt-affected soils. We conducted a pot experiment with four treatments including control (only fertilizers addition), biochar, vermicompost, and compost on non-saline and salt-affected soils, with the application on a carbon equivalent basis under wheat crop production. Our results revealed that the addition of vermicompost significantly increased soil organic carbon content by 18% in non-saline soil and 52% in salt-affected soil compared to the control leading to improvements in crop productivity i.e., plant dry biomass production by 57% in non-saline soil with vermicompost, while 56% with the same treatment in salt-affected soil. The grain yield was also noted 44 and 50% more with vermicompost treatment in non-saline and salt-affected soil, respectively. Chlorophyll contents were observed maximum with vermicompost in non-saline (24%), and salt-affected soils (22%) with same treatments. Photosynthetic rate (47% and 53%), stomatal conductance (60% and 12%), and relative water contents (38% and 27%) were also noted maximum with the same treatment in non-saline and salt-affected soils, respectively. However, the highest carbon dioxide emissions were observed in vermicompost- and compost-treated soils, leading to an increase in emissions of 46% in non-saline soil and 74% in salt-affected soil compared to the control. The compost treatment resulted in the highest nitrous oxide emissions, with an increase of 57% in non-saline soil and 62% in salt-affected soil compared to the control. In saline and non-saline soils treated with vermicompost, the global warming potential was recorded as 267% and 81% more than the control, respectively. All treatments, except biochar in non-saline soil, showed increased net GHG emissions due to organic amendment application. However, biochar reduced net emissions by 12% in non-saline soil. The application of organic amendments increased soil organic carbon content and crop yield in both non-saline and salt-affected soils. In conclusion, biochar is most effective among all tested organic amendments at increasing soil organic carbon content in both non-saline and salt-affected soils, which could have potential benefits for soil health and crop production.

Alterations of bacterial community related C cycle by affecting soil carbon fractions under aged biochar application

AbstractBiochar is a beneficial substance for sequestering organic carbon in soil. Application of fresh biochar (FB) to the soil leads to an increase in soil organic carbon (SOC). However, the effects of aged biochar on SOC stabilization in acidic soils are unclear. A 90‐day incubation study was assessed to evaluate the impact of adding rice straw biochar on acid soil. The study aimed to assess the alterations in carbon fractions, enzyme activity and bacterial communities in soil. We used different ageing processes (water‐washed biochar [WB] and H2O2 oxidation biochar [OXB]) at a rate of 2%, with control at 0% of biochar. The results indicated that aged biochar reduced CO2 efflux and increased microbial biomass carbon (MBC), reducing the microbial metabolic quotient (qCO2). The SOC and its fractions increased with ageing relative to the FB treatment. Compared with the FB treatment, the carbon pool management index (CPMI) also increased with the OXB application. Additionally, the application of OXB stimulated the soil enzymes involved in carbon cycling, specifically β‐1,4‐glucosidase (βG), β‐1,4‐xylosidase (βX) and cellobiohydrolase (CBH) relative to the FB and WB treatments. Moreover, biochar applications improved the structure and functions of the bacterial population in soil with high acidity. Proteobacteria, Acidobacteria, Actinobacteria and Chloroflexi were the most prevalent species in all treatments, as shown by their relative abundances. The redundancy analysis revealed that the DOC (dissolved organic carbon) and MBC significantly impacted on the microbial community. Furthermore, adding OXB altered the Bacterial community involved in the C cycle by affecting SOC. These findings help us learn more about how applying fresh or aged rice straw biochar changes different carbon fractions and microbial communities in soil. It may serve as an instance for studying the provision of soil organic carbon after applying biochar in acidic soil.

Carbon sequestration potential of biochar in soil from the perspective of organic carbon structural modification

Application of biochar derived from biomass resources in soil is an encouraging method to decelerate global warming via carbon sequestration. While there has been extensive research on the priming effect of biochar on the mineralization of native soil organic carbon (nSOC), its correlation with soil organic carbon (SOC) structural variations remains poorly understood. A series of incubation experiments with soils amended with biochar prepared at 300 °C, 450 °C, and 600 °C were performed to explore the shifts in nSOC structure and reveal the interconnections among soil properties, SOC structural variation, and the priming effect induced by biochar. Biochar exhibited an “inhibitory concentration” on soil microorganisms, where 1 % biochar enhanced bacterial and fungal richness and diversity, while 3 % biochar reduced bacterial richness and diversity although soil nutrient conditions were improved. Biochar-treated soil had higher humic acid- and humin-like fractions (HAL and HML) but lower fulvic acid-like components (FAL). Moreover, bulk SOC, FAL, HAL, and HML of soils with 300 °C and 450 °C biochar contained more aromatic-type species (e.g., lignin). Such changes were related to improvement of the soil nutrient condition and shifts in microbial community structures, in addition to the “accumulation of biochar-derived OC in the nSOC pool”. Stable carbon isotopes indicated that the inhibitory effect on SOC mineralization (−94.5 to −8.0 mg CO2-C kg−1 soil) induced by biochar was significantly explained by the change in FAL and HAL contents. The findings improved the understanding of the carbon sequestration potential of biochar in soils for SOC structural modification.

Potential for agronomic and environmental use of biochars derived from different organic waste

The application of biochars in soils has been generating excitement within the scientific community due to its benefits in both agronomic and environmental areas. The current challenge is to select suitable raw materials and preparation procedures to obtain biochars with appropriate properties for specific purposes. Therefore, the objective of this study was to characterize the properties of biochars derived from twenty different types of organic waste and correlate these properties with their potential agronomic and/or environmental use. Twenty types of raw materials available in the Brazilian Amazon were placed in closed porcelain crucibles and subjected to pyrolysis in a muffle furnace set at 350 °C for 2 h. Chemical, physicochemical, and spectroscopic analyses were conducted on the produced biochars. As a result, biochars derived from poultry litter, annatto seed, passion fruit peel, and coffee husk are suitable for improving the fertility of nutrient-deficient soils thanks to their high ash and nutrient contents, elevated pH, and low C/N ratios. Biochars derived from sugarcane bagasse and wood residues were characterized by their high carbon content and aromaticity, making them difficult to mineralize in soil. Consequently, these biochars show promise for environmental use, with the potential to sequester C and mitigate greenhouse gas emissions.

Biochar has positive but distinct impacts on root, shoot, and fruit production in beans, tomatoes, and willows

Positive relationships have been documented between the amount of biochar added to soils and various aspects of plant growth and fertility such as root, shoot, and fruit production. However, these effects depend on biochar source materials, soil characteristics and species of plant examined. This makes it impossible to systematically compare and generalize findings across previous studies that have used different soils and biochar. We conducted a novel investigation to assess the effects of a single source of biochar (hazelnut wood), in a constructed organic soil, on the different plant tissues in three functionally distinct species: tomatoes (Solanum lycopersicon), green beans (Phaseolus vulgaris), and willow (Salix sp.). Five levels of biochar soil amendment were assessed: 0% (control), 3, 9, and 26% by dry weight. We found a highly significant positive relationship between biochar concentration and total plant biomass (roots + shoots + fruits) in all species, with no significant difference in total biomass response among species. Fruit production increased with increased biochar in both beans and tomatoes. However, tomatoes exhibited significant differences in response among plant tissues; fruit production and shoot biomass increased significantly with biochar, but root tissue did not. Bean germination success increased significantly with biochar concentration. Date of first flowering was earlier with increasing soil biochar in beans but not in tomatoes. Control over both sources of biochar and soil composition in this experiment enables us to conclude that biochar addition can have different impacts on different plants and, in some cases, species-specific impacts on different plant tissues and other measures of fertility. Our results are contrary to prior research that found inhibiting effects of biochar at levels comparable to our 26% treatment. Biochar impacts on soil properties such as CEC and percent base cation saturation do not explain our findings, leading us to conclude that microbial interaction with biochar is an important factor that may explain the positive impacts of soil biochar on plant fertility observed. Further research that repeats this experiment in other soil types, with other biochar sources, and with other plant species is necessary to determine the generalizability of these important findings.

Jasmonates Improve Drought Tolerance of Hordeum vulgare L. After Biochar Treatment

To investigate how and in what amounts biochar and methyl jasmonate can improve drought tolerance of barley. A two-year experimental study was conducted in a factorial randomized complete block design (n = 5) in the research greenhouse of Zanjan University, Iran, to investigate the possible effects of biochar and methyl jasmonate on some traits of winter barley under drought conditions. Two irrigation regimes, D0 (full irrigation in soil field capacity as control) and D1 (withholding irrigation immediately after flowering stage), three methyl jasmonate spray densities [0 (M0), 50 (M50), and 100 (M100) μM] and four levels of biochar in soil [0% (B0), 0.25% (B0.25), 0.5% (B0.5), 1% (B1) per soil weight] were used in this experiment. In this study, drought reduced two-year average leaf area (LA) by 96%, stomatal conductance (gs) by 84%, and photosynthetic water use efficiency (PWUE) by 64%. In addition, drought reduced chlorophyll-b by 1.5% and 81% and transpiration rate (Tr) by 2.5% and 78% in the first and second years, respectively. However, the application of biochar and methyl jasmonate improved all the traits studied in both D0 and D1 drought-treated plants. For most of the parameters studied, the optimal combination of biochar and methyl jasmonate that optimized water use efficiency and alleviated drought was 0.25% and 50 μM, respectively. The synergistic action of biochar and jasmonates improved the tolerance of barley to water stress.