Biochar Addition Rate Research Articles

Mitigating invasive species using biochar derived from invasive plants in saline‐alkaline wetland plant communities dominated by Amaranthus palmeri

AbstractAimsEffective prevention and management of biological invasions are crucial. One promising approach involves introducing biochar to invaded plant communities to modify interspecific relationships among invasive and native plants, ultimately aiding in the suppression of invasive species. This study aimed to explore the effects of invasive‐plant biochar on an established invaded plant community.LocationTianjin coastal saline‐alkaline wetland, China (38°46′ N, 117°34′ E).MethodsInvaded plant communities were established using soils from an Amaranthus palmeri‐invaded wetland with an intact seed bank, incorporating invasive‐plant biochar derived from A. palmeri and Spartina alterniflora into the soil at 0%, 1%, 3%, and 5% addition rates (m/m). Plant above‐ground biomass, height, stem diameter, abundance, α/β‐diversity, niche breadth, and species co‐occurrence networks were analyzed.ResultsThe addition of invasive‐plant biochar significantly decreased the performance measures of the invaded plant community. The biochar addition rate had a more substantial impact on plant community structure than the type of biochar used. There was a decrease in the abundance of A. palmeri and an increase in native plants across most treatments, with S. alterniflora biochar exhibiting a more pronounced effect compared to A. palmeri biochar. Invasive‐plant biochar affected the niche breadth of A. palmeri and other dominant native species, particularly at higher addition rates, resulting in reduced niche overlap. At a 5% addition rate, A. palmeri and S. alterniflora biochar had contrasting effects on the complexity of interspecific relationships within the plant community. Phylogenetic β‐diversities were significantly correlated with the biochar addition rate and stochastic processes primarily governed plant community assembly across all treatments.ConclusionsOur findings underscore the potential of biochar derived from invasive plants to mitigate the impact of invasive species on saline‐alkaline wetland plant communities dominated by A. palmeri. This approach offers a promising avenue for managing biological invasions and restoring native plant species.

Biochar Addition Increased Soil Carbon Storage but Did Not Exacerbate Soil Carbon Emission in Young Subtropical Plantation Forest

Forests play a crucial role in mitigating global warming, contributing approximately 46% of the global terrestrial carbon sink. However, it remains uncertain whether the addition of biochar to forests enhances the ecosystem’s carbon sink capacity. This study aims to address this scientific question by investigating whether biochar application increases carbon storage, potentially leading to an overall rise in carbon emissions by influencing soil respiration and identifying the underlying mechanisms. A controlled experiment was conducted in a young plantation forest that had grown for three years, where soil CO2 efflux rate and physicochemical properties, photosynthesis, and plant growth traits were measured across varying biochar addition rates (0, 5, and 10 t/ha) over five seasons. Then, statistical methods including one-way ANOVA, regression analysis, and structural equation modeling (SEM) were employed to assess differences in biological and abiotic factors among biochar addition gradients and understand the influencing mechanisms of soil CO2 efflux change. The findings revealed that biochar addition significantly increased the contents of soil organic carbon (SOC) and microbial biomass carbon (MBC), consequently promoting photosynthesis and plant growth (p < 0.05). Biochar addition accounted for 73.8% of the variation in soil CO2 efflux by affecting soil physicochemical properties, photosynthesis, and plant basal diameter growth. However, the net effect of biochar addition on soil CO2 efflux was found to be low. The positive effects of biochar addition on soil CO2 efflux via factors such as soil bulk density, total nitrogen (TN), MBC, and photosynthesis were counteracted by its negative impact through soil total phosphorus (TP), water content, pH, SOC, and plant basal diameter growth. Overall, our findings indicate that there was no significant increase in soil CO2 efflux in the short term (totaling 16 months) over the biochar addition gradient. However, we observed a substantial increase in soil carbon storage and an enhancement in the soil’s capacity to act as a carbon sink. Therefore, adding biochar to forests may be a feasible strategy to increase carbon sinks and mitigate global climate change.

Biochar influences nitrogen and phosphorus dynamics in two texturally different soils

Nitrogen (N) and phosphorus (P) are vital for crop growth. However, most agricultural systems have limited inherent ability to supply N and P to crops. Biochars (BCs) are strongly advocated in agrosystems and are known to improve the availability of N and P in crops through different chemical transformations. Herein, a soil-biochar incubation experiment was carried out to investigate the transformations of N and P in two different textured soils, namely clay loam and loamy sand, on mixing with rice straw biochar (RSB) and acacia wood biochar (ACB) at each level (0, 0.5, and 1.0% w/w). Ammonium N (NH4-N) decreased continuously with the increasing incubation period. The ammonium N content disappeared rapidly in both the soils incubated with biochars compared to the unamended soil. RSB increased the nitrate N (NO3–N) content significantly compared to ACB for the entire study period in both texturally divergent soils. The nitrate N content increased with the enhanced biochar addition rate in clay loam soil until 15 days after incubation; however, it was reduced for the biochar addition rate of 1% compared to 0.5% at 30 and 60 days after incubation in loamy sand soil. With ACB, the net increase in nitrate N content with the biochar addition rate of 1% remained higher than the 0.5% rate for 60 days in clay loam and 30 days in loamy sand soil. The phosphorus content remained consistently higher in both the soils amended with two types of biochars till the completion of the experiment.

Interaction of Biochar Addition and Nitrogen Fertilizers on Wheat Production and Nutrient Status in Soil Profiles.

To investigate the responses of crop production and soil profile nutrient status to biochar (BC) application, we conducted a soil column experiment considering two BC addition rates (0.5 and 1.5 wt% of the weight of 0-20 cm topsoil) combined with two nitrogen (N) input levels (low N: 144 kg ha-1, LN; high N: 240 kg ha-1, HN). The results showed that BC application increased the soil pH. The soil pH of the 0-10 cm profile under LN and the 20-40 cm profile under HN were both significantly increased by 0.1-0.2 units after BC addition. Under LN, BC addition significantly increased NH4+-N (17.8-46.9%), total N (15.4-38.4%), and soil organic carbon (19.9-24.0%) in the 0-10 cm profile, but decreased NH4+-N in the 20-30 cm soil profile and NO3--N in the 10-30 cm profile by 13.8-28.5% and 13.0-34.9%, respectively. BC had an increasing effect on the available phosphorus, the contents of which in the 10-20 and 30-40 cm soil profiles under LN and 20-30 cm profile under HN were significantly elevated by 14.1%, 24.0%, and 23.27%, respectively. However, BC exerted no effect on the available potassium in the soil profile. BC had a strong improving effect (15.3%) on the wheat yield, especially the N144 + BC0.5% treatment, which could be compared to the HN treatment, but there was no yield-increasing effect when high N fertilizer was supplied. In summary, BC improved the fertility of agriculture soil (0-20 cm) with wheat. In particular, low N inputs together with an appropriate rate of BC (0.5 wt%) could not only achieve the low inputs but also the high outputs in wheat production. In future study, we will compare the effects of multiple doses of N and BC on soil fertility and crop production.

How Does Bio-Organic Fertilizer Combined with Biochar Affect Chinese Small Cabbage's Growth and Quality on Newly Reclaimed Land?

The cultivated land area in China is approaching the red line for farmland protection. Newly reclaimed land possesses a large exploratory potential to become a reserved land resource. Identifying a fertilization strategy is vital for improving the poor properties and weak fertility of newly reclaimed land. An experiment was conducted to study the effects of traditional compound fertilizer (Fc) or bio-organic fertilizer (Ft), alone or in combination with biochar addition (6.85 t·ha-1 and 13.7 t·ha-1) on the growth, photosynthesis, yield and quality of Chinese small cabbage (CSC) plant. The results showed that compared to single compound fertilizer application, bio-organic fertilizer application promoted the plant's growth, indicated by the plant height, stem diameter and leaf area index (LAI), and significantly enhanced the yield and dry matter accumulation of CSC. In terms of the combination with biochar, the promoting effects were positively related to the biochar addition rate in the compound fertilizer group, while it was better to apply bio-organic fertilizer alone or in combination with biochar at a low rate of 6.85 t·ha-1. The highest yield was obtained under B2Fc and B1Ft with 29.41 and 37.93 t·ha-1, respectively, and the yield under B1Ft was significantly higher than that under B2Fc. The water productivity (WP) significantly improved in response to both kinds of fertilizer combined with biochar at 6.85 t·ha-1. There was a significant difference between the photosynthetic characteristics of plants treated with single-compound fertilizer and those treated with bio-organic fertilizer. The photosynthetic characteristics increased under compound fertilizer combined with biochar, while they regressed under bio-organic fertilizer combined with biochar. The quality of CSC, especially that of soluble sugars and total phenolics, improved under single bio-organic fertilizer application compared with that under single-compound fertilizer. The nitrite content of the plants increased with increasing biochar addition rate in both fertilizer groups. In conclusion, there is a significant promoting effect of applying bio-organic fertilizer to replace chemical fertilizer alone or combining compound fertilizer with low-rate biochar addition on newly reclaimed land. It is a recommended fertilization strategy to substitute or partially substitute chemical fertilizer with bio-organic fertilizer combined with biochar in newly reclaimed land, and it is of great significance to achieve fertilizer reduction.

Post-sorption of Cd, Pb, and Zn onto peat, compost, and biochar: Short-term effects of ecotoxicity and bioaccessibility

Contamination by potentially toxic metals and metalloids (PTMs) has become a significant health and environmental issue worldwide. Sorption has emerged as one of the most prominent strategies for remediating both soil and water contamination. New sorbents are being developed to provide economically viable and environmentally sound alternatives, in alignment with the principles of the Sustainable Development Goals. This research aimed to assess the potential effects on human health and environmental toxicity following the sorption of cadmium (Cd), lead (Pb), and zinc (Zn) using peat, compost, and biochar as sorbents. The peat was collected in Brazil, a country with a tropical climate, while the compost and biochar were produced from the organic fraction of municipal solid waste (OFMSW). In terms of bioaccessibility, the results showed the following order: compost < biochar < peat for Pb, and compost < peat < biochar for Cd and Zn. There was a significant growth inhibition for Eruca sativa and Zea mays exposed to increasing concentrations of PTMs treated with peat and compost. The presence of contaminants played a decisive role on immobilization of neonates of Ceriodaphnia silvestrii after treatments with compost and, especially, peat. However, the biochar addition rate caused a significant influence on the outcomes of ecotoxicity across all tested species. Although the samples treated with biochar exhibited lower residual concentrations of PTMs than those treated with compost and peat, the inherent toxicity of biochar might be attributed to the material itself. The exposure to residual PTM concentrations post-desorption caused ecotoxic effects on tested species, emphasizing the need to assess PTM desorption potential. Peat, compost, and biochar are promising alternatives for the sorption of PTMs, but the addition rates must be properly adjusted to avoid the occurrence of undesirable ecotoxicological effects. This research offers valuable insights for sustainable environmental management and protection by thoroughly investigating the impacts of different sorbents and contaminants on aquatic and terrestrial ecosystems.

Biochar application alters soil metabolites and nitrogen cycle-related microorganisms in a soybean continuous cropping system

Biochar application is a promising practice to enhance soil fertility. However, it is unclear how field-aged biochar affects the soil metabolites and microbial communities in soybean fields. Here, the rhizosphere soil performance after amending with biochar addition rates at 0 (CK), 20 (B20), 40 (B40), and 60 t ha−1 (B60) was examined via a five-year in-situ field experiment based on a soybean continuous cropping system. Untargeted metabolomics and metagenomics analysis techniques were applied to study the regulatory mechanism of biochar on soybean growth from metabolomics and N cycle microbiology perspectives. We found that the contents of soil total N (TN), available N (Ava N), NH4+‐N, and NO3−‐N were significantly increased with biochar addition amounts by 20.0–65.7 %, 3.6–10.7 %, 29.5–57.1 %, and 24.4–46.7 %, respectively. The B20, B40, and B60 triggered 259 (236 were up-regulated and 23 were down-regulated), 236 (220 were up-regulated and 16 were down-regulated), and 299 (264 were up-regulated and 35 were down-regulated) differential metabolites, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis and topology analysis demonstrated that differential metabolites were highly enriched in seven metabolic pathways such as Oxidative phosphorylation and Benzoxazinoid biosynthesis. Moreover, ten differential metabolites were up-regulated in all three treatments with biochar. Biochar treatments decreased the Nitrospira abundance in soybean rhizosphere soil while increasing Bradyrhizobium abundance significantly in B60. Mantel test revealed that as the biochar addition rate grows, the correlation between Nitrospira and soil properties other than NO3−‐N became stronger. In conclusion, the co-application of biochar with fertilizers is a feasible and effective way to improve soil N supply, even though biochar has undergone field aging. This work offers new insights into the variations in soil metabolites and microbial communities associated with N metabolism processes under biochar addition in soybean continuous cropping soils.

Biochar-integrated reactive filtration of wastewater for P removal and recovery, micropollutant catalytic oxidation, and negative CO2 e: Life cycle assessment and techno-economic analysis.

Life cycle assessment (LCA) and techno-economic analysis (TEA) models are developed for a tertiary wastewater treatment system that employs a biochar-integrated reactive filtration (RF) approach. This innovative system incorporates the utilization of biochar (BC) either in conjunction with or independently of iron-ozone catalytic oxidation (CatOx)-resulting in two configurations: Fe-CatOx-BC-RF and BC-RF. The technology demonstrates 90%-99% total phosphorus removals, adsorption of phosphorus to biochar for recovery, and >90% destructive removal of observed micropollutants. In this work, we conduct an ISO-compliant LCA of a 49.2 m3 /day (9 gpm) field pilot-scale Fe-CatOx-BC-RF system and a 1130 m3 /day (0.3 MGD) water resource recovery facility (WRRF)-installed RF system, modeled with BC addition at the same rate of 0.45 g/L to quantify their environmental impacts. LCA results indicated that the Fe-CatOx-BC-RF pilot system is a BC dose-dependent carbon-negative technology at -1.21 kg CO2 e/m3 , where biochar addition constitutes a -1.53 kg/m3 CO2 e beneficial impact to the process. For the WRRF-installed RF system, modeled with the same rate of BC addition, the overall process changed from 0.02 kg CO2 e/m3 to a carbon negative -1.41 kg CO2 e/m3 , demonstrating potential as a biochar dose-dependent negative emissions technology. Using the C100 100-year carbon accounting approach rather than Cnet reduces these CO2 e metrics for the process by about 25%. A stochastic TEA for the cost of water treatment using this combinatorial P removal/recovery, micropollutant destructive removal, and disinfection advanced technology shows that at scale, the mean cost for treating 1130 m3 /day (0.3 MGD) WRRF secondary influent water with Fe-CatOx-BC-RF using the C100 metric is US$0.18 ± US$0.01/m3 to achieve overall process carbon neutrality. Using the same BC dose in an estimation of a 3780 m3 /day (1 MGD) Fe-CatOx-BC-RF facility, the carbon neutral cost of treatment is reduced further to US$0.08 ± $0.01 with added BC accounting for US$0.03/m3 . Overall, the results demonstrate the potential of carbon negativity to become a water treatment performance standard as important and attainable as pollutant and pathogen removal. PRACTITIONER POINTS: Life cycle assessment (LCA) of a pilot scale tertiary biochar water treatment process with or without catalytic ozonation at a WRRF shows a carbon negative global warming potential of -1.21-kg CO2e/m3 while removing 90%-99% TP and >90% of detected micropollutants. Biochar-integrated reactive filtration use can aid in long-term carbon sequestration by reducing the carbon footprint of advanced water treatment in a dose-dependent manner, allowing an overall carbon-neutral or carbon-negative process. A companion paper to this work (Yu et al., 2023) presents the details related to the process operation and mechanism and evaluates the pollutant removal performance of this Fe-CatOx-BC-RF process in engineering laboratory pilot research and field WRRF pilot-scale water resource recovery trials. Techno-economic analysis (TEA) of this biochar catalytic oxidation reactive filtration process using Monte Carlo stochastic modeling shows a forecasted carbon-neutral process cost with low P and micropollutant removal as US$0.11/m3 ± 0.01 for a 3780-m3/day (1 MGD) scale installation with BC cost at US$0.03/m3 of that total. The results demonstrate the potential of carbon negativity to become a water treatmentperformance standard as important and attainable as pollutant and pathogen removal.

Enhancing carbon sequestration and greenhouse gas mitigation in semiarid farmland: The promising role of biochar application with biodegradable film mulching

Long-term mulching has improved crop yields and farmland productivity in semiarid areas but also increased greenhouse gas (GHG) emissions and depleted soil fertility. Biochar application has emerged as a promising solution for addressing this issue. In this study, we investigated the effects of four biochar application rates (no biochar (N)=0 t ha–1, low (L)=3 t ha–1, medium (M)=6 t ha–1, and high (H)=9 t ha–1) under film mulching and no mulching over three growing seasons. We assessed the impact on greenhouse gas emissions, soil organic carbon sequestration (SOCS), and maize yield to evaluate the productivity and sustainability of farmland ecosystems. Our results demonstrated that mulching increased maize yield (18.68–41.80%), total fixed C in straw (23.64%), grain (28.87%), and root (46.31%) biomass, and GHG emissions (CO2, 10.78%; N2O, 3.41%), while decreasing SOCS (6.57%) and greenhouse gas intensity (GHGI; 13.61%). Under mulching, biochar application significantly increased maize yield (10.20%), total fixed C in straw (17.97%), grain (17.69%), root (16.75%) biomass, and SOCS (4.78%). Moreover, it decreased GHG emissions (CO2, 3.09%; N2O, 6.36%) and GHGI (12.28%). These effects correlated with the biochar addition rate, with the optimal rate being 9.0 t ha–1. In conclusion, biochar application reduced CO2 and N2O emissions, enhanced CH4 absorption, and improved maize yield under film mulching. It also improved the soil carbon fixation capacity while mitigating the warming potential, making it a promising sustainable management method for mulched farmland in semiarid areas.

Mathematical modeling of biochar's role in elevating co-composted poultry carcass temperatures

Previous studies reported that incorporating biochar into composting systems leads to an increase in compost temperatures. Although potential reasons, such as improved microbial activity or increased insulation, were suggested, no study has quantitatively determined the contribution of either aspect. In this study, we developed a heat transfer model for a biochar-amended co-composting system based on the measurements from our two previously published studies conducted to co-compost poultry carcasses with woodchips and wood-based (WBC), distillers grain (DGBC), and cow manure (CMB) biochar. The two composting studies were conducted over three heating cycles, with two turnings separating each cycle. The simulation for the second heating cycle, during which the compost materials began to degrade and were well-mixed, showed an average R2 value of 0.86 and was selected for further analyses. Results from the model suggested that incorporating biochar into the composting mixture increases thermal conductive losses. For example, at a biochar addition rate of 13 % (v/v), the predicted longitudinal conductive resistance of the compost pile was reduced by 24.9 %. However, the total heat unit still increased by 11.2 ± 3.17 % due to the enhancement of microbial activity as supported by elevated oxygen consumption (38.1–61.1 %). When biochar was applied in layers on the surface of the composting bins, its impact on microbial activity was minimal, primarily functioning as an insulator. Under these conditions, the total heat unit was 8.7 % higher than the control. These findings suggest that biochar's primary effect on temperature development was through promoting microbial activity.

Exploring biochar addition impacts on soil erosion under natural rainfall: A study based on four years of field observations on the Loess Plateau

Biochar’s potential impact on soil erosion has gained attention, but remained inconsistent, particularly lacks the results from continuous field monitoring under diverse rainfall conditions. This study aimed to explore the long-term variation in soil erosion induced by biochar addition under distinct natural rainfalls. Six runoff plots, treated with different amounts of biochar derived from apple tree branches (0, 1%, 2.5%, 4%, 5.5% and 7%), were established. Over a four-year period from 2017 to 2020, runoff and soil loss from these plots were continuously monitored and analyzed. Among 215 recorded rainfall events, 27 events resulted in runoff and sediment production were classified into three rainfall patterns (RI, RII and RIII) using K-means clustering. RIII characterized by high mean rainfall depth (138.80 mm), duration (3443 min), and erosivity (879 MJ.mm (ha. h)−1), but infrequent occurrence, followed by RII and RI with moderate and low mean depth, duration and erosivity, but higher frequency. Biochar addition, relative to control, resulted in an average annual runoff reduction, ranging from 9% to 36%, with a mean reduction of 28%, and reduced runoff for each rainfall, ranging from 4% to 28%, with a mean reduction of 12%. Similarly, biochar addition also reduced average annual soil loss, ranging from 43% to 79%, with a mean reduction of 61%, and reduced soil loss for each rainfall, ranging from 29% to 74%, with a mean reduction of 52%. The reduction of runoff and soil loss was positively correlated with biochar addition rates. Notably, the soil loss reduction was exceeded that of runoff. Soil erosion was negatively linked to surface area of soil particles (p < 0.05), total carbon, and total organic carbon (p < 0.01), but positively correlated with sand content (p < 0.01) and bulk density (BD) (p < 0.05) under biochar addition. Comparison of the mean reduction of runoff and soil loss among three rainfall patterns, the order was as follows: RII>RI>RIII. The optimal controlling of soil erosion was observed in 7% biochar addition under RII. Runoff-soil loss relationships well-fitted by power equation, showed soil incorporated with biochar treatments exhibited heightened susceptibility to erosion under RIII with high intensity compared to RII and RI with moderate or low rainfall intensity. Thus, the findings indicate biochar is a potential soil amendment to improve a degraded or degrading sloping farmland, however, the rainfall characteristics need to be considered when it is applied to the sloping farmland prone to erosion.

Response of soil respiration and carbon budget to irrigation quantity/quality and biochar addition in a mulched maize field under drip irrigation.

Biochar addition strongly alters net carbon (C) balance in agroecosystems. However, the effects of biochar addition on net C balance of maize field under various irrigation water quantities and qualities remains unclear. Thus, a field experiment combining two irrigation levels of full (W1) and deficit irrigation (W2 = 1/2 W1), two water salinity levels of fresh (S0, 0.71 g L-1 ) and brackish water (S1, 4 g L-1 ), and two biochar addition rates of 0 t ha-1 (B0) and 60 t ha-1 (B1) was conducted to investigate soil carbon dioxide (CO2 ) emissions, maize C sequestration and C budget. Compared with W1, W2 reduced average cumulative CO2 emissions by 6.5% and 19.9% for 2020 and 2021, respectively. The average cumulative CO2 emissions under W1S1 treatments were 5.4% and 22.3% lower than W1S0 for 2020 and 2021, respectively, whereas W2S0 and W2S1 had similar cumulative CO2 emissions in both years. Biochar addition significantly increased cumulative CO2 emissions by 17.8-23.5% for all water and salt treatments in 2020, and reduced average cumulative CO2 emissions by 11.9% for W1 but enhanced it by 8.0% for W2 in 2021. Except for W2S1, biochar addition effectively increased total maize C sequestration by 6.9-14.8% for the other three treatments through ameliorating water and salt stress over the 2 years. Compared with W1S0, W1S1 did not affect net C sequestration, but W2 treatments significantly decreased it. Biochar addition increased net C sequestration by 39.47-43.65 t C ha-1 for four water and salt treatments for the 2 years. These findings demonstrate that biochar addition is an effective strategy to increase both crop C sequestration and soil C storage under suitable water-saving irrigation methods in arid regions with limited freshwater resources. © 2023 Society of Chemical Industry.

The Responses of C, N, P and Stoichiometric Ratios to Biochar and Vermicompost Additions Differ from Alfalfa and a Mine Soil

The use of ecological stoichiometry is quite effective for exploring the nutrient dynamics and relationships between plants and soils. However, the way that the plant and soil stoichiometry changes with soil remediation in mining ecosystems remains unclear. Biochar and vermicompost are generally applied to remediate contaminated soil. In this study, a pot experiment was conducted with a mine soil planted with alfalfa. Biochar (B) and vermicompost (V) were added to the soil separately in three different proportions, equivalent to application rates (w/w) of 0% (control, CT), 2.5% (low rate, l), and 5% (high rate, h). This resulted in nine treatments, including control (CT), Bl, Bh, Vl, Vh, BlVl, BlVh, BhVl, and BhVh. The carbon (C), nitrogen (N), and phosphorus (P) concentrations and stoichiometric characteristics of the alfalfa aboveground parts (plant) and soil were investigated. The results showed that biochar application significantly increased the concentrations of soil organic C (SOC), soil total N (TN), soil total P (TP), soil C:N, and plant P concentration, but decreased plant N concentration, and plant C:P and N:P ratios. The effects of vermicompost addition on SOC, soil TN, TP, and stoichiometric characteristics depended on the biochar addition rates, but it increased plant N concentration and N:P, and decreased plant C:N under the condition of low biochar addition. Additionally, the plant N concentration was negatively correlated with soil N and total manganese (Mn) concentrations, whereas there was a positive correlation between plant and soil P concentrations. The soil total and available cadmium (Cd) were positively correlated with plant N concentration but negatively correlated with plant P concentration. The results indicated that the stoichiometric characteristics of plants and soil had diverse responses to biochar and vermicompost additions, and different soil heavy metal elements. Biochar and vermicompost application improved external P and N utilization by plants, respectively. Vermicompost addition enhanced biological N fixation in alfalfa. These findings suggest that vermicompost addition could be an optimal method by which to promote vegetation restoration in mine soils with poor N levels, and that biochar could be applied to low-P soils. The effects of heavy metals on plant and soil stoichiometric characteristics should be taken into consideration. Consequently, this study will provide scientific references for biochar and vermicompost applications in alfalfa planting and management, and vegetation restoration in mining areas.

A Study on Infiltration Characteristics and One-Dimensional Algebraic Model Simulation in Reclaimed Soil with Biochar

The cultivated land area in China is approaching the red line of farmland protection. The newly reclaimed land will become a vital reserved land resource, and it possesses a large exploratory potential. Newly reclaimed soil usually has low productivity with poor physical and chemical properties as well as weak fertility, and it is prone to serious soil erosion. The effects of corn straw biochar and rice husk biochar (at the mass ratio of 2%, 4%, and 8%) on the soil infiltration process and soil moisture distribution in the soil profile were studied. The results showed that the infiltration duration was prolonged, and the wetting front migration distance and infiltration rate were decreased under biochar addition treatments, except under the low addition rate for rice husk biochar. The Philip model and Kostiakov model accurately described the water infiltration process of the newly reclaimed soil with both kinds of biochar. The two kinds of biochar used in this study affected both the initial infiltration rates and stable infiltration rates, and water infiltration was more sensitive to rice husk biochar and its addition rate. The moisture in the soil profile after infiltration was simulated using a one-dimensional algebraic model. The surface soil moisture was improved with both kinds of biochar addition, and the water retention ability was enhanced with an increased biochar addition rate. In conclusion, corn straw biochar with a high addition rate is beneficial for inhibiting soil water infiltration and improving weak water retention ability in the newly reclaimed area, which is a recommended choice for efficient soil construction in newly reclaimed land.

Effects of Corn Straw Biochar, Soil Bulk Density and Soil Water Content on Thermal Properties of a Light Sierozem Soil

This research aimed to quantify the effects of biochar derived from corn straw on soil thermal conductivity, capacity, and diffusivity. Firstly, the amount of biochar application (w/w) added to light sierozem soil was 0% to 5%, and the mixtures were packed into soil columns at a consistent bulk density (1.20 g.cm-3). Secondly, soil columns with a consistent biochar addition rate (5%) were packed to different bulk densities of 1.30, 1.25, 1.20, 1.15, and 1.10 g.cm-3. Soil thermal characteristics were measured under the control of soil moisture content from 0% to 40%. Under consistent bulk-density conditions, biochar could significantly reduce soil thermal conductivity and diffusivity. Still, there wasn’t a significant influence on soil heat capacity in most soil moisture content levels. With the decrease of soil bulk density, soil thermal conductivity, capacity, and diffusion coefficient reduced significantly. As soil water content increased, all the indexes of thermal properties largely improved, and the effects were much more significant than those of biochar amendment and bulk density change on soil thermal performances. This research could supply an implication to evaluate the influence of biochar amendment on soil thermal performances.

Effect of Biochar on Labile Organic Carbon Fractions and Soil Carbon Pool Management Index

Biochar is useful for soil organic carbon (SOC) sequestration. However, the effects of biochar aging and addition rates on SOC stabilization are unclear. A field experiment with four biochar application rates (0% (control), 1% (LB), 2% (MB), and 4% (HB) of dry fluvo-aquic soil) was conducted. Soil samples were sampled after 8, 12, and 24 months of its application to clarify the question. In general, SOC gradually increased with the biochar application rate. SOC with HB was higher than that in other treatments, while the ratio of microbial biomass carbon (MBC)/SOC and readily oxidizable carbon (ROC)/SOC with HB was lower than that in other treatments (p &lt; 0.05), indicating a positive effect of HB for C stabilization over time. The effects of biochar on the soil carbon pool management index (CPMI) changed from negative to positive after 8 and 24 months of biochar application. The activities of β-D-glucosidase (βG), cellobiohydrolase (CBH), and β-N-acetylglucosaminidase (NAG) under HB were higher than with other treatments after 12 and 24 months of biochar application (p &lt; 0.05) and negatively correlated with the ratio of MBC/SOC and ROC/SOC over time. The CPMI was positively related with βG and CBH activities after 8 and 24 months of biochar application, respectively (p &lt; 0.05). HB increased the relative abundance of oligotrophs, including Acidobacteria, Actinobacteria, and Chloroflexi, but decreased the relative abundance of copiotrophs, including γ-Proteobacteria and Bacteroidetes over time (p &lt; 0.05). The ratio of dissolved organic carbon (DOC)/SOC was positively correlated with the bacterial oligotroph/copiotroph ratio and significantly affected the oligotrophic and copiotrophic bacterial communities, especially after 8 and 12 months of biochar application (p &lt; 0.05). These findings reinforce that increasing the biochar application rate and time enhances SOC stabilization by decreasing the proportions of labile organic carbon and making oligotrophic/copiotrophic communities and enzyme activities more conducive to C sequestration.

Does biochar addition improve soil physicochemical properties, bacterial community and alfalfa growth for saline soils?

AbstractBiochar addition has been proven to have great potential for improving soil physicochemical properties and crop growth in salt‐affected soils. However, whether adding biochar could affect alfalfa growth and soil bacterial community in salt‐affected soils of arid regions remains poorly understood. A pot experiment was carried out to investigate the effects of corn straw biochar addition on soil physicochemical properties, bacterial community and alfalfa yield in saline soils. There were 12 treatments in total, combining three biochar addition rates of 0, 20 and 40 g kg−1 (referred to as B0, B2 and B4, respectively) and four salinity levels of 0, 2, 4 and 6 g kg−1 (referred as to S0, S2, S4 and S6, respectively). The results indicated that biochar addition significantly increased soil organic carbon (SOC), electrical conductivity (EC), soil water content (SWC), available nitrogen (AN) and phosphorus (AP) and mesopores fraction, but decreased soil bulk density (BD), pH and macropores fraction for different salinity levels. In general, biochar addition had an adverse effect on alfalfa yield due to the aggregated stresses from the increased EC and mesopores fraction, especially at high salinity levels. On average, biochar addition decreased the total yield of the two years by 14.2%, 25.3%, 38.3% and 60.4% for S0, S2, S4 and S6, respectively. Biochar addition significantly changed bacterial community composition with higher relative abundances of Proteobacteria and Bacteroidetes but lower relative abundances of Actinobacteria and Acidobacteria under S2–S6. On average, both soil salinity and biochar treatments decreased soil bacterial richness by 5.7–14.6% and 4.1–8.8% compared with S0 and B0, respectively, but they did not significantly affect the bacterial diversity. The redundancy analysis (RDA) suggested that EC, SWC, pH, AN and AP were the most critical factors driving the change of soil bacterial community structure accounting for 69.9%, 64.7% 61.6%, 57.0% and 51.8% of the variation, respectively. Therefore, our results provided valuable insight into how biochar addition would affect alfalfa yield and soil properties, including bacterial community richness and composition and structure of saline soils in arid regions.

Biochar Addition and the Runoff Quality of Newly Constructed Green Roofs: A Field Study

Extensive nutrient leaching has been a major concern in the establishing stage of green roofs. Although an addition of biochar to the green roof substrates has been increasingly recommended, the extent to which this addition can affect the runoff quality is still largely unknown. Using biochars made from maize straws (MSB) and rice husks (RHB), this study investigated the effects of biochar addition rates (0%, 10%, 15%, and 20% biochar, v/v) on the runoff quality of new green roofs over 6 months. Our results show that the addition of biochar significantly affected the runoff quality. With an increasing biochar addition rate (10∼20%), the mean total nitrogen (TN) concentration in the runoff decreased from 103.68 mg L−1 (CK) to 26.21∼52.77 mg L−1 (RHB) and 10.12∼3.97 mg L−1 (MSB), the mean dissolved organic carbon (DOC) concentration decreased from 94.47 mg L−1 (CK) to 101.76∼59.41 mg L−1 (RHB) and 52.45∼26.73 mg L−1 (MSB), and the mean pH increased from 7.15 (CK) to 7.42∼7.50 (RHB) and 7.49∼7.71 (MSB). However, the mean total phosphorus (TP) concentration increased from 0.27 mg L−1 (CK) to 0.22∼0.57 mg L−1 (RHB) and 0.58∼1.07 mg L−1 (MSB). Generally, the N and DOC concentrations were lower in the treatment with added MSB than RHB, but the P concentrations and pH were higher. The N concentration was significantly negatively correlated with the single rainfall and cumulative rainfall in the CK- and RHB-added treatments but not in the MSB-added treatments, suggesting that the addition of MSB affected the process of N leaching from the substrate. Overall, we recommend adding 10% maize straw biochar to the green roof substrate to reduce the initial nutrient leaching from the new green roof and improve the runoff water quality.

Effects of biochar addition and deficit irrigation with brackish water on yield-scaled N2O emissions under drip irrigation with mulching

Biochar has been proven to have great potential for mitigating greenhouse gas emissions and improving crop growth. However, the effects of biochar addition on yield-scaled N2O emissions in a mulched and drip-irrigated maize field using different irrigation water qualities and quantities remain unclear. A two-year field experiment was conducted to examine the effects of biochar addition, irrigation level and water salinity on soil N2O emissions, maize yield and grain N uptake in Northwest China. Eight treatments in total included the combination of two biochar addition rates of 0 t/ha (B0) and 60 t/ha (B1), two irrigation levels of full (W1) and deficit irrigation (W2, W2 = 1/2 W1) and two water salinity levels of freshwater (S0, 0.71 g/L) and brackish water (S1, 4 g/L). The soil properties, N2O emission fluxes, maize yield and grain N uptake, along with the abundances of N-cycle functional marker genes were measured during the two growing seasons. Soil water-filled pore space (WFPS), soil NH4+-N and NO3--N contents accounted for the majority of the variation in the dynamic changes of N2O fluxes. Deficit irrigation had lower N2O emissions compared with full irrigation, which was more pronounced in the second year. Relative to freshwater irrigation, brackish water irrigation increased N2O emissions under W1, but freshwater and brackish water irrigation had similar N2O emissions under W2 in both years. Biochar addition effectively mitigated N2O emissions by 29.4–31.0% and 17.9–29.2% under different irrigation treatments in 2020 and 2021, respectively. The continuous drought induced by deficit irrigation weakened the effectiveness of biochar in reducing N2O emissions. The differences in N-cycle functional marker genes could not reflect the variation in cumulative N2O emissions among treatments. Under all irrigation treatments excluding W2S1, biochar addition improved the total maize yield and grain N uptake over the two-year period by 4.06–10.74% and 5.57–8.63%, respectively. Brackish water and deficit irrigation increased grain and grain N yield-scaled N2O emissions, whereas biochar addition reduced both of them. Overall, these findings suggest that biochar addition can effectively reduce N2O emissions and increase yield and grain N uptake under brackish water and deficit drip irrigation with mulching in a maize field system, and thus adding biochar can help with achieving the sustainability of agricultural production in areas with limited freshwater resources.

Effect of different biochar addition rates on Soil Physical Properties in rain-fed farmland

Biochar is extensively used for ameliorating soil structure. However, the evaluation of soil physical properties influenced by its large-scale use is still unclear. Moreover, research on biochar is mainly based on laboratory tests, lacking medium and long-term field positioning tests. In this study, a local field trial was conducted for 3 years on the Loess Plateau in central Gansu, China. Six levels of biochar treatment were set with application amounts of 0 t·ha-1, 10 t· ha-1, 20 t·ha-1, 30 t·ha-1, 40 t·ha-1, and 50 t·ha-1 (CK, T1, T2, T3, T4, and T5, respectively). The influence of various input levels of biochar on soil porosity, bulk density, aggregate stability, and soil saturated hydraulic conductivity from the 0 cm to 30 cm layer were studied during the three years of wheat field experiments. The experimental study indicates that the increase of biochar addition can significantly (p &lt; 0.05) reduce soil bulk density and increase not only soil saturated hydraulic conductivity but also total soil porosity, content of soil mechanically stable aggregates, and its MWD from the 0 cm to 30 cm soil layer. Among them, T5 treatment is the most significant (p &lt; 0.05). While its content determination of Water Stable aggregates and its MWD only have an obvious (p &lt; 0.05) improvement effect from the 0 cm to 20 cm soil layer, and T5 is the most significant. Therefore, large-scale biochar application is conducive to the improvement of farmland soil physical properties in this region.