Biochar Application Rate Research Articles

Effects of Biochar Application on Soil Bacterial Community Diversity and Winter Wheat Growth in Wheat Fields

A long-term field experiment was conducted to study the diversity of soil bacterial communities and the response of crop growth to biochar application, in order to provide a scientific basis for the rational application of biochar in agricultural fields. Four treatments were applied at 0 (B0 blank), 5 (B1), 10 (B2), and 20 t·hm-2(B3) to investigate the effects of biochar on soil physical and chemical properties, soil bacterial community diversity, and growth of winter wheat using Illumina MiSeq high-throughput sequencing technology. The results showed that soil water content, pH value, soil organic carbon, total nitrogen, nitrate nitrogen content, winter wheat biomass, nitrogen uptake, and yield showed an increasing trend with the increase in biochar amount. The high-throughput sequencing results showed that the B2 treatment significantly reduced the alpha diversity of the bacterial community at the flowering stage. The overall response of soil bacterial community composition to different application rates of biochar and phenological phases was taxonomically consistent. In this study, Proteobacteria, Acidobacteria, Planctomycetes, Gemmatimonadetes, and Actinobacteria were the dominant bacterial phyla. The relative abundance of Acidobacteria decreased, but the relative abundance of Proteobacteria and Planctomycetes increased with biochar application. The results of redundancy analysis, co-occurrence network analysis, and PLS-PM analysis indicated that bacterial community compositions were closely associated with soil parameters such as soil nitrate and total nitrogen. The average connectivity between 16S OTUs was higher under the B2 and B3 treatments (16.966 and 14.600) than under the B0 treatment. The variation in soil bacterial community (89.1%) was regulated by biochar and sampling period and partly explained the changes in the growth dynamics of winter wheat (0.077). In conclusion, biochar application could regulate the changes in the soil bacterial community and promote crop growth after seven years of application. It is suggested that 10-20 t·hm-2 biochar should be applied in semi-arid agricultural areas to achieve sustainable agricultural development.

Contrasting effects of biochar application rate in an alkaline desert cropland soil

Improving water and nutrient retention in desert croplands using soil organic amendments can be a major challenge because organic matter decomposes quickly under irrigated conditions in a hot climate. Biochar—a long-lasting carbon-rich soil organic amendment—has been proposed to improve soil water and nutrient retention, but only by carefully selecting an appropriate application rate. To better understand effects of biochar application rate on soil water and nutrient retention in desert croplands, we set up a mesocosm-scale experiment with biochar added at rates of 0, 19.8, 39.7, 79.4, 119.0, and 158.7 t ha−1 to an alkaline, sandy loam soil. After initial water retention measurements, we added fertilizer and then measured gaseous nitrogen losses as well as soil nitrate (NO3−) and phosphate (PO₄³⁻) leaching. Then, we measured biochar's effect on the soil's capacity to hold plant-available water (i.e., available water capacity, or AWC) using Tempe cells and a dewpoint potentiometer. We found contrasting effects of low and high biochar application rates. First, we found that applying a minimum of 79.4 t ha−1 biochar was necessary to improve soil water and PO₄³⁻ retention; application rates below 79.4 t ha−1 exacerbated PO₄³⁻ leaching whereas treatments above 79.4 t ha−1 improved AWC by up to 34% compared to the control treatment. While biochar application rate did not affect soil nitric oxide or ammonia emissions, we did find that low biochar application rates increased soil nitrous oxide emission while higher application rates reduced emission compared to soil with no biochar. Overall, we found that lower and higher rates of biochar application can have contrasting effects on soil water and nutrient retention in an alkaline, desert cropland soil. Therefore, farmers and other land managers must consider potential drawbacks of lower application rates and threshold responses of higher application rates prior to large-scale biochar use in arid agroecosystems.

Biochar rate-dependent regulation of extended nitrogen supply by modifying stable aggregates-N and microbial responses

Besides carbon sequestration, biochar amendment in soils can regulate the loss of applied fertilizer-nitrogen (N) into the environment. Soil aggregates are essential in controlling soil N stocks' stabilization and supply. However, unraveling the rate-dependent impact of biochar on stable soil aggregates and their associated N in fertilized soils over an extended period is a prerequisite to understanding its implications on soil-N dynamics. We unraveled how high and low biochar application rates combined with inorganic fertilizer (20- and 40-tons ha−1 [FB1 and FB2]) affected soil N fractions, stable soil aggregates, aggregates associated-N, and microbial responses to regulate N supply for Nageia nagi after one year. Results revealed that biochar amendment, especially at higher rate, increased the concentration of inorganic N and some amino acids compared to sole fertilizer (F). Available N increased by 16.5% (p = 0.057), 23.8% (p = 0.033), and 34.8% (p = 0.028) in F, FB1, and FB2, respectively, compared to the control (C). Also, 28.1% and 32.8% significant increases in the availability of NH4+-N were recorded in FB1 and FB2, respectively, compared to F. NO3−-N availability was significantly increased by 15.2%, 21.8%, and 20.8% in FB1, FB2, and C, compared to F. Biochar amendment, irrespective of rate, increased stable microaggregates (< 0.25 mm). However, FB2 significantly increased macro- and intermediate-aggregate-N, and urease activity, and hence higher N supply capacity to meet the N need of N. nagi even after one year. Hence, the N content of N. nagi was 41.3%, 28.8%, and 12.2% higher in FB2, FB1, and F, respectively, compared to the control. Biochar amendment decreased bacterial species diversity but increased the proportion of NH4+-oxidizers (especially the Betaproteobacteria) to maintain the mineralization and slow release of N. Although a low biochar rate was more beneficial than sole fertilization, higher biochar application rate could sustain higher N supply by stabilizing soil microaggregates and increasing macro- and intermediate-aggregates N, its mineralization, and slow-release over longer periods.

Can the co-application of biochar and different inorganic nitrogen fertilizers repress N2O emissions in acidic soil?

The sole application of nitrogen (N) fertilizer with lower N2O emission potential or combined with biochar may help for mitigating N2O production. However, how biochar applied with various inorganic N fertilizers affected N2O emission in acidic soil remains unclear. Thus, we examined N2O emission, soil N dynamics and relating nitrifiers (i.e., ammonia-oxidizing archaea, AOA) in acidic soil. The study contained three N fertilizers (including NH4Cl, NaNO3, NH4NO3) and two biochar application rates (i.e., 0% and 0.5%). The results indicated that the alone application of NH4Cl produced more N2O. Meanwhile, the co-application of biochar and N fertilizers enhanced N2O emission as well, especially in the combined treatment of biochar and NH4NO3. Soil pH was decreased with the application of various N fertilizers, especially with NH4Cl, and the average decrease rate was 9.6%. Meanwhile, correlation analysis showed a negative relationship between N2O and pH, dramatically, which might indicate that the alteration of pH was one factor relating to N2O emission. However, there was no difference between the same N addition treatments with or without biochar on pH. Interestingly, in the combined treatment of biochar and NH4NO3, the lowest net nitrification rate and net mineralization rate appeared during days 16–23. Meanwhile, the highest emission rate of N2O in the same treatment also appeared during days 16–23. The accordance might indicate that N transformation alteration was another factor relating to N2O emissions. In addition, compared to NH4NO3 alone application, co-applied with biochar had a lower content of Nitrososphaera-AOA, which was a main contributor to nitrification. The study emphasizes the importance of using a suitable form of N fertilizers and further indicates that two factors, namely alteration of pH and N transformation rate, are related to N2O emission. Moreover, in future studies, it is necessary to explore the soil N dynamics controlled by microorganisms.

Importance of Application Rates of Compost and Biochar on Soil Metal(Loid) Immobilization and Plant Growth.

In this study, we investigated the effect of different rates of compost (20%, 40%, 60% w/w) in combination with biochar (0%, 2%, 6% w/w) on soil physiochemical properties and the mobility of arsenic (As) and lead (Pb), in addition to the ability of Arabidopsis thaliana (ecotype Columbia-0) to grow and accumulate metal(loid)s. All modalities improved pH and electrical conductivity, stabilized Pb and mobilized As, but only the mixture of 20% compost and 6% biochar improved plant growth. Plants in all modalities showed a significant reduction in root and shoot Pb concentrations compared to the non-amended technosol. In contrast, As shoot concentration was significantly lower for plants in all modalities (except with 20% compost only) compared to non-amended technosol. For root As, plants in all modalities showed a significant reduction except for the mixture of 20% compost and 6% biochar. Overall, our results indicate that the mixture of 20% compost with 6% biochar emerged as the optimum combination for improving plant growth and As uptake, making it the possible optimum combination for enhancing the efficiency of land reclamation strategies. These findings provide a foundation for further research on the long-term effects and potential applications of the compost-biochar combination in improving soil quality.

Biochar application significantly increases soil organic carbon under conservation tillage: an 11-year field experiment

Biochar application and conservation tillage are significant for long-term organic carbon (OC) sequestration in soil and enhancing crop yields, however, their effects on native soil organic carbon (native SOC) without biochar carbon sequestration in situ remain largely unknown. Here, an 11-year field experiment was carried out to examine different biochar application rates (0, 30, 60, and 90 Mg ha−1) on native SOC pools (native labile SOC pool I and II, and native recalcitrant SOC) and microbial activities in calcareous soil across an entire winter wheat–maize rotation. The proportions of C3 and C4-derived native SOC mineralization were quantified using soil basal respiration (SBR) combined with 13C natural isotope abundance measurements. The results showed that 39–51% of the biochar remained in the top 30 cm after 11 years. Biochar application rates significantly increased native SOC and native recalcitrant SOC contents but decreased the proportion of native labile SOC [native labile SOC pool I and II, dissolved organic carbon (DOC), and microbial biomass carbon (MBC)]. Biochar application tended to increase the indicators of microbial activities associated with SOC degradation, such as SBR, fluorescein diacetate hydrolysis activity, and metabolic quotient (qCO2). Meanwhile, higher biochar application rates (B60 and B90) significantly increased the C4-derived CO2 proportion of the SBR and enhanced C4-derived native SOC mineralization. The effect of the biochar application rate on the content and proportion of native SOC fractions occurred in the 0–15 cm layer, however, there were no significant differences at 15–30 cm. Soil depth also significantly increased native labile SOC pool I and II contents and decreased qCO2. In conclusion, the biochar application rate significantly increased native SOC accumulation in calcareous soil by enhancing the proportion of native recalcitrant SOC, and biochar application and soil depth collectively influenced the seasonal turnover of native SOC fractions, which has important implications for long-term agricultural soil organic carbon sequestration.Graphical

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.

Influence of biochar on improving hydrological and nutrient status of two decomposed soils for yield of medicinal plant - Pinellia ternata

Abstract The root tuber of Pinellia ternata has been used as a traditional therapeutic herbal medicine. It is reported to impart beneficial attributes in recovering COVID-19 patients. To meet an increasing demand of P. ternata, this study is intended to investigate the effects of biochar on the soil hydrological and agronomic properties of two decomposed soils (i.e., completely decomposed granite (CDG) and lateritic soil) for the growth of P. ternata. The plant was grown in instrumented pots with different biochar application rate (0%, 3% and 5%) for a period of three months. Peanut shell biochar inclusion in both soils resulted in reduction of soil hydraulic conductivity and increase in soil water retention capacity. These alterations in hydrological properties were attributed to measured change in total porosity, biochar intra pore and hydrophilic functional groups. The macro-nutrient (i.e., N, P, K, Ca, and Mg) concentration of both soils increased substantially, while the pH and cation exchange capacity levels in the amended soils were altered to facilitate optimum growth of P. ternata. The tuber biomass in biochar amended CDG at all amendment rate increases by up to 70%. In case of lateritic soil, the tuber biomass increased by 23% at only 5% biochar application rate. All treatments satisfied the minimum succinic acid concentration required as per pharmacopoeia standard index. The lower tuber biomass exhibits a higher succinic acid concentration regardless of the soil type used to grow P. ternata. The biochar improved the yield and quality of P. ternata in both soils.

Biochar as a negative emission technology: A synthesis of field research on greenhouse gas emissions.

Biochar is one of the few nature-based technologies with potential to help achieve net-zero emissions agriculture. Such an outcome would involve the mitigation of greenhouse gas (GHG) emission from agroecosystems and optimization of soil organic carbon sequestration. Interest in biochar application is heightened by its several co-benefits. Several reviews summarized past investigations on biochar, but these reviews mostly included laboratory, greenhouse, and mesocosm experiments. A synthesis of field studies is lacking, especially from a climate change mitigation standpoint. Our objectives are to (1) synthesize advances in field-based studies that have examined the GHG mitigation capacity of soil application of biochar and (2) identify limitations of the technology and research priorities. Field studies, published before 2022, were reviewed. Biochar has variable effects on GHG emissions, ranging from decrease, increase, to no change. Across studies, biochar reduced emissions of nitrous oxide (N2 O) by 18% and methane (CH4 ) by 3% but increased carbon dioxide (CO2 ) by 1.9%. When biochar was combined with N-fertilizer, it reduced CO2 , CH4 , and N2 O emissions in 61%, 64%, and 84% of the observations, and biochar plus other amendments reduced emissions in 78%, 92%, and 85% of the observations, respectively. Biochar has shown potential to reduce GHG emissions from soils, but long-term studies are needed to address discrepancies in emissions and identify best practices (rate, depth, and frequency) of biochar application to agricultural soils.

Utilization of biochar in rainfed farming systems: A meta-analysis

Biochar application in rainfed farming can increase crop productivity by improving the water retention capacity and nutritional status of rhizosphere. This meta-analysis was carried out to assess the quantitative effects of biochar addition to the soil on the productivity of crops under rainfed conditions. The results indicated that increments in plant biomass and grain yield production of cereal crops in response to biochar application under rainfed conditions were higher than in legume crops. Low-temperature pyrolyzed biochar (≤500 °C) with high carbon (>50 %) and nitrogen (>1 %) contents and pH <8 was more effective in enhancing biomass and grain production, compared to other types of biochar. The ideal biochar application rate to improve biomass and grain yield of plants under rainfed conditions was about 20–40 tons ha−1. In general, biochar can increase plant biomass (by about 13 %) and grain yield (by about 14 %) of crops under rainfed conditions.

Short-Term Biochar Impacts on Crop Performance and Soil Quality in Arid Sandy Loam Soil

A two-year field study was conducted in sandy loam soil to evaluate the impacts of biochar on soil quality and the growth and yields of pinto bean (Phaseolus vulgaris) and sorghum–Sudan (Sorghum × drummondii). A wood-derived commercial biochar was applied at three rates to pinto bean (PB) and sorghum–Sudan (SS) plots. The biochar application rates applied annually for two years to PB plots were 0, 2.2, and 11.2 Mg ha−1, whereas the rates for SS plots were 0, 3.4, and 6.7 Mg ha−1. Crop growth and harvest parameters were evaluated. Assessed soil measurements included pH, electrical conductivity, available nutrients, soil organic matter (SOM), permanganate oxidizable carbon (POXC), soil aggregates, and volumetric soil moisture content. The results showed no significant differences in plant growth parameters and yields over the two growing seasons for both PB and SS. Compared to the control treatment, the biochar at 11.2 Mg ha−1 in PB plots improved soil moisture retention after irrigation by 19% in the first year and 25% in the second year. The SOM in the SS plot at 6.7 Mg ha−1 biochar rate was higher (1.02%) compared to the control plot (0.82%), whereas a similar increase was not observed in the PB plot. Although biochar rates did not affect most of the soil measurements, there were significant changes in soil properties over time, regardless of biochar treatments: POXC increased in the PB and SS plots; SOM increased in the SS plot; and electrical conductivity, sodium adsorption ratio, and most soil micronutrients decreased. This research was conducted over two years; the effects of biochar can persist for much longer, indicating the need for longer-term biochar field studies in arid agroecosystems.

Development of DNDC-BC model to estimate greenhouse gas emissions from rice paddy fields under combination of biochar and controlled irrigation management

Simulating the impacts of biochar and controlled irrigation (CI, a water-saving irrigation technology without surface ponding of water) combination on greenhouse gas (GHG) emissions from paddy fields is crucial, however, the original DNDC model is not capable of capturing these management impacts on emissions. In this study, we have created a new modelling approach called DNDC-Biochar-Controlled Irrigation (DNDC-BC) by adding two modules to the original DNDC: the water balance principle, and the two-pool biochar model. The performance of the DNDC-BC was tested and validated using a two-year field experiment, designed with two irrigation treatments (flood irrigation (FI), and CI) and three biochar application rates (0, 20, and 40 t ha−1), carried in the Lake Taihu region, China. Results revealed that the DNDC-BC model performed satisfactorily in simulating impacts of biochar-CI combination on emissions of CH4, N2O, SOC, and grain yield. The corresponding R2 values of DNDC-BC increased by 22.63%-35.66%, 43.00%-71.26%, 1.06%-60.87% and 15.38%-34.78% compared with those of the original model. Sensitivity analysis for the DNDC-BC showed that CH4 emissions were most sensitive to rainfall and irrigation; N2O emissions were sensitive to rainfall, irrigation and N fertilizer application rate, and SOC was sensitive to biochar application rates. Our results suggest that the combination of biochar- and CI can save water resources and mitigate GHG emissions without detrimental impacts on rice yield. The DNDC-BC can be used to estimate the long-term impacts of biochar-CI combination on GHG emission, crop productivity and climate change.

Biochar Application Maintains Photosynthesis of Cabbage by Regulating Stomatal Parameters in Salt-Stressed Soil

Salinity is one of the main abiotic stresses, and the stomatal conductance (gs) is an important physiological index in plants that is used to measure their responses to salt stress, as stomatal closure leads to lower yields. However, the factors that affect the gs after biochar application in saline soil remain unclear. To explore the stomatal adaptation mechanisms of facility vegetables under salt stress after the addition of biochar, Chinese cabbage was selected for the pot experiment in this study. The soil and plant Na+ and K+ concentrations, water status, and plant stomatal parameters were measured following treatments with different salt concentrations (25, 50, and 100 mM) and biochar application rates (0, 2, and 4%). The results showed that salt stress induced the physiological closure of the stomata in Chinese cabbage. Compared with the salt-stress treatment without biochar, the biochar application significantly increased the plant gs (20.29–128.79%). Moreover, in the biochar treatment, the open state of the stomata was maintained by sustaining the plant osmotic adjustment, reducing the abscisic acid (ABA) content, and improving the water status. The Na+/K+ ratio had the most pronounced effect on the stomata (0.702). The actual photochemical efficiency of the photosystem II (ΦPSII) and electron transport rate (ETR) of the Chinese cabbage increased by 0.75–3.41% and 0.65–2.88%, respectively, after the biochar application, which supported the photosynthetic capacity and yield formation. According to the current findings, biochar application can mitigate salt stress and regulate stomatal opening, thereby improving the photosynthesis and the overall yield of Chinese cabbage. Therefore, the application of biochar is a promising method to maintain the productivity of Chinese cabbage under salt stress.

Changes in the Availability and Distribution of Microelement Copper in Cadmium Contaminated Soil and its Accumulation in Rice (Oryza sativa L.) After Biochar Application.

This experiment explored the side effect of biochar application on the availability and distribution of the soil microelement copper (Cu) in cadmium (Cd) contaminated soil and its uptake in rice tissues. Biochar was added at 0, 10, 20, 30, and 40 t ha-1 on topsoil. Results observed that both the concentration of available Cu in the topsoil and subsoil layer decreased by 16.3%-28.9% and 7.5%-59.3%, respectively, after biochar application. The Cu concentration in the < 0.053mm and 1-2mm soil aggregates increased as biochar application rate increased. Increasing application rate of biochar reduced the proportion of exchangeable Cu, carbonate bound Cu, and Fe/Mn oxide Cu fraction in the soil profile. However, the fraction of organic bound and residual Cu increased by 5.0%-178.4% and 7.0%-15.6%, respectively. Biochar could immobilize microelement Cu in the soil profile and limit Cu uptake by rice.

Advances and prospects of biochar in improving soil fertility, biochemical quality, and environmental applications

With the global food deficit increasing and rising climate change issues, there is a need to find green solutions to improve soil fertility and productivity while enhancing soil biochemical quality and reducing the ecological impact of agriculture. Biochar is a potentially cost-effective, carbonaceous resource with many agricultural and environmental applications. As a soil amendment, it improves soil physical and biochemical properties and increases soil fertility and productivity—particularly over the long-term—increasing soil aggregation, water retention, pH, and microbial activities, thus, improving overall soil quality, potentially helping to reduce chemical fertilizer needs over time. The extent of biochar’s impact on soil physiochemical properties varies depending on biochar source, type, size, inherent soil characteristics, cropping system, etc. Moreover, biochar has significant potential in soil and water remediation, especially through its unique adsorption and chemical properties capable to capture and immobilize pollutants such as metal(loid)s, organic pollutants, and hazardous emerging contaminants such as microplastics. Further, biochar has also emerged as a key strategic, cost-effective material to tackle global issues such as climate change mitigation, reducing the net greenhouse gas emission to minimize global warming potential. However, a knowledge gap remains as to understanding the long-term persistence of biochar on agroecosystem, optimal biochar application rate for the diversity of biochar-soil-crop-environmental conditions, interaction of biochar with inherent soil carbon stock, specific mechanisms of biochar’s effect on soil biotic properties, quantification of carbon sequestration, greenhouse gas emissions, synergy or potential antagonistic effects with other carbon sources such as compost, manure, residues, etc., its modification for environmental applications and associated environmental and human risks over long-term. Further research is needed to evaluate the long-term impacts of types and sizes of biochar on overall soil quality to recommend suitable application practices based on soil management and cropping system. Also, its environmental applications need to be finetuned for wider and target specific applications to tackle pressing environmental issues such as soil and water pollution.

Effect of Biochar Application on Soil Fertility, Nitrogen Use Efficiency and Balance in Coastal Salt-Affected Soil under Barley–Maize Rotation

Coastal lands are often affected by salinization, which leads to a deterioration of soil structure and a decrease in land productivity. As a widely used soil amendment, biochar has been proven to improve poor soil properties and promote crop growth and N adsorption and utilization. However, the effects of biochar on soil fertility, N use efficiency (NUE) and balance in coastal salt-affected soil have rarely been reported. Therefore, we conducted a field micro-plot experiment to study the improvement effects of different biochar rates (0, 13.5, 20.25 and 27 t/ha, corresponding to CK, B1, B2 and B3 treatments, respectively) on coastal salt-affected soil. The results showed that biochar application increased soil water content (SWC) in seasons with abundant rainfall but decreased SWC in seasons with strong evaporation, and the increase or decrease in SWC was greater with the increase in biochar rates. Biochar application increased soil salinity and decreased soil pH, although high rates of biochar increased soil salinity to a lesser extent, while low rates of biochar decreased soil pH most. Biochar application was able to reduce soil bulk density, while B1and B2 treatments decreased it to a higher degree. Moreover, biochar application increased soil macro-aggregates (&gt;0.25 mm) and organic matter, while B2 and B3 treatments increased it to a higher degree. Biochar application improved soil fertility to an extent that crop grain increased yield by 2.84~19.88% in barley season and 12.27~16.74% in maize season. Meanwhile, biochar application also increased NUE because it promoted the increase of yield. In particular, the calculation of N balance between soil and plant systems suggested that biochar application could reduce the apparent N loss during crop planting, and B1 treatment was better at reducing apparent N loss. Overall, our study indicates that biochar application has great potential to improve poor physicochemical properties and N nutrient utilization in coastal salt-affected soil. More importantly, we suggest that biochar application rates should be controlled in coastal salt-affected soil.

How different is the remediation effect of biochar for cadmium contaminated soil in various cropping systems? A global meta-analysis

Cadmium (Cd) poses great threats to human health as a major contaminant in agricultural soil. Biochar shows great potential in the remediation of agricultural soil. However, it remains unclear whether the remediation effect of biochar on Cd pollution is affected by various cropping systems. Here, this study used 2007 paired observations from 227 peer-reviewed articles and employed hierarchical meta-analysis to investigate the response of three types of cropping systems to the remediation of Cd pollution by using biochar. As a result, biochar application significantly reduced the Cd content in soil, plant roots and edible parts of various cropping systems. The decrease in Cd level ranged from 24.9% to 45.0%. The feedstock, application rate, and pH of biochar as well as soil pH and cation exchange capacity were dominant factors for Cd remediation effect of biochar, and their relative importance all exceeded 37.4%. Lignocellulosic and herbal biochar were found to be suitable for all cropping systems, while the effects of manure, wood and biomass biochar were limited in cereal cropping systems. Furthermore, biochar exhibited a more long-lasting remediation effect on paddy soils than on dryland. This study provides new insights into the sustainable agricultural management of typical cropping systems.

Biochar related treatments improved physiological performance, growth and productivity of Mentha crispa L. plants under fluoride and cadmium toxicities

Modification of biochar with chemical reagents is an effort to increase the efficiency of this organic material to adsorb environmental pollutants. Typically, these chemically modified materials have special structural specifications that allow the adsorption and stabilization of high levels of environmental pollutants. Therefore, this research was carried out to assess the possible effects of solid and chemically engineered biochars (non-biochar, solid biochar, modified biochar with H2O2, KOH, and H3PO4) on reducing fluoride and cadmium toxicities (non-toxic, 600 mg NaF kg−1 soil, 60 mg Cd kg−1 soil and 600 mg NaF kg−1 soil + 60 mg Cd kg−1) in mint plants (Mentha crispa L.). The application rate of biochar and modified biochars was 25 g kg−1 soil. The addition of biochar and especially engineered biochars to the soil reduced the availability of fluoride and cadmium to the plants. Biochar and chemically modified biochars increased soil cation exchange capacity (CEC) (up to 31%), pH (up to 11%), leaf area (up to 22%), chlorophyll content index (up to 19%), maximum efficiency of photosystem II (up to 32%), biomass (up to 21%) and essential oil production (up to 28%) in mint plants. On the other hand, biochar-related treatments reduced the reactive oxygen species generation, antioxidant enzymes activities, and lipid peroxidation in the root (up to 41%) and leaf tissues (up to 40%). In general, modified biochars showed a better effect than solid biochar in reducing fluoride and cadmium toxicities. The H3PO4-modified biochar was a bit more successful than other biochar-related treatments in increasing mint performance under fluoride and cadmium toxicities. Therefore, the chemically engineered biochars are the superior treatments to improve mint growth and productivity under fluoride and cadmium toxicities, because of their excellent physicochemical specifications such as high level of CEC, functional groups, and specific surface area.

Effects of Biochar on Antibiotic Environmental Behaviors in Soil: A Meta-analysis

Biochar, as a soil amendment for synergizing the reduction of pollution and carbon emissions, shows great potential and future prospects in controlling antibiotic contamination. In order to research the effects of biochar on antibiotic behaviors in soil systematically, a Meta-analysis was conducted based on 20 studies published from 2011 to 2021. The results showed that the adsorption and degradation of antibiotics in the soil were significantly affected by the application rate and property of biochar. A 2% biochar application dose seemed to be the highest effect size (ES) of 0.19 on adsorption, while there was a significant effect (ES=0.23) on the degradation when the application rate was 5%. The specific surface area, polarity, stability, and aromaticity of biochar could increase the partition coefficient significantly, and the ES was 0.11, 0.13, 0.09, and 0.18, respectively, whereas the effects of antibiotic transport on the dose and property of biochar were insignificant. Biochar also indirectly controlled antibiotic behavior by altering the soil environment. However, the response of the coupling mechanism in antibiotic behaviors on biochar application into soil is still unclear. Moreover, the long-term and negative effects of biochar application in the field are still lacking basic data.

Growth and Yield Response of Tomato to Different Soil Amendment Techniques under Different Water Stress

The research was aimed at evaluating the growth and yield performance of tomato under different water regimes and different ricehusk biochar application rates. A trial was conducted during the 2022 dry season at Wudil in Kano State. The experiment was laid out in a Split Plot design. The experiment consisted of two factors; biochar at six different application rates (15, 13.75, 12.5, 11.25, 8.75 and 5tons/ha) and irrigation regimes (100, 50 and 25% irrigation). Which were combined to produce 18 treatments? Prior to planting, fifteen soil samples (0-15 cm) were collected randomly and bulked to obtained three composite soil samples for physical and chemical analysis using standard laboratory procedures. Growth and yield parameters were taken from 2WAT at 2 weeks intervals in each plot and. The result showed that aplication of biochar has a significant effect on crop growth and yield especially at 50% irrigation. Therefore it is recommended that 15tons/ha of rice husk biochar at 50% irrigation is very suitable for use by farmers in the study area.