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Organic amendments and nitrogen fertilization are common practices in agriculture, which have complex influences on the carbon cycle. To evaluate the effects of nitrogen‐organic carbon combination on CO2 efflux, we conducted a field incubation experiment with control, N fertilization without and with straw/biochar amendments for 20 months in a typical soil of North China Plain. CO2 efflux was measured every ~3–4 weeks, and water‐extractable organic carbon and soil microbial biomass carbon were analyzed in spring, summer, and autumn. Our results showed an asymmetric seasonality (slow increase in spring but rapid decrease in fall) in the control and biochar treatments, but a symmetric seasonality under straw treatments. Organic amendments with N fertilization caused an increase of CO2 efflux in most seasons (comparing without N fertilization), with a much greater increase in spring–summer of the first year (22%–35%) than the second year (1%–3%). Nitrogen fertilization caused a much greater increase in cumulative CO2 efflux with biochar (7%–13%) and with straw treatment (20%) than without organic amendments (3%) over the period of 20 months. SIC content showed an increase under organic amendments, with a greater increase under biochar amendments than straw amendments. The increases of CO2 efflux under nitrogen‐biochar and nitrogen‐straw combinations could be explained mainly by enhanced decomposition of SOC, biochar, and straw rather than SIC dissolution. Our study indicated that biochar amendments were more effective for carbon sequestration than straw amendments and nitrogen fertilization with organic amendments could cause changes in various processes of CO2 production in the cropland of north China. [ABSTRACT FROM AUTHOR]

Nitrate leaching from farmland pollutes the surrounding environment, such as groundwater, causing health hazards to inhabitants. To mitigate the leaching, biochar can be applied. The effect of biochar application differs depending on the application depth; however, the effect of the application depth remains unclear. To evaluate the effect, we conducted a pipe experiment with no plant using bagasse biochar with four treatments: no biochar application, surface application (0−5 cm), plow layer application (0−30 cm), and subsurface application (25−30 cm). The results showed that surface and plow layer applications reduced nitrate leaching, whereas subsurface application did not affect leaching. This difference was due to changes in the soil water movement and water budget. Surface application reduced evaporation, inducing increases in both drainage and the amount of water in the pipe. The increased amount of water might contribute to an increase in the amount of nitrogen in the pipe, reducing the leaching. Plow layer application increased evaporation, leading to decreased drainage and nitrate leaching. Subsurface application did not affect drainage and nitrate leaching; however, the change in the volumetric water content at a depth of 10 cm was the most significant among the treatments. Our study indicated that, although the same amount of biochar was applied, the effect of biochar application differs depending on the application depth. [ABSTRACT FROM AUTHOR]

Abstract The residue of atrazine in field soils poses a major threat to crop growth in the rotation system, raising concerns about grain security and food safety. Current agricultural production requires more efficient and cost-effective mitigation measures in response to the emerging threat. This study reported the critical concentration (0.1 mg L−1) of atrazine injury to soybean seedlings in soil pore water and how biochar amendment could influence the distribution of atrazine in different soil environments. The results showed that biochar significantly reduced the concentration of atrazine in soil pore water, for example, 0.5% biochar in red (cinnamon, fluvo-aquic, paddy, black) soil reduced atrazine concentration from 0.31 (0.20, 0.18, 0.12, 0.03) mg L−1 to 0.004 (0.002, 0.005, 0.013, 0.011) mg L−1 in pore water (P

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Purpose: The multiple benefits of biochar use as a soil amendment has garnered global attention. Biochar addition is a crucial factor to improve soil biomass, soil enzyme activities, microbial biomass and improve soil nutrient utilization rate. However, the precise mechanism of effects of biochar addition on microbial community structure and diversity, as well as enzyme activity, remains unclear, especially for biochar obtained from different pyrolysis temperatures and variable quantities in which it is applied to soil. Materials and methods: We compiled and summarized the existing literature on the impacts of biochar on microorganisms and enzymes, with a specific on articles published over a five-year period (2018–2022). This review provides a comprehensive review of the relevant literature on enzyme activity, microbial diversity, community structure and abundance following biochar amendment in soil, and further elucidates the underlying mechanisms of biochar-induced effects on various factors. Results and discussion: The impact of biochar on soil microorganisms could be categorized into three aspects: (1) biochar, due to its porous structure and high surface area, functions as a sanctuary for soil microorganisms; (2) biochar provides essential elements such as carbon (C) and nitrogen (N) sources to soil microorganisms, and finally (3) biochar improves the survival conditions of soil microorganisms by modifying soil pH, CEC, aggregation, and enzyme activity. Importantly, biochar produced at lower pyrolysis temperatures provides valuable C and N for soil microorganisms. Whereas biochar obtained at higher pyrolysis temperatures contains much less active C and N. However, it still contributes to microbial nutrition through diverse mechanisms, e.g., nutrient immobilization and increased nutrients residence time through its bonding with soil labile C. Conclusions: This review found that the type of source material and pyrolysis temperature were the primary determinants in the impacts of biochar on soil microbial abundance, community structure, and diversity. [ABSTRACT FROM AUTHOR]

The residue of atrazine in field soils poses a major threat to crop growth in the rotation system, raising concerns about grain security and food safety. Current agricultural production requires more efficient and cost-effective mitigation measures in response to the emerging threat. This study reported the critical concentration (0.1 mg L−1) of atrazine injury to soybean seedlings in soil pore water and how biochar amendment could influence the distribution of atrazine in different soil environments. The results showed that biochar significantly reduced the concentration of atrazine in soil pore water, for example, 0.5% biochar in red (cinnamon, fluvo-aquic, paddy, black) soil reduced atrazine concentration from 0.31 (0.20, 0.18, 0.12, 0.03) mg L−1 to 0.004 (0.002, 0.005, 0.013, 0.011) mg L−1 in pore water (P < 0.01). On the basis of these, a reliable mathematical model was developed to predict the atrazine concentration in soil pore water under (or without) biochar amendment conditions. The verification results showed that the mean absolute percentage error of the model was 14.1%, indicating that the prediction error was within a reasonable range. Our work provides a precise solution to crop injury caused by soil residual herbicides with the aid of biochar, which reduces the bioavailability of atrazine in soybean seedlings. This method not only maximizes the use of biochar but also provides effective crop protection and environmental benefits. Highlights: The critical value of atrazine injury to soybean seedlings in soil pore water was 0.1 mg L−1. Biochar amendment significantly reduced the concentration of atrazine in soil pore water. The distribution of atrazine in soil pore water can be predicted by a mathematical model. [ABSTRACT FROM AUTHOR]

In the UK, strawberry is mostly grown in coconut coir substrate under protection. Coir substrate is usually used only for one or two cropping seasons because the continuous reuse of coir without any treatment leads to yield decline. In this study, we investigated the changes in bacterial and fungal communities in strawberry roots and bulk coir in relation to (i) the coir substrate age (cropping seasons) and (ii) oak or beech biochar amendment at planting. Coir age did not affect fungal/bacterial alpha (within-sample) diversity but affected beta (between-sample) diversity. Amendment with either oak or beech biochar did not lead to significant changes in either alpha or beta diversity for both fungi and bacteria, but it did alter the relative abundance of 13 fungal ASVs. This study identified six bacterial and 20 fungal ASVs with a significant positive linear relationship with coir age and also eight bacterial and 22 fungal ASVs with a significant negative linear relationship with coir age. Notably, the observed strawberry yield decline in reused coir substrate could be associated with a generalist root pathogen, Ilyonectria destructans (ex. Cylindrocarpon destructans), of which the abundance increased annually by 225% and 426% in strawberry root and bulk coir, respectively. Future research is needed to confirmthe role of I. destructans in reused coir on strawberry plant health and fruit productivity and then to identify management strategies for yield decline mitigation. [ABSTRACT FROM AUTHOR]

The aim of this study was the characterization and evaluation of applicability as a soil amendment of biochar derived from rose pruning waste at different pyrolysis temperatures (200–500 °C) and process durations (20–60 min). The biochar properties were compared to the raw material. The biochars produced at 300 °C for 40 and 60 min demonstrated the best fuel properties. These variants showed high energy gain rates (77.6 ± 1.5% and 74.8 ± 1.5%, respectively), energy densification ratios (1.35 ± 0.00 and 1.37 ± 0.00, respectively), high heating values (24,720 ± 267 J × g−1 and 25,113 ± 731 J × g−1, respectively), and relative low ash contents (5.9 ± 0.5% and 7.1 ± 0.3%, respectively). Regarding fertilizer properties, such as pH value, ash content, heavy metal content, and pollutant elution, the biochars showed better qualities than the raw material. All tested biochar did not exceed the permissible values for heavy metals, including Cr, Cd, Ni, and Pb. The most optimal properties for soil amendments were noted for biochar variants of 400 °C for 40 min, 450 °C for 20 min, and 500 °C for 20 min. Generally, biochars produced at temperatures ≥400 °C did not inhibit root elongation, except for the material produced at 450 °C for 60 min (4.08 ± 23.34%). Biochars obtained at ≥300 °C showed a positive impact on seed germination (86.67 ± 18.48–100 ± 24.14%). [ABSTRACT FROM AUTHOR]

Global warming is one of the eco-environmental problems of most concern to scientists. N2O, an atmospheric greenhouse gas, has been widely studied because of its high warming potential. As an excellent soil conditioner, biochar has a very broad research value and application path in the farmland. This work examined the impact of biochar application on N2O emissions reduction potential of farmland soils in northern China by meta analysis and path analysis. The results were as follows: the N2O emissions reduction potential changes corresponded with different biochar preparation materials, preparation temperature, C/N ratio and pH. Biochar is more suitable for application in soil with a bulk density < 1.3 g cm−3, sandy loam texture, neutral pH, organic matter content 20–30 g kg−1, soil C/N ratio 10–20, and total nitrogen < 2 g kg−1. At the same time, the maximum reduction of N2O emissions can be achieved in a scenario where the biochar is applied at 20 t ha−1- 40 t ha−1 and the application of nitrogen fertilizer is 100–200 kg N ha−1. Under the above ideal conditions, this study selected the data of soil mineralized nitrogen (X1), soil organic matter content (X2), soil water content (X3), average temperature (X4), total nitrogen (X5), and N2O emissions (Y) for correlation analysis and path analysis, and finally obtained the multiple stepwise regression equation between N2O emissions and various impact factors as follows: Y = -45.9102 + 0.6874X1 + 0.4634X2 + 0.3249X3 + 0.2698X4 + 0.2218X5 (R2 = 0.826, p < 0.01, n = 87). The direct relationships between N2O and soil mineralized nitrogen and soil organic matter content were very significant (P < 0.01). The second is soil water content, average temperature and total nitrogen. Indirect relationships between N2O and average temperature, total nitrogen and mineralized nitrogen were significant (P < 0.05). [ABSTRACT FROM AUTHOR]

BACKGROUND: The accumulation of microplastics in agricultural soil poses a threat to the sustainability of agriculture, impacting crop growth and soil health. Due to the geocarpy feature of peanut, geocarposphere soil environment is critical to pod development and its nutritional quality. While the effects of microplastics in the rhizosphere have been studied, their impact on peanut pod in the geocarposphere remains unknown. Biochar has emerged as a potential soil agent with the ability to remediate soil contamination. However, the mechanisms of biochar in mitigating the toxic effects of microplastics-contaminated geocarposphere soil on peanut pod development remain largely unexplored. RESULTS: We evaluated the peanut pod performance and microbiome when facing microplastics contamination and biochar amendment in geocarposphere soil. The results showed that microplastics present in geocarposphere soil could directly enter the peanut pod, cause pod developmental disorder and exert adverse effects on nutritional quality. Aberrant expression of key genes associated with amino acid metabolism, lipid synthesis, and auxin and ethylene signaling pathways were the underlying molecular mechanisms of microplastics-induced peanut pod developmental inhibition. However, these expression abnormalities could be reversed by biochar application. In addition, peanut geocarposphere microbiome results showed that biochar application could restore the diversity of microbial communities inhibited by microplastics contamination and promote the relative abundance of bacteria correlated with pathogen resistance and nitrogen cycle of geocarposphere soil, further promoting peanut pod development. CONCLUSION: This study demonstrated that biochar application is an effective strategy to mitigate the toxic effects of microplastics-contaminated geocarposphere soil on pod development and nutritional quality. [ABSTRACT FROM AUTHOR]

Biochar amendment technique having been applied in the landfill cover or green roof was found to have the potential of erosion control. The strategy of utilizing excess biomass resource from an invasive weed (water hyacinth) in China and converting it into a new type of biochar is proposed to address the erosion issue. It is noted that the erosion process influenced by multiple factors (i.e., slope conditions, soil properties, and rainfall intensity) in biochar-amended soils has not been well understood. The aim of this study is to estimate the individual and coupled effects of five investigated factors (i.e., biochar content, soil compaction degree, slope gradient, slope length, and rainfall intensity) on infiltration, runoff, and soil erosion using in-house designed flume tests. Flume tests were planned based on factorial experiment design on bare soil (BS) and soil-biochar composites (SBCs). The results showed that biochar addition could reduce soil erosion by 10–69% and improve rainwater storage by 20–59%. Soil with 5% biochar amendment achieved the best amendment efficiency. This is likely due to the enhanced formation of water-stable macroaggregates in the presence of biochar. Biochar content was assessed as the most important factor in determining water retention and erosion reduction with 33% and 40% contribution, respectively. The total impact of slope conditions was vital on improving rainwater storage and erosion control by 29% and 43%, respectively. This study broadened the understanding of water erosion and hydrologic responses under the influence of biochar on SBCs and provided a sustainable perspective for the hydrologic management practice. [ABSTRACT FROM AUTHOR]

Abstract Biochar, a soil conditioner containing significant amounts of polycyclic aromatic hydrocarbons (PAHs), has gained widespread popularity in agricultural practices due to its advantages in improving soil fertility and carbon sequestration. While biochar may increase soil black carbon (BC) and PAH contents, the quantitative accumulation of BC and PAHs in different soil environments under varying biochar addition dosages remains poorly understood. Here, we investigated the content and composition of black carbon (evaluated using benzene polycarboxylic acids, BPCAs) and PAHs in soils treated with different biochar addition dosages from two long-term experimental farmlands in Ningxia (5-year) and Shandong (7- and 11-year), China. Results showed that increasing cumulative biochar dosage caused elevated contents of black carbon and PAHs, accompanied by decreases in their retention efficiencies. Contrasting retention was observed between sites, with the Shandong site characterized by higher retention efficiencies of BPCAs and lower retention efficiencies of PAHs, possibly owing to its higher temperature, more sandy soil texture, less irrigation, and lower sunlight intensity. Despite both black carbon and PAHs originating from biochar and sharing similar condensed aromatic structures, there was no significant correlation between the contents of black carbon and PAHs, indicating distinct behaviors and fates of these compounds. These findings emphasize the importance of optimizing biochar addition dosages and considering site-specific environmental factors for effective soil black carbon sequestration through biochar application. Graphical Abstract

Biochar, a soil conditioner containing significant amounts of polycyclic aromatic hydrocarbons (PAHs), has gained widespread popularity in agricultural practices due to its advantages in improving soil fertility and carbon sequestration. While biochar may increase soil black carbon (BC) and PAH contents, the quantitative accumulation of BC and PAHs in different soil environments under varying biochar addition dosages remains poorly understood. Here, we investigated the content and composition of black carbon (evaluated using benzene polycarboxylic acids, BPCAs) and PAHs in soils treated with different biochar addition dosages from two long-term experimental farmlands in Ningxia (5-year) and Shandong (7- and 11-year), China. Results showed that increasing cumulative biochar dosage caused elevated contents of black carbon and PAHs, accompanied by decreases in their retention efficiencies. Contrasting retention was observed between sites, with the Shandong site characterized by higher retention efficiencies of BPCAs and lower retention efficiencies of PAHs, possibly owing to its higher temperature, more sandy soil texture, less irrigation, and lower sunlight intensity. Despite both black carbon and PAHs originating from biochar and sharing similar condensed aromatic structures, there was no significant correlation between the contents of black carbon and PAHs, indicating distinct behaviors and fates of these compounds. These findings emphasize the importance of optimizing biochar addition dosages and considering site-specific environmental factors for effective soil black carbon sequestration through biochar application. Highlights: Increasing biochar dosage caused higher black carbon and PAH contents but lower retention efficiencies. The retention efficiencies of black carbon and PAHs were highly site-dependent. Optimal biochar dosages and site-specific considerations are crucial for effective soil carbon sequestration. [ABSTRACT FROM AUTHOR]

Introduction: Soil microbes are central in governing soil multifunctionality and driving ecological processes. Despite biochar application has been reported to enhance soil biodiversity, its impacts on soil multifunctionality and the relationships between soil taxonomic biodiversity and ecosystem functioning remain controversial in paddy soil. Methods: Herein, we characterized the biodiversity information on soil communities, including bacteria, fungi, protists, and nematodes, and tested their effects on twelve ecosystem metrics (including functions related to enzyme activities, nutrient provisioning, and element cycling) in biochar-amended paddy soil. Results: The biochar amendment augmented soil multifunctionality by 20.1 and 35.7% in the early stage, while the effects were diminished in the late stage. Moreover, the soil microbial diversity and core modules were significantly correlated with soil multifunctionality. Discussion: Our analysis revealed that not just soil microbial diversity, but specifically the biodiversity within the identified microbial modules, had a more pronounced impact on ecosystem functions. These modules, comprising diverse microbial taxa, especially protists, played key roles in driving ecosystem functioning in biochar-amended paddy soils. This highlights the importance of understanding the structure and interactions within microbial communities to fully comprehend the impact of biochar on soil ecosystem functioning in the agricultural ecosystem. [ABSTRACT FROM AUTHOR]

Soil dissolved organic matter (DOM) is the most reactive pool of soil organic matter. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) is a powerful tool for obtaining molecular-level DOM information. The ongoing atmospheric nitrogen (N) deposition could cause some negative effects on tropical and subtropical forest ecosystems, and biochar is considered to be an effective soil ameliorator. However, few studies have evaluated the effects of biochar and N deposition, either separately or in combination, on the molecular composition of soil DOM. In this study, we conducted a pot experiment using Chinese fir seedlings amended with biochar (0, 12, and 36 t biochar ha−1, prepared from corn stover at 450 °C) and inorganic N (NH4NO3: 0, 40, and 80 kg N ha−1 y-1) in a full factorial design (four replications per treatment) and characterized soil DOM using FT-ICR-MS. A total of 6084 types of formulas were identified in this study. All 36 samples had 2109 types of formulas in common, which had much lower N/C and P/C ratios than the bulk DOM samples. Permutation-based multivariate analysis of variance revealed that both N addition and biochar application had a significant impact on DOM chemodiversity. N addition increased the relative abundance of lignins and lipids, which may be a way for Chinese fir to acclimate to an acidic environment by expanding roots and fixing N. Biochar amendment increased the relative abundance of carbohydrates and tannins in soil DOM at each N application level. Soil pH is a key soil variable controlling DOM composition, and an increase in pH after biochar amendment contributed greatly to the occurrence of DOM compounds with an O/C > 0.5, which are easily degradable. In particular, lignins associated with low N/C were more abundant at higher pH. Biochar application also improved the efficiency of roots in acquiring nutrients, reduced the relative biomass of roots, and decreased the relative content of lignins or lipids, which primarily originated from the roots. In summary, biochar amendment effectively alleviated the negative effects of N addition by investing more N into the production of easily degradable DOM compounds and stimulating the biogeochemical cycle of N.

Abstract While biochar amendment and straw incorporation in soil have received great attention due to the potential of carbon sequestration and improvements in soil physicochemical properties, there were limited studies addressing their impacts on soil heterotrophic respiration over a seasonal cycle. Here, we conducted a field experiment to evaluate the effects of biochar amendment and straw incorporation on the temporal variations of soil heterotrophic respiration and desorption of soil organic carbon (SOC) in the North China Plain. We measured CO2 efflux over 1-year period in the field, together with water extractable organic carbon (WEOC) and soil microbial biomass carbon (SMBC). Our study showed a significant exponential relationship (P

The accumulation of microplastics in agricultural soil brings unexpected adverse effects on crop growth and soil quality, which is threatening the sustainability of agriculture. Biochar is an emerging soil amendment material of interest as it can remediate soil pollutants. However, the mechanisms underlying biochar alleviated the toxic effects of microplastics in crops and soil were largely unknown. Using a common economic crop, peanut as targeted species, the present study evaluated the plant physiologica and molecular response and rhizosphere microbiome when facing microplastic contamination and biochar amendment. Transcriptome and microbiome analyses were conducted on peanut root and rhizosphere soil treated with CK (no microplastic and no biochar addition), MP (1.5% polystyrene microplastic addition) and MB (1.5% polystyrene microplastic+2% peanut shell biochar addition). The results indicated that microplastics had inhibitory effects on plant root development and rhizosphere bacterial diversity and function. However, biochar application could significantly promote the expressions of key genes associated with antioxidant activities, lignin synthesis, nitrogen transport and energy metabolism to alleviate the reactive oxygen species stress, root structure damage, nutrient transport limitation, and energy metabolism inhibition induced by microplastic contamination on the root. In addition, the peanut rhizosphere microbiome results showed that biochar application could restore the diversity and richness of microbial communities inhibited by microplastic contamination and promote nutrient availability of rhizosphere soil by regulating the abundance of nitrogen cycling-related and organic matter decomposition-related microbial communities. Consequently, the application of biochar could enhance root development by promoting oxidative stress resistance, nitrogen transport and energy metabolism and benefit the rhizosphere microecological environment for root development, thereby improved the plant-soil system health of microplastic-contaminated agroecosystem.

The aim of this study was the characterization and evaluation of applicability as a soil amendment of biochar derived from rose pruning waste at different pyrolysis temperatures (200–500 °C) and process durations (20–60 min). The biochar properties were compared to the raw material. The biochars produced at 300 °C for 40 and 60 min demonstrated the best fuel properties. These variants showed high energy gain rates (77.6 ± 1.5% and 74.8 ± 1.5%, respectively), energy densification ratios (1.35 ± 0.00 and 1.37 ± 0.00, respectively), high heating values (24,720 ± 267 J × g−1 and 25,113 ± 731 J × g−1, respectively), and relative low ash contents (5.9 ± 0.5% and 7.1 ± 0.3%, respectively). Regarding fertilizer properties, such as pH value, ash content, heavy metal content, and pollutant elution, the biochars showed better qualities than the raw material. All tested biochar did not exceed the permissible values for heavy metals, including Cr, Cd, Ni, and Pb. The most optimal properties for soil amendments were noted for biochar variants of 400 °C for 40 min, 450 °C for 20 min, and 500 °C for 20 min. Generally, biochars produced at temperatures ≥400 °C did not inhibit root elongation, except for the material produced at 450 °C for 60 min (4.08 ± 23.34%). Biochars obtained at ≥300 °C showed a positive impact on seed germination (86.67 ± 18.48–100 ± 24.14%).

While biochar amendment and straw incorporation in soil have received great attention due to the potential of carbon sequestration and improvements in soil physicochemical properties, there were limited studies addressing their impacts on soil heterotrophic respiration over a seasonal cycle. Here, we conducted a field experiment to evaluate the effects of biochar amendment and straw incorporation on the temporal variations of soil heterotrophic respiration and desorption of soil organic carbon (SOC) in the North China Plain. We measured CO2 efflux over 1-year period in the field, together with water extractable organic carbon (WEOC) and soil microbial biomass carbon (SMBC). Our study showed a significant exponential relationship (P < 0.001) between CO2 efflux and temperature, with Q10 values in a range of 2.6–3. CO2 efflux was significantly higher in summer under straw incorporation (5.66 μmol m−2 s−1) than under biochar amendments (3.54–3.92 μmol m−2 s−1) and without amendment (3.76 μmol m−2 s−1). We found significantly lower WEOC:SOC ratio and SMBC:SOC ratio under biochar amendments than with straw incorporation and without amendment. Our study indicated that biochar amendment had a greater potential for reducing SOC desorption and CO2 efflux in the cropland of North China Plain. [ABSTRACT FROM AUTHOR]

Abstract Biochar applications have an enormous impact on the soil microbial community and functionality. However, the majority of the knowledge on biochar–microbe interaction derives almost exclusively from bacterial and fungal studies, while the vast majority of eukaryotic diversity, protists, are mostly neglected. Protists play important roles in the soil ecosystem as microbial predators, decomposers, photoautotrophs, pathogens, and parasites and they are essential for a healthy soil ecosystem. Toward a comprehensive understanding of the effects of biochar application, we need more studies on protists across the full breadth of eukaryotic diversity. The aim of this article is to highlight the research needs and discuss potential research ideas on biochar–protist interaction, which would advance our knowledge of biochar–microbe interaction. Highlights Biochar–microbe interaction is almost exclusively studied for bacteria and fungi. Only a few studies are available on how soil protists react to biochar application. More research on biochar–protist is needed for a better understanding of biochar–microbe interaction.

BACKGROUND: Undeviating climatic instabilities have increased the incidents of drought. Crop performance and yield attributes of tomatoes are negatively affected by drought stress. Biochar is an organic amendment that can increase crop yield and nutritional value under water‐deficient conditions by retaining water and providing nutrients (nitrogen, phosphorus, potassium, and other trace elements). RESULTS: The present study was designed to investigate the effects of biochar on tomato plant physiology, yield, and nutritional quality under deficit moisture regimes. Plants were subjected to two biochar levels (0.1% and 0.2%) and four moisture levels [100%, 70%, 60%, and 50% field capacities (FCs)]. Drought stress, especially 50D (50% FC), severely affected the plant morphology, physiology, yield, and fruit quality attributes. However, plants grown in biochar‐amended soil showed significant increase in the studied attributes. Plant height, root length, fresh and dry weight of root, the number of fruits per plant, fruit fresh and dry weight, ash percent, crude fat, crude fiber, crude protein, and lycopene contents were increased in plants grown in biochar‐amended soil under control and drought stress. CONCLUSION: Biochar at 0.2% application rate depicted a more pronounced increment in the studied parameters than 0.1% and can save 30% water without compromising tomato crop yield and nutritional value. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

A 3-year field experiment was conducted to determine the impact of corn residue-derived biochar on soil organic matter (SOM), soil nutrients, corn yield and partial factor productivity of synthetic fertilizer in Hetao Irrigation District, Inner Mongolia of China. Three rates of biochar, 15 (B15), 30 (B30) and 45 (B45) t ha−1, and a non-biochar control (B0) were applied to a corn field one time at the first crop growing season under film-mulched with drip-irrigation. Relative to B0, the B30 led to a significant increase in SOM at top 30 cm soil layer (15.3%) and partial factor productivity of fertilizers (12.8%) as averaged across 3 years. Amendment in B30 also increased the available nutrients in the soil (nitrogen, phosphorus and potassium), corn yield and economic benefit. In contrast, the first year showed the largest improvements for corn yield and economic benefit for B30, followed by the second year and the third year. The corn grain yield has potentially increased when the SOM and the available phosphorus were increased when compared to the available nitrogen and potassium. A single biochar amendment at the rate of 30 t ha−1 can be adequate for the corn production in 3 years under dry climatic conditions. [ABSTRACT FROM AUTHOR]

Evaluation of liming and fertility properties of biochar on acid soil was studied in this work. Selected soil properties such as pH, electrical conductivity (EC), exchangeable acidity (Ex Ac), exchangeable Al (Ex Al), exchangeable Fe (Ex Fe), available P and, soil organic carbon (SOC) were examined under the effect of biochar amendments. The acid soil was treated with biochar issued from coffee husk (CH) and cocoa pods (CP) pyrolyzed at 350°C and 550°C for 4 hours at amendment rate of 0, 20, 40 and 80 g kg−1 and an incubation time of 7, 14, 30, 40 and 60 d. Biochar amendments significantly increased soil pH, soil EC with respect to control and decrease in exchangeable acidity was observed. Results show that biochar improved available P in acid soil, though re-adsorption occurred with increasing incubation time. A significant increase in SOC is observed as compared to control. The impact of biochar on these acid soil chemical properties is due to the properties which are dependent on the biochar type and pyrolysis temperature. Thus, biochar can play the dual role of a liming agent and a source of P fertilizer nutrients. [ABSTRACT FROM AUTHOR]

Application of reductive soil disinfestation (RSD), biochar, and antagonistic microbes have become increasingly popular strategies in a microbiome-based approach to control soil-borne diseases. The combined effect of these remediation methods on the suppression of cucumber Fusarium wilt associated with microbiota reconstruction, however, is still unknown. In this study, we applied RSD treatment together with biochar and microbial application of Trichoderma and Bacillus spp. in Fusarium-diseased cucumbers to investigate their effects on wilt suppression, soil chemical changes, microbial abundances, and the rhizosphere communities. The results showed that initial RSD treatment followed by biochar amendment (RSD-BC) and combined applications of microbial inoculation and biochar (RSD-SQR-T37-BC) decreased nitrate concentration and raised soil pH, soil organic carbon (SOC), and ammonium in the treated soils. Under RSD, the applications of Bacillus (RSD-SQR), Trichoderma (RSD-T37), and biochar (RSD-BC) suppressed wilt incidence by 26.8%, 37.5%, and 32.5%, respectively, compared to non-RSD treatments. Moreover, RSD-SQR-T37-BC and RSD-T37 caused greater suppressiveness of Fusarium wilt and F. oxysporum by 57.0 and 33.5%, respectively. Rhizosphere beta diversity and alpha diversity revealed a difference between RSD-treated and non-RSD microbial groups. The significant increase in the abundance, richness, and diversity of bacteria, and the decrease in the abundance and diversity of fungi under RSD-induced treatments attributed to the general suppression. Identified bacterial (Bacillus, Pseudoxanthomonas, Flavobacterium, Flavisolibacter, and Arthrobacter) and fungal (Trichoderma, Chaetomium, Cladosporium, Psathyrella, and Westerdykella) genera were likely the potential antagonists of specific disease suppression for their significant increase of abundances under RSD-treated soils and high relative importance in linear models. This study infers that the RSD treatment induces potential synergies with biochar amendment and microbial applications, resulting in enhanced general-to-specific suppression mechanisms by changing the microbial community composition in the cucumber rhizosphere. [ABSTRACT FROM AUTHOR]

Soil salinization is a significant obstacle to agricultural development in arid and semiarid regions. While short-term experiments have demonstrated the effective improvement of saline soils through biochar amendment, the long-term efficacy in sustainably ameliorating such soils remains uncertain. Addressing this knowledge gap, this study investigated the long-term effects of biochar amendment in a field setting by applying different rates of biochar to a salt-affected soil and cultivating silage maize for three consecutive years. The comprehensive assessment includes not only maize growth but also changes in soil physical and chemical properties over the study period. The results reveal a notable elevation in maize above-ground dry matter, directly correlated to the enhanced uptake of nitrogen, phosphorous, and potassium. Additionally, biochar application improves saline soil physical properties, including reduced bulk density (1–23%), increased soil large pores (0.7–12%), and macroaggregates (24–141%), and chemical properties, including a decrease in exchangeable sodium percentage (35–48%), and an increase in soil total organic carbon (112–857%), total nitrogen (9–198%), available nitrogen (12–49%), phosphorus (141–538%) and potassium (57–895%). These improvements ultimately resulted in better maize growth. However, the amelioration effect of biochar on these soil properties gradually diminished over the three-year study. Consequently, this study suggests that biochar is a promising soil amendment that can enhance maize growth in saline soil for at least three years in a field experiment, providing valuable insights for sustainable agricultural practices in salt-affected regions. [ABSTRACT FROM AUTHOR]

Nitrogen (N) deposition is an important environmental factor that can change soil chemical properties. It can also alter the characteristics of microbial communities. The incorporation of biochar into soils is considered a potential strategy to enhance carbon (C) storage in soil and modify the impacts of N deposition. However, the impacts of biochar on the microbial characteristics of soil after short-term N deposition in subtropical plantations remain poorly understood. Here, we investigated the effects of biochar application (0, 5, 10 t ha−1) on soil chemical traits and microbial characteristics (extracellular enzyme activities, microbial community and microbial biomass) in a Larix kaempferi plantation in Shennongjia, China, under N addition (0, 50, 100 kg N ha−1 yr−1) during two growing seasons. We found that simulated N deposition significant increased soil total nitrogen (TN), nitrate nitrogen (NO3−-N) and total phosphorus (TP) concentrations, while heavy N deposition (100 kg N ha−1 yr−1) significant decreased soil microbial biomass nitrogen (MBN) concentration and β-glucosidase (β-GC) activity. Biochar amendment significantly increased soil microbial biomass, TN and soil organic carbon (SOC) concentrations. Both N addition and biochar amendment significantly altered Ascomycota and Basidiomycota relative abundance, with biochar amendment increasing Ascomycota relative abundance and decreasing Mortierellomycota relative abundance under heavy N deposition. Fungal diversity showed a positive correlation to TN, TP and NO3−-N concentrations, but a negative correlation to MBN. Biochar addition inhibited the increase in soil NO3−-N concentration caused by high N addition in the plantation, and influenced the change in the composition of microbial community caused by N addition. Our piecewise structural equation model suggested that N addition affected MBN and fungal diversity directly or indirectly via its effects on soil enzyme activities and properties. In contrast, there were no significant direct or indirect effects on bacterial diversity among all factors. These results improve our understanding of the influence and mechanisms of N addition and biochar amendment on soil microbial characteristics in subtropical coniferous plantations in the short term, and can provide a valuable reference for predicting the future effects of N deposition on soils in this region’s plantation.

Highlights 1. Biochar amendment impeded methanogenesis and facilitated methane oxidation whereas dung amendment facilitated methanogenesis and impeded methane oxidation in grassland soils. 2. Dung amendment generated undominated processes rather than homogeneous selection as the primary driving force in the community assembly of methanogen. 3. Biochar amendment raised the contribution of dispersal limitation in the community assembly of methanotrophs. 4. Diversity and association of the network among the functional genes involved in carbon and nitrogen cycling decreased after biochar and dung amendments.

Highlights Both biochar and organic substitution improved vegetable quality, yield and NEEB. Manure production is a hotspot in the foreground Nr loss and N leaching in the field. Organic substitution alone produced best NEEB while least in the combined treatment.

Salt stress and nutrient deficiency strongly limited the productivity of coastal saline-alkali land in the Yellow River Delta. Biochar has been widely used to improve soil health and promote crop yield, and the positive effects of nitrification inhibitors on fertilizer use efficiency, especially nitrogen, were also verified. However, there were few types of research on the combined application of biochar and nitrification inhibitor dicyandiamide (DCD) on saline-alkali soil of the Yellow River Delta, China. In this study, five treatments, including no nitrogen (CK), normal NPK (N), NPK + 1%biochar (B), NPK + 2%DCD (D), and NPK + 1%biochar + 2%DCD (BD) were set to investigate the single and combined effect of biochar and DCD on nitrogen transform, soil properties, bacterial community structure, and soybean production. Results showed that BD application inhibited nitrification and increased the soil's nitrate supply at the flowering stage, which reduced nitrogen waste and met the nitrogen demand for soybean growth. Biochar addition increased the soil's pH and decreased the soil's electrical conductivities and accelerated the soil's macroaggregates formation, with the soil's average mass diameter and geometric average diameter increasing by 78.69% and 30% in B, and 71.29% and 29.34% in BD relative to CK. Positive effects of inhibitors on soybean production were found in increasing soybean yield, hundred-grain weight, aboveground biomass, etc. Proteobacteria was the dominant phylum in the bacterial communities detected, and bacterial community diversity was significantly explained by nitrate content and soil aggregates (p < 0.05). Soil pH and DCD addition mainly influenced the abundance of the bacterial community, especially Actinobacteria. Biochar with DCD could be a feasible fertilization scheme for the coastal saline-alkali land in the Yellow River Delta, China. [ABSTRACT FROM AUTHOR]

Straw incorporation, a common agricultural strategy designed to enhance soil organic carbon (SOC), often leads to increased nitrous oxide (N 2 O) emission, potentially offsetting benefits of SOC sequestration. However, the mechanism and mitigation options for the enhanced N 2 O emission following straw incorporation remain unclear. Here, N 2 and N 2 O emission rate, as well as N 2 O/(N 2 O + N 2) ratio under four different fertilization treatments [i.e., non-fertilization (Control), conventional chemical fertilization (CF), conventional chemical fertilization plus straw incorporation (SWCF), and conventional chemical fertilization plus straw and biochar incorporation (SWBCF)] were investigated by a robotized sampling and analysis system. High-throughput sequencing was also employed to assess the variation of bacterial community across different treatments. The results showed CF, SWCF, and SWBCF fertilization treatments significantly increased N 2 O emission rate by 1.04, 2.01, and 1.29 folds, respectively, relative to Control treatment. Albeit no significant enhancements in N 2 emission rate, the N 2 O/(N 2 O + N 2) ratio significantly increased by 65.53%, 1.10 folds, and 69.49% in CF, SWCF, and SWBCF treatments, respectively. The partial least squares path modeling analysis further revealed that fertilization treatments slightly increased N 2 emission rate by increasing DOC content and keystone OTUs abundance. While the enhanced N 2 O emission rate and N 2 O/(N 2 O + N 2) ratio in the fertilization treatments was primarily determined by reducing DOC/NO 3 − ratio and specific bacteria module abundance dominated by Gaiellales, Solirubrobacterales, and Micrococcales. Furthermore, SWBCF treatment alleviated the increase in net global warming potential due to straw incorporation, as indicated by the higher SOC sequestration and lower N 2 O/(N 2 O + N 2) ratio therein. Collectively, these findings suggest that simultaneous application of straw and biochar has the potential to mitigate the risk of increased N 2 O emission from straw incorporation. This study provides valuable insights for developing targeted strategies in C sequestration and greenhouse gas mitigation, tackling the challenge presented by global climate change. [Display omitted] • Straw incorporation significantly increased N 2 O emission and SOC content. • Enhanced N 2 O emission was regulated by DOC/NO 3 − ratio and specific bacteria module. • Adding biochar reduced the N 2 O/(N 2 O + N 2) ratio compared to straw incorporation. • Co-application of straw and biochar alleviated the net global warming potential. [ABSTRACT FROM AUTHOR]

Applying biochar has beneficial effects on regulating plant growth by providing water and nutrient availability for plants due to its physicochemical characteristics. Nevertheless, it is still unclear how soil and biochar interactions strengthen crop lodging resistance. The objective of the current study was to find out how soil physicochemical conditions and alterations in biochar affect lodging resistance and crop productivity in cereals. To do this, a meta-analysis was carried out using nine groups of effective variables including type of feedstock, pyrolysis temperature, application rate, soil pH, total nitrogen, available phosphorus, potassium, organic matter (OM), and soil texture. Results showed that straw-derived biochar caused the highest positive effect size in the dry weight of biomass (20.5%) and grain yield (19.9%). Also, the lowest lodging index was observed from straw (−8.3%) and wood-based (−5.6%) biochars. Besides, the high application rate of biochar results in the highest positive effect sizes of plant cellulose (8.1%) and lignin content (7.6%). Soils that contain >20 g kg−1 OM, resulted in the highest positive effect size in dry biomass (27.9%), grain yield (30.2%), and plant height (4.7%). Also, fine-textured soil plays an important role in increasing polymers in the anatomical structure of plants. Overall, the strong connection between biochar and soil processes, particularly the availability of OM, could strengthen plants' ability to tolerate lodging stress and contribute to high nutrient efficiency in terms of crop output and cell wall thickening. [Display omitted] • High pyrolysis temperature (>550 °C) resulted in a 32.7% increase in grain yield. • The optimum level of soil available N caused the highest grain yield (15.7%). • Higher application rate of biochar caused a decrease in the lodging index. • The highest breaking force was observed in loamy texture (8.9%). • The highest cellulose content was observed in the optimum level of phosphorus. [ABSTRACT FROM AUTHOR]

【Background and objective】 Amending soil with biochar has seen a steady increase over the last few decades as an agent either to remediate soil contamination or to improve soil quality and nutrient availability. As the impact of biochar on crop growth is via changes in physical and biogeochemical properties of soil, its efficacy is likely to depend on inputs of other nutrients to soils. Taking maize as an example, this paper investigated how irrigation and nitrogen (N) fertilization combine to affect the effect of biochar amendment at different ratios on soil properties. 【Method】 The field experiment was conducted in plots, and compared four biochar application rates: 0 (C0), 5 (C1), 10 t/hm2 (C2) and 15 t/hm2 (C3). For each amendment, there were two irrigation treatments: normal irrigation by supplying 100% of water demand by the crop (I1) and deficit irrigation by halving that amount (I2), and two N treatments by fertilizing 200 kg/hm2 of N (N1) and halving that amount (N2). Change in soil properties and different N forms, as well as their impact on the ultimate grain yield were measured in each treatment. 【Result】 Biochar amendment at rates of 5 and 10 t/hm2 improved soil porosity and its water holding capacity, while reducing ammonium and nitrate leaching, especially the 10 t/hm2 treatment, all at significant level. They also promoted root growth and improved grain yield and water and nitrogen use efficiency as a result. Amending the soil with biochar at 10 t/hm2 increased yield, water use efficiency and partial productivity of N by 6.74% to 13.12%, 9.84% to 19.48% and 6.74% to 13.12%, respectively, compared with the control without biochar amendment. C0+I1+N2 increased grain yield and water use efficiency by 13.12% and 16.93%, respectively, compared to C0+I1+N1; the yield and nitrogen partial productivity of C2+I2+N2 and C0+I1+N2 were comparable, though the yield of the former was 12.84% higher than that of the latter (P

Mercury (Hg) and arsenic (As) are toxic and harmful heavy metals, with exceedance rates of 1.6% and 2.7%, respectively, in soils across China. Compared to soils contaminated with Hg or As alone, co-contaminated soils pose complex environmental risks and are difficult to remediate. Biochar is widely used as a soil amendment to adsorb and immobilize pollutants such as heavy metals. However, only a few studies have explored the efficiency of biochars produced from different crop straws to reduce the bioavailability of heavy metals in co-contaminated soils, and the effects on soil biological properties are often overlooked. The aim of this study was to investigate changes to the physicochemical properties, enzyme activities, and heavy metal bioavailability of an industrial soil co-contaminated with Hg and As upon the addition of different biochars from reed, cassava, and rice straws (REB, CAB, and RIB, respectively). The soil was amended with 1% biochar and planted with spinach in pots for 30 days. RIB was more effective than REB and CAB in increasing the soil pH, organic matter content, and cation exchange capacity. RIB and CAB exhibited similar positive effects on the soil dehydrogenase, catalase, invertase, and urease activities, which were higher than those of REB. The exchangeable fraction of both metals decreased upon biochar addition, and the residual fraction showed the opposite trend. All biochar amendments reduced the bioconcentration factors of heavy metals (especially Hg) in plants and decreased the metal bioavailability in soil. RIB is the optimal amendment for the stabilization of soil co-contaminated with Hg and As. [ABSTRACT FROM AUTHOR]

The freshwater deficit is the major constraint to winter wheat production. Saline water irrigation could alleviate wheat water stress while increasing the risk of soil salinization, which would result in wheat yield reduction due to additional salt stress. The objective of the present study is to explore the effect of a straw-returning mode to promote winter wheat production under saline water irrigation. A field experiment was conducted during the winter wheat growing seasons of 2017–2018 and 2018–2019. Four returning modes were set, based on an equivalent carbon input: straw mulching (SM), biochar amendment (BA), straw mulching combined with biochar amendment (SM+BA), and the control without straw-returning (CK), along with three salinity levels of irrigation water: 0.47 dS m−1 (I0, freshwater), 3.25 dS m−1 (I1), and 6.75 dS m−1 (I2). Saline water irrigation alone triggered soil salt accumulation and reduced the wheat grain yield by 9.43––18.19%. Returning straw to fields increased soil organic carbon content by 16.41––52.21% and decreased soil bulk density by 0.69––1.46%. The highest increase in wheat grain yield (16.60––21.80%) was always obtained when using treatment SM+BA, due to the increased soil moisture content (3.15––12.31%) and lower salt levels (24.79––44.29%) compared to CK. The results of the present study established that SM+BA provided better soil water–salt conditions and nutrient environment for winter wheat growth than a single treatment. Thus, the combined application of SM and BA was shown to be a proper mitigating strategy to cope with the adverse effects of saline irrigation on winter wheat production and to promote the sustainable use of saline water irrigation. [ABSTRACT FROM AUTHOR]

Biochar (BC) amendment has been proposed as a promising strategy for mitigating greenhouse gas (GHG) emissions, specifically carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O). Conducting a meta-analysis to evaluate the impact of biochar on microbial genetic profile, community structure, and phospholipid fatty acid (PLFA) contents can aid in identifying key microbial groups involved in GHG production and consumption, and assessing the overall effectiveness of biochar in reducing GHG emissions. The present meta-analysis revealed that the addition of biochar resulted in a 22 % and 41 % reduction in pmoA and mcrA genes of methanogenic microorganisms, respectively. The mcrA/pmoA ratio significantly increased by 81 %. Gene abundances exhibited a positive response to biochar amendment, with increases observed in nifH, nirK, nirS, nosZ, and nosZ (nirS + nirK) genes by 13 %, 32 %, 37 %, 42 %, and 79 %, respectively. Moreover, biochar amendment influenced the microbial community structure accordingly. The concentration of PLFAs increased in response to BC treatment in the following order: A-bacteria (+49 %) < Fungi (+30 %) < Gram-pb (+21 %) < G-bacteria (+17 %) < Gram-nb (+11 %). These findings indicate that biochar amendment shapes the microbial community structure, further emphasizing its significance in enhancing soil fertility., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Reducing chemical fertilizers and biochar amendment is essential for achieving carbon neutrality, addressing global warming, and promoting sustainable agricultural development. Biochar amendment, a carbon rich soil additive produced through biomass pyrolysis, enhances soil fertility, increases crop yield, and improves soil carbon storage. However, research on the combined effect of fertilizer reduction and biochar amendment on soil mineral associated organic carbon (MAOC) in jasmine gardens is limited. This study aims to determine if biochar can reduce industrial fertilizer usage without compromising soil quality. This study focuses on jasmine cultivation in southeastern China, employing four treatments: conventional fertilization (CK), biochar amendment without fertilizer (BA), fertilizer reduction (FR), and fertilizer reduction with biochar amendment (FRBA). The effects on MAOC, microbial abundance, and enzyme activity were investigated. The FRBA treatment significantly increased MAOC content by 19.98 % compared to CK (P < 0.05). The BA and FRBA treatments enhanced the diversity of soil bacteria, including Lactobacillus, Azospirillum, and Cutibacterium, which are associated with soil organic carbon sequestration and nutrient decomposition. The RandomForest model identified β-N-acetyl-glucosaminidase (NAG), electric conductivity (EC), β-1, 4-Glucosidase (BG), soil potential of Hydrogen (pH), soil bulk density (BD), and β-D-cellobiosidase (CBH) as key soil traits promoting MAOC accumulation (P < 0.05). The results indicate that BA and FRBA improve soil bacterial community structure, enzyme activity, and MAOC content, promoting soil carbon accumulation through environmental factors and dominant bacteria. This study encourages future fertilization protocols that enhance fertilizer efficiency and carbon storage in crop soils., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

【Objective】 Deficit irrigation and biochar amendment have been increasingly used to increase irrigation water use efficiency and improve soil quality respectively. However, how their combination affects the growth and physiological traits of crops is an issue that is not well understood. The aim of this paper is to address this in an attempt to provide guidance to improve the management of greenhouse tomato production in northwest China. 【Method】 The experiment was conducted in a greenhouse. We compared three irrigation levels by keeping the soil water content at 75%~85% (I1), 55%~65% (I2) and 40%~50% of the field capacity respectively. Added to each irrigation treatment were three biochar application rates: no amendment (B0), added 3% (w/w) (B1), and 6% (B2) of biochar. In each treatment, we measured the growth and physiological traits of the crop, as well as its ultimate shoot dry matter and water use efficiency at different growth stages. 【Result】 A moderate deficit irrigation did not reduce the photosynthetic rate at critical growth stage, but significantly increased the activities of antioxidant enzymes (SOD, POD, CAT) in leaves and reduced the final shoot dry matter. Biochar amendment combined with full irrigation reduced photosynthesis and the open ratio of photosystem II (PSⅡ), thereby resulting in a significant decrease in shoot dry matter and water use efficiency (WUEL). Combination of deficit irrigation and B2 biochar amendment enhanced the opening of PSⅡ and heat dissipation capacity (NPQ) of the crop, thereby increasing the shoot dry matter and WUEL. Dry shoot matters were affected significantly by all physiological traits, especially antioxidant enzyme activities (POD and CAT), the net photosynthetic rate (Pn) and stomatal conductance (Gs), during the critical period when dry matter started to accumulate in the shoot. Improving the photosynthetic capacity of the leaves and defence capacity of the antioxidant system can promote dry matter accumulation. Compared with I2+B0, I2+B2 increased dry shoot matter and WUEL by 6.1% (P>0.05) and 30.9% (P

【Background and objective】 Fertilization and soil amendments are common agronomic technologies to improve soil properties and safeguard crop production, but how to optimize their applications to save fertilizers without compromising crop yield is an issue that remains largely elusive. The objective of this paper is to fill this knowledge gap. 【Method】 We took rice grown in the reclaimed coastal saline soils as an example, and simulated its growth in response to biochar and nitrogen fertilization using the ORYZA_V3 crop model. Lysimeter experiments were conducted and the experimental results were used to calibrate the model. The calibrated model was then used to evaluate the impact of different nitrogen fertilizations and biochar amendments on crop growth and yield. 【Result】 The ORYZA_V3 model was capable of simulating the growth and yield of rice grown in the saline soils. When nitrogen application was low, amending the soil with biochar can increase the rice yield at significant level. However, the improvement depends on nitrogen application rate. When nitrogen application was more than 235 kg/hm2, nitrogen did not appear to be a limiting factor for the crop and the efficacy of amending the soil with biochar for improving crop growth and yield was also waning. For example, when the nitrogen fertilization was 235 kg/hm2, adding 2% of biochar (w/w) gave a yield 8 680.1 kg/hm2, while when the nitrogen fertilization was 141 kg/hm2, add 5% of biochar could increase the rice yield to 8 834.1 kg/hm2. Amending the saline soil with biochar is hence an effective way to reduce nitrogen application without compromising crop yield. 【Conclusion】 The efficacy of amending the reclaimed coastal saline soils with biochar to improve rice yield was when nitrogen fertilization application was low, and its efficacy waned as the nitrogen application increased. These results have important implications for rice production in regions with salt-affected soils.

Biochar has a great potential to sustainably improve the performance of bio-engineered slope due to its ability to retain water and to supply nutrients. Existing studies mainly focus on hydrological properties of biochar-amended soil. However, the effects of biochar on shear strength of soil are not well studied. This study aims to assess the shearing behaviour of biochar-amended completely decomposed granite (CDG). Soil specimens were prepared by mixing CDG with two types of biochar at a mass ratio of 5% and compacted at 95% of the maximum dry density. Although the peak shear strength of biochar-amended CDG is reduced by up to 20% because of lower initial dry density of the soil and crushing of biochar particles during shearing, both types of biochar have negligible effects on the ultimate shear strength, which is governed by friction between soil particles. This highlights that the ultimate friction angle can be adopted for designing bio-engineered slopes using biochar-amended soils. [ABSTRACT FROM AUTHOR]

Purpose: Drought and soil erosion are significant environmental challenges to agricultural production in the Loess Plateau of China. We hypothesized that ridge-furrow rainwater-harvesting, especially tied-ridge-furrow rainwater-harvesting, with biochar application would increase soil moisture, temperature, and alfalfa fodder yield, and reduce runoff and sediment yield. Materials and methods: A split-plot design experiment was conducted to determine the effects of biochar application patterns (biochar application pattern and no biochar application pattern) and tillage practices (tied-ridging, open-ridging, and flat-planting) on soil temperature, moisture, runoff, sediment yield, fodder yield, and water use efficiency (WUE) of alfalfa during two consecutive alfalfa-growing years: 2019 and 2020. Results: Biochar application decreased runoff, sediment yield, soil temperature, and increased soil water storage, compared to no biochar application. Open-ridging and tied-ridging significantly increased soil water storage, fodder yield, WUE of alfalfa, and decreased runoff and sediment yield, compared to flat-planting. Compared to no biochar application, soil water storage for biochar application increased by 34.51 mm during alfalfa growing season over two years. The mean runoff and sediment yield for no biochar application were 1.48–1.69 and 1.94–2.25 times greater than that for biochar application, respectively. Compared to flat-planting, the mean decrease of runoff and sediment yield was 27.4–31.9% and 60.1–64.7%, respectively, for open-ridging, while it was 37.1–55.2% and 71.8–82.4% for tied-ridging. The mean increase of soil water storage, fodder yield, and WUE of alfalfa for open-ridging was 39.5–52.1 mm, 26.2–31.7%, and 10.07–14.86 kg ha−1 mm−1, respectively, while it for tied-ridging was 31.2–60.5 mm, 26.5–35.2%, and 12.14–16.55 kg ha−1 mm−1 over two years. Conclusions: Tied-ridge-furrow rainwater-harvesting with biochar application is a potentially effective adaptation technology that could control soil erosion and increase alfalfa fodder yield in semiarid regions. [ABSTRACT FROM AUTHOR]

【Background】 Traditional rice production in paddy fields in subtropical regions in China is to keep the soil surface flooded. This is not only a waste of water resources but also acidifies the soil and leaks agrochemicals to water bodies. Improving water use efficiency and ameliorating soil acidity is a challenge facing sustainable rice production in these regions. 【Objective】 The purpose of this paper is to investigate the efficacy of using intermittent irrigation and biochar amendment to improve the ability of soil to hold water and deacidify paddy soil. 【Method】 The experiment was conducted in a rice-rice rotation field. It consisted of two irrigation treatments: continuous flooding (CF) irrigation and intermittent irrigation. Added to the intermittent irrigation were three biochar amendments by adding 0 (IF), 24 t/hm2 (LB) and 48 t/hm (HB) of biochar. In each treatment, we measured soil water content and soil pH during the growth season of both the early and late rice, as well as in the duration when the soil was temporally fallowed. 【Result】 Compared with CF, intermittent irrigation alone did not result in significant changes in soil water content due to the combined impact of precipitation and drainage. Amending the soil with biochar did not alter soil water content during the growth season of ether rice, but reduced it significantly when the soil was fallowed due to the fine texture of the biochar and structural change in the soil. The annual average soil water content under CF, IF, LB and HB treatments was 47.35%, 39.58%, 36.81% and 39.02%, respectively. Compared to CK, intermittent irrigation alone had no impact on soil pH when soil was fallowed but reduced it by 0.22 and 0.57 unit during the growth season of the early and the late rice, respectively. Biochar amendment deacidified the soil, increasing its pH by 0.23~0.68 unit in the early rice season and 0.17~0.60 unit in the late rice season, with the increase varying with biochar application rate. 【Conclusion】 Intermittent irrigation alone reduces soil pH, and combining it with biochar amendment, especially at a high amendment rate, can increase soil pH. These results have important implications for improving agricultural management and quality of paddy soils with rice-rice rotation as commonly cultivated in subtropical regions in south China.

【Background and Objective】 The dwindling water resources in north China over the past decades has called for improving irrigation water use efficiency and reducing groundwater extraction, especially for winter wheat whose production largely relies on irrigation. While various water-saving irrigation technologies have been developed and tested, how agronomic management can help improve water use efficiency remains absurd. The purpose of this paper is to investigate the efficacy of biochar amendment coupled with different irrigations to improve soil structure and boost winter wheat yield. 【Method】 The experiment was conducted from October 2018 to June 2019 in a field in central China. It consisted of four irrigations: flooding, drip, sprinkler and micro-sprinkler irrigations. Added to each irrigation were three biochar amendments at rates of 0, 10 t/hm2 and 20 t/hm2 respectively. All treatments were randomly arranged in the field. In each treatment, we measured the yield and yield traits, irrigation water use efficiency and apparent nitrogen fertilizer use efficiency of the wheat. 【Result】 Neither irrigation method nor biochar amendment showed noticeable effects on stem height and root length. Using 50% of the water used in flooding irrigation, drip irrigation, sprinkler irrigation and micro-sprinkler irrigation all reduced grain yield though not at significant level (p>0.05). Drip irrigation reduced straw yield but increased harvest index of the wheat. In contrast, sprinkler irrigation reduced grain numbers per ear and increased the ratio of defect grains, resulting in yield reduction. Biochar amendment did not show significant effect on irrigation water use efficiency and apparent nitrogen fertilizer use efficiency (p>0.05). Compared with flooding irrigation, drip, sprinkler and micro-sprinkler irrigations reduced the apparent nitrogen fertilizer use efficiency although the difference between them was not significant (p>0.05). Compared with flooding irrigation, drip irrigation, sprinkler irrigation and micro-sprinkler irrigation increased irrigation water use efficiency by 42.79%, 39.09% and 47.71% respectively (p0.05), probably due to the low amending rate. 【Conclusion】 Using 50% of the water used in flooding irrigation, drip, sprinkler and micro-sprinkler irrigations did not comprise grain yield. Considering plant growth, grain yield and irrigation water use efficiency, drip irrigation coupled with biochar amendment is a more suitable agronomic practice for winter wheat in north China.

Biochar impacts on soil respiration (R s) remain uncertain, particularly in dryland regions where significant CO 2 emissions result from rewetting. To examine these impacts, we conducted a three-year field experiment during the millet growing season to investigate the response patterns of R s to biochar-induced changes in vertical soil temperature (T s) and volumetric water content (VWC). Before R s observation, the experimental site underwent three years of biochar amelioration (no planting) with five application rates of 1 %, 2.5 %, 4 %, 5.5 % and 7 % (BC1, BC2.5, BC4, BC5.5 and BC7, applied to the 0–20 cm soil layer). R s was monitored within the 0–20 cm soil layer while T s and VWC were measured simultaneously at soil depths of 5, 10 and 20 cm (T s5 , T s10 , T s20 , VWC 5 , VWC 10 and VWC 20). Moisture status within the R s measurement range was partitioned by 0.093 m3 m−3 (the optimal VWC for R s) for non-biochar amended soil (control). Overall, compared with the control, BC4, BC5.5 and BC7 significantly increased R s (33.3–63.5 %) and experienced water stress earlier at a soil depth of 5 cm. In addition, high moisture levels caused significant differences in R s among treatments. In terms of the relationship between R s and T s , the Gaussian-T s model performed better than exponential-T s in control only at a soil depth of 5 cm under low moisture conditions. For biochar treatments, R s did not continue to rise with increasing T s for BC1 and BC2.5 treatments under low moisture conditions and for BC5.5 and BC7 treatments under high moisture conditions across soil depths. With biochar application rate, R s was dominantly shaped by VWC 20 and T s20 under low moisture conditions, while it was significantly influenced by T s under high moisture conditions. These findings elucidate how R s responds to biochar-induced changes in vertical T s and VWC across moisture levels, providing valuable insights for comprehensively evaluating the environmental effects of biochar-amended soil in dryland areas. • High biochar (BC) notably raised R s and suffered water stress earlier (only at 5 cm). • In low moisture (LM), thermal adaption of R s emerged in low BC levels (1 % and 2.5 %). • In high moisture (HM), thermal adaption of R s emerged in high BC levels (5.5 % and 7 %). • With BC level, R s was inhibited by VWC (20 cm) in LM and shaped by temperature in HM. [ABSTRACT FROM AUTHOR]

Biochar addition can change the physiochemical properties of soil, thus likely influencing soil's resistance to rill flow (reflected by rill erodibility (K r , s m−1) and critical shear stress (τ c , Pa). However, the persistent time effects of biochar on K r and τ c have remained unexplored. This study aimed to assess the impact of biochar composed of apple branches on K r and τ c , and to investigate the relationships between K r , τ c and soil properties. The undisturbed soil core samples to a depth of 5 cm were collected from field plots that had received biochar at rates of 0, 1, 2.5, 4, 5.5, and 7 % (w/w) after 1, 2, and 3 years, respectively. The K r and τ c of these samples were evaluated through a flume experiment, with scouring soil samples under three flow discharges (e.g., 0.00025, 0.00045, and 0.00065 m−3 s−1) and five slope gradients (e.g., 5.24, 8.75, 17.63, 26.79, and 40.40 %). The results revealed that the ranges of K r and τ c for no biochar treatments varied from 0.1947 to 0.2107 s m−1 and 1.6971–1.7314 Pa, with the averaged values of 0.2007 s m−1 and 1.7100 Pa, respectively. Compared with no biochar addition, the addition of 1–4 % biochar after 1–2 years generally resulted in a reduction in K r ranging from 20 % to 59 %, while increasing τ c by 2–4 %. Conversely, 5.5 and 7 % biochar addition increased K r by 31 and 5 %, and reduced τ c by 12 and 6 %. All biochar treatments after 3 years resulted in a 51 % reduction in K r and a 5 % increase in τ c relative to bare soil, showing an increasing trend with an increasing biochar addition rate. The fluctuations in K r and τ c could be elucidated by changes in cohesion (COH) and mean weight diameter of soil aggregates (MWD), with COH (total effect of −0.32 and 0.17, P <0.01) and MWD (total effect of −0.13 and 0.37, P <0.01) serving as reliable estimators of K r and τ c during the 1–2 years following biochar addition. After biochar addition for 3 years, total organic carbon (TOC) (total effect of −0.45 and 0.10, P <0.01) emerged as a significant factor influencing K r and τ c , making TOC a potential p r edictor of K r and τ c. The results demonstrate that biochar may be an effective measure for enhancing soil resistance to erosion on the Loess Plateau, especially when applied over the long term. • 1–4 % biochar increased rill erodibility (K r) but result was oppsite for 5.5 % and 7 % additions after 1–2 years. • Biochar addition after 3 years enhanced soil erosion resistance for all rates. • Total organic carbon (TOC) significantly affected K r as biochar addition duration increased. • MWD, soil cohesion and TOC could be used to estimate K r under biochar addition. [ABSTRACT FROM AUTHOR]

Soil erosion exacerbates the loss of soil nutrients and directly affects the soil stoichiometric characteristics. However, the impacts of different erosion conditions and farmland management measures on soil nutrients and their stoichiometry remain unclear. Herein, field observations were conducted in purple-soil sloping farmland in the Three Gorges Reservoir Area, China, using the artificial shovel soil test method. The soil nutrient contents and stoichiometric characteristics of the topsoil under three management measures (no fertilization, CK; chemical fertilizer, F; biochar+chemical fertilizer, BF) and five erosion conditions (erosion thicknesses of 0, 5, 10, 15, and 20 cm) were analyzed. The SOC, TN, TP, TK, AN, AP, and AK contents of the three management measures followed overall decreasing trends with increasing erosion thickness. Under the same erosion condition, the content of nutrient elements in the three treatments followed the trends of BF > F > CK, and the soil nutrient content of the BF treatment was significantly higher than that of the CK treatment (P <0.05). With the increasing erosion thickness, soil C/N, C/P, and N/P ratios of the three treatments showed decreasing trends. The average soil C/N, C/P and N/P ratios for the three treatments were 10.55, 16.92, and 2.09, respectively, i.e., lower than the global and national averages. A lower C/N ratio indicats a faster SOM mineralization rate in the region, with the SOM cumulative rate lower than the decomposition rate. Lower C/P and N/P ratios indicated that crop growth was limited by N, resulting in a state of N deficiency and P enrichment in the soil nutrient in this region, thereby limiting soil productivity. Based on multi-attribute decision making, soil nutrient recovery index, and the characteristics of the response surface, the application of biochar+chemical fertilizer is conducive to alleviating the supply-demand contradiction between crops and soil nutrients, representing an effective way of improving soil fertility. However, further research is required to determine when the application of biochar leads to SOM accumulation that exceeds decomposition. These results provide a scientific basis for the restoration and reconstruction of soil ecosystems in sloping farmlands. • The C–N–P stoichiometric ratios decrease with the increase of erosion thickness. • Crop growth was N-limited, and the soil were in a P-rich and N-deficient state. • The soil nutrient recovery index of biochar+fertilizer treatment was the highest. • Biochar+fertilizer alleviated the supply-demand imbalance of nutrient in crop-soil. • The interaction between erosion and soil management has a synergistic effect on soil. [ABSTRACT FROM AUTHOR]