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The use of saline water under drought conditions is critical for sustainable agricultural development in arid regions. Biochar is used as a soil amendment to enhance soil properties such as water-holding capacity and the source of nutrition elements of plants. Thus, the research was carried out to assess the impact of biochar treatment on the morphological and physiological characteristics and production of Solanum lycopersicum in greenhouses exposed to drought and saline stresses. The study was structured as a three-factorial in split-split-plot design. There were 16 treatments across three variables: (i) water quality, with freshwater and saline water, with electrical conductivities of 0.9 and 2.4 dS m− 1, respectively; (ii) irrigation level, with 40%, 60%, 80%, and 100% of total evapotranspiration (ETC); (iii) and biochar application, with the addition of biochar at a 3% dosage by (w/w) (BC3%), and a control (BC0%). The findings demonstrated that salt and water deficiency hurt physiological, morphological, and yield characteristics. Conversely, the biochar addition enhanced all characteristics. Growth-related parameters, such as plant height, stem diameter, leaf area, and dry and wet weight, and leaf gas exchange attributes, such rate of transpiration and photosynthesis, conductivity, as well as leaf relative water content were decreased by drought and salt stresses, especially when the irrigation was 60% ETc or 40% ETc. The biochar addition resulted in a substantial enhancement in vegetative growth-related parameters, physiological characteristics, efficiency of water use, yield, as well as reduced proline levels. Tomato yield enhanced by 4%, 16%, 8%, and 3% when irrigation with freshwater at different levels of water deficit (100% ETc, 80% ETc, 60% ETc, and 40% ETc) than control (BC0%). Overall, the use of biochar (3%) combined with freshwater shows the potential to enhance morpho-physiological characteristics, support the development of tomato plants, and improve yield with higher WUE in semi-arid and arid areas. [ABSTRACT FROM AUTHOR]

Organic soil amendments are a sustainable option for modifying soil structure and improving plant performance in the face of abiotic stressors such as drought and soil salinity. Of these amendments, biochar and compost have the added benefits of carbon sequestration and waste recycling. Establishment studies were conducted on tall fescue (Festuca arundinacea Schreb.) (syn., Schedonorus arundinaceus (Schreb.) Dumort and Lolium arundinaceum (Scop.) Holub) to assess the potential inhibition of establishment by compost and biochar products. Both green waste and biosolid compost impaired establishment rates, while biochar did not. In the field study, the green waste treatments were slower to reach 50% coverage than the untreated control or when biochar was added to the soil, but all treatments reached 75% and final coverage at a similar rate. Field application of compost had a positive effect on final root length and volume but a negative effect on tall fescue roots in the greenhouse. The negative effect of higher salts and volatiles in the biosolids compost was reduced when biosolids and biochar were incorporated into the soil simultaneously. This work represents one of the only large-scale field studies on turfgrass establishment comparing the impact of biochar and compost products on turfgrass establishment. [ABSTRACT FROM AUTHOR]

Enhancing soil stability through the incorporation of straw and biochar is well documented. Nevertheless, the combined impact of straw, biochar, and nitrogen supplementation on soil aggregates and organic carbon still needs to be explored, with limited attention given to various sieving methods in the existing literature. Therefore, the current experiment used four sieving methods—routine wet sieving (RoutW), fast-wetting sieving (FastW), slow-wetting sieving (SlowW), and wetting–stirring sieving (WetS)—to investigate the effects of adding straw (0 or 4.5 t ha−1), biochar (from maize straw, 0 or 15 t ha−1), and N (0 or 100 kg ha−1) on soil aggregate stability and soil organic C in silt–loam soil of rainfed farmland in northwest China. The field experiment was started in 2014; soil samples were collected in 2021. The results revealed that straw returned, biochar, and N addition significantly increased soil mean weight diameter (MWD) and soil organic C (SOC). Compared to CN0 (zero-amendment) plots, straw returned with nitrogen addition (SN100) significantly increased the MWD of aggregates by 130.3% (RoutW), 121.66% (FastW), 73.94% (SlowW), and 91.78% (WetS) in the 0–30 cm soil layer. The addition of biochar and nitrogen (BN100) treatment showed the most significant effects on the relative slaking index (RSI), relative mechanical breakdown index (RMI), and SOC; compared with CN0 treatment, BN100 plots can reduce RSI and RMI by 42.90% and 54.66% and increase SOC by 53.27% for all soil layers. Therefore, adding organic materials with N can enhance the stability of soil aggregates and SOC of silt–loam soils in northwest China. Integrating biochar as an organic soil amendment in the agricultural practices of northwest China presents a multifaceted solution that addresses soil health, crop productivity, and environmental sustainability. The current study provides valuable insights that support adopting this innovative approach, paving the way for future sustainable agricultural practices that can benefit both the region and the global community. [ABSTRACT FROM AUTHOR]

Simple Summary: To find improved solutions for controlling cadmium pollution in agricultural soil, in situ field experiments were conducted to evaluate the impact of physical measures, phosphate fertilizer application, and soil conditioners on lettuce growth and cadmium absorption. The results revealed that deep plowing and soil covering significantly lowered the cadmium concentration in lettuce. While the application of phosphate fertilizer raised the cadmium concentration in lettuce, the use of diammonium phosphate and calcium magnesium phosphate fertilizer showed a positive correlation with the cadmium concentration, whereas calcium superphosphate displayed a negative correlation. Additionally, upon the application of biochar, attapulgite, and nano-hydroxyapatite, the cadmium concentration in lettuce initially increased with the rising amount of application, but subsequently decreased at higher doses. In conclusion, physical measures are evidently effective in preventing and controlling cadmium pollution. However, the application of phosphate fertilizer can exacerbate cadmium pollution in farmland soil. Soil conditioners, on the other hand, are only effective when used at higher application levels. The findings of this study are crucial for guiding practical cadmium pollution control measures in the field. This study aimed to evaluate the effects of physical measures and the applications of phosphorus fertilizer and soil conditioner on the growth of lettuce (Lactuca sativa) and its uptake of cadmium (Cd). In a solar greenhouse that contained soil enriched with cadmium (Cd) (1.75 ± 0.41 mg/kg) with lettuce used as a test plant, field experimental methods were utilized to explore the influence of physical measures, such as deep plowing and soil covering, and the applications of phosphorus fertilizer, including diammonium phosphate (DAP), calcium magnesium phosphate (CMP), and calcium superphosphate (SSP), and soil conditioners, such as biochar, attapulgite clay, and nano-hydroxyapatite, on the uptake of Cd in lettuce. The results indicated that the concentrations of Cd in the aboveground parts of lettuce were 1.49 ± 0.45, 1.26 ± 0.02, 1.00 ± 0.21, and 0.24 ± 0.13 mg/kg when the soil was plowed 30, 40, and 50 cm deep, respectively, and when the soil was covered with 15 cm, this resulted in reductions of 27.5%, 38.3%, 51.4%, and 88.4%, respectively, compared with the control treatment that entailed plowing to 15 cm. When 75, 150, and 225 kg/ha of phosphorus pentoxide (P2O5) were applied compared with the lack of application, the contents of Cd in the aboveground parts of lettuce increased by 2.0%, 54.5%, and 73.7%, respectively, when DAP was applied; by 52.5%, 48.5%, and 8.1%, respectively, when CMP was applied; and by 13.1%, 61.6%, and 90.9%, respectively, when SSP was applied. When the amounts of biochar applied were 0, 2, 4, 6, 8, 10, and 12 t/ha, the contents of Cd in the aboveground parts of lettuce were 1.36 ± 0.27, 1.47 ± 0.56, 1.80 ± 0.73, 1.96 ± 0.12, 1.89 ± 0.52, 1.44 ± 0.30, and 1.10 ± 0.27 mg/kg, respectively. Under concentrations of 0, 40, 80, 120, 160, and 200 kg/ha, the application of nano-hydroxyapatite resulted in Cd contents of 1.34 ± 0.56, 1.47 ± 0.10, 1.60 ± 0.44, 1.70 ± 0.21, 1.31 ± 0.09, and 1.51 ± 0.34 mg/kg, respectively. The concentrations of Cd in the aboveground parts of lettuce treated with attapulgite clay were 1.44 ± 0.48, 1.88 ± 0.67, 2.10 ± 0.80, 2.24 ± 0.75, 1.78 ± 0.41, and 1.88 ± 0.48 mg/kg, respectively. In summary, under the conditions in this study, deep plowing and soil covering measures can reduce the concentration of Cd in the aboveground parts of lettuce. The application of phosphorus fertilizer increased the concentration of Cd in the aboveground parts of lettuce. The application of higher amounts of DAP and SSP led to greater concentrations of Cd in the aboveground parts of lettuce. The application of higher amounts of CMP caused a lower concentration of Cd in the aboveground parts of lettuce. When biochar, attapulgite clay, and nano-hydroxyapatite were applied, the concentration of Cd in the aboveground parts of lettuce increased in parallel with the increase in the concentration of application when low amounts were applied. In contrast, when high amounts were applied, the concentration of Cd in the aboveground parts of lettuce began to decrease. [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]

Soil amendment with biochar from oil palm biomass has been found to improve the quality of the infertile weathered soils and enhance crop productivity in the humid tropics. Meanwhile, the field information on microbial responses to oil palm-derived biochar application and its residual effect in acidic tropical soils is still limited. A field study was carried out over three cropping cycles of sweet corn on a Haplic Acrisol of Peninsular Malaysia. The soil was amended once with oil palm kernel shell (OPKS) biochar before the first cropping cycle, with or without inorganic fertiliser. Soil samples were taken at each harvesting stage and analysed for soil pH, cation exchange capacity (CEC), organic C, total N, available P, microbial biomass (C (MBC), N (MBN), and P (MBP)). Microbial biomass ratios (MBC : MBN, MBC : MBP) were calculated. The total bacterial and fungal populations were quantified from soil genomic DNA, employing qPCR amplification of the 16S rDNA and ITS gene. The sole application of biochar and its combined application with fertiliser, increased soil pH, CEC, organic C and N. Coapplication of OPKS biochar and NPK fertiliser hindered N loss in the second cycle. The bacterial and fungal abundance was stimulated following biochar treatment majorly due to the elevation of soil pH and CEC. The ratio of MBC : MBN had a significant negative correlation with N, signifying that this ratio could reflect soil N content and be used as a soil fertility indicator. [ABSTRACT FROM AUTHOR]

The residual effect of compost and biochar amendment on soil properties and durum wheat response was evaluated under field conditions in a Mediterranean environment. The treatments compared in a randomized complete block experimental design with three replications were: mineral fertilizer (100 kg N ha−1), compost applied at the rate of 25 Mg ha−1, biochar applied at the rates of 10 and 30 Mg ha−1, unfertilized control. Wheat was the second crop included in a sorghum–wheat cropping system and did not receive fertilizer supply. A hierarchical statistical analysis was carried out to investigate how different treatments could impact the cropping system performance. The findings highlight the significant influence of soil properties, particularly total N, WEOC, and TOC, on wheat and protein yield. One year after the amendment and fertilizer application, compost and biochar significantly increased soil total organic carbon content. The highest soil water extractable organic carbon was found with the compost application (76.9 mg kg−1), whereas the lowest value (50 mg kg−1) was with the highest rate of biochar. Soil respiration rates and hydraulic properties were not affected by the investigated treatments. This behavior is probably related to the short experimental duration and to the silty clayey soil texture. Significant correlations were observed between bulk density and water content at pressure heads in the −20 and −100 cm range; this range accounts for the effect of soil macro and mesopores. Multiple linear regression analysis revealed strong predictive power for grain (R2_adj = 0.78; p < 0.001) and protein yield (R2_adj = 0.77; p < 0.001). The highest grain yield (3.36 Mg ha−1) was observed with compost, and the lowest (2.18 Mg ha−1) with biochar at a rate of 30 Mg ha−1. These findings lay the basis for understanding how different soil amendment management may impact soil quality and wheat performance, even in consideration of climate change. [ABSTRACT FROM AUTHOR]

Important properties of biochar as an effective soil amendment are its high water-holding capacity (WHC) and inhibition of water evaporation. However, the mechanism and the importance of biochar properties in controlling its own WHC and bound water evaporation remain little known. In this study, wheat straw and pine sawdust biochars were pyrolyzed in N2-flow, CO2-flow, and air-limitation environments at 300–750 ℃, and a series of the produced biochars' properties were characterized to explore the dominant controlling factors of their WHC and bound water evaporation. The results have shown that with the increasing contents of hydrogen, nitrogen, and oxygen as well as such ratios as H/C, and (O + N)/C, WHC of the biochars was also increasing while the evaporation of biochar-bound water was decreasing. With an increase in the other studied factors, such as carbon content, pH, and specific surface area (SSA), WHC of the biochars was decreasing, and the evaporation of biochar-bound water was increasing. That was connected with the fact that biochar-nitrogen was mainly in pyridinic and pyrrolic forms, while oxygen was in the form of C = O and C–O bonds. These forms of nitrogen and oxygen could be the receptors of hydrogen bonds to link to H2O molecules. Aliphatic hydrogen with a weak positive charge could be a donor of hydrogen bonds to link to H2O molecules. However, high carbon content, as well as high SSA, indicated more exposed aromatic carbon (hydrophobic sites) that could suppress the binding of H2O molecules. Additionally, high pH indicated that H2O molecules were dominated by OH–, which generated strong electrostatic repulsion with the negatively charged nitrogen- and oxygen-containing groups of biochar. It was also shown that the nitrogen-containing groups played a more important role (importance – 0.31) in WHC of the biochar than other parameters, including carbon, oxygen, hydrogen, ash contents, pH, SSA (importance from 0.02 to 0.09). Nitrogen, oxygen, and carbon contents had the most important influence on the evaporation of biochar-bound water in all studied factors. Furthermore, wheat straw biochar produced at low pyrolysis temperatures in N2 atmosphere (with high nitrogen and oxygen contents) had the highest WHC and the lowest evaporation of biochar-bound water. Consequently, it can be suggested that biochar rich in nitrogen can be an effective water retention agent and can improve agricultural soil moisture. Highlights: Nitrogen-containing groups (pyridinic and pyrrolic nitrogen) played a crucial role in the improvement of biochar water-holding capacity. Nitrogen- and oxygen-containing groups inhibited the evaporation of biochar-bound water. Biochar rich in nitrogen and oxygen may be an effective water retention agent to maintain soil moisture. [ABSTRACT FROM AUTHOR]

Globally, salinity is an important abiotic stress in agriculture. It induced oxidative stress and nutritional imbalance in plants, resulting in poor crop productivity. Applying silicon (Si) can improve the uptake of macronutrients. On the other hand, using biochar as a soil amendment can also decrease salinity stress due to its high porosity, cation exchange capacity, and water-holding capacity. That's why the current experiment was conducted with novelty to explore the impact of silicon nanoparticle-based biochar (Si-BC) on wheat cultivated on salt-affected soil. There were 3 levels of Si-BC, i.e., control (0), 1% Si-BC1, and 2.5% Si-BC2 applied in 3 replicates under 0 and 200 mM NaCl following a completely randomized design. Results showed that treatment 2.5% Si-BC2 performed significantly better for the enhancement in shoot and root length, shoot and root fresh weight, shoot and root dry weight, number of leaves, number of tillers, number of spikelets, spike length, spike fresh and dry weight compared to control under no stress and salinity stress (200 mM NaCl). A significant enhancement in chlorophyll a (~ 18%), chlorophyll b (~ 22%), total chlorophyll (~ 20%), carotenoid (~ 60%), relative water contents (~ 58%) also signified the effectiveness of treatment 2.5% Si-BC2 than control under 200 mM NaCl. In conclusion, treatment 2.5% Si-BC2 can potentially mitigate the salinity stress in wheat by regulating antioxidants and improving N, K concentration, and gas exchange attributes while decreasing Na and Cl concentration and electrolyte leakage. More investigations at the field level are recommended for the declaration of treatment 2.5% Si-BC2 as the best amendment for alleviating salinity stress in different crops under variable climatic conditions. [ABSTRACT FROM AUTHOR]

The land application of sewage sludge can cause different environmental problems due to the high content of potentially toxic elements (PTEs). The objective of this study was to compare the effect of urban biological sewage sludge (i.e. the waste of activated sludge process) and its derived biochar as the soil amendments on the bioavailability of PTEs and their bioaccumulation by corn (Zea mays L.) under two months of greenhouse conditions. The soil was treated by adding biochar samples at 0 (control), 1, 3, 5% w/w. The diethylenetriamine pentaacetic acid (DTPA)-extractable concentrations of PTEs including Zn, Pb, Cd, Cr, Ni, Fe, and Cu in soil and their accumulation by plant shoot and root were measured. Conversion of the biological sewage sludge into the biochar led to decrease the PTEs bioavailability and consequently decreased their contents in plant tissues. The DTPA extractable metal concentrations of produced biochar in comparison to the biological sewage sludge reduced 75% (Cd), 65% (Cr), 79% (Ni and Pb), 76% (Zn), 91% (Cu) and 88% (Fe). Therefore, the content of Ni, Fe, Zn and Cd in corn shoot was decreased 61, 32, 18 and 17% respectively in application of 5% biochar than of raw sewage sludge. Furthermore, the application of 5% biochar enhanced the physiological parameters of the plants including shoot dry weight (twice) and wet weight (2.25 times), stem diameter (1.70 times), chlorophyll content (1.03 times) in comparison to using 5% raw sewage sludge. The results of the study highlight that application of the biochar derived from urban biological sewage sludge in soil could decrease the risk of PTEs to the plant. [ABSTRACT FROM AUTHOR]

The utilization of biochar's as soil amendments for enhancing nutrient retention in subsoils present potential limitations. To address this issue, we conducted a greenhouse experiment to assess the effects of various biochar's derived from animal manures (swine manure, poultry litter, cattle manure) and plant residues (rice straw, soybean straw, corn straw) when applied to surface of an acidic soil. Our study focused on wheat crops under a no-tillage system, with a subsequent evaluation of the residual impacts on soybeans. The experimental design involved the application of biochar's at different rates i.e. 10 and 20 Mg ha−1, followed by the assessment of their influence on NPK levels, pH, and exchangeable Al in stratified soil layers (0–5, 5–10, 10–15, and 15–25 cm). Furthermore, we investigated the interplay between biochar doses and the application of nitrogen (N) in the top 5 cm of soil, specifically examining NO 3 - , NH 4 + , P and K levels. Our findings revealed that in the top 5 cm of soil, biochar doses and N application significantly affected NO 3 - , NH 4 + , P and K concentrations. However, in deeper soil layers, no significant differences were observed among biochar doses with or without N application. Interestingly, K levels were impacted throughout all soil depths, regardless of the presence or absence of N application. Moreover, biochar application up to a 5 cm depth induced favorable changes in soil pH and reduced exchangeable Al. In contrast, deeper layers experienced a decrease in soil pH and an increase in exchangeable Al following biochar treatment. In conclusion, our study demonstrates that biochar's can effectively retain NPK nutrients, enhance soil pH, and decrease exchangeable Al, independent of the type and dosage of application under a no-tillage system. Nonetheless, the efficacy of biochar amendments may vary with soil depth and type of nutrient, warranting careful consideration for maximizing their benefits in sustainable agricultural practices. [ABSTRACT FROM AUTHOR]

Biochar and plant growth-promoting rhizobacteria (PGPR) are widely used as an amendment for soil physicochemical properties and soil bacterial community diversity. In Guangxi, China, we carried out a study to determine how PGPR and biochar influence the soil's environmental stability in an Eucalypt plantation. We applied biochar and PGPR in a contrasting application manner to an acidic red loam soil. Thus, three treatments were set up as 5 × 1010 CFU·mL−1 PGPR-only (MB0), 20 t·hm−2 biochar-only (B20), and co-application of 20 t·hm−2 biochar and 5 × 1010 CFU·mL−1 PGPR (MB20), as well as no biochar and no PGPR (M0B0). Our results indicated that MB20 significantly decreased the soil total nitrogen (TN) and increased the soil total phosphorus (Soil TP), soil ammonium nitrogen (NH4+), and soil water content (SWC) when compared with the control. The MB20 also significantly increased the Simpson, ACE, and Chao indices of the soil bacterial community's diversity relative to the control. We also observed a significant effect of the Soil TN on both the bacterial community and the functional diversity in soil. These findings may indicate that assessing the soil N status is expected to be an essential indicator of the soil microenvironment's response to biochar and PGPR applications. [ABSTRACT FROM AUTHOR]

Biochar is produced by burning biomass under oxygen‐limited conditions, and it has been widely used as a soil amendment to improve soil functions such as nutrient retention. However, whether the impact of biochar application on soil nitrogen (N) transformation and N2O emission varies with the pyrolysis temperature remains unclear, especially in different forest types in subtropical regions. In this study, a 60‐day laboratory incubation experiment was conducted to evaluate the impact of biochar with different pyrolysis temperatures (300°C [BC300], 500°C [BC500], and 800°C [BC800]) on net N transformation rates and N2O emission in soils collected from Castanopsis kawakamii dominated natural forest (NF) and Chinese fir (Cunninghamia lanceolate, CF) plantation in subtropical China. The results showed that the application of biochar significantly increased soil ammonium (NH4+) content (p < 0.001) but reduced nitrate (NO3−) content (p < 0.001) compared with the control. The soil NH4+ content of the BC800 treatment was significantly higher than that of other treatments (p < 0.001). Biochar application significantly reduced soil net N mineralization (NRmin) and nitrification (NRnit) rate (p < 0.001), but increased net ammonification (NRamm) rate (p < 0.001). The application of biochar led to a remarkable decrease in cumulative N2O emission compared to the control (p < 0.001). In particular, soils treated with high‐temperature biochar emitted significantly lower N2O compared to other treatments (p < 0.001). The partial least squares path model demonstrated that biochar influenced N2O emission through a direct effect in NF soil and an indirect effect in CF soil. This study highlights the distinct role of biochar, particularly that produced under high pyrolysis temperatures as a soil amendment to mitigate N2O emission and promote N retention in both subtropical natural and planted forests. [ABSTRACT FROM AUTHOR]

Forest management in drained forested peatlands can negatively affect water quality due to the increase in exports of organic matter and nutrients. Therefore, new methods to alleviate this impact are needed. In laboratory conditions, biochar has been shown to be a strong sorbent of organic and inorganic nutrients due to its high surface area and ion‐exchange capacity. However, evidence of the adsorption capacity in field conditions is lacking. Here, we studied the water purification performance of two different biochar feedstocks (wood‐ and garden residue‐based) in a 10‐day laboratory experiment where we incubated biochar with runoff water collected from drainage ditches in clear‐cut peatland forests. We measured changes in pH and concentrations of inorganic phosphorus (PO4), total dissolved nitrogen (TDN), and dissolved organic carbon (DOC). The biochar with the best adsorbent capacity in the laboratory experiment was then tested in field conditions in a replicated catchment‐scale experiment, where both clear‐cutting and ditch cleaning were performed. We determined the nutrient concentration of water at the inlet and outlet of biochar filters placed in outflow ditches of four catchments. We found that under laboratory conditions wood‐based biochar efficiently adsorbed TDN and DOC, however, it released PO4. Furthermore, we found that the biochar filters reduced TDN and DOC concentration in field conditions. However, the percentage decrease in concentration was dependent on the initial concentrations of nutrients in the water and could be considered low. Moreover, we found that the biochar in the filters increased in TN content over the course of the experiment. This suggests that a wood‐based biochar filter has the potential to be a water protection tool for reducing the export of nutrients from catchments with high nutrient concentration. And that the biochar from the ditches could be applied back to the regenerating forest catchment as a potential soil amendment, closing the nutrient cycle. [ABSTRACT FROM AUTHOR]

The soil in a lead–zinc mining area, contaminated with heavy metals like cadmium (Cd) and lead (Pb), poses a risk to crops such as maize. Experiments using biochar and sepiolite as soil ameliorants in potted maize showed these substances can mitigate heavy metal contamination. Biochar increased potassium and phosphorus in the soil and maize, while sepiolite significantly boosted overground phosphorus by 73.2%. Both ameliorants transformed Cd and Pb into a more stable state in the soil, reducing their accumulation in maize, especially with biochar, which effectively inhibited metal migration during leaching events. This study provided insights for further improvement of soil amendments and multi-factor application experiments. [ABSTRACT FROM AUTHOR]

Soil degradation due to loss of soil organic carbon is a serious concern in semiarid agroecosystems. Biochar and other organic char products have long been known to increase soil organic carbon. In this study, three-year field observations were carried out on use of coal char (CC) and biochar (BC) as soil amendments in unirrigated semiarid rangeland soil. Coal was pyrolyzed at three different temperatures of 650, 750, and 800 °C to form CC650, CC750, and CC800, respectively, and BC was obtained from a local commercial producer. Manure, CC, and BC were incorporated in soil at 10% (v/v). Analyses of plant growth (aboveground biomass) and soil properties were performed and compared with the control treatment without char. In all three years, CC applied with manure (CC650M) produced significantly greater grass biomass, by 95, 42, 101%, and BC applied with manure (BCM) increased grass biomass by 89, 39, 52% in 2018, 2019, and 2020, than the controls in the respective years. Soil tests a year after application of char indicated significantly increased soil organic matter (OM) with CC and BC treatments (1.60–2.93%) compared with the control (1.37%). However, further detailed studies are required to investigate CC and BC interactions with soil in unirrigated semiarid rangelands. [ABSTRACT FROM AUTHOR]

In this study, biochar (BC) and hydrochar (HC) composites were synthesized with natural kaolinite clay and their properties, stability, carbon (C) sequestration potential, polycyclic aromatic hydrocarbons (PAHs) toxicity, and impacts on maize germination and growth were explored. Conocarpus waste was pretreated with 0%, 10%, and 20% kaolinite and pyrolyzed to produce BCs (BC, BCK10, and BCK20, respectively), while hydrothermalized to produce HCs (HC, HCK10, and HCK20, respectively). The synthesized materials were characterized using X-ray diffraction, scanning electron microscope analyses, Fourier transform infrared, thermogravimetric analysis, surface area, proximate analyses, and chemical analysis to investigate the distinction in physiochemical and structural characteristics. The BCs showed higher C contents (85.73–92.50%) as compared to HCs (58.81–61.11%). The BCs demonstrated a higher thermal stability, aromaticity, and C sequestration potential than HCs. Kaolinite enriched-BCs showed the highest cation exchange capacity than pristine BC (34.97% higher in BCK10 and 38.04% higher in BCK20 than pristine BC), while surface area was the highest in kaolinite composited HCs (202.8% higher in HCK10 and 190.2% higher in HCK20 than pristine HC). The recalcitrance index (R50) speculated a higher recalcitrance for BC, BCK10, and BCK20 (R50 > 0.7), minimal degradability for HCK10 and HCK20 (0.5 < R50 < 0.7), and higher degradability for biomass and HC (R50 < 0.5). Overall, increasing the kaolinite enrichment percentage significantly enhanced the thermal stability and C sequestration potential of charred materials, which may be attributed to changes in the structural arrangements. The ∑ total PAHs concentration in the synthesized materials were below the USEPA's suggested limits, indicating their safe use as soil amendments. Germination indices reflected positive impacts of synthesized charred materials on maize germination and growth. Therefore, we propose that kaolinite-composited BCs and HCs could be considered as efficient and cost-effective soil amendments for improving plant growth. [ABSTRACT FROM AUTHOR]

The composition of microbial communities and the functioning of ecosystems are greatly influenced by the nutrient inputs. Despite this fact, our knowledge regarding the impact of phosphorus (P) inputs on soil P availability and microbial community structures in subtropical acidic soils remains limited. We hypothesized that diverse P inputs, incubation temperatures, and soil types could significantly alter soil P availability and microbial communities. To address this gap, we conducted a laboratory incubation experiment, investigating the effects of biochar and inorganic P amendments on soil available P, soil pH, acid phosphatase enzymes, and bacterial abundance. We employed two different incubation temperatures (15 °C and 25 °C) using acidic paddy soil and red soil from the subtropical Southern China region. Our results indicate a notable increase in soil pH, reaching 37% and 39% at 15 °C and 40% and 40.6% at 25 °C, respectively, following the application of biochar and inorganic P amendments in paddy soil. In the case of red soil, we observed pH increases of 41% and 43% at 15 °C and 44% and 45% at 25 °C after the application of biochar and inorganic P amendment, respectively. The addition of inorganic P amendment resulted in the highest available P contents in paddy soil, reaching 111.47 mg/kg at 15 °C and 100.17 mg/kg at 25 °C, respectively. However, Proteobacteria decreased after inorganic P addition, which showed that P might not be the only limiting nutrient for various bacterial communities. Bacterial diversity and richness indices were found to be higher after biochar application in both soils. Gemmatimonadetes, Acidobacteria, and Actinobacteria were found to be strongly influenced by incubation temperatures, whereas most of the top abundant bacterial phyla, such as Gemmatimonadetes, Actinobacteria, Chloroflexi, Acidobacteria, Planctomycetes, Firmicutes, Patescibacteria, and Bacteroidetes, were highly dependent on soil type. At the genus level, various important P solubilizing genera (Pseudomonas, Bradyrhizobium, Streptomyces jietaisiensis, Massilia) significantly increased after biochar and inorganic P addition in both soils. The correlation analysis proved that P-solubilizing genera were significantly associated with changes in soil pH, as well as soil available P after biochar and inorganic P addition. Conclusively, in a short-term incubation experiment, inorganic P amendment greatly increased the soil pH and available phosphorus contents compared to biochar and control treatments; however, the microbial community was observed to be strongly associated with biochar application, soil type, and incubation temperature. [ABSTRACT FROM AUTHOR]

Simple Summary: Solenopsis invicta (Hymenoptera: Formicidae), also known as the red imported fire ant, is a social insect and a worldwide invasive pest. Biochar is a widely used soil amendment. In this work, we investigated the effects of varying soil biochar levels on irritability and contact toxicity as well as the behavioral and physiological changes in red fire ant behavior. High doses of biochar were toxic and repulsive to red fire ants, impairing their ability to walk, grasp, attack, and gather while also causing an increase in the activity of enzymes associated with oxidative stress. This study supports the prudent utilization of biochar as well as the prevention and management of red fire ants. Solenopsis invicta, often known as the red imported fire ants (RIFAs), is a well-known global invasive ant species that can be found in agricultural, urban, and natural environments worldwide. Simultaneously, it also inhabits the soil. Biochar is generated by the pyrolysis of organic matter under high-temperature anoxic environments and widely used in agricultural ecosystems and soil amendment. However, to date, it remains unknown as to whether soil application of biochar has a negative effect on RIFAs. In our study, we investigated the toxicity and irritability effects of different amounts of biochar (0%, 1%, 2%, 5%, 10%, and 20%) introduced into the soil on red fire ants; upon comparison with the control soil (0% biochar), the application of 1%, 2%, and 5% biochar did not result in significantly different results. But the utilization of biochar at a concentration over 10% effectively repelled the RIFAs, resulting in their departure from the treated soils. High doses of biochar were able to cause death of red fire ants; the mortality rate of red fire ants reached 55.56% after 11 days of 20% biochar treatment. We also evaluated the effects of biochar on four behaviors of red fire ants, namely aggregation, walking, grasping, and attacking; 20% of the biochar treatment group reduced aggregation by 64.22% and this value was 55.22%, 68.44%, and 62.36% for walking, grasping, and attacking. Finally, we measured the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) enzyme activity and malondialdehyde (MDA) content in red fire ants; the results showed that the activities of the three enzymes increased with the increase in biochar addition, which indicated that a high dose of biochar induced oxidative stress in red fire ants. Our results indicate that biochar has the potential to cause toxicity and repel red imported fire ants (RIFAs) in a manner that is dependent on the concentration. We propose that biochar could be utilized in the control and manufacturing of baits for red fire ant management. This work establishes a foundation for the prevention and management of red fire ants and the logical utilization of biochar. [ABSTRACT FROM AUTHOR]

The biochar amendment plays a vital role in maintaining soil health largely due to its effects on soil microbial communities. However, individual cases and the variability in biochar properties are not sufficient to draw universal conclusions. The present study aimed to reveal how the biochar application affects soil microbial communities. Metadata of 525 ITS and 1288 16S rRNA sequencing samples from previous studies were reanalyzed and machine learning models were applied to explore the dynamics of soil microbial communities under biochar amendment. The results showed that biochar considerably changed the soil bacterial and fungal community composition and enhanced the relative abundances of Acidobacteriota, Firmicutes, Basidiomycota, and Mortierellomycota. Biochar enhanced the robustness of the soil microbial community but decreased the interactions between fungi and bacteria. The random forest model combined with tenfold cross-validation were used to predict biomarkers of biochar response, indicating that potentially beneficial microbes, such as Gemmatimonadetes, Microtrichales, Candidatus_Kaiserbacteria, and Pyrinomonadales, were enriched in the soil with biochar amendment, which promoted plant growth and soil nutrient cycling. In addition, the biochar amendment enhanced the ability of bacteria to biosynthesize and led to an increase in fungal nutrient patterns, resulting in an increase in the abundance and diversity of saprophytic fungi that enhance soil nutrient cycling. The machine learning model more accurately revealed how biochar affected soil microbial community than previous independent studies. Our study provides a basis for guiding the reasonable use of biochar in agricultural soil and minimizing its negative effects on soil microecosystem. Highlights: Biochar considerably affected the soil community composition of bacteria and fungi. 14 bacterial orders and 7 fungal families were enriched in biochar-amended soils. Biochar enhanced positive interactions and the stability of soil community. Biochar led to an increase in soil fungal nutrient patterns. [ABSTRACT FROM AUTHOR]

Applying biochar amendment and manure in tea plantation ecosystems can diminish soil acidification and degradation. However, the impact of these practices on soil respiration and associated mechanisms remains unclear. In this study, we combined a two-year field experiment and laboratory analyses based on soil properties, functional genes, and microbial co-occurrence networks to explore the determinants of soil respiration intensity in a subtropical tea plantation with biochar amendment and manure application. The results showed that the effect of biochar amendment on soil respiration was unconspicuous. Although biochar amendment increased bacterial richness and Shannon index, biochar amendment did not alter the abundance of species associated with C-cycling functional genes. Besides directly adding recalcitrant C to the soil, biochar also indirectly enhanced C sequestration by weakly increasing soil carbon dioxide (CO2) emissions. However, replacing mineral fertilizer with manure significantly stimulated soil respiration in the tea plantation, resulting in a 36% increase in CO2 emissions over two years. The increase in CO2 emissions under the manure treatment was mainly attributed to the increased soil labile C pool, the activity of hydrolytic enzymes (e.g., cellobiohydrolase and acetylglucosaminidase), and the relative abundance of functional genes associated with the C-cycle. This may also be related to the application of manure that increased the abundance of Gemmatimonadetes and altered ecological clusters in bacterial co-occurrence networks. Our correlation network analysis suggested that Gemmatimonadetes might be the potential hosts for C-cycling genes due to their strong positive correlation with the abundance of C-cycling genes. Overall, these findings provide new insights into soil respiration under biochar amendment and manure application in tea plantations and broaden the options for carbon sequestration in soils. Highlights: Manure application rather than biochar amendment increased acidic soil respiration. Biochar application promoted soil C sequestration in the tea plantation. Manure application stimulated CO2 emissions by altering ecological clusters' abundance. Gemmatimonadetes might be the dominant hosts for C-cycling genes. [ABSTRACT FROM AUTHOR]

Biochar soil amendments, along with non-tillage agriculture, are often proposed as a strategy for carbon sequestration. It is still questionable how the quality of biochar might influence the priming effect on soil organic matter and whether the addition of unprocessed organic amendments will affect biochar stability. In the study, six different biochars and three exogenous organic matter sources were added to two distinct arable soils. CO2 emission was monitored for 100 days of incubation and CO2 flux was estimated. Results showed that biochar increased soil CO2 fluxes. The highest peaks, up to 162 µg C-CO2 h−1 100 g−1, were recorded in treatments with food waste biochars, suggesting that they serve as a source of easily available carbon to soil microbes. Co-application of raw organic materials (manure and fresh clover biomass) enhanced CO2 emission and carbon losses, especially in sandy soil, where 0.85–1.1% of total carbon was lost in the short-term experiment. Biochar properties and content of labile C can stimulate CO2 emission; however, in a long-term period, this contribution is negligible. The findings of our study showed that more attention should be paid to priming effects caused by the addition of exogenous organic matter when applied to biochar-amended soils. [ABSTRACT FROM AUTHOR]

With the global population continuing to increase, the demand for food and energy has escalated, resulting in severe environmental pressures. Traditional methods of food and energy production have left a significant footprint on the environment, primarily due to the emission of greenhouse gases and a notable surge in waste production. Nevertheless, scientists have recently focused on developing sustainable solutions by managing biomass waste and converting it into useful products. Various biomass conversion technologies, including pyrolysis, gasification, and fermentation, have emerged to transform waste materials into valuable commodities like biofuels, fertilizers, and chemicals. These technologies present an alternative to conventional energy production methods and decrease reliance on non-renewable resources. Furthermore, the by-products generated through biomass conversion, such as biochar, possess utility as valuable soil amendments. This review emphasizes the potential of biomass conversion technologies in providing sustainable solutions for waste management, food and energy production, and reducing negative environmental impacts while providing valuable by-products for agricultural use. The focus is on Lebanon, which is facing a waste and energy crisis, with an aim to encourage and promote sustainable practices by highlighting different green waste management technologies. Focusing on the application of biochar in soil, our goal is to provide cost-effective and eco-friendly solutions to various agricultural and environmental challenges in Lebanon. This includes using biochar from biomass waste as a soil amendment to boost crop yields, remediate soil pollution, reduce soil drought stress, and address other related issues. [ABSTRACT FROM AUTHOR]

Biochar has been widely recommended as an effective soil amendment for reducing nitrous oxide (N2O) emissions and nitrogen (N) leaching. However, the effects of biochar application to Lei bamboo plantations on soil N2O emissions and N leaching remain unclear. These effects on soil N2O emissions and N leaching were investigated in the present study using five treatments applied with the same amount of N: rice husk at 10 t ha−1 (10H) and 30 t ha−1 (30H), biochar at 10 t ha−1 (10B) and 30 t ha−1 (30B), and no additions (control, CK). Both the 10H and 30H treatments significantly increased cumulative N2O emissions compared to the CK treatment, with an increment of 0.78 and 2.20 kg N ha−1, respectively. The 30B treatment significantly reduced cumulative N2O emissions by 0.90 kg N ha−1, whereas the 10B treatment had no significant effect. The reduction in N2O emissions following the high-rate biochar addition was probably due to the increased pH and the total abundance of nosZ I and nosZ II genes. The 30H treatment significantly increased nitrate N (NO3−–N) and dissolved organic N (DON) leaching by 38% and 170% respectively compared to the CK treatment, and had the largest N loss via N2O emissions and N leaching, while the 30B treatment had the lowest N loss. Partial least squares path modeling revealed that soil chemical properties [ammonium nitrogen (NH4+–N), NO3−–N, DON, dissolved organic C (DOC), total N (TN), soil organic C (SOC), and pH] dominantly affected soil N2O emissions, while the total abundance of denitrifying genes (nirS, nirK, nosZ I, and nosZ II) were the key factors involved in reducing NO3−–N leaching. There was a strong positive correlation between cumulative N2O emissions and N leaching loss, which may be related to excessive N surplus in the soil. Our results suggest that the replacement of rice husk by its biochar at a high-rate would reduce the risk of N2O emissions and N leaching loss effectively from Lei bamboo forests in subtropical China. [ABSTRACT FROM AUTHOR]

This study explores the suitability of different biomass feedstocks for biochar production and their effects on soil health and crop yield. Two planting seasons were conducted, involving cucumber as the test crop and eleven treatments combining biochar and poultry manure. Soil analysis revealed initial soil conditions with high sand content and low pH. Poultry manure and biochar exhibited pH, organic carbon, and nutrient level variations. Significant differences in cucumber growth and yield were observed, with the longest vine length in plots treated with palm kernel husk biochar and poultry manure. Residual effects in the second planting season displayed similar trends. Soil pH, organic carbon, and total nitrogen remained consistent between seasons, while available phosphorus increased significantly in plots amended with goat manure biochar and poultry manure. Calcium, magnesium, potassium, and sodium contents also varied. Fruit length, weight, and yield were significantly improved by biochar treatments, with the combination of palm kernel husk biochar and poultry manure yielding the highest fruit weight. Correlation and structural equation analyses (p < 0.05) highlighted the relationships between plant characteristics, soil properties, and fruit indices, emphasizing the importance of nitrogen and phosphorus in supporting fruit development. The study suggests that biochar application enhances soil nutrients, crop growth, and fruit yields while reducing reliance on chemical fertilizers. It recommends considering biochar for land reclamation and as an alternative to traditional fertilizers, supported by appropriate regulations. [ABSTRACT FROM AUTHOR]

Drought stress (DS) is one of the most destructive abiotic stresses that negatively affects plant growth, and yield. The intensity of DS is continuously increasing due rapid of water sources, less rainfall, and an increase in global warming. The world's population is increasing at an alarming rate which needs a substantial increase in crop production to meet global food needs. Therefore, in this context, we must have to increase crop production in the scenarios of rapid climate change and increasing intensity of abiotic stresses. Globally, different measures are used to mitigate the adverse impacts of DS, recently biochar (BC) has emerged as an excellent soil amendment to mitigate the toxic effects of DS and improve crop production. The application maintains membrane integrity, plant water relations, nutrient homeostasis, photosynthetic performance, hormonal balance and osmolytes accumulation, and gene expression thereby improving plant performance under DS. Moreover, BC application under DS also improves soil organic matter, water holding capacity, soil structure stability, and activity of beneficial microbes which can improve the plant performance under DS. In the present review different mechanisms through which BC mitigates the adverse impacts of DS on plants are discussed. This review provides new suggestions on the role of BC in mitigating the adverse impacts of DS. [ABSTRACT FROM AUTHOR]

Two of the most significant issues confronting arid and semi-arid countries are soil degradation and the need to reclaim sandy soils and improve their properties to enhance the agricultural area and ensure food security. Many attempts to improve sandy soil properties have been attempted using soil amendments, but further research is needed to explore the combined impact of cost-effective amendments. To that purpose, we investigated the impact of various soil amendments, including single and combination applications of synthetic Super Absorbent Polymer (SAP), compost, and biochar, on sandy soil physiochemical characteristics and bean (Vicia faba L.) production and quality throughout three growing seasons. In a randomized complete block design with three replicates per treatment, different treatments such as control (without application), lower dose of SAP (SAP1), higher dose of SAP (SAP2), biochar, compost, SAP1 plus biochar, SAP1 plus compost, SAP2 plus biochar, SAP2 plus compost, and biochar plus compost were used. The combined treatments, such as SAP2 plus biochar (T8), SAP2 plus compost (T9), and biochar plus compost (T10), improved soil physiochemical characteristics and crop production significantly. Application of T10 decreased soil bulk density by 15%, 17%, and 13% while increasing soil available water by 10%, 6%, and 3% over the first, second, and third growing seasons, respectively, compared to untreated soil (T1). The application of treatment (T9) surpassed other treatments in terms of yield, quality, and economic return, significantly increasing the seed yield by 24%, 26%, and 27% for the first, second, and third season compared with untreated soil. The higher rate of polymer combined with compost could be considered a cost-effective soil amendment to improve sandy soil productivity in arid and semi-arid regions. [ABSTRACT FROM AUTHOR]

Biochar is an effective soil amendment with capabilities of boosting carbon sequestration and enhancing soil fertility, thus enhancing plant growth and productivity. While numerous studies have documented the positive effects of biochar on improving soil properties, a number of studies have reported conflicting results. Therefore, the current study was conducted to evaluate the impact of Prosopis juliflora biochar (0, 2.5, 5.0, and 7.5 t ha−1) on soil biochemical properties in Coastal Kenya to ascertain biochar's potential for soil fertility improvement. A randomized complete block design was used for setting up the experiment with three replicates, while Casuarina equisetifolia L. was planted as the test crop. Soil sampling for nutrient analysis was conducted quarterly for 12 months to assess nutrient dynamics under different biochar rates in the current study. Compared to soil untreated with Prosopis juliflora biochar, the results showed that there was a significant increase in soil pH by 21% following biochar utilization at the rate of 7.5 t ha−1. Total nitrogen was increased by 32% after the biochar application, whereas the total organic carbon was increased by four folds in comparison to biochar-untreated soil. Available phosphorus was increased by 264% following biochar application in comparison to the control treatment. In addition, the application of biochar resulted in an increment in the soil exchangeable cations (Ca2+, K+, Mg2+) across the assessment periods. Soil cation exchange capacity (CEC), bacteria and fungi were enhanced by 95, 33 and 48%, respectively, following biochar application at 7.5 t ha−1 in comparison to untreated soil. In conclusion, these results strongly suggest improvement of soil biochemical properties following Prosopis juliflora biochar application, thus providing potential for soil fertility improvement in regions such as the one in the study. [ABSTRACT FROM AUTHOR]

Biochar has been considered an effective approach as soil amendment for decreasing incidences of disease and regulating microbial populations in continuous-cropping soil. Although researches have extensively focused on changes of soil microbes and unbalance of nutrition in continuous-cropping soil, the relationship between soil properties and pathogens by biochar application remains poorly understood. In this study, we applied ITS ribosomal RNA gene profiling to analyze tobacco root microbiota of biochar and non-biochar treatment in a 3-year continuous-cropping tobacco field, comparing firstly planting tobacco as control. We found that biochar application decreased the relative abundance of the soil fungal pathogens (Ceratobasidium and Monosporascus), which are the prime pathogens of tobacco root rot in continuous-cropping soil. Using RDA, co-occurrence and PLS-PM approaches, we provided evidence that there was a negative correlation between fungal genera (especially for Ceratobasidium and Monosporascus) and soil polyphenol oxidase (PPO) activity (R2incidence rate = − 0.930, R2disease index = − 0.905, both p < 0.001). The PPO was up-regulated by different biochar treatment intensities. Together, we demonstrated that biochar in continuous-cropping soil regulated the soil PPO activity to suppress pathogens, and further decrease incidence of root rot. Notably, biochar application forward continuous cropping was more effective for the continuous-cropping soil improvement than the other treatments. The data should help in appropriate timing of biochar application for alleviating continuous-cropping obstacle. Highlights: Biochar significantly decreased the incidence rate of tobacco root rot to alleviate the continuous-cropping obstacle, especially biochar application forward the continuous-cropping. Biochar directly decreased the relative abundance of fungal pathogens such as Ceratobasidium and Monosporascus. Biochar increased polyphenol oxidase activity to suppress the fungal pathogens. [ABSTRACT FROM AUTHOR]

Drought is a major stressor of tree seedlings regarding both natural and artificial regeneration, especially in excessively drained, sandy outwash soils. While climate change is expected to cause an increase in the total annual precipitation in the Upper Midwest, USA, the timing of the precipitation is predicted to result in longer periods of drought during the growing season. Biochar, a material created through the pyrolysis of organic matter, such as wood waste, has been proposed as a soil amendment that may increase the water holding capacity of a soil. Biochar has mostly been studied in agricultural settings, and less is known about the impact of biochar on forest soils and tree seedlings. We used a greenhouse experiment to test the ability of biochar to improve the drought tolerance of jack pine (Pinus banksiana) seedlings via increased soil water holding capacity. The seedlings were planted in sandy soil treated with three levels of biochar (none, 3% by weight, and 6% by weight) in two experiments, one manipulating the timing of drought onset and the other controlling the amount of water that seedlings received. Our results showed no significant effects of biochar on seedling survival, growth, or physiology under drought conditions. While this outcome did not support the hypothesis that biochar would increase seedling performance, the biochar amendments did not negatively affect seedlings, indicating that biochar may be added to soil for carbon storage without having negative short-term impacts on tree seedlings. [ABSTRACT FROM AUTHOR]

The use of inorganic nitrogen (N) fertilizers has increased drastically to meet the food requirements of the world's growing population. However, the excessive use of chemical nitrogen fertilizer has caused a series of soil and environmental problems, such as soil hardening, lower nitrogen use efficiency (NUE), nitrate pollution of water sources, nitrous oxide emissions, etc. In this review, we aimed to elaborate and discuss the role of engineered biochar in inducing the stability of water-stable macroaggregates, improving inorganic N transformation, and utilization efficiency to address the current uncertainties of nitrogen loss and maintaining soil and water quality. Firstly, we elucidated the characteristics of engineered biochar in improving biochar quality to work as a multifunctional player in the ecosystem and promote resource utilization, soil conservation, and ecosystem preservation. Secondly, we discussed how the engineered biochar modulates the stability of water-stable macroaggregates and soil inorganic nitrogen transformation to enhance plant response under various toxic or deficient nitrogen conditions in the soil. Thirdly, the role of engineered biochar in biological nitrogen fixation, mediating nirK, nirS, and nosZ genes to promote the conversion of N2O to N2, and decreasing denitrification and N2O emission was reviewed. Altogether, we suggest that engineered biochar amendment to soil can regulate soil water-stable macroaggregates, reduce N input, improve nitrogen metabolism, and finally, NUE and crop growth. To the best of our knowledge, this is the first time to evaluate the combined interactions of "engineered biochar × soil × NUE × crop growth," providing advantages over the increasing N and water utilization and crop productivity separately with the aim of enhancing the stability of water-stable macroaggregates and NUE together on a sustainable basis. Highlights: Excessive application of nitrogen (N) chemical fertilizers causes N loss and lower nitrogen use efficiency. Engineered biochar can build micro and macro soil structures and induce the stability of water-stable macroaggregates. Engineered biochar can improve biological nitrogen fixation, promote the conversion of N2O to N2, and decrease denitrification and N2O emissions. Engineered biochar compensates for high and low N stress by regulating N metabolism, transformation, and remobilization in plants. Engineered biochar improves NUE by reducing N input and denitrification and enhancing soil water-stable macroaggregates and N transformation. [ABSTRACT FROM AUTHOR]

Manure, a globally used soil amendment, can contribute to excessive N and P runoff, leading to water pollution. Biochar (BC) shows promise in mitigating nutrient loss by retaining soil nutrients. However, there is limited research exploring the combined effects of tillage practices, biochar, manure, forage crops, and soil types on soil nutrient characteristics in a single field study. Our objectives are to determine if, in North Central Texas, differing soil types, soil amendments, forage crops, and tillage practices affect soil nutrients when applied short term, and whether correlations exist among soil nutrient characteristics as affected by soil amendments, tillage practices, and the presence of forage crops. The study encompasses three field sites with five factors, including soil types, manure rates, biochar rates, tillage practices, and forage crop types. Soil samples were assayed for pH, electrical conductivity (EC), macronutrients, and micronutrients. Data analyses involved variance analysis, Fisher's tests, and Pearson's correlations using R in Rstudio (the IDE). Microplots treated with manure (average 2.16 ppm) retained 60% greater average nitrate levels at the end of the growing season than those treated with a synthetic fertilizer (average 1.35 ppm) (p ≤ 0.05). Moderate and strong correlations were observed between EC and S (r (106) = 0.43, p < 0.001 in loamy sand soil; r (106) = 0.80, p < 0.001 in clay loam soil) and between nitrate and Zn, (r (106) = 0.36, p < 0.001 in loamy sand soil; r (106) = 0.44, p < 0.001 in sandy loam soil) across different soil types. Soil type (texture) emerged as the primary influencing factor on plant-available soil nutrients and characteristics, followed by manure application and tillage practices. The impact of BC and forage crop type varied depending on other experimental factors. Understanding the influence of soil type, amendment application, and tillage on soil nutrient characteristics can guide sustainable forage production practices and soil nutrient management strategies. [ABSTRACT FROM AUTHOR]

Global population is increasing massively and so is the demand for food. To meet the requirements, crops are being grown and harvested by using modern technologies. Also, food crops are at risk of some abiotic and biotic factors mainly pathogens (soil or airborne). To boost the production of food crops and to reduce the damage caused by biotic factors the farmer community increases the use of chemical fertilizers, insecticides, and pesticides. However, these are effective to overcome the problems but also make the pathogens resistant, affecting food quality and polluting the environment. To minimize the pathogenic attack and enhance the crop yield there is a need of adapting an ecofriendly way. Soil organic amendments are the best preventive practice for the suppression of soil-borne pathogens. Improving the soil’s physical, chemical, and microbial characteristics. Some organic amendments enhance the soil particles, increase pore size, and decrease soil bulk density which influences a positive effect on soil aeration and structure. Different types of organic amendments such as biochar, animal manure, green manure, and compost are reported to be effective against diseases caused by different pathogens and enhance plant nutrient uptake ability, and improve soil health. This current review focuses on the use of different soil organic amendments and their capability for suppressing plant disease caused by soil-borne pathogens in a natural and eco-friendly manner. [ABSTRACT FROM AUTHOR]

Biochar and manure can be used for sustainable land management. However, little is known about how soil amendments might affect surface and belowground microbial processes and subsequent wood decomposition. In a split‐split‐split plot design, we amended soil with two rates of manure (whole plot; 0 and 9 Mg ha−1) and biochar (split plot; 0 and 10 Mg ha−1). Wood stakes of three species (hybrid poplar, triploid Populus tomentosa Carr.; aspen, Populus tremuloides Michx.; and pine, Pinus taeda L.) were placed in two positions (horizontally on the soil surface, and inserted vertically in the mineral soil), which served as a substrate for fungal growth. In 3 years, the decomposition rate (density loss), moisture content, and fungal community (via high‐throughput sequencing methods) of stakes were evaluated. Results indicated that biochar and/or manure increased the wood stake decomposition rates, moisture content, and operational taxonomic unit abundance. However, the richness and diversity of fungi were dependent on wood stake position (surface > mineral), species (pine > the two Populus), and sample dates. This study highlights that soil amendment with biochar and/or manure can alter the fungal community, which in turn can enhance an important soil process (i.e., decomposition). [ABSTRACT FROM AUTHOR]

Plant-biochar interaction has been recognized to affect the hydraulic properties of landfill cover soils, while its influence on landfill gas emission is rarely studied. This study investigated the coupled effects of biochar and vegetation on gas permeability and emission in unsaturated landfill cover through an integrated theoretical modelling and laboratory investigation. First, a gas permeability model was developed for vegetated coarse-grained soils with biochar addition. Then, a well-instrumented laboratory column test and two tests from the literature, considering bare, grass, biochar and grass + biochar conditions, were used for model validation. Finally, a numerical parametric study was conducted to investigate the influence of root growth and drought conditions on the gas emission rate. Results showed that the developed model can satisfactorily capture the gas permeability of unsaturated soils at various degrees of saturation. The lowest water retention capacity, the highest gas permeability and gas emission rate after 24 months of growth were observed in the grassed column. However, adding biochar in vegetated soils can maximize the water retention capacity and decrease the gas permeability, resulting in the lowest gas emission rate. The measured gas emission rates for the four cases meet the recommended value by the design guideline. The parametric study showed that the increased root depth from 0.2 m to 0.4 m improved the gas emission rate by 170% in the grass case but decreased by 97% in the grass + biochar case. Under the severe drought condition with soil suction around 500 kPa, the gas emission rate in the grassed case exceeded the design value by 18%, while those in the biochar cases were far below the allowable value. Therefore, peanut shell biochar should be considered to amend the grassed landfill cover using coarse-grained soils as it can significantly improve engineering performance in reducing gas emissions under extreme drought conditions. [ABSTRACT FROM AUTHOR]

Biochar is commonly used to improve acidic soil and reduce nitrogen loss. However, the impact of biochar on soil nitrogen retention, especially at varying pH levels, is not fully understood. Soil samples were obtained from an acidic red soil citrus orchard. The soil pH was adjusted using CaO, with five levels (4.0, 5.1, 5.8, 6.6, and 7.2), and two biochar doses (0% and 1%) were applied. The study used 15N-Tracer and Ntrace to investigate biochar's influence on soil nitrogen retention at different pH levels. The results showed that soil amendment with biochar improved gross mineralization rates (TM) and gross NH4+ immobilization rates (TI), except at pH 4.0 for TI. Biochar enhanced heterotrophic nitrification (ONrec) within pH 4.0–7.4, with a threshold for autotrophic nitrification (ONH4) at pH 6.4. The findings revealed biochar's positive effect on soil nitrogen retention within pH 4.5–6.4. Biochar had a greater impact on TI than TM and inhibited ONH4, potentially enhancing nitrogen retention in this pH range. These results highlight the significance of considering biochar incorporation for improving nitrogen use efficiency and reducing NO3−-N loss in subtropical pomelo orchards. [ABSTRACT FROM AUTHOR]

Basil is a plant that can be cultivated in Psamment (coastal sandy soil). Basil requires nitrogen (N) and sulfur (S), so the NS balance is needed to obtain optimal results. Psamment contains low colloid, causing nutrients to be barely bound and easily lost. Zeolite and biochar can be a solution. This study aimed to determine the composition and frequency of fertilization, as well as the use of soil amendment for basil growth. This research consisted of two interrelated studies arranged in a Randomized Complete Block Design. The research was conducted in Bugel, Panjatan, Kulon Progo, and the analysis was performed at the Soil Department Laboratory, Faculty of Agriculture, Universitas Gadjah Mada. The first study consisted of two factors, namely UreaZA composition (0:0, 60:40, 70:30, 80:20, 90:10, and 100:0) and frequency of fertilization (every 1 and 2 weeks). The application of UreaZA (80:20) gave the best freshdry weight, NS content, and NS uptake of basil, and this result was used as the reference for the second study. The second study consisted of two factors, namely UreaZA fertilizer doses (50%, 75%, and 100%), and types and doses of soil amendment (without amendment, zeolite 7.5 t/ha, zeolite 15 t/ha; biochar 7.5 t/ha, and biochar 15 t/ha). It can be concluded that soil amendments application improved the chemical properties of psamment, freshdry weight, NS content, and NS uptake of basil. Furthermore, biochar and zeolite could increase the effectiveness of fertilization, so the dose of UreaZA fertilizer could be reduced until 50%. [ABSTRACT FROM AUTHOR]

Biochar is a promising amendment to promote cadmium (Cd) sorption and fixation in agricultural soil, where microplastics are emerging contaminants in soil. Herein, a greenhouse pot experiment was conducted to elucidate the effects on Cd availability in a soil–plant system by biochar and fresh/aged microplastics application. The fresh microplastics led to an obvious increase in soil Cd availability and Cd uptake by wheat plant, while the aged microplastics increased the available Cd in soil but had no effect on Cd uptake by wheat plant, which was likely attributed to the blocking effect of the aged microplastics on Cd transportation from the soil to the wheat plant. Unexpectedly, biochar had increased Cd availability and Cd uptake. The increased soil soluble Cd was because of both decreased soil pH and elevated dissolved organic matter (DOM) content resulted by biochar addition. Also, the unchanged Cd adsorption of the soil was likely responsible for the increased tested soil Cd availability. In addition, the combined effects of a greater decrease in soil pH, an increase in soil DOM content, and a reduction in Cd adsorption after the addition of microplastics to biochar‐amended soil resulted in a significant increase (ranging from 2.63% to 47.73%) in Cd availability compared to soil treated with biochar alone. Moreover, fresh microplastics inhibited wheat growth, and greater inhibition effect was observed for their aged ones. The biochar elevated the wheat biomass; however, the coexistence of microplastics and biochar decreased the wheat plant biomass compared with biochar alone, due to the negative influence of microplastics in plant growth. [ABSTRACT FROM AUTHOR]

Urban soil is often compacted during anthropogenic activities, which presents a challenging substrate for tree growth. Two techniques for decompacting soils (air spading and vertical mulching) were evaluated alone and in combination with the soil amendment biochar and/or a woodchip mulch. Effects on soil quality (bulk density, organic matter, vegetation ground cover, cotton strip degradation, root dry mass, and earthworm counts) were monitored over 5 years. A combined treatment of air spading, biochar, and a woodchip mulch layer proved optimal in improving the soil quality of a heavily compacted soil over the 5-year period. This treatment was, however, the most expensive and time-consuming. A woodchip mulch was the most effective of the individual treatments and the most cost-effective. Air spading alone proved reasonably effective in improving soil quality over the 5-year study period. Effects of air spading could be improved by addition of a woodchip mulch. Vertical mulching alone or in combination with biochar had little influence on soil quality over 5 years. Results demonstrated that effective long-term soil decompaction measures exist for arborists to improve compacted soils. [ABSTRACT FROM AUTHOR]

Maintenance of soil quality for sustainable crop production is a key factor in maximizing the potential of cropland in all climate zones. This field study evaluated the influence of biochar, maize straw (MS), mixtures of both, and poultry manure (PM) on soil properties and maize yield in an agricultural soil in northeast China. Seven treatments comprising CK, control; MS, 12.5 Mg ha-1 maize straw; B1, 12.5 Mg ha-1 biochar; B2, 25 Mg ha-1 biochar; SB1, 12.5 Mg ha-1 maize straw + 12.5 Mg ha-1 biochar; SB2, 12.5 Mg ha-1 maize straw + 25 Mg ha-1 biochar; and PM, 25 Mg ha-1 poultry manure were applied and replicated four times. Soil samples were collected at four depths 0-10, 10-20, 20-30 and 30-40 cm. Results showed that organic amendments reduced soil bulk density (BD), increased total porosity (TP) and soil moisture content across the top soil (0-20 cm) when compared with the control. Lowest soil BD (1.28 Mg m-3) was recorded for B2 at 0-10 cm depth. Soil pH and soil organic carbon (Corg) were also increased by organic amendments across 0-40 cm depth relative to the control. A signifi cant negative linear relationship was observed between soil BD and Corg. across the 0-40 cm depth. Maize grain yield (5.3 to 24.2%) and total biomass yield (2.9 to 14.9%) were significantly improved by organic amendments, compared to the unamended control. Our study concludes that biochar, biochar-straw-based soil management approach, and poultry manure can improve soil quality, maize biomass and grain yields. [ABSTRACT FROM AUTHOR]

Biochar-amended soils influence the degradation of herbicides depending on the pyrolysis temperature, application rate, and feedstock used. The objective of this study was to evaluate the influence of sugarcane straw biochar (BC) produced at different pyrolysis temperatures (350 °C, 550 °C, and 750 °C) and application rates in soil (0, 0.1, 0.5, 1, 1.5, 5, and 10% w/w) on metribuzin degradation and soil microbiota. Detection analysis of metribuzin in the soil to find time for 50% and 90% metribuzin degradation (DT50 and DT90) was performed using high-performance liquid chromatography (HPLC). Soil microbiota was analyzed by respiration rate (C-CO2), microbial biomass carbon (MBC), and metabolic quotient (qCO2). BC350 °C-amended soil at 10% increased the DT50 of metribuzin from 7.35 days to 17.32 days compared to the unamended soil. Lower application rates (0.1% to 1.5%) of BC550 °C and BC750 °C decreased the DT50 of metribuzin to ~4.05 and ~5.41 days, respectively. BC350 °C-amended soil at high application rates (5% and 10%) provided high C-CO2, low MBC fixation, and high qCO2. The addition of low application rates (0.1% to 1.5%) of sugarcane straw biochar produced at high temperatures (BC550 °C and BC750 °C) resulted in increased metribuzin degradation and may influence the residual effect of the herbicide and weed control efficiency. [ABSTRACT FROM AUTHOR]

The application of biochar as an environmentally friendly additive for agricultural soils has recently gained significant attention. However, the influence of biochar addition on unsaturated hydraulic behavior at high suction ranges (i.e., exceeding 100 kPa) remains largely understudied. This study investigates the impact of biochar addition on the unsaturated hydraulic properties of biochar amended soil (BAS). The effects of biochar content, particle size, and soil compaction on the unsaturated hydraulic properties of BAS were also considered. Peanut shell biochar was utilized in this investigation and was amended into a compacted silty sand with distinct particle size groups. Soil water retention curves and unsaturated permeability were measured through a series of evaporation tests. Results demonstrate that the impact of soil compaction on the unsaturated hydraulic properties of BAS diminishes at high suction range, regardless of biochar particle size and content. A high degree of compaction reduces the saturated permeability of BAS by minimising soil macropores. On the other hand, incorporating high biochar contents with fine particles into the soil enhances the reduction of unsaturated permeability and the improvement of water holding capacity, thereby making biochar an effective application in soil for sustainability of the agroecological environment. [ABSTRACT FROM AUTHOR]

Intensive rice cultivation for a long time resulted in increasing soil degradation and less yield. This study aimed to evaluate effects of the combining reducing nitrogen fertilizer (N) with biochar amendment on soil chemical properties, rice growth parameters, and grain yield in the rice cultivation system in the Mekong Delta region, Vietnam (VMD). Field experiment was designed in the split-plot design with two factors, including N fertilizer (main plot) and biochar (sub-plot). Two N fertilizer rates were: (N50)—50 kg N ha–1 and (N100)—100 kg N ha–1, which is the farmer's practice. Biochar was amended with three rates: no applied biochar (B0), 5 t ha–1 (B5), and 10 t ha–1 (B10). The results indicated that reducing N fertilizer by 50% combined 5–10 t biochar ha–1 resulted in maintaining soil pH, soil electrical conductivity, soil organic carbon, cation exchange capacity, and rice biomass. Applying biochar at a rate of 5–10 t ha–1 significantly increased the available N, available P, and rice height compared to the treatment with no applied biochar (B0). Rice yield in the treatments applied with 5–10 t ha–1 was significantly higher than the treatment without the use of biochar by 11.6–14.7%. The findings of this study confirmed that reducing 50% N fertilizer combined with 5 t ha–1 or 10 t ha–1 of biochar could improve soil available N, available P, rice growth, and grain yield in intensive rice cultivation systems in the VMD region. [ABSTRACT FROM AUTHOR]

Biochar made from seaweed biomass of marine farms established for water pollutant remediation may be a promising amendment for soil remediation in the same coastal territory. The study aimed to assess the soil Cu-immobilizing, pH neutralizing, and nutrient improvement capabilities of a seaweed biochar when incorporated into degraded soil of the same coastal territory (Puchuncaví District, central Chile). Experimental design considered five treatments; degraded soil of Puchuncaví valley (C-), C- amended with either local seaweed biochar (B), vermicompost (V), or its mixture (BV), and a background soil (C+). Experimental soils were placed in pots and kept in a greenhouse (4 weeks). Lolium perenne was then sown and cultivated until week 11. Treatments amended with biochar (B and BV) significantly increased soil pH, available nitrogen and decreased Cu2+ ions. These treatments reached very high EC values but had no negative effect on plant yield. Regarding plant growth, V and BV significantly increased biomass, but V resulted in higher yield because of its higher nutritional status. It was concluded that seaweed biochar, made from local seaweed biomass of a coastal marine water pollutant remediation farm, may be an effective soil amendment for degraded soils of the same coastal territory, although its combination with an organic amendment should be considered. [ABSTRACT FROM AUTHOR]

Biochar (BC) is presented as an amendment based on biomass pyrolysis residue that promotes an increase in the amount of beneficial bacterial and mycorrhizal communities and the quantity of elemental nutrients for plant fertility; in addition, by its characteristics, it provides recalcitrant carbon, generates physicochemical changes, such as an increase in pH, increase in water retention in soil and cation exchange capacity. Most studies about BC focus on evaluating the results in physicochemical variables into soils, however, few studies show and explain reasons because BC increases beneficial bacterial and mycorrhizal communities to plant growth, for this reason is necessary to selectively analysis to define the mechanisms between BC and microorganisms. This review examines publications of the last 12 years of research on BC in different databases (ScienceDirect, Scopus, Springerlink, SciELO, Google Scholar), focusing on the years (2020-2022), to elucidate the underlying mechanisms that let the interaction between BC-soil microbial communities and its benefits as an agricultural amendment. An accepted hypothesis is the high porosity into BC that serves as a “microhabitat” since it allows ideal conditions of space, temperature, humidity, air, and food growing levels of rhizobacteria and mycorrhizal fungus involved in the solubilization of nutrients such as N, P and K increasing the exo-enzymatic activity of dehydrogenase, β-glucosidase, urease between others improving soil fertility and plant growth. [ABSTRACT FROM AUTHOR]

Given that rice husk biochar has been shown to modulate salinity in salt-affected acid soils, the objective of this study was to investigate the effects of organic amendment of salinized acid soils on P fractions, enzyme activities, and associated rice yield. Four treatments, viz. Rice–Rice–Rice, [RRR]; Fallow–Rice–Rice, [FRR]; Fallow–Rice–Rice + 3 Mg ha−1 of compost [FRR + Comp]; and Fallow–Rice–Rice + 10 Mg ha−1 of biochar [FRR + BC] were established at Ben Tre and Kien Giang sites, Viet Nam, over six consecutive crops. Soil properties at harvest of the sixth crop showed that there were diverse patterns of fractionation between P forms with respect to treatment. Overarchingly, biochar increased labile and moderately labile inorganic P and organic P by 30% to 70%, respectively, whilst compost had a relatively modest effect on these pools. Soil phosphatase activities at crop tillering increased following the FRR + Comp and FRR + BC treatments compared with those in RRR, except for acid phosphatase at Ben Tre. At harvest, there were no significant differences between the enzyme activities among the treatments. Rice yield was positively correlated with the more labile forms of P, soil C, and acid phosphatase activity. In the absence of organic amendments, there was no effect of triple versus double rice crops being grown in one-year cycle. Repeated application of biochar (10 Mg ha−1 × 5 times) showed potential to increase grain yields and total soil C in salt-affected acid soils, via modulation of P transformations to more plant-available forms. [ABSTRACT FROM AUTHOR]

Although various studies have investigated biochar (BC) soil amendments for improving soil microbial abundance, functions, and community structure, a comparison of dairy manure biochar (MBC) to wood biochar (WBC) is warranted given the large volume of manure produced in high-intensity dairy production. Additionally, the synergistic effects of different BC sources and loading percentages on microbial functions and community composition using massively parallel 16S DNA sequencing in BC-amended soils with different types of crops are limited. In this study, the synergistic effects of BC type, BC loading percentage, and crop types on soil fertility, prokaryote community diversity, and functions were investigated in a greenhouse study. The MBC and WBC were used to amend sandy loam soils at increasing BC loading percentages (0, 5, and 10%) to grow the cool-season forages crimson clover (Trifolium incarnatum; an annual legume) and Italian ryegrass (Lolium multiflorum Lam.; an annual forage grass) for 120 days. High nutrient concentrations in MBC shifted microbial communities towards r-strategists and alkaliphiles, potentially increasing the rate of nutrient bioremediation from high nitrogen- and phosphorus-containing soil amendments. This study enables emerging biochar agronomic use recommendations with different crops. [ABSTRACT FROM AUTHOR]

The bioavailability of trace metals in soils poses a major threat to the environment, especially with massive mineral fertilizers added to increase plant yield. A plot experiment was conducted for the effectiveness evaluation of compost and vermicompost, recycled from agro-industrial wastes, in immobilizing chromium, cadmium, and lead added to calcareous soil (artificially contaminated). Moreover, immobilization efficiency was compared to the natural occurrence of these metals in the soil without metal addition (uncontaminated soil). In both soils, amendments and mineral fertilizers were applied at three different levels alone and combined to each other. The experimental design was arranged in factorial complete randomized blocks using contamination, organic and mineral fertilizer levels, and their combination as categorical factors. The distribution of metal fractions and their bioavailability in soils and bioaccumulation in wheat grains were evaluated. Soil alkalinity, the contents of soil organic carbon and nitrogen, available phosphorus, and soil micronutrients were significantly improved under vermicompost and compost compared to mineral fertilizer and control. Vermicompost was more effective than compost in reducing metals bioavailability in contaminated soils by increasing the immobilized organic fractions, but it regressed when combined with mineral fertilizers. The bioavailability of the naturally occurring metal levels in uncontaminated soil did not change significantly compared to contaminated soil. Likewise, wheat yield, plant biomass, and nutrient enrichment in wheat grains improved due to enhanced soil nutrient availability. These composted agro-industrial residues, by-products from food industries, can be classified as environmentally-friendly soil amendments for their great potential to enrich soil nutrients, reduce mineral fertilizer addition, enhance plant growth, and stabilize Cr, Cd, and Pb in contaminated calcareous soils under wheat plants. [ABSTRACT FROM AUTHOR]

This study assessed the effect of soil amendment with biochar on the production of some Mediterranean crops. Pine-derived biochar (B1) and partially pyrolyzed pine-derived biochar (B2) were used with a dose of 8 L/m2 in a corn crop, reporting a production increase of 38–270% over three years with B1, and no effect of B2 due to its poor quality. Olive stone-derived biochar (B3) was used in lavandin and vineyard crops with doses of 0.04–0.9 L/m2 and 0.37–2.55 L/m2, respectively. An increase of 23–25% in plant volume of lavandin was reported, while the production of grapes per plant was not significantly altered, although it increased by up to 66%. Soil analysis indicated that biochar does not significantly alter soil physicochemical parameters; therefore, biochar may affect plants by altering soil structure and increasing its cation exchange capacity and water management efficiency. Depending on its price, biochar application may be profitable for lavandin and corn crops, with a return-on-investment period ranging from 1 to 4 years. However, the profitability of its use in vineyards is questionable, particularly for the varieties with the lowest market price. Studies examining the economics of biochar application indicate that CO2 abatement certification may help in covering biochar application costs. [ABSTRACT FROM AUTHOR]

Biochar is a potential amendment for the remediation of Cd-contaminated soils. Although the immobilization effect of biochar on soil Cd has been studied under indoor laboratory conditions, the effect of biochar on rice Cd uptake and soil Cd fractions under field conditions is still poorly understood. Here, the Cd content of the different organs of rice and the Cd fractions in soil were characterized for three years after the application of different amounts of biochar (0, 7.5, 15, 30 t ha−1, and 3 t ha−1 year−1). The Cd content of brown rice, husk, leaf, stem and sheath, and root under biochar treatment could be maximally reduced by up to 26.25%, 20.16%, 20.74%, 33.2%, and 26.89%, respectively. Biochar altered the Cd fractions in soil, including the decrease in exchangeable Cd content and the increase in Fe-Mn oxide bound Cd and organic bound Cd. The concentration factor of Cd uptake by rice was reduced by 32% under biochar application, while biochar had little influence on the transfer factor and distribution factor. The immobilization effect of biochar on soil Cd lasted for at least three years, but the trend of Cd immobilization efficiency over time for different amounts of biochar treatment was different. The Risk Assessment Code (RAC) of Cd in soil with biochar amendment could be reduced to a medium risk level from a high risk level. Redundancy analysis (RDA) revealed that changes in soil pH and Fe-Mn oxide bound Cd content caused by biochar application contributed most to the reduction in the Cd content of rice organs. These findings would enhance our understanding of the immobilization effect of biochar on Cd in paddy soil under field conditions. [ABSTRACT FROM AUTHOR]