Maize Straw Biochar Research Articles

Reduction of tobacco alkaloid bioaccumulation in pea shoots: a comparative study of biochar derived from cow dung and maize straw

Tobacco alkaloids in tobacco-cultivated soils pose potential risks for succeeding crops, due to their allelopathy and toxicity. Effects of biochar on the dissipation of tobacco alkaloids in soil-crop systems remain poorly understood. In this study, a 40-day pot experiment was conducted to explore the effect of cow dung biochar (CDBC) and maize straw biochar (MSBC) on the uptake of nicotine and nornicotine by pea (Pisum sativum L.) and their dissipation in an agricultural soil. The results revealed that the bioaccumulation of nicotine and nornicotine by pea shoots in the soils added with CDBC and MSBC at 1.5% and 3.0% significantly decreased by 46.97–79.13% and 33.64–71.59%, respectively. CDBC more effectively decreased the uptake and bioaccumulation of nicotine and nornicotine by pea shoots than MSBC due to the higher soil pH and nutrient content. In addition, the enhanced relative abundances of soil nicotine-degrading bacteria belonging to the genera Arthrobacter and Gemmatimonas also contributed to the decreasing uptake of nicotine by pea plants. The decreased bioavailability in the soils due to the increased adsorption was the key factor for the reduced bioaccumulation of tobacco alkaloids. This study provides guidance to protect subsequent crops in tobacco-cultivated soil from tobacco alkaloids with biochar.

Maize-Straw Biochar Enhances Soil Properties and Grain Yield of Foxtail Millet in a Newly Reclaimed Land

Large-scale land reclamation has become common in northwestern China; however, low soil fertility and poor soil water-holding capacity limit agricultural production on these reclaimed lands, requiring increased fertilizer and irrigation inputs. Biochar, produced from agricultural waste, has shown potential in improving soil quality and water-holding capacity. In this two-year field study (2021 and 2022), we investigated the effects of biochar produced from maize straw on soil properties and grain yield of foxtail millet grown on newly reclaimed land. Three biochar treatments (3000, 4500, and 6000 kg ha−1) were compared to a control (CK) with no biochar application. Biochar application resulted in increased soil organic matter, total phosphorus, total nitrogen, soil enzyme activity, and soil organic acid content. It also significantly decreased soil pH and bulk density. Compared with the CK, biochar increased available nitrogen from 29.7% to 108% in 2021 and 37.0% to 88.4% in 2022. Similarly, biochar increased available phosphorus from 64.7% to 143% in 2021 and 41.9% to 96.5% in 2022. Grain yields ranged from 3092 to 4753 kg ha−1. Biochar treatments increased grain yield compared to the CK, ranging from 12.2% to 24.6% in 2021 and 27.1% to 53.7% in 2022. Correlation analysis revealed that soil pH was negatively related to soil oxalic acid content, phosphorus content, and sucrase activity. Available nitrogen and phosphorus contents were negatively related to soil bulk density and positively related to catalase activity. Soil water content was negatively correlated with soil bulk density and positively correlated with organic matter. In conclusion, biochar improved the rhizosphere soil pH and the effectiveness of soil fertility in the newly reclaimed soil, resulting in an enhanced grain yield of foxtail millet.

The effect of biochar amendment on Cd accumulation in Bidens pilosa L: Changing Cd subcellular distribution, cell wall polysaccharide Cd-binding capacity and composition

Biochar can reduce Cd uptake by plants, thereby reducing its biotoxicity, but the mechanisms involved at the subcellular level have not been thoroughly elucidated. In this work, we explored the effect of maize straw biochar on Cd accumulation by Bidens pilosa L. and its mechanism at subcellular levels. After 90 days of potting experiment, the subcellular fractions were extracted by differential centrifugation, and the polysaccharide fractions of root cell walls were extracted by leaching centrifugation, and then the Cd content of each fraction was determined. Results showed that Cd was preferentially distributed in cell walls of three organs. Additionally, biochar addition resulted in a greater distribution of Cd from cell wall to soluble fractions and organelles in stems. These results suggested that cell wall immobilization and intracellular compartmentalization were critical detoxification mechanisms tackling Cd stress with biochar addition of Bidens pilosa L. Pectin was the main sink where Cd was stored. And galacturonic acid content in pectin occupied the highest ratio among the three polysaccharide fractions. After biochar addition, in hemicellulose the change of Cd content was consistent with the change of galacturonic acid content. These results suggested that the galacturonic acid in hemicellulose played an important role in Cd binding. Biochar addition reduced the bioavailability of soil Cd and improved the growth environment, thus inducing Bidens pilosa L. to change the composition of root cell wall in response to Cd stress.

A biochar-based amendment improved cadmium (Cd) immobilization, reduced its bioaccumulation, and increased rice yield

Cadmium (Cd) contamination of soil threatens human health, food security, and ecosystem sustainability. The in situ stabilization of Cd has been recognized as a potentially economical technology for the remediation of Cd-contaminated soil. Recently, biochar (BC) and activated carbon (AC) have received widespread attention as eco-friendly soil amendments that are more beneficial for plant growth, soil health, and remediation of contaminated soil. An experiment was performed in a paddy field to investigate the effects of two different types of BC (maize straw biochar and bamboo biochar) and AC (coconut shell activated carbon) in combination with rape organic fertilizer (R), calcium magnesium phosphate fertilizer (P), and fulvic acid (F), respectively, on soil Cd immobilization, Cd accumulation in rice, and yield. The results indicated that the BC/AC-based amendments reduced soil bioavailable Cd (DTPA-Cd) and brown rice Cd by 9.58%–27.06% and 19.30%–71.77%, respectively. The transformation of exchangeable Cd (Ex-Cd) to carbonate-bound Cd (Ca-Cd), Fe-Mn oxide bond (Ox-Cd), and residual (Re-Cd) in soil accounted for the mitigation of Cd uptake and enrichment by rice. Additionally, BC-/AC-based amendments altered soil physicochemical properties, which significantly increased the soil pH and cation exchange capacity (CEC), total nitrogen (TN), total phosphorus (TP), soil organic carbon (SOC), and dissolved organic carbon (DOC), directly promoting soil health. All BC-/AC-based amendments significantly increased FeIMP and MnIMP concentrations by 47.31%–160.34% and 25.72%–73.09% in the Fe/Mn plaque (IMP), respectively. Maize straw and bamboo biochar-based amendments significantly increased rice yield by 10.46%–20.41% and 9.94%–16.17%, respectively, while coconut shell-activated carbon severely reduced rice yield by 65.06%–77.14%. The correlation analysis revealed that leaf Cd and IMP primarily controlled Cd uptake by rice, and soil pH, Eh, CEC, SOC, IMP, and TP influenced DTPA-Cd in soil. This field study demonstrated that maize straw and bamboo biochar-based amendments not only reduced soil DTPA-Cd in paddy fields but also decreased the accumulation of Cd in brown rice, as well as improved rice yield, which has potential application in Cd-contaminated agriculture fields. Coconut shell-activated carbon severely decreased rice yields, which is not appropriate for rice production.

Efficacy of Agricultural Residue-Derived Biochar for Tackling Cadmium Contamination in an Aqueous Solution.

This study aimed to investigate the efficacy of biochar, produced from different agricultural residues varying in lignin and cellulose content and subjected to different pyrolysis temperatures, in removing cadmium ions (Cd (II)) from an aqueous solution. This removal process is crucial for protecting human health and the environment. Specifically, the study focused on the adsorption behaviors of Cd (II) by the biochars made from rice husk biochar (RHB), maize straw biochar (MSB), peanut shell biochar (PSB), cottonseed shell biochar (CHB), and mulberry leaf biochar (MLB), which were prepared at 300 °C and 600 °C. The results indicated that the type of agricultural residue used to produce biochar significantly influenced the adsorption of Cd (II). Notably, mulberry leaf biochar prepared at 300 °C (MLB-300) demonstrated the highest adsorption efficiency, achieving a maximum adsorption capacity of 42.2 mg g-1. Batch adsorption experiments assessed the impact of various factors, including system pH, NO3- concentration, and adsorption duration. The adsorption kinetics were better described by the pseudo-second-order model than the pseudo-first-order model. Moreover, the study found that the lignin content of the biochar plays a major role in determining the adsorption capacity. The surface characteristics of biochar, influenced by the types of agricultural residues and preparation temperature, directly impact its adsorption mechanism and capacity. While biochar produced at 300 °C showed optimal Cd(II) adsorption, those processed at 600 °C were less effective, likely due to the loss of functional groups at higher temperatures.

Maize straw biochar improved soil nitrogen, but no effect on phosphorus in desert under mulched drip irrigation

Maize straw biochar improved soil nitrogen, but no effect on phosphorus in desert under mulched drip irrigation

Combined biochar and water-retaining agent application increased soil water retention capacity and maize seedling drought resistance in Fluvisols

Global climate change has accelerated the occurrence of agricultural drought events, which threaten food security. Therefore, improvements in the soil water retention capacity (WRC) and crop drought resistance are crucial for promoting the sustainability of the agricultural environment. In this study, we explored the effects of applying biochar and water-retaining agent (WRA) on soil WRC and crop drought resistance in a Fluvisols, along with their potential mechanisms. We applied two types of biochar (based on wheat and maize straw) and two WRAs (polyacrylamide and starch-grafted sodium acrylate) to Fluvisols with different textures, and then evaluated soil water retention and crop drought physiological resistance. The combined biochar and WRA treatment increased the WRC in both the sandy loam and clay loam Fluvisols. Biochar and WRA increased the relative content of soil hydrophilic functional groups. Compared with the control (CK), the combined application of biochar and WRA increased the field capacity, reduced soil water volatilization under drought conditions, and slowed water infiltration into the Fluvisols. The soil WRC was higher with the wheat straw biochar (WBC) treatment than with the maize straw biochar (MBC) treatment. It was also higher with polyacrylamide treatment than with the starch-grafted sodium acrylate treatment. The combined application of biochar and WRA improved crop drought physiological resistance by significantly increasing the maize seedling potassium (K) and soluble sugar contents, increasing antioxidant enzyme activity, and reducing the malondialdehyde (MDA) content. The results indicate that the application of biochar and WRA alleviated drought stress by increasing the soil WRC and improving crop drought resistance in Fluvisols.

Maize straw biochar can alleviate heavy metals stress in potato by improving soil health

Maize straw biochar can alleviate heavy metals stress in potato by improving soil health

Aged biochar for simultaneous removal of Pb and Cd from aqueous solutions: Method and mechanism

In this study, we prepared maize stover biochar and used artificial simulated aging to prepare three types of aged biochar. The effects of aging on the adsorption capacity of Pb and Cd of biochar were studied. It was found that the pH, ash, and aromaticity of the aged biochar decreased compared to fresh maize straw biochar. On the contrary, the polarity, oxygenated functional groups, specific surface area, and average pore size of the aged biochar increased. The sorption behavior of Pb2+ and Cd2+ on biochar can be well explained by quasi-second-order kinetics and the Langmuir equation. The maximum adsorption of Pb2+ in the single metal system was CBC-N (74.401 mg g−1) > CBC (72.959 mg g−1) > CBC-H (69.421 mg g−1) > CBC-F (66.460 mg g−1), the maximum adsorption of Cd2+ was CBC-N (52.983 mg g−1) > CBC-H (52.728 mg g−1) > CBC-F (50.692 mg g−1) > CBC (45.966 mg g−1). The adsorption of both Pb2+ and Cd2+ by biochar is lower in the binary metal system than in the single metal system, implying a competitive relationship and that biochar is more selective for Pb2+ than Cd2+. The mechanisms for removing Pb2+ and Cd2+ from solution by aged biochar consist mainly of pore filling, electrostatic adsorption, ion exchange, mineral precipitation, π−π interaction, and surface complexation. This paper demonstrates that aged biochar is an ideal adsorbent but that environmental changes and pollutant types should be considered in practical applications.

Effect of the application of peanut shell, bamboo, and maize straw biochars on the bioavailability of Cd and growth of maize in Cd-contaminated soil

Biochar is a versatile, carbon-rich, organic material that can effectively immobilize Cd in the soil. In this study, peanut shell biochar (SP), maize straw biochar (MS), and bamboo straw biochar (BS) were applied in different proportions to evaluate their effects on the remediation of Cd-contaminated farmland soil and plant growth. The results revealed that both single and mixed applications of biochar substantially increased corn biomass and chlorophyll content compared to the unamended control treatment, while the malondialdehyde (MDA) and proline contents were largely unaffected. The bamboo straw block biochar with maize straw biochar at a mass ratio of 2:1 (DBM) significantly increased the dry total biomass of maize (+107.24% compared to the unamended soil). SP application has highly increased the SPAD value. PB with BS application at a mass ratio of 1:1 (MSB) significantly decreased the soluble sugar content (+21.81% compared to the unamended control soil). Soil pH was increased by the application of biochar alone and in combination with feedstocks. The soil content of Fe/Mn oxide-bound (OX) and exchangeable-bound Cd (EX) was decreased, whereas that of carbonate-bound Cd (CA), residue-bound Cd (RE), and organic-bound Cd (OM) contents increased. The Cd content in corn grains under MSB and SP application was markedly reduced by 42.62% and 31.48%, respectively, compared to the unamended control soil. Overall, MSB and SP applications were effective in improving soil quality and crop growth.

Effects of maize straw and its biochar application on soil organic carbon chemical composition and carbon degradation genes in a Moso bamboo forest.

We investigated the effects of maize straw and its biochar application on soil organic carbon chemical composition, the abundance of carbon degradation genes (cbhI) and the composition of cbhI gene community in a Moso bamboo forest, to provide the theoretical and scientific basis for enhancing carbon sequestration. We conducted a one-year field experiment in a subtropical Moso bamboo forest with three treatments: control (0 t C·hm-2), maize straw (5 t C·hm-2), and maize straw biochar (5 t C·hm-2). Soil samples were collected at the 3rd and 12th months after the treatment. Soil organic carbon chemical composition, the abundance and community composition of cbhI gene were determined by solid-state 13C NMR, real-time fluorescence quantitative PCR, and high-throughput sequencing, respectively. The results showed that compared with the control, maize straw treatment significantly increased the content of O-alkyl C and decreased aromatic C content, while maize straw biochar treatment showed an opposite effect. Maize straw treatment significantly increased the abundance of cbhI gene and the relative abundance of Penicillium, Gaeumannomyces and Marasmius. However, maize straw biochar treatment reduced the abundance of this gene. The relative abundance of dominant cbhI in soils was positively correlated with the content of O-alkyl C and negatively correlated with the content of aromatic C. Results of redundancy analysis showed that maize straw treatment had a significant effect on the microbial community composition of cbhI gene by changing soil O-alkyl C content, while maize straw biochar affected the microbial community composition of cbhI gene by changing soil pH, organic carbon, and aromatic C content. Maize straw biochar treatment was more effective in increasing soil organic carbon stability and reducing microbial activity associated with carbon degradation in the subtropical Moso bamboo forest ecosystem compared with maize straw treatment. Therefore, the application of biochar has positive significance for maintaining soil carbon storage in subtropical forest ecosystems.

Biochar regulates biogeochemical cycling of iron and chromium in a soil-rice system by stimulating Geobacter and Clostridium

In soil-rice systems, microbial reduction of iron (Fe) has been recognized as a crucial biogeochemical process that regulates Fe and chromium (Cr) translocation; however, the underlying processes are unknown. To investigate the impacts of biochar on the biochemical cycling of Fe and Cr and their toxicity to rice, maize straw biochar was applied at 1% (weight/weight) to a paddy soil spiked with 300 mg kg-1 Cr under two phosphorus (P) levels (0 or 90 mg kg-1) in a pot experiment. The key microbial groups affecting Fe dissimilatory reduction and their environmental drivers were explored. Biochar inhibited root Cr uptake by 36%, owing to the promoted iron plaque (IP) formation on the rice root surface. Correlation analysis showed that Fe concentration in pore water was strongly linked to the abundances of Geobacter (r = 0.81–0.94, P < 0.05) and Clostridium (r = 0.83–0.95, P < 0.05), indicating that Geobacter and Clostridium played essential roles in Fe reduction. Redundancy analysis showed that labile carbon and pore water P concentrations were the key determinants influencing Fe-reducing bacterial abundances, accounting for 42% and 32% of the variation in community composition, respectively. Besides, biochar increased Fe and P concentrations in root cell walls, which retained more Cr. Overall, Cr stress in rice under biochar treatment was relieved through increasing IP formation and altering subcellular distribution. These mechanistic insights had important implications for reducing Cr uptake by rice.

Improving the ability of straw biochar to remediate Cd contaminated soil: KOH enhanced the modification of K3PO4 and urea on biochar

In recent years, the improvement of soil cadmium (Cd) contamination remediation effect of biochar by modification has received wide attention. However, the effect of combined modification on biochar performance in soil Cd contamination remediation and the mechanism are still unclear. In this study, cotton straw biochar and maize straw biochar were co-modified by KOH (0, 3, 5 mol L-1), K3PO4, and urea. Then, two modified biochars with high Cd adsorption capacity were selected to test the soil Cd contamination remediation effect through a pot experiment. The results showed that the combined modification by using KOH, K3PO4, and urea significantly increased the specific surface area and nitrogen (N) and phosphorus (P) contents of biochar, providing more adsorption sites for Cd. Among the modified biochar, the cotton straw biochar modified with KOH (3 mol L-1), K3PO4, and urea (m3-CSB) had the highest adsorption capacity (111.25 mg g-1), which was 7.86 times that of cotton straw biochar (CSB). The m3-CSB for adsorption isotherm and kinetics of Cd conformed to the Langmuir model and Pseudo-second-order kinetic equation, respectively. In the pot experiment, under different exogenous Cd levels (0 (Cd0), 4 (Cd4), and 8 (Cd8) mg kg-1), m3-CSB treatment decreased soil available Cd content the most (51.68%–63.4%) compared with other biochar treatments. Besides, m3-CSB treatment significantly promoted the transformation of acid-soluble Cd to reducible, oxidizable, and residual Cd, reducing the bioavailability of Cd. At the Cd4 level, the application of m3-CSB significantly reduced cotton Cd uptake compared to CK, and the maximum reduction of Cd content in cotton fibers was as high as 81.95%. Therefore, cotton straw biochar modified with KOH (3 mol L-1), K3PO4, and urea has great potential in the remediation of soil Cd contamination.

Identifying the specific pathways to improve nitrogen fixation of different straw biochar during chicken manure composting based on its impact on the microbial community

The application of straw biochar to chicken manure composting mitigated nitrogen loss. However, the impact of biochar derived from different types of straw on nitrogen fixation in chicken manure composting is discrepant, and the specific pathways remain unclear. Therefore, this study aimed to clarify the specific pathways of maize straw biochar (M) and rice straw biochar (R) to improve nitrogen fixation during chicken manure composting. The nitrogen losses in control (no addition, CK), M, and R composting were 51.84 %, 33.47 %, and 38.24 %, respectively, suggesting that adding straw biochar effectively improved nitrogen fixation. Microbial community analysis suggested that inhibiting denitrification and NH4+-N transformation by microorganisms was the primary means of improving nitrogen fixation. Meanwhile, biochar addition reduced the number of bacteria participating in nitrogen transformation and strengthened the NO3–-N and total organic nitrogen transformation processes, among which the effect of M composting was stronger. The stronger effect was attributed to the significant role of the core microorganisms in M composting in shifting the transformation processes of the nitrogen components (P < 0.05). Therefore, the function of different straw biochar was determined by its different impacts on the microbial community, highlighting the important role of microbial community variability.

Maize straw is more effective than maize straw biochar at improving soil N availability and gross N transformation rate

AbstractSoil nitrogen (N) transformation is vital in determining farmland N availability. Although many studies have investigated the effect of biochar on N retention and loss via leaching and gaseous emissions, few have determined the dynamics of gross N transformation during crop growth in long‐term biochar‐amended soils and compared the effect of the biochar with that of its feedstock. In this study, we conducted a five‐time field measurement of soil gross N turnover rates via 15N isotope pool dilution during maize growth in 2021. Three treatments were employed, including no amendment, biochar and straw applied annually at rates of 2.63 and 7.50 t ha−1, respectively, since 2013. The results showed that biochar did not change the rate of gross N mineralisation when compared with no amendment, but straw increased it by 139% in August, resulting in significantly higher cumulative gross N mineralisation than biochar and no amendment (701 vs 489 and 499 mg kg−1 in 200 d). The inconsistent influence was attributed to the fact that inherent biochar‐N was recalcitrant and could not be mineralized like the straw. The gross nitrification rate was decreased by 72.9% and 77.4% by biochar and straw application, respectively, in June relative to no amendment, but then it increased from July to August in the straw treatment as a result of the elevated gross N mineralisation rate. The decreased nitrification in the biochar treatment was an outcome of the synergetic effect of a low ammonium pool (−59.4%) and a high gross ammonium immobilisation rate (+263%), which was likely due to excessive fertilizer N loss and abiotic adsorption to biochar. Meanwhile, biochar amendment inhibited bacterial 16S and fungal ITS genes, as well as ureC and bacterial and archaea‐amoA gene copies. In conclusion, straw is more effective than biochar at improving soil N transformation and availability in the long term.

Biochar-immobilized Bacillus megaterium enhances Cd immobilization in soil and promotes Brassica chinensis growth

Phosphate solubilizing bacteria (PSB) has been considered an environmental-friendly phosphate fertilizer without cadmium (Cd) input into soils, but its possibility of Cd fixation in soil needs to be explored. Since direct inoculation results in a rapid decline of the population and activity, we immobilized Bacillus megaterium with maize straw biochar (B-PSB) and investigated its feasibility in remediating Cd-contaminated soil. Pot experiments showed that the application of B-PSB significantly ameliorated the growth of Brassica chinensis under Cd stress, with a fresh weight increased by 59.08% compared to the Cd-control. B-PSB reduced Cd accumulation in Brassica chinensis by 61.69%, and promoted the uptake of P and N by 134.97% and 98.71% respectively. Microbial community analysis showed B-PSB recruited more plant growth-promoting bacteria in near-rhizosphere soil, which provides a favorable microenvironment for both PSB and crops. Column leaching experiments verified that B-PSB achieved the dissolution of stable P while fixing Cd. Batch tests further revealed that biochar served as a successful carrier facilitating the growth of B. megaterium and Cd immobilization. Given the widespread Cd contamination in agricultural soils, our results indicate that B-PSB is a promising soil amendment to secure food safety.

Effects of nitrogen co-application by different biochar materials on rice production potential and greenhouse gas emissions in paddy fields in northern China

The effects of the co-application of nitrogen (N) fertilizers and different biochar materials on rice yields and the GWP of paddy fields in northern China remain unclear. Herein, we conducted a 2-year field experiment to evaluate the effect of combined N fertilizer (three levels: N0, 0 kg N ha−1; N1, 210 kg N ha−1; and N2, 168 kg N ha−1) and biochar application (two levels: BM, maize straw biochar; and BR, rice-husk biochar) on rice yield and greenhouse gas (GHG) emissions. BR and BM significantly increased rice yield, in particular when applied with N2 fertilizer, by 4.89% and 4.48%, respectively, compared with no biochar. This was associated with a substantial increase in the effective panicles. Generally, the soil NH4+-N after BR application was greater than that of BM, however, biochar addition reduced NO3−-N. BM and BR addition also significantly reduced N2O emissions by 44.04–50.53% and 52.13–55.37%, and CH4 emissions by 38.72–39.74% and 26.40–33.55%, respectively. Moreover, N2 levels can further mitigate N2O and CH4 emissions. For each level of N application, BM and BR significantly reduced the GWP and GHGI, with the N2BM showing the best outcome. Overall, biochar application (especially maize straw biochar) in combination with 168 kg N ha−1 can stabilize rice yields and reduce GHG emissions from agricultural areas in northern China.

Chemical fractions, mobility and release kinetics of Cadmium in a light-textured calcareous soil as affected by crop residue biochars and Cd-contamination levels

ABSTRACT The aim of this study was to examine the effect of maize straw biochar (MSB), cotton residue biochar (CRB) and wheat straw biochar (WSB) application (1.5% wt.) on Cd immobilisation in a light-textured calcareous soil with varying levels of Cd-contamination. Application of all three crop residue biochars were found to significantly enhance the immobilisation of Cd in the sandy loam calcareous soil. Cotton residue biochar was by far the most effective biochar for reducing the more labile soluble and exchangeable (WsEx-Cd) (−44.4%) and carbonate (Car-Cd) (−44.7%) Cd fractions and increasing the less available residual (Res-Cd) fraction (+82.9%) compared to the maize and wheat straw biochars (WsEx-Cd: −18.8–20.3%; Car-Cd: −27.1–29.0%; Res-Cd: +43.8–44.8%). Application of CRB also significantly reduced EDTA-extractable Cd by 45–52%, and specifically reduced the two-first-order kinetic model Q1 parameter (−55.3%) and increased the Q3 parameter (26.1%). The greater effectiveness of the CRB was associated with its substantially higher C and lower ash content compared to the other crop residue biochars. Results of this study demonstrate the potential use of crop residue biochars, especially cotton residue biochar, in remediation of Cd contaminated calcareous soils.

Insight into mechanisms of biochar-fertilizer induced of microbial community and microbiology of nitrogen cycle in acidic soil

Biochar has been shown to affect the nitrogen (N) cycle in soil, however, it is unknown how this occurs. Therefore, we used metabolomics, high-throughput sequencing, and quantitative PCR to explore biochar and nitrogen fertilizer effects on the mitigation mechanisms of adverse environments in acidic soil. In the current research, we used acidic soil and maize straw biochar (pyrolyzed at 400 °C with limited oxygen). Three maize straw biochar levels (B1; 0t ha−1, B2; 45 t ha−1, and B3; 90 t ha−1) along with three N fertilizer (urea) levels (N1; 0 kg ha−1, N2; 225 kg ha−1 mg kg−1, and N3; 450 kg ha−1 mg kg−1) were employed in a sixty-day pot experiment. We found that the formation of NH+ 4-N was faster at 0–10 days, while the formation of NO- 3-N occurred at 20–35 days. Furthermore, the combined application of biochar and N fertilizer most effectively boosted soil inorganic N contents compared to biochar and N fertilizer treatments alone. The B3 treatment increased the total N and total inorganic N by 0.2–24.2% and 55.2–91.7%, respectively. Soil microorganism, N fixation, and nitrification capabilities increased with biochar and N fertilizer addition in terms of N-cycling-functional genes. Biochar-N fertilizer had a greater impact on the soil bacterial community and their diversity and richness. Metabolomics revealed 756 distinct metabolites, including 8 substantially upregulated metabolites and 21 significantly downregulated metabolites. A significant amount of lipids and organic acids were formed by biochar-N fertilizer treatments. Thus, biochar and N fertilizer triggered soil metabolism by affecting bacterial community structure, and N-cycling of the soil micro-ecological environment.

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

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