Maize Straw Biochar Research Articles

Biochar affects the distribution of phosphorus in the soil profile by changing the capacity of soil to adsorb phosphorus and its distribution within soil macroaggregates

AbstractA large number of studies suggested that biochar can affect the adsorption of phosphorus (P) in soil and the distribution of P in soil aggregates, but it is still unclear whether biochar can indirectly affect the distribution of P in soil profiles through the influence of these two factors. Therefore, the ability of maize straw biochar to mitigate the risk of loss of P and improve the distribution of P in soil profile was evaluated by studying the capacity of soil to adsorb P from the soil and distribution fractions of it in diverse grain‐sized aggregates of soil. A 5‐year field trial site had received NPK fertilizer inputs at the same rate and one‐time biochar inputs at different rates (0, 15.75, 31.5 and 47.25 t ha−1) at the beginning of the experiment. Langmuir and Freundlich equations were fitted to the sorption data of the soil and suggested that the applicataion of biochar can promote P absorption capacity of soil, particularly when the rates of biochar applied were 31.5 and 47.25 t ha−1. Biochar can improve the stability of soil aggregates, and aggregates with particle sizes of 0.25–2 mm have the highest relative rate of contribution to various fractions of P in the soil. Biochar can promote the accumulation of most of the P fractions in soil aggregates, particularly when the rates of biochar applied were 31.5 and 47.25 t ha−1. The TP, Ca2‐P, Al‐P, Ca8‐P, moderately labile organic phosphorus (MLOP) and moderately resistant organic phosphorus (MROP) were primarily distributed in the 0–20 cm soil layer. Biochar increased the contents of MLOP and highly resistant organic phosphorus in the soil layer of 0–20 cm while reducing the contents of Al‐P, Fe‐P and occluded phosphorus (O‐P) in the soil layer of 0–20 cm and decreased the contents of TP, Ca8‐P, O‐P and MROP under the 20 cm soil layers. Biochar can change the distribution of P fractions along the soil profile by improving the adsorption of soil P and its distribution in the soil aggregates (0–20 cm).

Impact of maize straw biochar and tied‐ridge‐furrow rainwater harvesting on soil erosion and soil quality in a semiarid region

AbstractIn dryland areas, integrating biochar soil amendment with in situ rainwater harvesting systems may decrease soil erosion, improve soil quality, and increase crop productivity and yield. This study was conducted to investigate the effect of maize straw biochar amendment and ridge‐furrow rainwater harvesting systems on run‐off, sediment yield and the physico‐chemical properties of a Calcic Cambisol soil in semiarid areas. The experiment was conducted on alfalfa (Medicago sativa) production land at the Anjiagou Catchment experimental station in Gansu province, China. The experimental layout was a split‐plot design with three replications. Biochar was applied at a rate of 0 and 30 t ha−1, respectively. The tillage treatments were flat planting, open‐ridging, and tied‐ridging (TR). Overall, the integration of maize straw biochar with TR decreased soil bulk density at 0–40 cm depth. Biochar application reduced run‐off by 37.8% and soil loss by 55.5% during alfalfa‐growing seasons compared to the control. In general, biochar addition increased soil total potassium, but the same effect was not observed for soil pH, total nitrogen, total phosphorus, and available phosphorus. These findings demonstrate the potential of integrating maize straw biochar and tillage systems to reduce soil erosion and improve soil quality for rainfed crop production in semiarid areas. Further studies on the effect of biochar‐tillage system interaction are warranted to improve soil conditions for plant growth and increase crop yield in dryland areas.

Biochar reduces uptake and accumulation of polycyclic aromatic hydrocarbons (PAHs) in winter wheat on a PAH-contaminated soil

Biochar has been used previously for remediation of polycyclic aromatic hydrocarbons (PAHs) in contaminated soils for years, which has achieved remarkable results in improving removal of soil PAHs and reducing PAHs uptake in crops. However, the underlying mechanism of biochar application in reducing the uptake and accumulation of PAHs in winter wheat remains unclear. Pot trials using PAHs-contaminated soils were conducted for whole plant growth period of winter wheat, which were amended with 2% (w/w) bamboo biochar (BB), coconut shell biochar (CB) and maize straw biochar (MSB) or not (CK). Compared with CK, application of the three types of biochar significantly (p < 0.01) reduced grain PAHs concentration, the total equivalent concentration (TEC) values and the incremental lifetime cancer risk (ILCR) of grain PAHs, indicating that application of biochar reduced the exposure risk of PAHs in wheat grain, especially for MSB. Consistently, application of the three types of biochar significantly (p < 0.05) reduced uptake and accumulation of PAHs in root and stem of wheat, which may be due to that application of biochar enhanced the degradation of PAHs in the rhizosphere soil. Compared with CK, application of the three types of biochar significantly (p < 0.05) reduced the concentration of PAHs in the rhizosphere soil by 15.9%, 26.1% and 33.7%, respectively. It was found that the degradation rate of HMW PAHs (high molecular weight PAHs, 5-6 ring PAHs) was significantly (p < 0.05) higher than that of LMW PAHs (low molecular weight PAHs, 2-4 ring PAHs) regardless of types of biochar used. Additionally, application of the three types of biochar significantly increased the relative abundance of dominant bacterial phyla and genera in soil. Redundancy analysis and correlation analysis results also showed that there was a strong correlation between the removal rate of PAHs and dominant bacteria in the rhizosphere soil. The present study indicated that biochar could reduce dietary risk of PAHs in wheat grains mainly by increasing the abundance of bacteria related to PAHs degradation, promoting the biodegradation of PAHs in the rhizosphere soil and consequently reducing PAHs uptake in wheat.

Modification of Soil Physical Properties by Maize Straw Biochar and Earthworm Manure to Enhance Hydraulic Characteristics under Greenhouse Condition

The deterioration of soil physical properties had led to a decrease in soil–water availability in facility agriculture. Thus, an experiment was set up with five soil treatments of 0% (CK, No additives), 3% biochar (BA3, Mass ratio), 3% earthworm manure (QA3), 5% biochar (BA5), and 5% earthworm manure (QA5) to investigate the effects on soil physical properties and hydraulic characteristics under greenhouse conditions. The physical properties of soil including the soil bulk density (BD) and total porosity (TP) were measured; the results showed that BA5 provided the lowest soil BD (1.24 g·cm−3) and the highest TP (53.09%) and was 13.8% higher than CK. More importantly, the saturated hydraulic conductivity (KS), field capacity (FC), permanent wilting point (PWP), and available water content (AWC) of the soils treated with biochar and earthworm manure were significantly higher than those of CK. At the same application rate, the effect of biochar on soil–water permeability and water-retention capacity was significantly higher than that of earthworm manure, in which the soil–water-characteristic curve (SWCC) showed that as BA5 &gt; BA3 &gt; QA5 &gt; QA3 &gt; CK, the FC and AWC increased from 28.90% and 14.13% under CK, respectively, to 40.73% and 21.91% under BA5, respectively; and the KS, FC, PWP and AWC of BA5 increased by 45.93%, 40.91%, 27.46% and 54.96% compared with CK, respectively. The results revealed that the improvement of the soil TP was conducive to the enhancement of the soil KS and FC, enhanced the soil–water permeability and the water-retention capacity, and ultimately increased the AWC. From the perspective of improving the facility soil and economic benefits, the application of 5% biochar is considered to be the most beneficial.

Effects of biochar addition on nitrous oxide emission during soil freeze-thaw cycles.

Biochar applied to soil can reduce nitrous oxide (N2O) emissions produced by freeze-thaw processes. Nonetheless, how biochar modification affects N2O emissions during freeze-thaw cycles is not completely clear. In our research, during freeze-thaw cycles, microcosm experiments were conducted to investigate the effects of maize straw biochar (MB) or rice straw biochar (RB) addition on soil N2O emissions under different water conditions. The N2O emissions peaked at the initial stage of thawing in all the soils, and the total N2O emissions were considerably greater in the flooded soils than in the nonflooded soils. Compared with the soils without biochar addition, RB and MB amendments inhibited N2O emissions by 69 and 67%, respectively. Moreover, after biochar addition, the abundance of AOB amoA genes decreased by 9-13%. Biochar addition significantly decreased the content of microbial biomass nitrogen (MBN) in flooded soil during thawing, which was significantly correlated with N2O emissions and nitrification and denitrification communities. The PLS-PM further revealed that biochar can inhibit the production and emission of soil N2O by reducing soil MBN during soil thawing. In addition, soil moisture directly significantly affects N2O emissions and indirectly affects N2O emissions through its influence on soil physicochemical properties. Our results revealed the important function of biochar in decreasing the emission of N2O in flooded soil during freeze-thaw cycles.

Responses of Soil Carbon Pools and Carbon Management Index to Nitrogen Substitution Treatments in a Sweet Maize Farmland in South China.

In China, excessive nitrogen fertilizer application in sweet maize fields contributes to greenhouse gas emissions. This study used maize straw (MS), cow dung (CD), biogas residue (BR), and straw-based biochar (CB) to substitute the mineral nitrogen fertilizer at 20% and 50% ratios in the Pearl River Delta in China. In comparison with a conventional amount of mineral nitrogen fertilizer (CK), the soil organic carbon (SOC) storages of the different treatments increased by 6.5–183.0%. The CB treatment significantly improved the inert organic carbon pool in the soil, while other types of organic materials promoted the formation of activated carbon pools. The treatments increased the soil carbon pool management index by 21.1–111.0% compared to the CK. Moreover, the CB treatments increased the soil carbon sequestration index by 78.3% and 155.8% compared to the CK. In general, substituting the mineral N fertilizer with BR, CB, and CD could improve the SOC accumulation in sweet maize farmland in South China. The CB at the high substitution level was the best measure for stabilizing carbon sequestration in the sweet maize cropping system. This experiment provides valuable information for ensuring the clean production of sweet maize in a typical subtropical area in East Asia.

Biochar addition regulates soil and earthworm gut microbiome and multifunctionality

The earthworm gut bacterial community and enzyme activities play a key role in many soil ecosystem functions, but how the addition of different types of biochar (used to improve soil quality) regulates soil and earthworm gut bacterial communities and associated enzyme activities is scarcely understood. An experiment was conducted using soil microcosms and seven treatments: no biochar application as control, and two types of biochar (maize straw and cow dung biochar, hereafter SB and CB treatments, respectively) with three biochar application rates (20, 50, and 100 g/kg soil). Eight enzymatic activities related to C-, N- and P-cycling (used to compute a “multifunctionality” index) and the abundance and composition of bacterial communities were assessed in both the soil and earthworm guts. Our results show that earthworm gut content, characterized by lower bacterial abundance but higher enzymatic activities than soil, was strongly influenced by biochar addition. Increasing biochar application rates significantly increased the nutrient content, bacterial abundance, and multifunctionality in the earthworm guts. Owing to the difference in physicochemical properties between SB and CB, the increased gut multifunctionality was linked to the significantly modified gut bacterial community composition in CB treatments but not in SB treatments. Structural equation modeling further revealed that the changed gut multifunctionalities in both biochar treatments were mostly related to the soil and gut physicochemical properties, especially in CB treatments, while the impacts of gut microbial variables on soil multifunctionality were higher in the SB than CB treatments. These results demonstrate that the influence of biochar amendment on earthworm gut microbiome and multifunctionality depends on the type of biochar, which also regulates the contributions of earthworm gut biochemical processes to soil ecosystem functions.

Effect of Pyrolysis Temperature on Removal Efficiency and Mechanisms of Hg(II), Cd(II), and Pb (II) by Maize Straw Biochar

Pyrolysis temperature significantly affects the properties of biochar, which in turn can affect the removal of heavy metal ions and the underlying mechanism. In this work, biochars from the pyrolysis of maize straw at 300, 400, and 500 °C (BC300, BC400, and BC500, respectively) and wheat straw at 400 °C (WBC400) were investigated. The influence of production temperature on the adsorption of Hg2+, Cd2+, and Pb2+ by maize straw biochar was investigated by the characterization of the biochars and by adsorption tests. The adsorption capacities of maize and wheat straw biochar were compared in an adsorption experiment. Biochar BC400 showed the best physical and chemical properties and had the largest number of surface functional groups. The pseudo-second-order kinetic model was more suitable for describing the adsorption behavior of metal ions to biochar. The Langmuir model better fit the experimental data. Biochar BC400 had a higher adsorption speed and a stronger adsorption capacity than WBC400. The sorption of Pb2+ and Hg2+ to maize straw biochar followed the mechanisms of surface precipitation of carbonates and phosphates and complexation with oxygenated functional groups and delocalized π electrons. The adsorption mechanism for Cd2+ was similar to those of Hg2+ and Pb2+, but precipitation mainly occurred through the formation of phosphate. In the multi-heavy-metal system, the adsorption of Cd2+ by BC400 was inhibited by Pb2+ and Hg2+. In summary, BC400 biochar was most suitable for the adsorption effect of heavy metals in aqueous solution.

Influence of Tied-Ridge with Maize Straw Biochar on Alfalfa Fodder Yield, Nutritional Quality, and Production Economics

Influence of Tied-Ridge with Maize Straw Biochar on Alfalfa Fodder Yield, Nutritional Quality, and Production Economics

Influence of Peat and Biochar on Gas Emissions and Microbial Metabolism During Co-composting of Chicken Manure and Maize Straw

This study investigated the effects of peat (PT) and maize straw biochar (MSB) on gas emissions and microbial metabolism characteristics during chicken manure (CM) and maize straw (MS) composting. Three treatments with different additives (0%, 5% PT, 5% MSB added on dry weight basis) were designed to conduct 30-day aerobic composting experiments in nine insulated polyvinyl chloride (PVC) reactors. The results showed that PT and MSB addition increased the temperature and nitrate-nitrogen (NO3−–N) content but decreased the ammonium nitrogen (NH4+–N) content of compost. Compared with control, the total emissions of methane (CH4), nitrous oxide (N2O) and ammonia (NH3) in PT and MSB were reduced by 20.13–30.57%, 28.88–47.46% and 37.35–52.71%, respectively. In addition, PT and MSB amendments improved the microbial utilization capacity on carbohydrates, esters and carboxylic acids. Redundancy analysis revealed that temperature, NH4+–N, pH and microbial metabolism were positively correlated with CH4, N2O and NH3 emissions. Meanwhile, temperature, NH4+–N and pH also had positive correlations with microbial metabolism. Together these results indicated that PT and MSB amendment improved the metabolism capacity of microbes and reduced CH4, N2O and NH3 emissions, eventually mitigating nitrogen loss and promoting the quality of compost product.Graphical

Effects of ridge-furrow rainwater harvesting with maize straw biochar on fodder yield and water use efficiency of alfalfa in semiarid regions of China

Effects of ridge-furrow rainwater harvesting with maize straw biochar on fodder yield and water use efficiency of alfalfa in semiarid regions of China

The residual impact of straw mulch and biochar amendments on grain quality and amino acid contents of rainfed maize crop

The inability of humans and many farm animals to synthesize certain amino acids has long triggered tremendous interest in increasing the levels of these so-called essential amino acids in crop plants. Hence, a two-year field experiment was conducted to evaluate the effects of straw mulch (8 t ha−1) and biochar applied at various rates (0, 4, 12, 36 t ha−1) on the chlorophyll, photosynthesis, total nitrogen in soil, essential and nonessential amino acid (AA) contents of maize grain. The maize straw mulch and biochar significantly increased chlorophyll contents, photosynthesis rate of maize crop and total soil nitrogen. The application of biochar (12 t ha−1) increased the chlorophyll contents and photosynthesis rate and total soil nitrogen during both years. However, excessive biochar applications (more than 12 t ha−1) had negative effects on chlorophyll contents, photosynthesis rate of maize crop and total soil nitrogen of soil. The AAs were significantly affected by biochar, depending on the application rate. In conclusion, the application of straw mulch and biochar improved the rate of leaf chlorophyll contents, photosynthesis rate and amino acid contents in maize grain when applied at appropriate rates, but the effects were negative when biochar was overused.

Influence of biochar remediation on Eisenia fetida in Pb-contaminated soils

In this study, the remediation influence of maize straw biochar on earthworms (Eisenia fetida) in contaminated soils (with Pb at 0, 300, 700, and 1000 mg kg−1) amended with different amounts of biochar (0%, 1%, 3%, and 5%) was investigated. The results showed that applying biochar to metal-polluted soils effectively reduced the mobility of Pb, promoting the transformation of Pb from exchangeable (EXC) and bound-to-carbonate (Carb) fractions to Fe/Mn oxide (FeMnOx), organic bound (ORG) and residual (RES) fractions. Consequently, a reduction in the mortality and weight loss of earthworms was also achieved by biochar. The accumulation amount of Pb in earthworms steadily increased with exposure time, and with the increasing dosage of biochar, the accumulated Pb decreased by 50.8–78.0% (300 mg kg−1), 30.9–67.3% (700 mg kg−1), and 17.4–55.1% (1000 mg kg−1), which was significantly positively correlated with the mortality of earthworms. Simultaneously, the application of biochar increased the soil pH (0.05–0.23 units), cation exchange capacity (CEC) (0.26–4.54 cmol kg−1), and content of organic matter (0.54–11.66%). There were higher soil enzyme activities (including sucrase activity, urease activity, and alkaline phosphatase activity) in the treatments with a biochar addition of 3%. Through remediation, Proteobacteria (50.82%), Actinobacteriota (32.37%), Firmicutes (4.83%) and Bacteroidota (1.88%) were the most important phyla in the microbiota communities. Furthermore, soil pH value and leaching toxicity concentration showed the most striking effects on earthworms. Therefore, the influence of earthworms must be taken into account in the remediation of Pb-contaminated soil with biochar.

Assessing the impacts of biochar‐blended urea on nitrogen use efficiency and soil retention in wheat production

AbstractImproving nitrogen (N) use efficiency (NUE) in crop plants is important to reduce the negative impact of excessive N on the environment. Although biochar‐blended fertilizer had been increasingly tested in crop production, the fate of fertilized N in soil and plant had not been elucidated in field conditions. In this study, a novel biochar‐blended urea (BU) was prepared by pelleting maize straw biochar, bentonite, sepiolite, carboxymethylcellulose sodium, and chitosan with urea (commercial urea without biochar [CU]). N fertilization in a winter wheat field was treated with BU and CU at both 265 kg N ha−1 (HL) and 186 kg N ha−1 (LN). Within a treatment plot, a microplot was fertilized with 15N‐labeled urea at a relevant N level. We investigated the influence of fertilizer management on biomass, grain yield, bioaccumulation of nutrient, soil properties, 15N isotopic abundance, and greenhouse gas emissions. Microscopic and spectroscopic analysis showed that micro/nanonetwork of biochar could bind N to form a loss control agglomerated particle, and organo‐mineral coatings on BU may protect N from quick release. Compared with CU, BU significantly increased grain yield by 13% and 38%, and grain N allocation by 19% and 55%, respectively, at HN and LN level. The total recovery of urea 15N in wheat plant (15N based NUE) was 32.8% under CU regardless of N rates but increased to 41.7% (HN rate) and 56.3% (LN rate) under BU. Whereas, the soil proportion (soil residual 15N) was 20.1% and 13.4% under CU but 32.5% and 18.8% under BU, in 0‐20cm topsoil, respectively, at HN and LN rate. Compared with the CU, BU had no effect on CO2 and CH4 emissions but significantly reduced the total N2O emission by 23%–28%. These important findings suggested that BU can be beneficial to uplift plant NUE to reduce reactive N loading but boost crop production.

Transformation of biochar into extracted humic substances under short-term laboratory incubation conditions: Evidence from stable carbon isotopes

Agricultural waste can be made into biochar, which serves to raise soil fertility and fix carbon (C). When biochar is added to soil, a small part of biochar could be transformed into soil organic C in a short time to promote soil fertility. However, it is still unknown how much biochar can be stored in the soil as stable C and whether it plays a role in C sequestration. In this study, a 540-day incubation experiment was conducted to evaluate the transformation of maize straw biochar into humus fractions using a 13C isotopic labelling technique. The treatments were CK (no biochar applied) and AB (21.3 g kg-1 of biochar + CK). The results showed that: 1) Compared with those in the CK treatment, the concentrations of organic and humus C in the bulk soil were significantly higher under the AB treatment. 2) The δ13C values of soil humus C were higher (ranging between 0% and 23.45%) in the AB treatment than those in the CK treatment. 3) The proportions of biochar transformed into humic acid (HA), fulvic acid (FA), water-soluble substances (WSS), and water floating substances (WFS) were 2.66–4.30%, 1.11–1.57%, 0.49–0.88%, and 0.68–1.40%, respectively. The remaining biochar (59.44–98.00%) remained in the crude humin form, retaining the inert nature of the biochar itself. Although biochar is relatively stable, approximately 4.22–5.40% of biochar was transformed into extracted humic substances (HA+FA). We concluded that a relatively small amount of biochar could be transformed into soil organic matter under short-term (540 days) incubation conditions.

Effect of crop straw biochars on the remediation of Cd-contaminated farmland soil by hyperaccumulator Bidens pilosa L.

Cadmium (Cd) due to its strong toxicity and high mobility, which poses a considerable threat to soil environment and human health, has aroused widespread concern. Biochar has been used for remediating Cd-contaminated soil recently, however this method has the risk of fixed-Cd re-release. Phytoremediation can make up for its shortcoming. In this study, a pot experiment was carried out, where Bidens pilosa L. (B.pilosa) was as the tested plant and biochars (maize straw biochar and wheat straw biochar with two particle sizes) were as amendments. The mechanism of how biochars promoted B.pilosa Cd accumulation in Cd-contaminated farmland soil was explored. Results showed that the application of 5% wheat straw fine biochar (WF), wheat straw coarse biochar (WC), maize straw fine biochar (MF) and maize straw coarse biochar (MC) increased the total Cd accumulation of B.pilosa to 251.57%, 217.41%, 321.64% and 349.66%, respectively. Biochars amendment significantly promoted B.pilosa growth and increased Cd accumulation by improving soil physical properties, nutrient levels (available nitrogen, available phosphorus (AP), available potassium (AK) and organic matter (OM)) and microbial activity, and changing the nutrients distribution in B.pilosa organs although tissues although DTPA-Cd reduced to some extent. The effect of MF on AP increase was better than MC, while the effect of WF on AK increase was better than WC. Fine-particle was superior to coarse-particle in increasing B.pilosa biomass of aboveground, OM and microbial activity in soil. The changes of N, P and K concentrations in B.pilsosa roots, stems and leaves were closely related to the changes of AN, AP and AK in soil after biochars application. The results indicated that the combination of straw biochars and hyperaccumulators had the synergistic effect. This study can provide data support and meaningful reference values for remediating actual Cd-contaminated soil.

Assessment of the biochemical degradability of crop derived biochars in trace elements polluted soils

This study assesses the biochemical degradability of biochars produced from five contrasting crop residues (rice husk, olive pit, almond shell, maize straw and wood chips) in acidic soils contaminated with trace elements. For this purpose, highly and moderately acid soils were amended with each of the proposed biochars and subjected to a microbial degradation experiment under controlled conditions for 155 days. CO2 production of pure biochars fitted with a single exponential model, indicating that they only had one C pool. Among the biochars studied, those derived from olive pit and almond shell showed the greatest stability, with mean residence times (MRT) of 293 and 214 years, respectively, whereas, maize straw biochar revealed MRT of 82 years. Despite that the average MRT of all tested biochars under controlled conditions were shorter than usually reported, biochar addition increased the MRT of the recalcitrant C pool of the studied soils by a factor from 2x to 13 × . Solid-state 13C NMR spectra confirmed a partial cracking of the biochar aromatic network during the experiment due to microbial degradation or physical alteration processes. It was further noted that biochar degradability depended on its aromaticity but we have also observed that in highly acidic and metal-contaminated soils biochar is less degraded, probably due to the difficulties for microbial development at these soils.

Contrasting effects of maize residue, coal gas residue and their biochars on nutrient mineralization, enzyme activities and CO2 emissions in sandy loess soil

Mismanagement of crop straw and coal gas residue threatens the atmosphere and the economy. Nevertheless, thermal-pyrolysis is an option for management that turns bio-waste into biochar; its viability and adoption by the public as soil amendments is dependent on the agronomic and environmental values compared between biochar and the raw materials. We undertook a 60-day short-term analysis to assess the impact of various wastes and biochars, as well as inorganic nutrients (N), on carbon dioxide (CO2) fluxes, soil enzyme activities, soil fertility status, and microbial activities. There were eight treatments of soil amendments: without an amendment (CK), Nutrients (N), straw + nutrients (S+N), straw biochar + nutrients (SB+N), coal gas residue + nutrients (C+N), coal gas residue biochar + nutrients (CB+N), straw + straw biochar + nutrients (S+SB+N) and coal gas residue waste + coal gas residue biochar + nutrients (C+ CB +N). The results indicated that soil EC, pH, nitrate N (NO3–- N), SOC, TN and available K were significantly (p < 0.05) increased coal gas residue biochar and combined with coal fly ash as compared to maize straw biochar and combined with maize straw and N treatments. The higher concentrations of soil MBC and MBN activities were increased in the maize straw application, while higher soil enzyme activity such as, invertase, urease and catalase were enhanced in the coal fly ash derived biochar treatments. The higher cumulative CO2 emissions were recorded in the combined applications of maize straw and its biochar as well as coal gas residue and its biochar treatment. Our study concludes, that maize straw and coal fly ash wastes were converted into biochar product could be a feasible substitute way of discarding, since land amendment and decreased CO2 fluxes and positive changes in soil microbial, and chemical properties, and can be confirmed under long-term conditions for reduction of economical and environment issues.

Investigations of the effect of the amount of biochar on soil porosity and aggregation and crop yields on fertilized black soil in northern China.

The combination of chemical fertilizer and biochar is regarded as a useful soil supplement for improving the properties of soil and crop yields, and this study describes how the biochar of maize straw can be used to improve the quality of the degraded black soil. This has been achieved by examining the effects of combining different amounts of biochar with chemical fertilizer on the porosities and aggregate formation of soil and exploring how these changes positively impact on crop yields. A field trial design combining different amounts of maize straw biochar [0 (NPK), 15.75 (BC1), 31.5 (BC2), and 47.25 t ha−1 (BC3)] with a chemical fertilizer (NPK) has been used to investigate changes in the formation of soil aggregate, clay content, soil organic carbon (SOC), and crop yields in Chinese black soil over a three year period from 2013 to 2015. The results of this study show that the addition of fertilizer and biochar in 2013 to black soil results in an increased soybean and maize yields from 2013 to 2015 for all the treatments, with BC1/BC2 affording improved crop yields in 2015, while BC3 gave a lower soybean yield in 2015. Total porosities and pore volumes were increased for BC1 and BC2 treatments but relatively decreased for BC3, which could be attributed to increased soil capillary caused by the presence of higher numbers of fine soil particles. The addition of biochar had a positive influence on the numbers and mean weight diameters (MWD) of soil macroaggregates (>0.25 mm) that were present, with the ratio of SOC to TN in soil macroaggregates found to be greater than in the microaggregates. The most significant amount of carbon present in macroaggregates (>2 mm and 0.25–2 mm) was observed when BC2 was applied as a soil additive. Increasing the levels of maze straw biochar to 47.25 t ha−1 led to an increase in the total organic carbon of soil, however, the overall amount of macroaggregates and MWD were decreased, which is possibly due to localized changes in microbial habitat. The supplementation of biochar increased in the amount of aromatic C present (most significant effect observed for BC2), with the ratio of aliphatic C to aromatic C found to be enhanced due to a relative reduction in the aliphatic C content with >2 mm particle fraction. These changes in organic carbon content and soil stability were analyzed using univariate quadratic equations to explain the relationship between the type of functional groups (polysaccharide C, aliphatic C, aromatic C, aliphatic C/aromatic C) present in the soil aggregates and their MWDs, which were found to vary significantly. Overall, the results of this study indicate that the use of controlled amounts of maize-straw biochar in black soil is beneficial for improving crop yields and levels of soil aggregation, however, the use of excessive amounts of biochar results in unfavorable aggregate formation which negatively impacts the yields of crop growth. The data produced suggest that aromatic C content can be used as a single independent variable to characterize the stability of soil aggregate when biochar/fertilizer mixtures are used as soil additives to boost growth yields. Analysis of soil and crop performance in black soil revealed that the application of maize-straw biochar at a rate of 15.75 and 31.5 t ha−1 had positive effects on crop yields, soil aggregation and accumulation of aromatic C in the aggregate fractions when a soybean-maize rotation system was followed over three years.

Microcystin-LR sorption and desorption by diverse biochars: Capabilities, and elucidating mechanisms from novel insights of sorption domains and site energy distribution

This study accurately assessed microcystin-LR (MCLR)-trapping capabilities of diverse biochars based on sorption and sequential desorption (SDE), and elucidated MCLR sorption-desorption mechanisms from novel views of sorption domains and site energy distribution along sorption-SDE process. Results showed that maize straw biochar (MSB) and chicken manure biochar (CMB) excelled in trapping MCLR (91.0%–97.4% and 85.7%–96.4%, respectively, at 60–600 μg/L of initial MCLR amount), followed by their respective HCl-treated ones (HCMB, HSMB), while HCl-treated bamboo biochar and pine sawdust biochar poorly trapped MCLR (48.9%–77.8% for HBB, 22.6%–67.2% for HPSB). Non-partition sorption domains (NPSD) contributed more than partition sorption domain (PSD) to MCLR sorption by each biochar. Higher NPSD contribution to MCLR sorption in CMBs and MSBs than other biochars resulted from their higher pHPZC and mesoporosity, which provided stronger electrostatic and pore-filling interaction for MCLR. Desorption hysteresis was weaken with rising aqueous MCLR amount for most biochars. Along SDE process, remaining MCLR in PSD of MSBs, HPSB and HBB could transfer to NPSD, thus desorption ratio continuously decreased with increasing desorption cycle. Differently, remaining MCLR in NPSD of CMBs converted into PSD during 1st–3rd desorption, causing fluctuated desorption ratio without obvious decrease as desorption cycle increased. These implied that MCLR in PSD was more easily desorbed than NPSD for each biochar. Site energy distribution dynamics supported the results of PSD and NPSD contribution changes along SDE. This study was greatly implicated in cost-efficient emergent MCLR-pollution remediation and deeply understanding MCLR sorption-desorption mechanisms of diverse biochars.