Effects Of Rice Straw Biochar Research Articles

Effects of biochar on the manganese enrichment and oxidation by a microalga Scenedesmus quadricauda in the aquatic environment

Microalgae play a significant impact in the biogeochemical cycle of Mn(II) in the aquatic ecosystem. Meanwhile, the inflow of biochar into the water bodies is bound to impact the aquatic organisms. However, the influence of biochar on the manganese transformation in algae-rich water has not drawn much attention. Thus, we studied the effects of rice straw biochar on manganese enrichment and oxidation by a common type of algae in freshwater (Scenedesmus quadricauda). The results showed that Mn(II) was absorbed intracellularly and adsorbed extracellularly by active algal cells. A significant portion of enriched Mn(II) was oxidized to amorphous precipitates MnO2, MnOOH, and Mn2O3. Moreover, the extracellular bound Mn(II) content in the coexistent system of algae and biochar increased compared with the pure Scenedesmus quadricauda system. Nevertheless, the intracellular Mn content was continually lowered as the biochar dose rose from an initial 0.2 to 2.0 g·L−1, suggesting that Mn assimilation of the cell was suppressed. It was calculated that the total enrichment ability of Scenedesmus quadricauda in the algae-biochar coexistent system was 0.31- 15.32 mg Mn/g biomass, more than that in the pure algae system. More importantly, with biochar in the algae system, the amount of generated MnOx increased, and more Mn(II) was oxidized into highly-charged Mn(IV). This was probably because the biochar could relieve the stress of massive Mn(II) on algae and support the MnOx precipitates. In brief, moderate biochar promoted the Mn(II) accumulation by algal cells and its oxidation activity. This study offers deeper insight into the bioconversion of Mn(II) by algae and the potential impact of biochar application to the aquatic system.

Pristine/magnesium-loaded biochar and ZVI affect rice grain arsenic speciation and cadmium accumulation through different pathways in an alkaline paddy soil

Cadmium (Cd) and arsenic (As) co-contamination has threatened rice production and food safety. It is challenging to mitigate Cd and As contamination in rice simultaneously due to their opposite geochemical behaviors. Mg-loaded biochar with outstanding adsorption capacity for As and Cd was used for the first time to remediate Cd/As contaminated paddy soils. In addition, the effect of zero-valent iron (ZVI) on grain As speciation accumulation in alkaline paddy soils was first investigated. The effect of rice straw biochar (SC), magnesium-loaded rice straw biochar (Mg/SC), and ZVI on concentrations of Cd and As speciation in soil porewater and their accumulation in rice tissues was investigated in a pot experiment. Addition of SC, Mg/SC and ZVI to soil reduced Cd concentrations in rice grain by 46.1%, 90.3% and 100%, and inorganic As (iAs) by 35.4%, 33.1% and 29.1%, respectively, and reduced Cd concentrations in porewater by 74.3%, 96.5% and 96.2%, respectively. Reductions of 51.6% and 87.7% in porewater iAs concentrations were observed with Mg/SC and ZVI amendments, but not with SC. Dimethylarsinic acid (DMA) concentrations in porewater and grain increased by a factor of 4.9 and 3.3, respectively, with ZVI amendment. The three amendments affected grain concentrations of iAs, DMA and Cd mainly by modulating their translocation within plant and the levels of As(III), silicon, dissolved organic carbon, iron or Cd in porewater. All three amendments (SC, Mg/SC and ZVI) have the potential to simultaneously mitigate Cd and iAs accumulation in rice grain, although the pathways are different.

Soil aggregate stability quantified by different methods is unaffected by rice straw biochar in the long term

AbstractHighly weathered tropical soils are susceptible to disaggregation due to disruptive forces like water and mechanical disturbances. However, a few studies have investigated how biochar and cropping systems together affect the aggregate stability of tropical soils. This study investigated the long‐term (∼7 years) effect of rice straw biochar on the aggregate stability of a tropical Acrisol using the dry aggregate stability (DAS) method and SLAKES (a wet aggregate stability technique), and assessed the extent of agreement or otherwise of the aggregate stability quantified by the two methods for different treatments. Maize (Zea mays L.) and okra (Abelmoschus esculentus L.) were rotated on plots amended with rice straw biochar at rates of 0, 15, and 30 Mg ha−1. Seven years after biochar amendment, bulk soil samples were collected at 0–15 cm depth for laboratory analyses. Aggregate stability was assessed by determining erodible fraction (EF) and DAS, and by quantifying the SLAKES parameters (slaking index [SI] and slaking index at 600 seconds [SI‐600]). Neither biochar nor crop type or their interaction significantly changed the soil aggregate stability assessed by the two methods (p > 0.05). The EF and DAS weakly correlated with SI and SI‐600, which could be attributed to the differences in the mechanisms underlying soil aggregate breakdown assessed by the two methods. The study highlighted that observed challenges of the SLAKES method namely, inability in some cases to detect soil aggregates and the disaggregation process could offset its advantages as a tool for rapid detection of soil structural problem areas within agricultural fields.

Impacts of biochar and phosphorus application on soil phosphorus availability and soybean phosphorus uptake

Biochar is beneficial to soil phosphorus (P) availability and crop growth, but the effects vary greatly across different soil types. We investigated the effects of rice straw biochar (4% of total mass) and P application (0, 30, and 90 kg P·hm-2) on soil P availability, phosphomonoesterase activity, and soybean P uptake by using lateritic red soil (pH 4.91) and cinnamon soil (pH 7.24) as test materials. The results showed that biochar application at different P levels significantly increased available P and total P in both soils. Biochar application with 30 kg P·hm-2 increased soil available P with maxima at 192.6% and 237.1% in lateritic red soil and cinnamon soil, respectively. Biochar application with 30 kg P·hm-2 in lateritic red soil significantly increased the activity of alkaline phosphomonoesterase by 78.9%, decreased the content of active organic P by 39.3%, and subsequently stimulated soybean P absorption and growth. Biochar amendment significantly reduced active organic P content in cinnamon soil, but did not affect soil phosphomonoesterase activity and plant growth. The content of active organic P was significantly negatively correlated with soil available P content. In summary, the effect of biochar on soil P availability varied across different soil types (lateritic red soil > cinnamon soil) and P levels (better at 30 kg P·hm-2). Our results could provide scientific basis for a promising application of biochar in reducing the amount of P fertilizer and increasing soybean P uptake, especially in lateritic red soil.

Effect of Rice-Straw Biochar Application on the Acquisition of Rhizosphere Phosphorus in Acidified Paddy Soil

A serious acidification trend currently affects paddy soil and soil phosphorus (P) availability has declined in rice production. This study investigated the effect of rice-straw biochar on P availability and the adaptability of rice roots in acidified soil. Rice was grown in rhizoboxes, allowing for the precise sampling of rhizosphere and bulk soil for the sequential extraction of P fractions. Biochar may provide a liming effect and strong nutrient adsorption, leading to soil improvement. The results confirmed that biochar application significantly improved plant growth and P accumulation in shoots by 29% and 75%, respectively. However, the application of washed biochar and equivalent lime only increased shoot biomass and P accumulation by 13.4% and 11.2%, and by 42% and 38%, respectively. Compared with the control, applying biochar increased the plant-available P component contents in rhizosphere and bulk soil. Biochar affected the chemical balance among the different P fractions, increased aluminum-bound phosphate (Al-P) pool, calcium-bound phosphate (Ca-P) pool and decreased the occluded phosphate pool in acidic paddy soil. Biochar amendment significantly improved root growth of and increased the citrate exudation from roots under low P supply, accompanied by the enhanced expression of the anion-transporter-related OsFRDL4 gene and the OsPT1 phosphate transporter. The results showed that biochar application in degraded acidic soils could improve rice potential for P acquisition to increase available P component and maintain high citrate exudation.

Incorporation of engineered nanoparticles of biochar and fly ash against bacterial leaf spot of pepper

In agriculture, the search for higher net profit is the main challenge in the economy of the producers and nano biochar attracts increasing interest in recent years due to its unique environmental behavior and increasing the productivity of plants by inducing resistance against phytopathogens. The effect of rice straw biochar and fly ash nanoparticles (RSBNPs and FNPs, respectively) in combination with compost soil on bacterial leaf spot of pepper caused by Xanthomonascampestris pv. vesicatoria was investigated both in vitro and in vivo. The application of nanoparticles as soil amendment significantly improved the chili pepper plant growth. However, RSBNPs were more effective in enhancing the above and belowground plant biomass production. Moreover, both RSBNPs and FNPs, significantly reduced (30.5 and 22.5%, respectively), while RSBNPs had shown in vitro growth inhibition of X.campestris pv. vesicatoria by more than 50%. The X-ray diffractometry of RSBNPs and FNPs highlighted the unique composition of nano forms which possibly contributed in enhancing the plant defence against invading X.campestris pv. vesicatoria. Based on our findings, it is suggested that biochar and fly ash nanoparticles can be used for reclaiming the problem soil and enhance crop productivity depending upon the nature of the soil and the pathosystem under investigation.

Effects of rice straw biochar on microbial community structure and metabolic function during anaerobic digestion

Anaerobic digestion technology mitigates agricultural organic waste pollution, thereby alleviating the energy crisis. Biochar materials increase the utilisation rate of biomass resources and promote the enrichment and growth of microorganisms. Biochar is an effective exogenous additive that stabilises the anaerobic digestion, improves anaerobic digestion efficiency and gas production. Herein, biochar materials were prepared from rice straw utilising the sequencing batch anaerobic digestion process. The biochar microstructure was characterised by scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) analysis, and microbial succession and metabolic pathways were analysed using 16S rRNA sequencing to reveal the molecular mechanisms. Rice straw biochar addition increased gas production during anaerobic fermentation. SEM revealed that numerous cocci and microbacteria became agglomerated and attached to the surface and pores of biochar, which was revealed by BET analysis to be a good habitat for microorganisms. After anaerobic digestion, the specific surface area and total pore volume of biochar decreased. 16S rRNA gene sequencing showed that biochar affected the abundance of certain bacteria and archaea. Biochar had no obvious effect on the function of bacterial flora but inhibited carbohydrate metabolism by bacteria and glycan biosynthesis and metabolism by archaea in the anaerobic fermentation system while promoting lipid metabolism by archaea. Biochar addition inhibited acetic acid production in the anaerobic fermentation system and promoted methane production based on hydrogen and carbon dioxide levels.

Effect of rice straw biochar on three different levels of Cd-contaminated soils: Cd availability, soil properties, and microbial communities

Biochar can be effective in immobilizing soil cadmium (Cd), but the difference in its immobilization mechanisms for different levels of Cd-contaminated soils was overlooked. In this study, rice straw biochar (BC) was added to three Cd-contaminated soils following 180 days of incubation, in the process of which the dynamic changes of Cd speciation, soil properties and microbial community diversity were determined. BC could significantly reduce the ratio of acid-soluble in the three soils, especially in light and medium Cd-contaminated soils by more than 20%. The addition of biochar could significantly increase the soil pH, soil organic matter, cation exchange capacity, and the activities of catalase, but decrease the richness and diversity of bacterial communities in all soils. The associations between microbial communities were inhibited in light and medium Cd-contaminated soils, but promoted in heavy Cd-contaminated soils. Furthermore, the main pathway of BC effect on soil Cd availability was also analyzed by partial least squares model (PLS-PM), which indicated that BC indirectly reduced Cd availability mainly by regulating the microbial community in light Cd-contaminated soil, whereas BC directly reduced Cd availability primarily by its own adsorption in medium and heavy Cd-contaminated soils. This research deepened understanding of the mechanisms of stabilization of Cd by biochar for agricultural soils.

Compost and biochar impact on immobilisation of pesticide residues in alkaline soils under canola (

Context The application of soil amendments to immobilise pesticide residues is a promising technology for meeting human health requirements, environmental protection and cost-effective remediation. Aims This study aims to evaluate the effect of rice straw biochar (RB), rice straw compost (RC) and their mixtures at rates of 0.5% and 1.0% in pots, on the immobilisation of pesticides (such as atrazine, glyphosate and chlorpyrifos) in contaminated soil, using spectroscopy analysis under grown canola (Brassica napus L.) plants. Methods Determination of immobilisation of pesticide residues by GC or HPLC and chemical properties of RB and RC and adding them at differentrates to the contaminated soil. Keyresults The results showed that the addition of RB or RC alone or their mixtures led to a significant increase in the exchangeable Ca2+ contents, organic matter (OM), cation exchange capacity (CEC), uptake of N, P and K and dry weight of canola plants. Pesticide concentrations decreased with increasing OM, CEC, and exchangeable Ca2+ with the soil amended by RC and RB. The data indicated that adding RB at levels of 0.5% and 1.0% resulted in reductions in chloropyrifos by 43.2% and 63.1%, glyphosate by 32.8% and 77.3%, and atrazine by 21.9% and 72.2%, respectively, as compared to the control. Addition of (RC + RB) at 0.5% gave the highest pesticide immobilisation, followed (RC+RB) at 1.0%. Conclusion These results indicate that the dominant mechanisms of pesticides immobilisation in the alkaline soils amended with RC and RB by FTIR and XRD analysis were π–π interaction, pore filling, hydrophobic effect, H-bonding, degradation as well as improvement of soil properties and dry yield of canola plants. Implications Our results suggested the possibility of adding recycled rice straw in the form of compost or biochar to the contaminated soil to improve its properties, immobilise pesticides and increase its production capacity.

An Insight into the Effect of Rice Straw Biochar on Compressive Strength and Thermal Conductivity of Cement

It is well known that is very important to improve the quality of cement material concerning its compressive strength and thermal conductivity, which may reduce its quantity of usage and improve the heat maintenance of a structure compared with the traditional cement. In order to improve the properties of cement and other building materials, the test pieces were prepared by incorporating rice straw biochar with different pyrolysis temperatures into cement paste, and the compressive strength and thermal conductivity were tested after curing under both wet and dry conditions. The results showed that with the increase of biochar incorporation, the strength and thermal conductivity of the test blocks were decreased, but the thermal insulation performance of them was increased, and the quality and density of the test block were reduced. Under the condition of wet curing, the strength of the test pieces enhanced greatly with the dosage of 1% and 5%. When the dosage was 1%, the strength of the wet curing test block was the highest, which was increased by 51.06% compared with the blank control. The block strength increased by 14.98%; the thermal conductivity of the test piece incorporating biochar was reduced, and the test piece with 10% of the dry curing showed better thermal insulation performance, and the thermal conductivity was reduced by 39.21%. It can be seen that the addition of biochar improves the strength of the test block and optimizes the thermal insulation performance of the cement.

Rice Straw and Peanut Residues Biochars as Eco-Friendly Approaches for Controlling Root-Knot Nematode, Meloidogyne incognita Infecting Eggplant

Biochar is a vital carbon complex and can improve plant growth and suppress of soil-borne pathogens. Root-knot nematode, Meloidogyne incognita is identified as one of the most demoralizing pests blighting roots of many crops and lead to notable decrease in their productivities. So, the present study was carried out with a hypothesis that the application of biochar from various feed-stocks may cause significant enhancements in the tolerance of eggplant for M. incognita infection. Two types of biochars were manufactured by the slow pyrolysis process of rice straw and peanut residues. A pot experiment was conducted to explore the effects of rice straw biochar (RSB) and peanut residues biochar (PRB) on M. incognita and the growth and yield performances of eggplant in loamy soil. Eight treatments were achieved in the current experiment, resulted from the combination between RSB and PRB at four applied rates [zero =no addition, 5.25, 10.5 and 21 g/pot, which were equated to 0, 5, 10 and 20 t/ha, respectively]. Treatments were arranged in a randomized complete block design (RCBD) and with five replicates. The individual incorporation of RSB and PRB at rates of 5.25, 10.5, and 21 g/pot exhibited significant enhancements in growth parameters (length, fresh and dry weight of shoots and roots), and productivity of eggplant. Application of RSB or PRS at 21 g/pot caused superior impacts in enhancing the fresh fruit yield of eggplant (946 and 1012 g/pot). Soil pH increased after applications of RSB and PRB from 5.85 in the control treatment to 6.12-6.39 and 6.28-6.75, respectively. Both RSB and PRB revealed variable degrees in lessening numbers of egg masses and galls/root system and J2/250 g soil of M. incognita and this caused marked improvements in eggplant growth parameters in comparison to the control. The use of high doses of RSB and PRB was responsible for larger efficiency in declining the above-mentioned M. incognita parameters than their low rates. The largest declines in galls/ root system (80 and 93%), egg-masses/ root system (90 and 96%), egg/egg-mass (76 and 90%) and J2/250g soil (83 and 92%) at 50 and 90 days after transplanting (DAT) were shown after application of PRB at a rate of 21 g/pot. This study indicated that RSB and PRB can be used as effective materials in dropping the harmful effects of M. incognita and also can be recommended as eco-friendly alternatives to synthetic pesticides with marked nematicidal activity to control M. incognita infection.

Enhancing Soil Nitrogen Availability and Rice Growth by Using Urea Fertilizer Amended with Rice Straw Biochar

Urea fertilizer as a nitrogen source is used widely and globally. However, N loss through ammonia volatilization from applied urea has become a major drawback to agriculture. A pot experiment was conducted to determine the effect of rice straw biochar on (1) total N, soil exchangeable NH4+, and available NO3− (2) uptake of N, P, and K in rice plants. The treatments evaluated were: (S: Soil only, U: soil + 175 kg ha−1 urea, B1: soil + 175 kg ha−1 urea + 5 t ha−1 rice straw biochar, B2: soil + 175 kg ha−1 urea + 10 t ha−1 rice straw biochar, CB1: 50% soil + 50% commercial biochar potting media and CB2: 100% commercial biochar potting media). The addition of rice straw biochar at 5–10 t ha−1 in the pot experiment significantly increased the soil total N availability by 33.33–46.67%. Treatments B1 and B2 also had significantly increased exchangeable NH4+, NO3−, P, and K in the soil over U. The soil availability nutrients increment in soil was attributed to the higher adsorption capacity of the rice straw biochar. Increment in soil nutrient availability such as N, P, and K increased the plant height, tiller number, greenness, and panicle number because of effective rice plant absorption. This resulted in dry matter production increment in line with plant nutrient uptake and use efficiency. Rice straw biochar at 5–10 t ha−1 can improve the productivity of rice plants by increasing N retention in soil.

Effects of rice straw biochar and nitrogen fertilizer on ramie (Boehmeria nivea L.) morpho-physiological traits, copper uptake and post-harvest soil characteristics, grown in an aged-copper contaminated soil

Copper (Cu) contamination in soils is becoming a serious problem. Therefore, an experiment in plastic pots was carried out to investigate interactive influence of rice straw BC (BC0:0, BC1:5, and BC2:10% w/w) and nitrogen fertilizer (N0:0, N1:140, N2:280, and N3:420 kg ha − 1) on plant growth, Cu mobility and phytoavailability to Boehmeria nivea in Cu polluted soil. Results revealed that BC × N fertilizer had significantly (p ≤ 0.05) increased the growth of B. nivea in terms of biomass, height of plant, diameter of stem and number of leaves. Furthermore, BC × N fertilizer resulted in significant changes in pH, electrical conductivity and cation exchange capacity of soil after harvesting in comparison with control. However, the influence of BC × N fertilizer on soil extractable Cu and Cu uptake by plant varied with levels of N fertilizer. The BC2N1 treatment significantly increased the shoot biomass of B. nivea by 635% (fresh biomass) and 452% (dry biomass), but reduced Cu contents in roots, stems and leaves i.e., 52, 23 and 34 mg kg − 1, respectively. Thereby, high dose of BC along with low N fertilizer could be considered as an efficient soil amendment combination for Cu stabilization and higher biomass production of B. nivea in highly Cu contaminated soil.

Effects of biochar, farm manure, and pressmud on mineral nutrients and cadmium availability to wheat (Triticum aestivum L.) in Cd-contaminated soil.

The contamination of agricultural soils with cadmium (Cd) is one of the serious worldwide concerns for food security. Biochar and organic manures have been known for enhancing plant growth and minimizing toxic trace element stress in plants. However, less is known about the effect of different organic amendments on Cd and uptake of essential nutrients by wheat. Thus, the effects of rice straw biochar (RSB), maize stalk biochar (MSB), farmyard manure (FYM), and pressmud (PRM) at a rate of 1% w/w were tested for Cd immobilization in soil and mineral nutrient availability to wheat crop grown in Cd-spiked soil (6.0mg kg1 ). The amendments were added in Cd-spiked soil before 12 days of seed sowing and wheat plants were harvested after maturity (115 days after sowing). The findings revealed that the use of amendments improved the number of grains per spike, straw and grain yield of wheat relative to control treatment. The treatments minimized the Cd and enhanced the contents of zinc (Zn), nitrogen (N), phosphorus (P), and potassium (K) in the leaves and grain of the wheat plants. Cadmium concentrations decreased by 35, 38, 68, and 63% in wheat grain, and grain yield increased by 19, 31, 68, and 58% with the application of FYM, PRM, MSB, and RSB, respectively. Overall, the application of MSB was more efficient in decreasing Cd concentrations in leaf and grains of wheat as compared to other conventional organic amendments.

Short-term effects of rice straw biochar on hydraulic properties and aggregate stability of an Acrisol

Biochar application to a structurally poor tropical soil could potentially alter the soil’s aggregate strength and hydraulic properties. However, very few field studies have investigated the impact of biochar on the aggregate strength and hydraulic properties of tropical soils. A field experiment was therefore conducted to investigate the short-term effects of rice straw biochar on soil hydraulic properties and aggregate stability of an Acrisol in Ghana. The biochar was broadcast at rates of 10 t ha−1 and 20 t ha−1 as single applications that were incorporated into the top 20 cm of the soil using a spade and then the soil was levelled using a rake. Field saturated hydraulic conductivity and laboratory-measured soil water retention, aggregate stability and water-repellency were determined 10 months after the biochar application. Biochar increased aggregate stability against fast wetting by up to 33% compared to the control. This implies that biochar might improve the stability of aggregate of an Acrisol against slaking and erosivity of heavy rainfall. However, aggregate stability against slow wetting and mechanical breakdown after pre-wetting were unaffected by the biochar. Biochar did not affect field saturated hydraulic conductivity, water retention characteristics and water-repellency. Further field studies on weathered tropical soils with low native soil organic matter is recommended to elucidate the effect of repeated biochar addition on soil hydraulic and aggregate characteristics.

Effect of Biochar and Compost Amendments on Soil Biochemical Properties and Dry Weight of Canola Plant Grown in Soil Contaminated with Heavy Metals

ABSTRACT Soil contamination with heavy metals has resulted in a reduction of crop productivity and soil quality. We studied the effects of rice straw biochar (RB), rice straw compost (RC), and their mixtures at rates 0.5% and 1.0% on soil biochemistry and dry weight of the canola plant (Brassica napus) grown in contaminated soil with heavy metals. The results showed that the addition of the RB or RC alone or their mixtures together significantly increased contents of soil exchangeable cations, microbial biomass carbon (MBC), organic matter (OM), cations exchange capacity (CEC), availability of nutrients, NPK uptake, and dry weight of the canola plant. Soil microbial biomass carbon increased by 20.2% and 59.3% for RB, while it increased by 69.5% and 79.8% for RC with the addition of 0.5% and 1.0%, respectively, compared to the control. The results of this study reveal that the co-application of biochar with compost can be a promising strategy for improving soil productivity and soil quality in soil contaminated with heavy metals.

Effect of rice straw and swine manure biochar on N2O emission from paddy soil

We analyzed the effects of rice straw biochar (RSBC) and swine manure biochar (SMBC) on N2O emission from paddy soil. The biochars were added to soil at the rates of 1% and 5% (w/w), and N2O emission, soil properties and soil enzyme activities were determined at the elongation, heading and maturation stages of rice growth. The N2O flux started within 2 h of adding the biochar, and decreased significantly thereafter during the three growth stages. The cumulative N2O emission was suppressed by 45.14–73.96% following biochar application, and 5% SMBC resulted in the lowest cumulative emission. In addition, biochar application significantly increased soil pH, soil organic carbon (SOC), NO3− levels and urease activity, and decreased soil NH4+ and nitrate reductase activity. Regression analysis indicated that cumulative N2O emission was correlated positively to NH4+, and negatively to soil pH, SOC and NO3−. SEM further revealed that biochar application weakened the denitrification process, and the NH4+ level had the most significant impact on N2O emission. Taken together, RSBC and SMBC regulated the nitrogen cycle in paddy soil and mitigated N2O emission by increasing soil pH, decreasing nitrate reductase activity and NH4+ content.

Rice straw biochar impact on physiological and biochemical attributes of Fokienia hodginsii in acidic soil

ABSTRACTIncreasing the forest's productivity is a global concern and there is a need to develop innovative technologies. The use of biochar (BC) in the restoration of degraded sites is mounting. Therefore, to assess the effects of rice straw biochar (BR) on soil physicochemical properties and physiology of Fokienia hodginsii, a one-year greenhouse pot experiment was conducted. The soil was mixed with BR at four different levels; 0, 5, 20, and 80 g kg−1of soil as B0, BR5, BR20, and BR80, respectively. The light-response curves of photosynthesis were constructed by using the modified model of rectangular hyperbola including photosynthetic pigments and biochemical attributes quarterly. BR treated seedlings responded with a significant increase in the photosynthetic rate at first, second, and fourth season, respectively. Increasing the proportion of BR in the soil significantly influenced the soil pH and P availability. At the final harvest, improved soil and physiology promoted the seedling biomass (36%) under BR80 compared to B0. Therefore, these findings suggest that BR can be used to combat soil acidification and P availability in P deficit soil. Its amendment into the soil can be useful to alleviate the physiological performance of the conifer seedlings, but its effects may vary with soil type and BC feed-stock.

Effect of rice straw biochar on the bioavailability of cadmium in soil to Indian Mustard (Brassica juncea L. czern.) in relation to cadmium spiking

A screenhouse experiment was conducted to study the effect of four rates of rice straw biochar (0, 1, 2 and 4%) on the bioavailability and accumulation of cadmium (Cd) by Indian mustard (Brassica juncea) in sewage water irrigated soil artificially spiked with Cd. Immobilization of Cd by rice straw biochar was assessed on the basis of DTPA-extractable Cd in soil and its content in shoots of Indian mustard. The results revealed a linear decrease in DTPA-Cd with the addition of rice straw biochar. Addition of biochar at the highest level (4%) decreased the mean Cd content in soil and in plant by 38.1 and 60.1%, respectively. Biochar addition increased dry matter yield (DMY) of Indian mustard and maximum yield increase of 19.3% was observed at 2% addition. The increase in DMY was decreased to 2.6% at 4% addition of biochar. The study indicated that rice straw biochar can be used as a remediation measure for contaminated sites and may prove to be a viable option for managing agricultural residues.

Effect of amendment of biochar supplemented with Si on Cd mobility and rice uptake over three rice growing seasons in an acidic Cd-tainted paddy from central South China

To examine the effect of rice straw biochar and the synergism with silicon on Cd immobilization, a Cd-contaminated acidic sandy loam paddy, polluted from emissions from industrial activity, was chosen in central South China. A field trial was conducted over three rice growing seasons during 2016–2017. Rice straw biochar (BR), produced by the pyrolysis of rice straw pellets at 450 °C, was amended at 10 t/ha (BR1), 20 t/ha (BR2), and supplemented with 0.75 t/ha sodium silicate (SS) at 10 t/ha, (BR1 + SS) and 20 t/ha (BR2 + SS), compared to the control without biochar and sodium silicate (BR0). BR supplemented with Si enhanced Cd soil immobilization and decreased Cd accumulation in rice plant within three rice seasons. Compared to BR0, BR + SS reduced Cd concentrations in grains by 19.5–73.7%, higher than that of 8.6–50.2% following BR. Cd bio-concentration factor of the root was reduced by an average of 54.6% from BR + SS and by 19.0% from BR, compared to BR0 in last two rice seasons. BR + SS significantly increased soil pH and available Si, and soil CaCl2-Cd was negatively related to soil available Si (p < 0.05). The synergistic effect of BR and Si induced liming effect and co-precipitation of Cd with Si compounds during the aging process of biochar. Thus, we suggest that an alkaline silicon supplementation is used as an amendment to BR, which could be used as a strategic approach for tackling Cd contamination in South China rice paddies.