Biochar Addition Rate Research Articles

Alteration of extracellular enzyme activity and microbial abundance by biochar addition: Implication for carbon sequestration in subtropical mangrove sediment

Biochar has attracted more and more attention due to its essential role in adsorbing pollutants, improving soil fertility, and modifying greenhouse gas emission. However, the influences of biochar on extracellular enzyme activity and microbial abundance are still lack and debatable. Currently, there is no information about the impact of biochar on the function of mangrove ecosystems. Therefore, we explored the effects of biochar on extracellular enzyme activity and microbial abundance in subtropical mangrove sediment, and further estimated the contribution of biochar to C sequestration. In this study, sediments were amended with 0 (control), 0.5, 1.0 and 2.0% of biochar and incubated at 25 °C for 90 days. After incubation, enzyme activities, microbial abundance and the increased percentage of sediment organic C content were determined. Both increase (phenol oxidase and β-glucosidase) and decrease (peroxidase, N-acetyl-glucosaminidase and acid phosphatase) of enzyme activities were observed in biochar treatments, but only peroxidase activity showed statistical significance (at least p < 0.01) compared to the control. Moreover, the activities of all enzymes tested were significantly related to the content of biochar addition (at least p < 0.05). On the other hand, bacterial and fungal abundance in biochar treatments were remarkably lower than control (p < 0.001), and the significantly negative relationship (p < 0.05) between bacterial abundance and the content of biochar was found. Additionally, the increased percentage of organic C gradually increased with biochar addition rate, which provided evidence for applying biochar to mitigate climate change. Given the importance of microorganisms and enzyme activities in sediment organic matter decomposition, the increased C sequestration might be explained by the large decrease of microbial abundance and enzyme activity after biochar intervention.

Long-term effect of biochar application on yield-scaled greenhouse gas emissions in a rice paddy cropping system: A four-year case study in south China

To evaluate long-term effect of biochar application on yield-scaled greenhouse gas emissions (YSGE) in a paddy rice cropping system, a 4-year field experiment by static chamber - gas chromatograph method was conducted in South China. Principal component analysis and terminal restriction fragment length polymorphism (T-RFLP) and real-time qPCR was used to unravel the microbial mechanisms of biochar addition. Six treatments were included: control (CK), application of 5tha−1 biochar (BC1), application of 10tha−1 biochar (BC2), application of 10tha−1 biochar (BC3), rice straw return at 2400kgha−1(RS) and inoculated rice straw return at 2400kgha−1(RI). The results indicated that biochar amendment significantly decreased methane (CH4) and gross greenhouse gas (GHG) emissions. This may primarily be ascribed to the stimulated biodiversity and abundance of methanotrophic microbes, increased soil pH and improved aeration by reducing bulk density after biochar incorporation. Compared with CK, RS and RI, 26.18%, 70.02%, 66.47% of CH4 flux and 26.14%, 70.16%, 66.46% of gross GHG emissions were reduced by biochar (mean of three biochar treatments), respectively. Furthermore, biochar significantly increased harvest index of double rice production (p<0.05). In comparison with CK, RS and RI, 29.14%, 68.04%, 62.28% of YSGE was reduced by biochar, respectively, and the highest biochar addition rate (20tha−1) contributed most to the mitigation of GHG emissions (36.24% decrease compared to CK) and improvement of rice yield (7.65% increase compared to CK). Results of our study suggested that long-term application of biochar should be the potential way to mitigate GHGs emissions and simultaneously improve rice productivity in the paddy rice system.

Relative influence of soil- vs. biochar properties on soil phosphorus retention

Properties of biochar are thought to determine whether phosphorus (P) sorption or increased P availability occur following biochar application to sandy acidic soil; the effect of soil properties on P retention in biochar-amended acid soils remains largely unexplored. Our objective was to determine effects of hardwood biochar and poultry litter biochar on P sorption and release from two soils differing in P retention properties at three rates of biochar addition. Soils as well as soil+biochar mixtures were treated with 12 levels of solution P concentrations. Phosphorus concentration and the amount of P sorbed for each level of P addition at the end of the incubation showed that after P addition corresponding to the soil P storage capacity (SPSC) as determined prior to biochar application, P retention abruptly declined for all treatments irrespective of biochar type. Biochar did not diminish the capacity of the two soils to tenaciously bind P added as a soluble inorganic source. Also, the maximum P retention capacity of the soil (Smax) increased as amount of biochar applied increased. Biochar-enhanced P sorption at high solution concentrations would be environmentally beneficial only if the sorption were strongly hysteretic such that subsequent P release is minimal as concentrations approach background levels. X-ray diffraction analysis of the biochar after incubating at high P solution concentration did not reveal formation of a stable crystalline P phase. This study provides evidence that the amount of P that can be “safely” added to soils amended with biochar depends significantly upon the P retention property of the soil, and not only the biochar characteristics.

Restoration of carbon and microbial activity in salt-induced soil by application of peanut shell biochar during short-term incubation study

For the present study, soil samples of four artificially-induced salinity gradients (S0: control, S1: 2.0, S2: 4.0, S3: 6.0 ECiw) was incubated with fine-textured peanut shell biochar at various ratios (B0: control, B1: 2.5%, B2: 5.0%, B3: 10% w/w) for 30 days. At 1, 3, 7, 15, 30 days of incubation, samples were analyzed for soil carbon and selected enzyme activities. Results showed that biochar could increase soil organic carbon on application of highest rate of biochar addition (B3), hence potentially restored the saline soils by less C mineralization, and more sequestration of soil C. However, soil enzyme activities were biochar rate(s), day(s) of incubation and enzyme dependent. The lowest rate of biochar addition (B1) showed highest dehydrogenase (20.5 μg TPF g−1 soil h−1), acid phosphatase (29.1 μg PNP g−1 soil h−1) and alkaline phosphatase (16.1 μg PNP g−1 soil h−1) whereas the higher rate (B2) increased the urease (5.51 μg urea-N g−1 soil h−1) and fluorescein diacetate hydrolyzing activities (3.95 μg fluorescein g−1 OD soil h−1) in soil. All the positive changes persisted at higher levels of salinity (S2, S3) suggesting biochar-amended soil may be potential for better nutrient cycling. Soil enzymes were found to be correlated with soil carbon and with each other while principal component analysis (PCA) extracted the most sensitive parameters as the acid and alkaline phosphatases and urease activities in the present experimental condition. This is the first time report of examining soil microbial environment using peanut shell biochar under a degraded (saline) soil.

Addition impact of biochar from different feedstocks on microbial community and available concentrations of elements in a Psammaquent and a Plinthudult

Biochars generated from swine manure, fruit peels, Phragmites australis and Brassica rapa were applied to a Psammaquent and a Plinthudult. The Phospholipid (PLFA) markers indicating different microbial communities and available concentrations of elements (K, Ca, Na, Mg, Al, Cr, Cu, Zn, Cd, Pb, Ni, As, Mn, Fe, B, Mo) were measured. Relationships between microbial communities and available concentrations of elements were also calculated. Microbial communities such as bacteria, fungi, protozoa, actinobacteria, G+ve and G-ve were significantly changed within biochar type and application rate compared to the control soils. The ratio of PLFAs indicating nutritional and environmental stress in microbial communities were increased in all biochar treatments to the Plinthudult but reduced in the Psammaquent compared to the control soils. The biochar addition to soils also changed the soil available element concentrations. Such as, swine manure biochar 3% significantly increased the Ca, Mg, Cu, Zn, As and Mo available concentrations in both soils. Study concludes that different biochar types and addition rates to soils changed the microbial community structure and available element concentrations in soils. Furthermore, biochars containing lower concentration of elements such as fruit peel and B. rapa biochar application to soils can reduce the availability of elements in soils.

Soil N transformation and microbial community structure as affected by adding biochar to a paddy soil of subtropical China

We have had little understanding on the effects of different types and quantities of biochar amendment on soil N transformation process and the microbial properties. In this study, various biochars were produced from straw residues and wood chips, and then added separately to a paddy soil at rates of 0.5, 1 and 2% (w/w). The effects of biochar application on soil net N mineralization and nitrification processes, chemical and microbial properties were examined in the laboratory experiment. After 135 d of incubation, addition of straw biochars increased soil pH to larger extent than wood biochars. The biochar-amended soils had 37.7, 7.3 and 227.6% more soil organic carbon (SOC), available P and K contents, respectively, than the control soil. The rates of net N mineralization and nitrification increased significantly as biochars quantity rose, and straw biochars had greater effect on N transformation rate than wood biochars. Soil microbial biomass carbon increased by 14.8, 45.5 and 62.5% relative to the control when 0.5, 1 and 2% biochars (both straw- and wood-derived biochars), respectively, were added. Moreover, biochars amendments significantly enhanced the concentrations of phospholipid fatty acids (PLFAs), as the general bacteria abundance increased by 161.0% on average. Multivariate analysis suggested that the three rice straw biochar (RB) application levels induced different changes in soil microbial community structure, but there was no significant difference between RB and masson pine biochar (MB) until the application rate reached 2%. Our results showed that biochars amendment can increase soil nutrient content, affect the N transformation process, and alter soil microbial properties, all of which are biochar type and quantity dependent. Therefore, addition of biochars to soil may be an appropriate way to disposal waste and improve soil quality, while the biochar type and addition rate should be taken into consideration before its large-scale application in agro-ecosystem.

Soil amendment with biochar increases maize yields in a semi-arid region by improving soil quality and root growth

Biochar has been widely proposed as a relatively novel approach to improve soil quality and increase crop productivity, but its underlying mechanisms are not well understood. A large root system in plants is either a constitutive or an inducible trait dependent on the uptake of resources and the production of shoot dry matter. Here a field experiment was conducted to investigate the effects of biochar amendment on the dynamic growth and development of maize (Zea mays L.), both above- and belowground, and to explore the relationship between soil condition, root traits and shoot biomass over two growing seasons on the Loess Plateau in northern China. Biochar was added to a maize field at rates of 0, 10, 20 and 30 t ha–1 without mulching and at rates of 0 and 20 t ha–1 with film mulching before sowing the first crop. The application of straw biochar with 30 t ha–1 decreased soil bulk density by 12% and increased soil total porosity by 13% in the 0–10-cm soil layer 6 months after biochar addition. Biochar amendment increased soil organic carbon, total soil nitrogen, carbon : nitrogen ratio, and available phosphorus and potassium at the end of each growing season. Although, root growth was inhibited at a rate of 30 t ha–1 in the early stage of the first year, biochar amendment exhibited a positive effect in other stages, resulting in higher root weight density, root length density and root surface-area density. These responses led to higher growth rates, maize biomass, grain yields and uptake of nitrogen, phosphorus and potassium as the rate of biochar addition increased. Film mulching with biochar amendment achieved the greatest root and shoot biomass and grain yield in both crops, despite differences in climate conditions. Biochar aged in the field for 2 years had the same effect on soil properties and crop production, suggesting that the application of straw biochar may be a promising option for increasing productivity in semi-arid farmland.

Maize biochar addition rate influences soil enzyme activity and microbial community composition in a fluvo-aquic soil

Biochar addition to soil has been proposed as a strategy to enhance soil quality and crop productivity, which may also affect microbial activity. However, the response of soil enzymes and microbial community composition to biochar addition and the main factors that drive their consequent behavior have rarely been studied. Therefore, to investigate the combined effect of different amounts of biochar (0, 0.5, 1.0, 2.5 and 5.0% by mass) and urea application on soil nutrients, enzymatic activities and microbial community in a fluvo-aquic soil, we conducted a 90-day laboratory study. Increased maize biochar addition led to significantly increased soil organic carbon (SOC), total N, and exchangeable K and reduced soil exchangeable Ca. Soil total N and exchangeable Ca were dominant factors affecting soil enzyme activities. Activities of soil extracellular enzymes involved in C and S cycling (except β-xylosidase) suggested lower amounts of biochar addition (0.5% by mass) could increase soil enzyme activities, while higher amounts of biochar addition reduce soil enzyme activities. However, the activities of l-leucine aminopeptidase and urease, both of which are involved in N cycling, increased with the increase of biochar addition rate. Total phospholipid fatty acid content and the relative abundance of bacteria were significantly reduced with increasing biochar addition rate. The relative abundance of fungi in the urea-amended soil was significantly higher than that in the other treated soils, and abundance of actinomycetes did not show a clear response to biochar addition. The changes in the microbial community composition were mainly related to SOC and total N contents, with a significant negative correlation. We concluded that the effect of biochar addition on soil enzymes and microbial community composition was highly variable. There is an urgent need to further estimate both the positive and negative long-term effects of biochar on the soil quality and crop productivity in this region.

Controls and dynamics of biochar decomposition and soil microbial abundance, composition, and carbon use efficiency during long-term biochar-amended soil incubations

The process-level understanding of biochar-C decomposition and microbial utilization in soils is poorly understood as well as how these dynamics vary across different addition rates and soil types. We present results from a 30-month laboratory incubation, where oak-derived biochar was added at 0, 1, 5, 10, and 20 % rate by weight to four soils varying in soil properties. We determined biochar-C loss using natural abundance 13C isotope coupled to measurements of CO2 efflux. We measured microbial abundance, composition, and C use efficiency (CUE) using phospholipid fatty acid biomarkers and 13C labeled glucose, respectively. After 30 months, the amount of the remaining biochar-C was insignificantly different between different biochar addition rates, suggesting that biochar-C loss is proportional to biochar addition rates. In soils with higher C contents (i.e., >1.5 %), biochar decomposition rates appeared to slow down after initial fast decomposition; while biochar decomposition rates followed one-pool model for soils with lower C. Soil microbial composition significantly changed at 10 or 20 % addition rate after 30 months, which was correlated with the increase in soil C/N. The highest CUE was found at 1 or 5 %, depending on soil types.

Biochar Reduces Zinc and Cadmium but not Copper and Lead Leaching on a Former Sewage Field.

The leaching of trace metals from anthropogenically contaminated sites poses the risk of groundwater pollution. Biochar has recently been proposed as a soil additive to reduce trace-metal concentrations in the soil solution and to increase water retention, thus reducing drainage. However, field studies on the effects of biochar addition on trace-metal leaching are scarce. Therefore, we added 0, 1, 2.5, and 5 g 100 g of biochar derived from giant miscanthus ( × J.M. Greef & Deuter ex Hodk. & Renvoize) to soil contaminated by former wastewater irrigation and examined water retention and cumulative leaching of Zn, Cd, Cu, and Pb in a 2-yr field study. Cumulative trace-metal leaching was determined by self-integrating accumulators (SIAs) based on ion-exchange resins and compared with data calculated from mean concentrations in the soil solution collected with tension lysimeter plates and groundwater recharge rate. The highest rate of biochar addition increased water retention and thus reduced the amount of drainage water. Mean cumulative Zn and Cd fluxes decreased due to both reduced concentrations in the soil solution and reduced drainage. Although Cu and Pb concentrations in the soil solution increased with biochar addition, the reduced drainage resulted in similar fluxes in the biochar and the control treatment. The cumulative Zn, Cd, and Cu fluxes determined with SIAs were in the same range as the calculated values, while SIA-based Pb fluxes were much higher than those calculated. Since the suction plates excluded colloids, the high SIA-based Pb fluxes indicate colloidal transport and reveal the importance to elucidate the colloidal pathway for risk assessment.

Changes in microbial community structure due to biochars generated from different feedstocks and their relationships with soil chemical properties

Biochars produced from swine manure (SM), fruit peels (FP), Phragmites australis (PA) and Brassica rapa (BR) were applied at different rates to a sandy loam soil at 70% moisture. Phospholipid fatty acid (PLFA) measurements showed that feedstock type, biochar type and application rate significantly affected the soil microbial communities. PLFAs derived from bacteria, fungi, actinomycetes, G+ve and G−ve bacteria and sulfate reducers were higher with FP biochar at 3% and 1% weight: weight (wt:wt), respectively, followed by SM at 1% and PA biochar at 3%, than in the control soil. The control soil also contained higher concentrations of certain iso:anteiso PLFAs, which are indicative of environmental stress, than did biochar treated soils. Protozoa PLFAs only increased in PA 3% and BR 1% treatments. Redundancy analysis illustrated the relationships between microbial communities and chemical properties within biochar types and addition rates to soil. The analysis indicated that different biochars induced different chemical changes such as increased pH, dissolved organic carbon and total carbon and nitrogen in soil and changed the microbial community structure. These properties may be used as indicators of both soil improvement and C sequestration.

Biochar addition rate influences soil microbial abundance and activity in temperate soils

SummaryBiochar (BC) amendment to soils is a proposed strategy to improve soil fertility and mitigate climate change. However, before this can become a recommended management practice, a better understanding of the impacts of BC on the soil biota is needed. We determined the effect of addition rates (0, 1, 5, 10 and 20% by mass) of a fast‐pyrolysis wood‐derived BC on the extraction efficiency (EE), abundance and temporal dynamics of phospholipid fatty acids (PLFAs, microbial community biomarkers) in four temperate soils during a 1‐year incubation. Additionally, the effects on microbial mineralization/incorporation of BC‐C were determined by measuring CO2 efflux and the BC contribution to CO2 and PLFA‐C using the natural 13C abundance difference between BC and soils. Biochar addition proportionally increased microbial abundance in all soils and altered the community composition, particularly at the greatest addition rate, towards a more gram‐negative bacteria‐dominated (relative to fungi and gram‐positive) community. Though chemically recalcitrant, the BC served as a substrate for microbial activity, more so at large addition rates and in soil with little organic matter. Microbial utilization of BC‐C for growth could only partially explain the observed increase in microbial biomass, suggesting that other, potentially abiotic, mechanisms were involved. The strong decrease in PLFA EE (−77%) in all soils with biochar addition emphasizes the need to measure and correct for EE when using PLFA biomarkers to estimate soil microbial responses to BC additions. Overall, our study provides support for BC use as a soil amendment that potentially stimulates microbial activity and growth.

Soil Nematode Response to Biochar Addition in a Chinese Wheat Field

While studies have focused on the use of biochar as soil amendment, little attention has been paid to its effect on soil fauna. The biochar was produced from slow pyrolysis of wheat straw in the present study. Four treatments, no addition (CK) and three rates of biochar addition at 2 400 (B1), 12 000 (B5) and 48 000 kg ha−1 (B20), were investigated to assess the effect of biochar addition to soil on nematode abundance and diversity in a microcosm trial in China. The B5 and B20 application significantly increased the total organic carbon and the C/N ratio. No significant difference in total nematode abundance was found among the treatments. The biochar addition to the soil significantly increased the abundance of fungivores, and decreased that of plant parasites. The diversity of soil nematodes was significantly increased by B1 compared to CK. Nematode trophic groups were more effectively indicative to biochar addition than total abundance.

Phosphorus availability in soils amended with wheat residue char

Plant availability and risk for leaching and/or runoff losses of phosphorus (P) from soils depend among others on P concentration in the soil solution. Water-soluble P in soil measures soil solution P concentration. The aim of this study was to understand the effect of wheat residue char (biochar) addition on water-soluble P concentration in a wide range of biochar-amended soils. Eleven agricultural fields representing dominant soil texture classes of Swedish agricultural lands were chosen. Concentrations of water-soluble P in the soils and in biochar were measured prior to biochar incorporation to soils in the laboratory. Experiments with three dominant soil textures—silt loam, clay loam, and an intermediate loam soil with different rates of biochar addition (i.e., 0.5, 1, 2, and 4 %; w/w) showed that the highest concentration of water-soluble P was achieved at an application rate of 1 %. At higher application rates, P concentrations decreased which coincided with a pH increase of 0.3–0.7 units. When the 11 soils were amended with 1 % (w/w) biochar, water-soluble P concentrations increased in most of the soils ranging from 11 to 253 %. However, much of the water-soluble P added through the biochar was retained (33–100 %). We concluded that wheat residue char can act as a source of soluble P, and low and high additions of biochar can have different effects on soil solution P concentration due to possible reactions with Ca and Mg added with biochar.

Co‐generated fast pyrolysis biochar mitigates green‐house gas emissions and increases carbon sequestration in temperate soils

AbstractChar is a product of thermochemical conversion of biomass via pyrolysis, together with gas (syngas), liquid (bio‐oil), and heat. Fast pyrolysis is a promising process for bio‐oil generation, which leaves 10–30% of the original biomass as char. Char produced for soil application, is defined biochar (BC), and it may increase soil C storage, and reduce soil emissions of greenhouse gases (GHG), such as N2O and CH4 –potentially making fast pyrolysis bioenergy generation a C‐negative system. However, differences in production conditions (e.g., feedstock, pyrolysis temperature and speed, post handling, and storage conditions) influence the chemical properties of BC and its net effect when added to soils. Understanding if fast pyrolysis BC can increase C sequestration and reduce GHG emissions will enable full assessment of the economic value and environmental benefits of this form of bioenergy. We characterized a BC produced by fast pyrolysis for bio‐oil generation and examined GHG (CO2, N2O and CH4) efflux, C partitioning using δ13C, and soil C sequestration across four temperate soils and five BC rates; 0%, 1%, 5%, 10%, and 20% w/w. The fast pyrolysis process created a highly aromatic, low N, ash‐rich BC with a O : C ratio of 0.01, which we expected to be highly recalcitrant. Across soils, CO2 emissions increased linearly and N2O emissions decreased exponentially with increasing BC addition rates. Despite still being actively respired after 2 years, total BC‐derived C‐CO2 comprised less than the BC volatile C content (4%). Expressed as CO2 equivalents, CO2 was the primary GHG emitted (97.5%), followed by N2O. All GHG emissions were small compared to the total SOC sequestered in the BC. Fast pyrolysis produced a highly recalcitrant BC that sequestered C and reduced GHG emissions. The recovery and soil application of BC would contribute to a negative carbon balance for this form of bioenergy generation.