Physical activation of biochar and its meaning for soil fertility and nutrient leaching – a greenhouse experiment

The slow alteration of the surface of charred biomass (biochar) over time may contribute to an improved nutrient retention and thus fertility of tropical soils. Here, we investigated soils from temperate climates and investigated whether a technical steam activation of biochar could accelerate its positive effects on nutrient retention and uptake by plants relative to nonactivated biochar. To this aim, we performed microcosm experiments with sandy or silty soil, mixed with 2.0, 7.5 and 15.0 g/kg soil of fine (<2 mm) or coarse‐sized (2–10 mm) biochar from beech wood (Fagus sp.). After initial fertilizer (NPK), ashes and excess nutrients were leached with water, and the microcosms were planted for 142 days with Italian Ryegrass (Lolium multiflorum ssp. italicum). Thereafter, leachate, soil and plant samples were analysed for their nutrient contents. The results showed that biochar additions of ≤15 g/kg soil left elevated contents of available P and N in the surface soil but reduced their uptake into the plants. As a result, total biomass production was unchanged. Different particle size and application amounts influenced these findings only marginally. Nitrate leaching was enhanced in the sandy soil (+41% for nitrate, but reduced in the silty soil ?17%) and P was immobilized. Hence, the fertility of the temperate soils under study was only marginally affected by pure biochar amendments. Steam activation, however, almost doubled the positive effects of biochars in all instances, thus being an interesting option for future biochar applications.     

Biochar for crop production: potential benefits and risks

Purpose

Biochar, the by-product of thermal decomposition of organic materials in an oxygen-limited environment, is increasingly being investigated due to its potential benefits for soil health, crop yield, carbon (C) sequestration, and greenhouse gas (GHG) mitigation.

Materials and methods

In this review, we discuss the potential role of biochar for improving crop yields and decreasing the emission of greenhouse gases, along with the potential risks involved with biochar application and strategies to avoid these risks.

Results and discussion

Biochar soil amendment improves crop productivity mainly by increasing nutrient use efficiency and water holding capacity. However, improvements to crop production are often recorded in highly degraded and nutrient-poor soils, while its application to fertile and healthy soils does not always increase crop yield. Since biochars are produced from a variety of feedstocks, certain contaminants can be present. Heavy metals in biochar may affect plant growth as well as rhizosphere microbial and faunal communities and functions. Biochar manufacturers should get certification that their products meet International Biochar Initiative (IBI) quality standards (basic utility properties, toxicant assessment, advanced analysis, and soil enhancement properties).

Conclusions

The long-term effects of biochar on soil functions and its fate in different soil types require immediate attention. Biochar may change the soil biological community composition and abundance and retain the pesticides applied. As a consequence, weed control in biochar-amended soils may be difficult as preemergence herbicides may become less effective.

     

Medium-term effects of corn biochar addition on soil biota activities and functions in a temperate soil cropped to corn

Biochar addition to soil has been generally associated with crop yield increases observed in some soils, and increased nutrient availability is one of the mechanisms proposed. Any impact of biochar on soil organisms can potentially translate to changes in nutrient availability and crop productivity, possibly explaining some of the beneficial and detrimental yield effects reported in literature. Therefore, the main aim of this study was to assess the medium-term impact of biochar addition on microbial and faunal activities in a temperate soil cropped to corn and the consequences for their main functions, litter decomposition and mineralization. Biochar was added to a corn field at rates of 0, 3, 12, 30 tons ha⁻¹ three years prior to this study, in comparison to an annual application of 1 t ha⁻¹.Biochar application increased microbial abundance, which nearly doubled at the highest addition rate, while mesofauna activity, and litter decomposition facilitated by mesofauna were not increased significantly but were positively influenced by biochar addition when these responses were modeled, and in the last case directly and positively associated to the higher microbial abundance. In addition, in short-term laboratory experiments after the addition of litter, biochar presence increased NO₂ + NO₃ mineralization, and decreased that of SO₄ and Cl. However, those nutrient effects were not shown to be of concern at the field scale, where only some significant increases in SOC, pH, Cl and PO₄ were observed.Therefore, no negative impacts in the soil biota activities and functions assessed were observed for the tested alkaline biochar after three years of the application, although this trend needs to be verified for other soil and biochar types.     

Effects of biochars derived from different feedstocks and pyrolysis temperatures on soil physical and hydraulic properties

Purpose

Biochar addition to soils potentially affects various soil properties, and these effects are dependent on biochars derived from different feedstock materials and pyrolysis processes. The objective of this study was to investigate the effects of amendment of different biochars on soil physical and hydraulic properties.

Materials and methods

Biochars were produced with dairy manure and woodchip at temperatures of 300, 500, and 700 °C, respectively. Each biochar was mixed at 5 % (w/w) with a forest soil, and the mixture was incubated for 180 days, during which soil physical and hydraulic properties were measured.

Results and discussion

Results showed that the biochar addition significantly enhanced the formation of soil macroaggregates at the early incubation time. The biochar application significantly reduced soil bulk density, increased the amount of soil organic matter, and stimulated microbial activity at the early incubation stage. Saturated hydraulic conductivities of the soil with biochars, especially produced at high pyrolysis temperature, were higher than those without biochars on the sampling days. The treatments with woodchip biochars resulted in higher saturated hydraulic conductivities than the dairy manure biochar treatments. Biochar applications improved water retention capacity, with stronger effects by biochars produced at higher pyrolysis temperatures. At the same suction, the soil with woodchip biochars possessed higher water content than that with the dairy manure biochars.

Conclusions

Biochar addition significantly affected the soil physical and hydraulic properties. The effects were different with biochars derived from different feedstock materials and pyrolysis temperatures.     

Nitrification,acidification, and nitrogen leaching from subtropical cropland soils as affected by rice straw-based biochar: laboratory incubation and column leaching studies

Purpose

Few studies have examined the effects of biochar on nitrification of ammonium-based fertilizer in acidic arable soils, which contributes to NO₃ ^? leaching and soil acidification.

Materials and methods

We conducted a 42-day aerobic incubation and a 119-day weekly leaching experiment to investigate nitrification, N leaching, and soil acidification in two subtropical soils to which 300 mg N kg^?1 ammonium sulfate or urea and 1 or 5 wt% rice straw biochar were applied.

Results and discussion

During aerobic incubation, NO₃ ^? accumulation was enhanced by applying biochar in increasing amounts from 1 to 5 wt%. As a result, pH decreased in the two soils from the original levels. Under leaching conditions, biochar did not increase NO₃ ^?, but 5 wt% biochar addition did reduce N leaching compared to that in soils treated with only N. Consistently, lower amounts of added N were recovered from the incubation (KCl-extractable N) and leaching (leaching plus KCl-extractable N) experiments following 5 wt% biochar application compared to soils treated with only N.

Conclusions

Incorporating biochar into acidic arable soils accelerates nitrification and thus weakens the liming effects of biochar. The enhanced nitrification does not necessarily increase NO₃ ^? leaching. Rather, biochar reduces overall N leaching due to both improved N adsorption and increased unaccounted-for N (immobilization and possible gaseous losses). Further studies are necessary to assess the effects of biochar (when used as an addition to soil) on N.     

Reducing CH<Subscript>4</Subscript> and CO<Subscript>2</Subscript> emissions from waterlogged paddy soil with biochar

Purpose  

A potential means to diminish increasing levels of CO₂ in the atmosphere is the use of pyrolysis to convert biomass into biochar, which stabilizes the carbon (C) that is then applied to soil. Before biochar can be used on a large scale, especially in agricultural soils, its effects on the soil system need to be assessed. This is especially important in rice paddy soils that release large amounts of greenhouse gases to the atmosphere.     

The effect of biochar loading rates on soil fertility,soil biomass,potential nitrification,and soil community metabolic profiles in three different soils

Purpose

Biochar is increasingly being used as a soil amendment to both increase soil carbon storage and improve soil chemical and biological properties. To better understand the shorter-term (10 months) impacts of biochar on selected soil parameters and biological process in three different textured soils, a wide range of loading rates was applied.

Materials and methods

Biochar derived from eucalypt green waste was mixed at 0, 2.5, 5, 10 % (wt/wt) with a reactive black clay loam (BCL), a non-reactive red loam (RL) and a brown sandy loam (BSL) and placed in pots exposed to the natural elements. After 10 months of incubation, analysis was performed to determine the impacts of the biochar rates on the different soil types. Also, microbial biomass was estimated by the total viable counts (TVC) and DNA extraction. Moreover, potential nitrification rate and community metabolic profiles were assayed to evaluate microbial function and biological process in biochar-amended soils.

Results and discussion

The results showed that biochar additions had a significant impact on NH₄ and NO₃, total C and N, pH, EC, and soil moisture content in both a soil type and loading-dependent manner. In the heavier and reactive BCL, no significant impact was observed on the available P and K levels, or the total exchangeable base cations (TEB) and CEC. However, in the other lighter soils, biochar addition had a significant effect on the exchangeable Al, Ca, Mg, and Na levels and CEC. There was a relatively limited effect on microbial biomass in amended soils; however, biochar additions and its interactions with different soils reduced the potential nitrification at the higher biochar rate in the two lighter soils. Community metabolic profile results showed that the effect of biochar on carbon substrate utilization was both soil type and loading dependent. The BCL and BSL showed reduced rates of substrate utilization as biochar loading levels increased while the opposite occurred for the RL.

Conclusions

This research shows that biochar can improve soil carbon levels and raise pH but varies with soil type. High biochar loading rates may also influence nitrification and the function and activity of microbial community in lighter soils.

     

Sorption and transport of sulfonamides in soils amended with wheat straw-derived biochar: effects of water pH,coexistence copper ion,and dissolved organic matter

Purpose

Sulfonamides are widely used for the prevention and treatment of bacterial infections, hard-degraded contaminants distributed in the environment if they are discharged into the soil and water. Biochar could probably influence the geochemical behavior of ionized antibiotics in the soils.

Materials and methods

To determine the sorption/desorption of three representative sulfonamides (SAs) in soils amended with biochar, we investigated the effects of water pH, Cu²⁺, and dissolved humic acid on the sorption of sulfamethoxazole (SMX), sulfamethazine (SMZ), and sulfadiazine (SD) onto two different soil samples (S1 pH?=?5.13 and S2 pH?=?7.33) amended with wheat straw-derived biochar (size 0.5～0.6 mm).

Results and discussion

Batch experiments showed that the sorption/desorption isotherms of SAs on soil with/without biochar followed the Freundlich model. The biochar had a strong adsorption potential for SMX, SMZ, and SD both in S1 and S2 at low water pH. Except for SMX, the presence of Cu²⁺ inhibited the sorption of SMZ and SD through competing hydrophobic adsorption region in soils. HA suppressed the sorption of three sulfonamides in soil S2 by electrostatic repulsion under alkaline condition. The soil leaching column experiments showed the SA transport in soils, and S1 and S2 amended with biochar (0.5 and 1.0 wt%) brought about 12–20 % increase in SMX, SMZ, and SD retention compared to the untreated soil.

Conclusions

The results indicated that the presence of biochar effectively mitigated the mobility of ionized antibiotics such as SMX, SMZ, and SD in soils, which helps us reconsider the potential risk of antibiotics in the environment.

     

High biochar rates may suppress rice (Oryza sativa) growth by altering the ratios of C to N and available N to P in paddy soils

Although most studies have indicated that biochar can boost rice (Oryza sativa) growth, the material may also suppress it, depending on ratios of carbon (C) to nitrogen (N) and available N to available phosphorous (P). The current study sought to examine the impacts of biochar on rice growth and to identify underlying mechanisms. A pot experiment was conducted using two soils of high (3.05%) and low (0.54%) organic carbon (OC) content, mixed with 0, 1.5, 3, 6, and 12% biochar and planted with rice. Rice growth components, five rice tissue nutrients, and nine soil properties were measured. The results showed that the response of rice growth to biochar rates could be described using an exponential-growth function in high-OC soil but an inverted U-shaped curve in low-OC soil. In high-OC soil, the 12% biochar rate led to the greatest total biomass, increased by 47%, whereas in low-OC soil, the 3 and 6% rates exhibited the highest total biomass, increased by 44%, compared to the no-biochar added soils. Biochar elevated the C:N ratio from 11.5 to 39.1, with an optimal range of 20–30 corresponding to the highest rice growth. Biochar declined the ratio of NH₄-N to Mehlich-1 P, causing N deficiency. In brief, high biochar rates may suppress rice growth when the soil C:N ratio exceeds 30. The applied biochar rate should be considered based on soil properties typically OC and N content to obtain the C:N ratio between 20 and 30 for optimal rice growth.     

Mitigating Negative Microbial Effects of <Emphasis Type="Italic">p</Emphasis>-Nitrophenol,Phenol, Copper and Cadmium in a Sandy Loam Soil Using Biochar

Biochars are adsorptive solids potentially of benefit to soil microbes by providing improved nutrient retention, a carbon substrate and contaminant adsorption. A 28-day incubation experiment gauged the interactive effects of biochar application and contaminants on the microbial biomass and respiration of a sandy loam soil. Soil was amended with 250 mg/kg phenol or p-nitrophenol (two toxic but nevertheless biodegradable organic contaminants) or 50 mg/kg cadmium or copper. Biochar application generally caused increased microbial respiration and biomass relative to non-amended controls. Of the heavy metal-amended soils, Cu effected significant reductions in microbial biomass carbon and basal respiration, which were improved with concurrent biochar amendment. The biochar’s functional groups are likely to have mitigated the metals’ negative effects via complexation and sorption, while the soil’s proportion of negative pH-dependent sites was increased by the pH rise induced by biochar application, allowing more cationic retention. Organic contaminant-spiked soils had higher microbial biomass-specific respiration without biochar amendment, indicating that surviving microbes utilised the compounds and necromass as substrates. Paranitrophenol proved to be particularly toxic without biochar application, causing marked reductions in the microbial quotient and biomass carbon. Remarkably, concurrent biochar and pNP application led to hugely increased microbial biomass carbon and nitrogen, significantly higher than those in contaminant-free replicates. It is likely this arose from biochar sorbing the contaminant and allowing its microbial utilisation as a carbon and nitrogen source, stimulating growth. Biochar application is a highly promising strategy for reducing the soil microbial toxicity of heavy metals and aromatic organic contaminants, particularly p-nitrophenol.     

The Impact of Woody Biochar on Microbial Processes in Conventionally and Organically Managed Arable soils

ABSTRACT

Although environmental impacts of biochar are well characterized, impacts on soil quality, nutrient availability and crop productivity, still remain a challenge due to the diverse response of different soil types to different types of biochar, namely those obtained at low temperature. The impact of an alkaline woody biochar (two doses 5% and 10%) obtained at 280°C, on soil enzyme activity, soil microbial respiration rate, mineral nitrogen (N) availability and ammonia volatilization was studied in one conventionally and one organically managed soils, with and without the addition of urea or composted farmyard manure. Biochar additions had different effects on soil enzyme activity in both soils, suggesting lower decomposing microbial activity processes promoted by biochar. Both soils showed a similar decreasing trend regarding soil respiration rates for all treatments, and significant relationships were observed between the treatments with different rates of applied biochar, but not constant for the entire incubation period. Urea application increased soil mineral N concentrations, especially nitrate concentrations when biochar was applied as well. Biochar decreased ammonia volatilization from conventionally managed soil fertilized with urea, but did not have a significant effect when compost was added to the organically managed soil. Biochar altered microbial behavior in soil, and was affected by previous soil management. So, the impact of biochar produced at low temperatures on soil biological processes is similar to those obtained at high temperature, thus proving that there is no need to increase the energy expenditure to produce biochar, to obtain a good product.     

柳枝稷生物炭对来自不同地区的两种土壤上植物生物量和微生物动态的影响

Biochar amendments to soils may alter soil function and fertility in various ways, including through induced changes in the microbial community. We assessed microbial activity and community composition of two distinct clayey soil types, an Aridisol from Colorado (CO) in the U.S. Central Great Plains, and an Alfisol from Virginia (VA) in the southeastern US following the application of switchgrass (Panicum virgatum) biochar. The switchgrass biochar was applied at four levels, 0%, 2.5%, 5%, and 10%, approximately equivalent to biochar additions of 0, 25, 50, and 100 t ha^-1, respectively, to the soils grown with wheat (Triticum aestivum) in an eight-week growth chamber experiment. We measured wheat shoot biomass and nitrogen (N) content and soil nutrient availability and N mineralization rates, and characterized the microbial fatty acid methyl ester (FAME) profiles of the soils. Net N mineralization rates decreased in both soils in proportion to an increase in biochar levels, but the effect was more marked in the VA soil, where net N mineralization decreased from -2.1 to -38.4 mg kg^-1. The 10% biochar addition increased soil pH, electrical conductivity, Mehlich- and bicarbonate-extractable phosphorus (P), and extractable potassium (K) in both soil types. The wheat shoot biomass decreased from 17.7 to 9.1 g with incremental additions of biochar in the CO soil, but no difference was noted in plants grown in the VA soil. The FAME recovery assay indicated that the switchgrass biochar addition could introduce artifacts in analysis, so the results needed to be interpreted with caution. Non-corrected total FAME concentrations indicated a decline by 45% and 34% with 10% biochar addition in the CO and VA soils, respectively, though these differences became nonsignificant when the extraction efficiency correction factor was applied. A significant decline in the fungi:bacteria ratio was still evident upon correction in the CO soil with biochar. Switchgrass biochar had the potential to cause short-term negative impacts on plant biomass and alter soil microbial community structure unless measures were taken to add supplemental N and labile carbon (C).     

Biochar nutrient availability rather than its water holding capacity governs the growth of both C3 and C4 plants

Purpose

Biochar has been suggested as a soil conditioner to improve soil fertility and crop productivity while simultaneously mitigate global climate change by storing carbon in the soil. This study investigated the effect of pine (Pinus radiata) biochar application on soil water availability, nitrogen (N) and carbon (C) pools and growth of C3 and C4 plants.

Materials and methods

In a glasshouse pot trial, a pine biochar (untreated) and nutrient-enriched pine biochar were applied to a market garden soil with C3 (Spinacia oleracea L.) and C4 (Amaranthus paniculatus L.) plants at rates of 0, 1.0, 2.0, and 4.0 % (w/w). Plant biomass, soil pH, moisture content, water holding capacity (WHC), hot water extractable organic C (HWEOC), and total N (HWETN), total C and N, and their isotope compositions (δ ¹³C and δ ¹⁵N) of soils and plants were measured at the end of the experimentation.

Results and discussion

The soil moisture content increased while plant biomass decreased with increasing untreated biochar application rates. The addition of nutrient-enriched biochar significantly improved plant biomass in comparison to the untreated biochar addition at most application rates. Biochar application also increased the levels of labile organic C and N pools as indicated by HWEOC and HWETN.

Conclusions

The results suggested that the addition of pine biochar significantly improved soil water availability but not plant growth. The application of nutrient-enriched pine biochar demonstrated that the growth of C3 and C4 plants was governed by biochar nutrient availability rather than its water holding capacity under the pot trial condition.

     

Response of CaCl<Subscript>2</Subscript>-extractable heavy metals,polychlorinated biphenyls,and microbial communities to biochar amendment in naturally contaminated soils

Purpose

Biochar can be used to reduce the bioavailability and leachability of heavy metals, as well as organic pollutants in soils through adsorption and other physicochemical reactions. The objective of the study was to determine the response of microbial communities to biochar amendment and its influence on heavy metal mobility and PCBs (PCB52, 44, 101, 149, 118, 153, 138, 180, 170, and 194) concentration in application of biochar as soil amendment.

Materials and methods

A pot (macrocosm) incubation experiment was carried out with different biochar amendment (0, 3, and 6 % w/w) for 112 days. The CaCl₂-extractable concentration of metals, microbial activities, and bacterial community were evaluated during the incubation period.

Results and discussion

The concentrations of 0.01 M CaCl₂-extractable metals decreased (p?>?0.05) by 12.7 and 20.5 % for Cu, 5.0 and 15.6 % for Zn, 0.2 and 0.5 % for Pb, and 1.1 and 8.9 % for Cd, in the presence of 3 and 6 % of biochar, respectively, following 1 day of incubation. Meanwhile, the total PCB concentrations decreased from 1.23 mg kg^?1 at 1 day to 0.24 mg kg^?1 at 112 days after 6 % biochar addition, representing a more than 60 % decrease relative to untreated soil. It was also found out that biochar addition increased the biological activities of catalase, phosphatase, and urease activity as compared with the controls at the same time point. Importantly, the Shannon diversity index of bacteria in control soils was 3.41, whereas it was 3.69 and 3.88 in soils treated with 3 and 6 % biochar soil. In particular, an increase in the number of populations with the putative ability to absorb PCB was noted in the biochar-amended soils.

Conclusions

The application of biochar to contaminated soils decreased the concentrations of heavy metals and PCBs. Application of biochar stimulated Proteobacteria and Bacteroides, which may function to absorb soil PCB and alleviate their toxicity.

     

Biochar addition affected the dynamics of ammonia oxidizers and nitrification in microcosms of a coastal alkaline soil

Biochar amendments have frequently been reported to alter microbial communities and biogeochemical processes in soils. However, the impact of biochar application on bacterial (AOB) and archaeal ammonia oxidizers (AOA) remains poorly understood. In this study, we investigated the responses of AOB and AOA to the application of biochar derived from cotton stalk at rates of 5, 10, and 20 % by weight to a coastal alkaline soil during a 12-week incubation. The results showed that the amoA gene of AOB consistently outnumbered that of AOA, whereas only the AOA amoA gene copy number was significantly correlated with the potential ammonia oxidation (PAO) rate (P?<?0.01). The significant decrease of PAO rates in biochar treatments occurred after incubation for 4–6 weeks, which were distinctly longer than that in the control (2 weeks). The PAO rates were significantly different among treatments during the first 4 weeks of incubation (P?<?0.05), with the highest usually in the 10 % treatment. Biochar application significantly increased the abundance of both nitrifiers in the 4 weeks of incubation (P?<?0.05). Biochar amendment also decreased AOA diversity, but increased AOB diversity, which resulted in different community structures of both nitrifiers (P?<?0.01), as shown by the differences between the 5 % biochar and the control treatments. We conclude that biochar application generally enhanced the abundance and altered the composition of ammonia oxidizers; the rate of biochar application also affected the rate and dynamics of nitrification, and the risk for increasing the alkalinity and N leaching of the studied soil was lower with a lower application rate.     

Nutrient availability and corn growth in a poultry litter biochar‐amended loam soil in a greenhouse experiment

Nutrient‐rich biochar produced from animal wastes, such as poultry litter, may increase plant growth and nutrient uptake although the role of direct and indirect mechanisms, such as stimulation of the activity of mycorrhizal fungi and plant infection, remains unclear. The effects of poultry litter biochar in combination with fertilizer on mycorrhizal infection, soil nutrient availability and corn (Zea mays L.) growth were investigated by growing corn in a loam soil in a greenhouse with biochar (0, 5 and 10 Mg/ha) and nitrogen (N) and phosphorus (P) fertilizer (0, half and full rates). Biochar did not affect microbial biomass C or N, mycorrhizal infection, or alkaline phosphomonoesterase activities, but acid phosphomonoesterase activities, water‐soluble P, Mehlich‐3 Mg, plant height, aboveground and root biomass, and root diameter were greater with 10 Mg/ha than with no biochar. Root length, volume, root tips and surface area were greatest in the fully fertilized soil receiving 10 Mg/ha biochar compared to all other treatments. The 10 Mg/ha biochar application may have improved plant access to soil nutrients by promoting plant growth and root structural features, rather than by enhancing mycorrhizal infection rates.     

Biochar mediated alterations in herbicide breakdown and leaching in soil

Biochar application to soil has been proposed as a mechanism for improving soil quality and the long term sequestration of carbon. The implications of biochar on pesticide behavior, particularly in the longer term, however, remains poorly understood. Here we evaluated the influence of biochar type, time after incorporation into soil, dose rate and particle size on the sorption, biodegradation and leaching of the herbicide simazine. We show that typical agronomic application rates of biochar (10-100 t ha⁻¹) led to alterations in soil water herbicide concentrations, availability, transport and spatial heterogeneity. Overall, biochar suppressed simazine biodegradation and reduced simazine leaching. These responses were induced by a rapid and strong sorption of simazine to the biochar which limits its availability to microbial communities. Spatial imaging of ¹⁴C-labeled simazine revealed concentrated hotpsots of herbicide co-localized with biochar in the soil profile. The rate of simazine mineralization, amount of sorption and leaching was inversely correlated with biochar particle size. Biochar aged in the field for 2 years had the same effect as fresh biochar on the sorption and mineralization of simazine, suggesting that the effects of biochar on herbicide behavior may be long lasting. We conclude that biochar application to soil will reduce the dissipation of foliar applied pesticides decreasing the risk of environmental contamination and human exposure via transfer in the food chain, but may affect the efficacy of soil-applied herbicides.     

Biochar-mediated changes in soil quality and plant growth in a three year field trial

While many laboratory studies have focused on the short term effects of biochar addition to soil), there have been comparatively few tracing its longer term effects in the field. This study investigated the multiyear impact of biochar on crop performance and soil quality with specific emphasis on carbon (C) and nitrogen (N) cycling over a 3 y period. Biochar was added to an agricultural field at 0, 25 and 50 t ha^?1 and planted with maize (year 1) and grass (years 2 and 3). Biochar addition affected plant performance in the grass crop with significant increases in foliar N (year 2) and above-ground biomass (year 3). Below-ground, biochar increased soil respiration, fungal and bacterial growth rate and turnover in year 2. This change coincided with a shift toward a bacterial dominated decomposer community, suggesting a decrease in the potential for microbially mediated C sequestration. Biochar did not affect dissolved organic C (DOC) and N (DON), NO₃^? or NH₄⁺ pool sizes. Similarly, biochar addition had limited effects on the turnover of ¹⁴C-labelled SOC (plant litter), DOC (sugars and organic acids) and DON (amino acids) and no long term effect on N mineralization, NH₃ volatilization, denitrification and NH₄⁺ sorption. After 3 years in the field, the alkalinity associated with the biochar had been fully neutralized and biochar lost most of its cations (K, Na, Ca) but had built up an associated microbial community. We conclude that biochar addition to soil causes small and potentially transient changes in a temperate agroecosystem functioning. Importantly, many of the short-term effects of biochar on plant growth and soil behavior reported from laboratory studies were not observed in the field emphasizing the need for long term field trials to help inform agronomic management decisions involving biochar.     

Biochar concomitantly increases simazine sorption in sandy loam soil and lowers its dissipation

Biochar application has been receiving much attention as pesticide pollution mitigator because it reduces harmful chemicals. However, direct comparisons between the effect of biochar and straw on the simazine fate in soils remain poorly understood. We explored the impact of biochars and straw on the simazine behavior in a soil using a ¹⁴C labeling approach. Biochar was produced by the thermal treatment of wheat straw at four contrasting temperatures (250, 350, 450 and 550°C) and was incorporated into a sandy loam soil. The sorption of simazine in the biochar soil from 83.9% to 87.5% was significantly higher than 43.0% in the unamended soil and 35.7% in the soil amended with unprocessed straw, thus resulting in low samizine leaching from 21.8% to 42.6% in the biochar soil. However, biochar application suppressed the simazine decomposition, which is contrast in the straw soil. Furthermore, the biogeochemical behavior of simazine varied with the pyrolysis temperature. These results indicate biochar application can significantly increase simazine adsorption and reduce leaching, which is benefit to the environmental pollution. In conclusion, the simazine behaviors in the soil are strongly influenced by the biochar properties. In comparison to straw, biochar has potential to mitigate simazine pollution.     

生物质炭施用及老化对石灰性紫色土中磺胺类抗生素迁移特征的影响

以长江上游低山丘陵区广泛分布的石灰性紫色土旱地的耕作层土壤为对象,采用室内批量平衡吸附试验和填装土柱穿透试验,研究了施用1%生物质炭及3年老化作用对2种磺胺类抗生素(磺胺嘧啶和磺胺二甲基嘧啶)吸附和迁移特征的影响。结果表明,Freundlich方程能更好地拟合抗生素在土壤中的等温吸附曲线,施用生物质炭提高了土壤对抗生素的吸附能力,吸附常数KF值依次为:老化1%施炭土>新鲜1%施炭土>对照土;土柱出流液的磺胺嘧啶和磺胺二甲基嘧啶相对浓度峰值均表现为:老化1%施炭土<新鲜1%施炭土<对照土,说明生物质炭的添加能有效减少控制紫色土中抗生素的淋失迁移,以对磺胺二甲基嘧啶的阻控效果较好;生物质炭老化3 a后土壤对抗生素的吸附作用与阻控效果均有所提高,主要归因于土壤pH的提高。