•A one-year experiment was conducted in a field used to grow annual ryegrasses.•Manure was applied at a rate of 150m3ha−1 (410kgNha−1) to all treatments.•We included a control and two biochar ...treatments (5.7tha−1 and 18.8tha−1).•Biochar did not impact GHG emission but temporarily decreased NO3 in leachate.•Biochar increased K in leachate and temporarily increased P and NH4 in leachate.
Manure generated by dairy cattle is a useful soil amendment but contributes to greenhouse gas (GHG) emissions and water pollution from nutrient leaching. In order to assess the impact of pine chip biochar produced at a peak temperature of 550°C when added to a dairy grassland system, a one-year field study was conducted on a sandy loam soil under annual ryegrass (Lolium multiflorum Lam.) grown for silage in Petaluma, California. Manure was applied to all plots at a rate of ca. 150m3ha−1 (410kgNha−1). Control plots received no biochar, high application biochar plots (HB) received biochar (with a 17% ash content) at a rate of 18.8tha−1, and low application biochar plots (LB) received the same biochar at 5.7tha−1. Although the HB plots demonstrated the lowest cumulative nitrous oxide (N2O) and methane (CH4) emissions, there was no significant difference between treatments (p=0.152 and p=0.496, respectively). Soil pH results from samples collected throughout the year indicated a significant treatment effect (p=0.046), though Tukey test results indicated that there was no difference between mean values. Soil total carbon was significantly higher in HB plots at the end of the experiment (p=0.025) and nitrate (NO3−) intensity throughout the year (which expresses potential exposure of NO3− to the soil microbial community) was significantly lower in HB plots compared to the control (p=0.001). Annual cumulative potassium (K+) loss from HB plots was significantly higher than from the other treatments (p=0.018). HB plots also demonstrated a short-term increase in phosphorus (P) and ammonium (NH4+) in leachate during the first rainfall event following manure and biochar application (p<0.0001 and p=0.0002, respectively) as well as a short-term decrease of NO3− in leachate during a heavy rainfall event following a long dry spell (p=0.036), though differences between treatments for cumulative nutrient losses were not significant (p=0.210, p=0.061, and p=0.295, respectively for P, NH4+, and NO3−). These data indicate that biochar produced from pine wood chips at 550°C having high ash content (17%) is not likely to impact GHG emissions in systems with high manure application rates. Further research should be conducted in order to investigate the impact of biochar amendment on the dynamics and mobility of nutrients applied in subsequent repeated applications of dairy manure.
Manure generated by intensive livestock operations poses potential ecological risk in the form of water pollution and greenhouse gas emission. To assess the impact of biochar on coarse‐textured soils ...under contrasting nutrient management regimes, a 55‐d incubation was conducted using unplanted soil columns amended with manure, slurry, or fertilizer (plus unamended control), each with or without biochar applied at 2% soil mass (dry weight basis). Under repeated leaching, the cumulative N2O emission from the columns was significantly affected by the presence of biochar (p < 0.0001), although these data were not normally distributed. Results indicated that the biochar‐amended soils emitted significantly less N2O than their unamended counterparts, with the exception of manure‐amended soils. The presence of biochar increased the pH of column leachate by 0.08 to 1.70 and significantly decreased the cumulative amount of mineral N leached from the soil. The presence of biochar significantly increased the amount of PO43−–P in soil leachate, but there was no significant difference between the means for any of the amendments used on their own relative to their biochar‐amended counterparts. The data demonstrate that biochar could potentially aid in the mitigation of N2O emissions from certain soils and in N loss in leachate from soil amended with slurry, manure, or fertilizer used in livestock systems.
Although increasing numbers of research papers regarding biochar are being published worldwide, in some countries growing interest in biochar has only recently been observed; this is true of Poland. ...We analysed information on biochar research in Poland alongside lessons learned elsewhere in order to identify the significant opportunities and risks associated with biochar use. This data fed into a GIS-based multicriteria analysis to identify areas where biochar application could deliver greatest benefit. We found that 21.8% of agricultural land in Poland has at least moderate indication for biochar use (soil organic matter below 2% and pH below 5.5), while 1.5% was categorized as a priority as it also exhibited contamination. Potential barriers identified included biomass availability and associated risks of indirect land-use change due to possible national and transnational biomass production displacement. Biochar use could have positive global consequences as a climate change mitigation strategy, particularly relevant in a country with limited alternatives. Scaling up a mitigation technology that is viable on account of its co-benefits might be cost-effective, which could, in turn, adjust national perspectives and stronger involvement in developing mitigation policies at the regional level. Biochar has much promise in temperate conditions and further research should therefore be assigned to explore biochar's environmental and socio-economic impacts.
A range of spectroscopic, ‘wet’ chemical, gas chromatographic (GC) and mass spectrometric (MS) techniques was applied to the characterisation of three soil organic matter (SOM) fractions that have ...been proposed as the basis of a new SOM turnover model based on measurable, physically defined fractions. The fractions were: the free light fraction (obtained by density separation in NaI solution at a density of 1.80
g
cm
−3, without disruption of aggregates), the intra-aggregate light fraction (obtained using a second density separation after disrupting aggregates using ultrasonic dispersion) and the organomineral fraction corresponding to the residual heavy material. The techniques employed to investigate the composition of the organic constituents of each fraction were:
13C nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), and pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) to study bulk composition. Lipid, lignin and carbohydrate fractions were assessed using GC and GC/MS with appropriate derivatisation, following oxidative and hydrolytic treatments, respectively, in the case of the latter two classes. Proteinaceous components were determined as amino acids using reversed-phase high performance liquid chromatography (HPLC) following 6
M HCl treatment and derivatisation. Each technique revealed marked differences in chemical composition between the organomineral and the two light fractions, with the results being consistent with the organomineral fraction having different biological sources or having undergone a greater degree of degradation or transformation. Several techniques detected differences between the composition of the free light fraction and the intra-aggregate light fraction. With the exception of carbohydrate composition, the results were consistent with the order of reactivity previously proposed from incubation studies with isotopically labelled substrates, namely: free
>
intra-aggregate
>
organomineral. The investigation illustrates the importance of using a range of different chemical characterisation techniques in studies of complex SOM fractions as each has limitations that could, if used alone, produce ambiguous findings or fail to detect differences between them.
Fractions of soil organic matter (SOM) were obtained from three soils using alternative physical fractionation procedures, and evaluated against the requirements of model pools. We compared two‐stage ...density fractionation (isolating free and intra‐aggregate fractions, before and after dispersion, respectively) with particle‐size separation of dispersed soil. For full comparison, the organomineral fraction residual from density fractionation was also size separated. In standardizing the density‐based method, we found recovery of intra‐aggregate organic matter highly sensitive to separation density as compared with the free. Recovery of the intra‐aggregate was also influenced by dispersion energy. The greatest amount was obtained using a combination of the highest density (1.80 g cm−3) and dispersion energy (1500 J g−1). Analysis by 13C nuclear magnetic resonance (NMR) showed O‐alkyl/alkyl‐C ratios 1.38 to 2.30 times greater in intra‐aggregate organic matter than in the free. Diffuse reflectance Fourier transform infrared spectroscopy (DRIFT) also indicated a greater proportion of aliphatic hydrocarbon, carboxylic anions, and aromatic C in intra‐aggregate organic matter. The findings suggest this fraction comprises more decomposed and transformed organic matter relative to the free. Higher signal/noise ratios in NMR spectra of particle‐size fractions (compared with their organomineral equivalents) were attributed to C in particulate SOM, not removed by prior density separation. Whilst particle‐size fractions confuse particulate SOM with that attached to mineral surfaces, fractions isolated by two‐stage density separation are small in number and display distinct chemical properties. We suggest they provide a sound basis for a model of SOM turnover based on measurable pools.
Drawing on the increased range of response variables monitored in such work, they consider not only the relative impacts on yield separately from biomass productivity but also distinguish above‐ and ...belowground biomass production. Several articles in this Special Issue include important ‘case studies’ in this context, collectively reflecting the diversity of technology and system configurations involving biochar – from the perspective of life cycle analysis (LCA), energy yield and product mix, and the impact on soil and crop. At the laboratory scale, Ronsse et al. ( ) apply slow pyrolysis to feedstock ranging from pine wood to micro‐algae and examine the biological, chemical and physical properties considered relevant in soil. Crombie et al. ( ) use the direct simulated ageing method of Cross & Sohi ( ), comparing results against recognized indicators of relative stability based on elemental ratios of carbon, oxygen and hydrogen – and methods from fuel science, namely proximate and ultimate analysis.
We used thermal analysis to compare the proportions of active and more stable components in soil organic matter (SOM) fractions and whole soil under contrasting agricultural land-uses. The fractions ...(free light, intra-aggregate, and organomineral fractions) were isolated using density fractionation. Exothermic weight loss between 300 and 350 degrees C was attributed to a relatively labile portion comprising carboxyl and aliphatic C, and that between 400 and 450 degrees C to the decomposition of material rich in aromatic components. Under arable cultivation, free light SOM showed much greater weight loss in the first exothermic range than intra-aggregate SOM. In soil receiving very small inputs of organic matter (a long-term bare fallow) the free light and intra-aggregate fractions displayed similar characteristics and resembled the intra-aggregate fraction from the arable soil. The difference between the free light and intra-aggregate fractions was also small for the grassland soil but the fractions resembled the free light fraction from the arable soil. Small total weight loss for whole soil and organomineral fractions demonstrated the value of physical fractionation techniques in establishing the effect of land-use on SOM with greater precision than is possible whole (unfractionated) soil.
Second-generation bioenergy crops, including Short Rotation Forestry (SRF), have the potential to contribute to greenhouse gas (GHG) emissions savings through reduced soil GHG fluxes and greater soil ...C sequestration. If we are to predict the magnitude of any such GHG benefits a better understanding is needed of the effect of land use change (LUC) on the underlying factors which regulate GHG fluxes. Under controlled conditions we measured soil GHG flux potentials, and associated soil physico-chemical and microbial community characteristics for a range of LUC transitions from grassland land uses to SRF. These involved ten broadleaved and seven coniferous transitions. Differences in GHGs and microbial community composition assessed by phospholipid fatty acids (PLFA) profiles were detected between land uses, with distinctions between broadleaved and coniferous tree species. Compared to grassland controls, CO2 flux, total PLFAs and fungal PLFAs (on a mass of C basis), were lower under coniferous species but unaffected under broadleaved tree species. There were no significant differences in N2O and CH4 flux rates between grassland, broadleaved and coniferous land uses, though both CH4 and N2O tended to have greater uptake under broadleaved species in the upper soil layer. Effect sizes of CO2 flux across LUC transitions were positively related with effect sizes of soil pH, total PLFA and fungal PLFA. These relationships between fluxes and microbial community suggest that LUC to SRF may drive change in soil respiration by altering the composition of the soil microbial community. These findings support that LUC to SRF for bioenergy can contribute towards C savings and GHG mitigation.
•Land use change to Short Rotation Forestry alters soil greenhouse gas fluxes.•Differences in GHG fluxes between SRF types (coniferous and broadleaved).•Accounting for differences in soil C alters apparent effect of SRF type.•Change in GHG fluxes related to changes in microbial community composition.•Short Rotation Forestry for bioenergy can mitigate GHG emissions.
Land-use change (LUC) is a major influence on soil organic carbon (SOC) stocks and the global carbon cycle. LUC from conventional agricultural to biomass crops has increased in Britain but there is ...limited understanding of the effects on SOC stocks. Results from paired plot studies investigating site-specific effects document both increasing and decreasing SOC stocks over time. Such variation demonstrates the sensitivity of SOC to many factors including environmental conditions. Using a chronosequence of 93 biomass crop sites in England and Wales, mainly of 1–14 y age, empirical models were developed of SOC trajectory following LUC from arable and grassland to short rotation coppice (SRC) willow and Miscanthus production. SOC stocks were calculated for each site using a fixed sampling depth of 30 cm and changes were estimated by comparing with typical pre-conversion SOC stocks. Most LUCs had no demonstrable net effect on SOC stocks. An estimated net SOC loss of 45.2 ± 24.1 tonnes per hectare (±95% confidence intervals) occurred after 14 y following LUC from grassland to SRC willow. Soil texture and climate data for each site were included in multivariable models to assess the influence of different environmental conditions on SOC trajectory. In most cases the addition of explanatory variables improved the model fit. These models may provide some preliminary estimates of more region-specific changes in SOC following LUC. However, the model fit did not improve sufficiently as to provide a basis for adopting a more targeted LUC strategy for lignocellulosic biomass crop production.
•SOC stocks were assessed for LUC from agricultural to bioenergy crops.•LUC from arable crops to SRC willow or Miscanthus did not impact SOC.•LUC from grass to SRC willow caused a decline in SOC stocks.•LUC from grass to Miscanthus did not impact SOC.•SOC stock changes are sensitive to factors such as climate and soil texture.
If soil communities rely on plant-derived carbon, is biodiversity lost when this primary source is removed? Soil microbial and mesofaunal communities at the Rothamsted Highfield site were compared ...under a mixed grass sward, arable rotation and a section maintained as a bare-fallow for the past 50 years by regular tillage. Organic matter reserves have been degraded and microbial and mesofaunal numbers and mite diversity have declined in this unique bare-fallow site, where fresh carbon inputs have been drastically reduced. However, it supports a species-rich metabolically active bacterial community of similar diversity to that in soil maintained as grass sward. Thus in contrast to soil mesofauna, bacterial diversity (but not abundance) is apparently independent of plant inputs.
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