Potential greenhouse gases emissions by different plant communities in maritime Antarctica.

Antarctic plant communities show a close relationship with soil types across the landscape, where vegetation cover changes, biological influence, and soil characteristics can affect the dynamic of greenhouse gases emissions. Thus, the objective of this study was to evaluate greenhouse gases emissions in lab conditions of ice-free areas along a topographic gradient (from sea level up to 300 meters). We selected 11 distinct vegetation compositions areas and assessed greenhouse gases production potentials through 20 days of laboratory incubations varying temperatures at -2, 4, 6, and 22 °C. High N2O production potential was associated with the Phanerogamic Community under the strong ornithogenic influence (phosphorus, nitrogen, and organic matter contents). Seven different areas acted as N2O sink at a temperature of -2 °C, demonstrating the impact of low-temperature conditions contributing to store N in soils. Moss Carpets had the highest CH4 emissions and low CO2 production potential. Fruticose Lichens had a CH4 sink effect and the highest values of CO2. The low rate of organic matter provided the CO2 sink effect on the bare soil (up to 6 °C). There is an overall trend of increasing greenhouse gases production potential with increasing temperature along a toposequence.

The Role of Nanoengineered Biochar Activated with Fe for Sulfanilamide Removal from Soils and Water.

Biochar is a nanoengineered sorbent proposed to control the contamination derived from the presence of residual concentrations of sulfonamides in soil. In this work, we evaluated the sorption of sulfanilamide (SFA) in commercial biochar (BC) produced at 500 °C from oak hardwood (Quercus ilex) and its analog activated with 2% (w/w) Fe (BC-Fe). Subsequently, the effect on dissipation and transport of SFA in untreated soil and soil treated with BC and BC-Fe was also assessed. Laboratory batch studies revealed that BC-Fe increased the sorption of SFA as compared to the pristine BC with Kd of 278 and 98 L/kg, respectively. The dissipation of SFA in either untreated soil or soil treated with BC or BC-Fe was similar, displaying half-lives ranging between 4 and 6.4 days. Conversely, the concurrent determination of sorption during the incubation experiment showed that lower amounts of SFA in solution at the beginning of the experiments were bioavailable in BC-Fe-treated soil when compared to the rest of the treatments shortly after application. Leaching column studies confirmed the amendment's capability to bind the SFA compound. Therefore, the decrease in bioavailability and movement of SFA in treated soils suggest that biochar soil application can reduce SFA soil and water contamination. According to our results, BC surface modification after Fe activation may be more appropriate for water decontamination than for soil since there were no significant differences between the two types of biochar when added to the soil. Therefore, these outcomes should be considered to optimize the SFA mitigation potential of biochar.

Phytostabilization of acidic mine tailings with biochar, biosolids, lime, and locally-effective microbes: Do amendment mixtures influence plant growth, tailing chemistry, and microbial composition?

Abandoned mine lands present persistent environmental challenges to ecosystems and economies; reclamation an important step for overcoming these challenges. Phytostabilization is an elegant and cost-effective reclamation strategy, however, establishing plants on severely degraded soils is problematic, often requiring soil amendment additions. We evaluated whether amendment mixtures composed of lime, biochar, biosolids, and locally effective microbes (LEM) could alleviate the constraints that hinder phytostabilization success. We hypothesized that 1) plants grown in tailings amended with lime, biochar, and biosolids (LBB) would establish faster and grow larger than plants grown in tailings amended with lime only, and 2) the LEM source would influence microbial community function and structure in amended mine tailings. We conducted a greenhouse study that simulated in situ conditions to measure the influence of LBB-LEM amendment blends on plant growth, plant nutrients, metal concentrations, microbial function, and microbial community structure. Blue wildrye [Elymus glaucus Buckley ssp. Jepsonii (Burtt Davy) Gould] was grown in tailings collected from the Formosa mine site amended with various combinations of LBB-LEM. The above and below ground biomass of plants grown in mine tailings amended with LBB was 3 to 4 times larger than the biomass of plants grown in tailings amended only with lime. Although the LEM addition did not influence immediate plant growth, it did affect nutrient content and altered the rhizosphere community membership. As such, it is not yet clear if LEM-driven alterations in microbial membership will advance mine reclamation strategies by improving long-term growth.

Carbon Dosing Increases Nitrate Removal Rates in Denitrifying Bioreactors at Low-Temperature High-Flow Conditions.

Nitrogen losses from croplands contribute to impairment of water bodies. This laboratory experiment evaluated various C sources for use in a denitrifying bioreactor, a conservation practice designed to reduce N losses. The nitrate removal efficiency of candidate treatments (corn cobs [CC], corn cobs with modified coconut coir [CC+MC], corn cobs with modified coconut coir and modified macadamia shell biochar [CC+MC+MBC], wood chips [WC], wood chips with hardwood biochar [WC+BC], and wood chips with continuous sodium acetate addition [WC+A]) were tested with up-flow direction. Effluent was sampled after a repeated weekly flow regime with hydraulic residence times of 1.5, 8, 12, and 24 h. Column temperatures were 15°C for 14 wk (warm), 5°C for 13 wk (cold), and again 15°C for 7 wk (rewarm). Cumulative nitrate N load reduction was greatest for WC+A (80, 80, and 97% during the warm, cold, and rewarm runs, respectively). Corn cob treatments (CC, CC+MC, and CC+MC+MBC) had the second greatest cumulative load reductions for all three temperature experiments, and WC and WC+BC had the lowest performance under these conditions. The nitrate removal rate was optimum at the 1.5-h hydraulic residence time for the WC+A treatment: 43, 30, and 121 g N m d for the warm, cold, and rewarm runs, respectively. Furthermore, acetate addition greatly improved wood chip performance and could be used to enhance nitrate N removal under the cold and high-flow-rate conditions of springtime drainage for the north-central United States.

Pesticide sorption and leaching potential on three Hawaiian soils.

On the Hawaiian Islands, groundwater is the principal source of potable water and contamination of this key resource by pesticides is of great concern. To evaluate the leaching potential of four weak acid herbicides [aminocyclopyrachlor, picloram, metsulfuron-methyl, biologically active diketonitrile degradate of isoxaflutole (DKN)] and two neutral non-ionizable herbicides [oxyfluorfen, alachlor], their sorption coefficients were determined on three prevalent soils from the island of Oahu. Metsulfuron-methyl, aminocylcopyrachlor, picloram, and DKN were relatively low sorbing herbicides (K(oc) = 3-53 mL g(-1)), alachlor was intermediate (K(oc) = 120-150 mL g(-1)), and oxyfluorfen sorbed very strongly to the three soils (K(oc) > 12,000 mL g(-1)). Following determination of K(oc) values, the groundwater ubiquity score (GUS) indices for these compounds were calculated to predicted their behavior with the Comprehensive Leaching Risk Assessment System (CLEARS; Tier-1 methodology for Hawaii). Metsulfuron-methyl, aminocyclopyrachlor, picloram, and DKN would be categorized as likely leachers in all three Hawaiian soils, indicating a high risk of groundwater contamination across the island of Oahu. In contrast, oxyfluorfen, regardless of the degradation rate, would possess a low and acceptable leaching risk due to its high sorption on all three soils. The leaching potential of alachlor was more difficult to classify, with a GUS value between 1.8 and 2.8. In addition, four different biochar amendments to these soils did not significantly alter their sorption capacities for aminocyclopyrachlor, indicating a relatively low impact of black carbon additions from geologic volcanic inputs of black carbon. Due to the fact that pesticide environmental risks are chiefly dependent on local soil characteristics, this work has demonstrated that once soil specific sorption parameters are known one can assess the potential pesticide leaching risks.

Phosphorus reclamation through hydrothermal carbonization of animal manures.

Projected shortages of global phosphate have prompted investigation of methods that could be employed to capture and recycle phosphate, rather than continue to allow the resource to be essentially irreversibly lost through dilution in surface waters. Hydrothermal carbonization of animal manures from large farms was investigated as a scenario for the reclamation of phosphate for agricultural use and mitigation of the negative environmental impact of phosphate pollution. Hydrothermal reaction conditions were identified for poultry, swine, and cattle manures that resulted in hydrochar yields of 50-60% for all three manures, and >90% of the total phosphorus present in these systems was contained in the hydrochars as precipitated phosphate salts. Phosphate recovery was achieved in yields of 80-90% by subsequent acid treatment of the hydrochars, addition of base to acid extracts to achieve a pH of 9, and filtration of principally calcium phosphate. Phosphate recovery was achieved in yields of 81-87% based on starting manures by subsequent acid treatment of the hydrochars, addition of base to acid extracts to achieve a pH of 9, and filtration of principally calcium phosphate. Swine and cattle manures produced hydrochars with combustion energy contents comparable to those of high-end sub-bituminous coals.

Greenhouse gas production in mixtures of soil with composted and noncomposted biochars is governed by char-associated organic compounds.

Biochar application to soil has the potential to increase soil productivity while reducing anthropogenic greenhouse gas (GHG) emissions to the atmosphere. However, techniques for conditioning this material for maximizing its effects as a soil amendment require elucidation. We examined changes of organic matter associated with two biochars after 175 d of composting and the resulting effects on GHG emissions during a 150-d incubation period. Composting decreased the amount of organic compounds that could be thermally released from the biochars and affected their molecular nature. These thermally desorbable organic compounds from initial biochars likely stimulated the oxidation of CH and inhibited the production of NO in soil-biochar mixtures. However, these reductions of GHG emissions disappeared together with thermally desorbable organic compounds after the composting of chars. Instead, addition of composted gasification coke and charcoal stimulated the formation of CH and increased NO emissions by 45 to 56%. Nitrous oxide emissions equaled 20% of the total amount of N added with composted biochars, suggesting that organic compounds and N sorbed by the chars during composting fueled GHG production. The transient nature of the suppression of CH and NO production challenges the long-term GHG mitigation potential of biochar in soil.

2-Methyl-4-chlorophenoxyacetic acid (MCPA) sorption and desorption as a function of biochar properties and pyrolysis temperature.

2-Methyl-4-chlorophenoxyacetic acid (MCPA) is a highly mobile herbicide that is frequently detected in global potable water sources. One potential mitigation strategy is the sorption on biochar to limit harm to unidentified targets. However, irreversible sorption could restrict bioefficacy thereby compromising its usefulness as a vital crop herbicide. This research evaluated the effect of pyrolysis temperatures (350, 500 and 800°C) on three feedstocks; poultry manure, rice hulls and wood pellets, particularly to examine effects on the magnitude and reversibility of MCPA sorption. Sorption increased with pyrolysis temperature from 350 to 800°C. Sorption and desorption coefficients were strongly corelated with each other (R2 = 0.99; P < .05). Poultry manure and rice hulls pyrolyzed at 800°C exhibited irreversible sorption while for wood pellets at 800°C desorption was concentration dependent. At higher concentrations some desorption was observed (36% at 50 ppm) but was reduced at lower concentrations (1-3% at < 5 ppm). Desorption decreased with increasing pyrolysis temperature. Sorption data were analyzed with Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. Freundlich isotherms were better predictors of MCPA sorption (R2 ranging from 0.78 to 0.99). Poultry manure and rice hulls when pyrolyzed at higher temperatures (500 and 800°C) could be used for remediation efforts (such as spills or water filtration), due to the lack of desorption observed. On the other hand, un-pyrolyzed feedstocks or biochars created at 350°C could perform superior for direct field applications to limit indirect losses including runoff and leaching, since these materials also possess the ability to release MCPA subsequently to potentially allow herbicidal action.

Biochar: a synthesis of its agronomic impact beyond carbon sequestration.

Biochar has been heralded as an amendment to revitalize degraded soils, improve soil carbon sequestration, increase agronomic productivity, and enter into future carbon trading markets. However, scientific and economic technicalties may limit the ability of biochar to consistently deliver on these expectations. Past research has demonstrated that biochar is part of the black carbon continuum with variable properties due to the net result of production (e.g., feedstock and pyrolysis conditions) and postproduction factors (storage or activation). Therefore, biochar is not a single entity but rather spans a wide range of black carbon forms. Biochar is black carbon, but not all black carbon is biochar. Agronomic benefits arising from biochar additions to degraded soils have been emphasized, but negligible and negative agronomic effects have also been reported. Fifty percent of the reviewed studies reported yield increases after black carbon or biochar additions, with the remainder of the studies reporting alarming decreases to no significant differences. Hardwood biochar (black carbon) produced by traditional methods (kilns or soil pits) possessed the most consistent yield increases when added to soils. The universality of this conclusion requires further evaluation due to the highly skewed feedstock preferences within existing studies. With global population expanding while the amount of arable land remains limited, restoring soil quality to nonproductive soils could be key to meeting future global food production, food security, and energy supplies; biochar may play a role in this endeavor. Biochar economics are often marginally viable and are tightly tied to the assumed duration of agronomic benefits. Further research is needed to determine the conditions under which biochar can provide economic and agronomic benefits and to elucidate the fundamental mechanisms responsible for these benefits.

Seasonal greenhouse gas emissions (methane, carbon dioxide, nitrous oxide) from engineered landfills: daily, intermediate, and final California cover soils.

Compared with natural ecosystems and managed agricultural systems, engineered landfills represent a highly managed soil system for which there has been no systematic quantification of emissions from coexisting daily, intermediate, and final cover materials. We quantified the seasonal variability of CH, CO, and NO emissions from fresh refuse (no cover) and daily, intermediate, and final cover materials at northern and southern California landfill sites with engineered gas extraction systems. Fresh refuse fluxes (g m d [± SD]) averaged CH 0.053 (± 0.03), CO 135 (± 117), and NO 0.063 (± 0.059). Average CH emissions across all cover types and wet/dry seasons ranged over more than four orders of magnitude (<0.01-100 g m d) with most cover types, including both final covers, averaging <0.1 g m d with 10 to 40% of surface areas characterized by negative fluxes (uptake of atmospheric CH). The northern California intermediate cover (50 cm) had the highest CH fluxes. For both the intermediate (50-100 cm) and final (>200 cm) cover materials, below which methanogenesis was well established, the variability in gaseous fluxes was attributable to cover thickness, texture, density, and seasonally variable soil moisture and temperature at suboptimal conditions for CH oxidation. Thin daily covers (30 cm local soil) and fresh refuse generally had the highest CO and NO fluxes, indicating rapid onset of aerobic and semi-aerobic processes in recently buried refuse, with rates similar to soil ecosystems and windrow composting of organic waste. This study has emphasized the need for more systematic field quantification of seasonal emissions from multiple types of engineered covers.

Biochar changes the bioavailability and bioefficacy of the allelochemical coumarin in agricultural soils.

BACKGROUND: Allelochemicals can act as biopesticides or enhance the action of synthetic pesticides. In this work, we assessed the bioavailability of the allelochemical coumarin in soils amended with fresh or field-aged biochars (BCs). The fresh BC from oak wood (Fresh BC) was prepared at 550 °C and was buried for aging in two different places: in a sandy loam soil in Spain for 15 months (Aged BC_1) and a sandy loam soil in USA for six months (Aged BC_2). RESULTS: Sorption experiments showed that all BCs were able to increase the affinity of soil towards coumarin, with the distribution coefficient following the order: unamended soil < Aged BC_2-amended soil < Aged BC_1-amended soil < Fresh BC-amended soil. All biochars ensure greater persistence of coumarin and the effect was more pronounced at high chemical dose (10 mg kg-1 ). Conversely, leaching studies in soil columns revealed that BCs were able to maintain coumarin within the first 5 cm of top-soil with total amount extracted ranging between 17% and 22% for BC-amended soil and <1% for unamended soil. Leaching was only observed when coumarin was added at the highest rate. Likewise, the bioefficacy of coumarin against lettuce was enhanced only at 10 kg ha-1 with BC-amended soil. CONCLUSIONS: Biochar application to agricultural soils is a promising tool for the management of natural compounds with potential use as biopesticides, such as coumarin, because it increases sorption, persistence and, in some cases, bioefficacy. The results reveal that this effect still persists with aging of BC in soils.

Relative proportions of organic carbon functional groups in biochars as influenced by spectral data collection and processing.

Solid-state 13C Nuclear Magnetic Resonance (NMR) and synchrotron-based X-ray Absorption Near-Edge Structure (XANES) have applications for determining the relative proportions of organic C functional groups in materials. Spectral data obtained by NMR is typically processed using integration (INTEG) whereas XANES spectral data is typically processed using deconvolution (DECONV). The objective of this study was to examine the impact of spectral data collection and processing on the estimated relative proportions of organic C functional groups in biochars. Biochars showed large variations in aromatic C (45-97%), alkyl C (0-23%), O-alkyl C (1-41%), phenolic C (0-20%) and carboxylic C (0-20%). NMR had a better ability than XANES to differentiate % aromatic C across biochars, and the mean % aromatic C was always greater for NMR-INTEG and NMR-DECONV than for XANES-INTEG or XANES-DECONV. NMR-INTEG showed significant associations with NMR-DECONV and XANES-INTEG for % aromatic C and alkyl C, but there were no significant associations between NMR and XANES for % O-alkyl C, phenolic C and carboxylic C. As well, there was no association between NMR-INTEG and XANES-DECONV for any organic C functional group, and in some cases, spectral data collection and processing influenced the quantification of organic C functional groups in a given biochar to the extent that the differences observed were as large as differences observed between biochars when analyzed using the same spectral data collection and processing technique. We conclude that great caution must be taken when comparing studies that determined organic C functional groups in materials using NMR-INTEG versus XANES-DECONV.

Microbial Response to Phytostabilization in Mining Impacted Soils Using Maize in Conjunction with Biochar and Compost.

Even after remediation, mining impacted soils can leave behind a landscape inhospitable to plant growth and containing residual heavy metals. While phytostabilization can be used to restore such sites by limiting heavy metal spread, it is reliant on soil capable of supporting plant growth. Manure-based biochars, coupled with compost, have demonstrated the ability to improve soil growth conditions in mine impacted soils, however there is a paucity of information regarding their influence on resident microbial populations. The objective of this study was to elucidate the impact of these soil amendments on microbial community structure and function in mine impacted soils placed under phytostabilization management with maize. To this aim, a combination of phospholipid fatty acid (PLFA) and enzymatic analyses were performed. Results indicate that microbial biomass is significantly increased upon addition of biochar and compost, with maximal microbial biomass achieved with 5% poultry litter biochar and compost (62.82 nmol g-1 dry soil). Microbial community structure was impacted by biochar type, rate of application, and compost addition, and influenced by pH (r2 = 0.778), EC (r2 = 0.467), and Mg soil concentrations (r2 = 0.453). In three of the four enzymes analyzed, poultry litter biochar treatments were observed with increased activity rates that were often significantly greater than the unamended control. Overall, enzyme activities rates were influenced by biochar type and rate, and addition of compost. These results suggest that using a combination of biochar and compost can be utilized as a management tool to support phytostabilization strategies in mining impacted soils.

Microbial response to designer biochar and compost treatments for mining impacted soils.

The Oronogo-Duenweg mining belt is a designated United States Environmental Protection Agency Superfund site due to lead-contaminated soil and groundwater by former mining and smelting operations. Sites that have undergone remediation - in which the O, A, and B horizons have been removed alongside the lead contamination - have an exposed C horizon and are incalcitrant to revegetation efforts. Soils also continue to contain quantifiable Cd and Zn concentrations. In order to improve soil conditions and encourage successful site revegetation, our study employed three biochars, sourced from different feedstocks (poultry litter, beef lot manure, and lodge pole pine), at two rates of application (2.5%, and 5%), coupled with compost (0%, 2.5% and 5% application rates). Two plant species - switchgrass (Panicum virgatum) and buffalograss (Bouteloua dactyloides) - were grown in the amended soils. Amendment of soils with poultry litter biochar applied at 5% resulted in the greatest reduction of soil bioavailable Cd and Zn. Above ground biomass yields were greatest with beef lot manure biochar applied at 2.5% with 5% compost, or with 5% biochar at 2.5% and 5% compost rates. Maximal microbial biomass was achieved with 5% poultry litter biochar and 5% compost, and microbial communities in soils amended with poultry litter biochar distinctly clustered away from all other soil treatments. Additionally, poultry litter biochar amended soils had the highest enzyme activity rates for ß-glucosidase, N-acetyl-ß-D-glucosaminidase, and esterase. These results suggest that soil reclamation using biochar and compost can improve mine-impacted soil biogeophysical characteristics, and potentially improve future remediation efforts.

Dynamic Effect of Fresh and Aged Biochar on the Behavior of the Herbicide Mesotrione in Soils.

In this study, we assessed the sorption, dissipation, and leaching of the herbicide mesotrione in soil amended with fresh and field-aged biochars, when added to the soil. The aging process was performed by burying the fresh biochar at 10 cm depth in three soils located in different points across the USA [Wisconsin (ABC_WI), Idaho (ABC_ID), and South Carolina (ABC_SC)] for six months. ABC_ID and ABC_SC slightly increased the sorption of mesotrione in soils, whereas ABC_WI removed greater amounts of herbicide from the solution. This was attributed to differences in water-soluble components and metal content of this aged biochar. Consequently, the persistence of the herbicide in the amended soils with fresh biochar and ABC_ID and ABC_SC were similar to that in unamended soils, while ABC_WI slightly increased mesotrione half-life. Differences between treatments were detected in leaching studies although no direct relationship with the dissipation batch studies was observed. Mesotrione leaching could not be detected in soil columns amended with ABC_WI and was high for the rest of treatments. The outcomes from this work demonstrate that temporal variability of biochar sorption capacities due to soil exposure can occur altering mesotrione's behavior in biochar-amended soils.

Pyrolysis biochar has negligible effects on soil greenhouse gas production, microbial communities, plant germination, and initial seedling growth.

Biochar has been promoted as a soil amendment that enhances soil quality and agronomic productivity and reduces greenhouse gas production. However, these benefits are not always realized. A major hurdle to the beneficial use of biochar is our limited knowledge regarding the mechanisms directing its effects on soil systems. This project aimed to eliminate some of this uncertainty by examining the biological responses (plant productivity, greenhouse gas production, soil microbial community structure) of a suite of soils (10) to the addition of biochars produced by different processes (pyrolysis, gasification, burning) from a range of feedstocks (corn stalks, hardwood, grass). Results indicated that these three responses were not significantly impacted by the addition of pyrolysis biochars from different feedstocks at 1 and 5% (w/w) addition levels. On the other hand, both an open-air burned corn stalk (5%) and raw corn stalks (1 and 5%) additions did alter the measured soil functionality. For example, the 5% burnt corn stalks addition reduced total above ground plant biomass (∼30%), increased observed N2O production by an order of magnitude, and altered soil bacterial community structure. The bacterial groups that increased in relative abundance in the burnt corn stalks-amended soils included families associated with cellulose decomposition (Chitinophagaceae), plant pathogens (Xanthomonadaceae), and biochar/charcoal-amended media (Gemmatimonadetes). In contrast, the abundance of these bacterial groups was not impacted by the pyrolysis biochars. Therefore, this research suggests that pyrolysis biochar represents a stabilized form of carbon that is resistant to microbial mineralization and has negligible effects on soil biological responses.

Biochar, soil and land-use interactions that reduce nitrate leaching and N2O emissions: A meta-analysis.

Biochar can reduce both nitrous oxide (N2O) emissions and nitrate (NO3-) leaching, but refining biochar's use for estimating these types of losses remains elusive. For example, biochar properties such as ash content and labile organic compounds may induce transient effects that alter N-based losses. Thus, the aim of this meta-analysis was to assess interactions between biochar-induced effects on N2O emissions and NO3- retention, regarding the duration of experiments as well as soil and land use properties. Data were compiled from 88 peer-reviewed publications resulting in 608 observations up to May 2016 and corresponding response ratios were used to perform a random effects meta-analysis, testing biochar's impact on cumulative N2O emissions, soil NO3- concentrations and leaching in temperate, semi-arid, sub-tropical, and tropical climate. The overall N2O emissions reduction was 38%, but N2O emission reductions tended to be negligible after one year. Overall, soil NO3- concentrations remained unaffected while NO3- leaching was reduced by 13% with biochar; greater leaching reductions (>26%) occurred over longer experimental times (i.e. >30 days). Biochar had the strongest N2O-emission reducing effect in paddy soils (Anthrosols) and sandy soils (Arenosols). The use of biochar reduced both N2O emissions and NO3- leaching in arable farming and horticulture, but it did not affect these losses in grasslands and perennial crops. In conclusion, the time-dependent impact on N2O emissions and NO3- leaching is a crucial factor that needs to be considered in order to develop and test resilient and sustainable biochar-based N loss mitigation strategies. Our results provide a valuable starting point for future biochar-based N loss mitigation studies.

Global Diversity of the Brachypodium Species Complex as a Resource for Genome-Wide Association Studies Demonstrated for Agronomic Traits in Response to Climate.

The development of model systems requires a detailed assessment of standing genetic variation across natural populations. The Brachypodium species complex has been promoted as a plant model for grass genomics with translation to small grain and biomass crops. To capture the genetic diversity within this species complex, thousands of Brachypodium accessions from around the globe were collected and genotyped by sequencing. Overall, 1897 samples were classified into two diploid or allopolyploid species, and then further grouped into distinct inbred genotypes. A core set of diverse B. distachyon diploid lines was selected for whole genome sequencing and high resolution phenotyping. Genome-wide association studies across simulated seasonal environments was used to identify candidate genes and pathways tied to key life history and agronomic traits under current and future climatic conditions. A total of 8, 22, and 47 QTL were identified for flowering time, early vigor, and energy traits, respectively. The results highlight the genomic structure of the Brachypodium species complex, and the diploid lines provided a resource that allows complex trait dissection within this grass model species.

Sorption of ammonium and nitrate to biochars is electrostatic and pH-dependent.

Biochars are potentially effective sorbents for NH4+ and NO3- in water treatment and soil applications. Here we compare NH4+ and NO3- sorption rates to acid-washed biochars produced from red oak (Quercus rubra) and corn stover (Zea mays) at three pyrolysis temperatures (400, 500 and 600 °C) and a range of solution pHs (3.5-7.5). Additionally, we examined sorption mechanisms by quantification of NH4+ and NO3- sorption, as well as Ca2+ and Cl- displacement for corn stover biochars. Solution pH curves showed that NH4+ sorption was maximized (0.7-0.8 mg N g-1) with low pyrolysis temperature (400 °C) biochar at near neutral pH (7.0-7.5), whereas NO3- sorption was maximized (1.4-1.5 mg N g-1) with high pyrolysis temperatures (600 °C) and low pH (3.5-4). The Langmuir (r2 = 0.90-1.00) and Freundlich (r2 = 0.81-0.97) models were good predictors for both NH4+ (pH 7) and NO3- (pH 3.7) sorption isotherms. Lastly, NH4+ and NO3- displaced Ca2+ and Cl-, respectively, from previously CaCl2-saturated corn stover biochars. Results from the pH curves, Langmuir isotherms, and cation displacement curves all support the predominance of ion exchange mechanisms. Our results demonstrate the importance of solution pH and chemical composition in influencing NH4+ and NO3- sorption capacities of biochar.

Glyphosate sorption/desorption on biochars - interactions of physical and chemical processes.

BACKGROUND: Biochar, a carbon-rich product of biomass pyrolysis, could limit glyphosate transport in soil and remediate contaminated water. The present study investigates the sorption/desorption behavior of glyphosate on biochars prepared from different hardwoods at temperatures ranging from 350 to 900 °C to elucidate fundamental mechanisms. RESULTS: Glyphosate (1 mg L-1 ) sorption on biochars increased with pyrolysis temperature and was highest on 900 °C biochars; however, total sorption was low on a mass basis (<0.1 mg g-1 ). Sorption varied across feedstock materials, and isotherms indicated concentration dependence. Biochars with a greater fraction of micropores exhibited lower sorption capacities, and specific surface groups were also found to be influential. Prepyrolysis treatments with iron and copper, which complex glyphosate in soils, did not alter biochar sorption capacities. Glyphosate did not desorb from biochar with CaCl2 solution; however, up to 86% of the bound glyphosate was released with a K2 HPO4 solution. CONCLUSION: Results from this study suggest a combined impact of surface chemistry and physical constraints on glyphosate sorption/desorption on biochar. Based on the observed phosphate-induced desorption of glyphosate, the addition of P-fertilizer to biochar-amended soils can remobilize the herbicide and damage non-target plants; therefore, improved understanding of this risk is necessary. © 2017 Society of Chemical Industry.