Effects of softwood biochars on soil biota in medium-term field experiments in Finland

Biochar soil amendment could be used to sequester carbon, enhance soil fertility and potentially increase crop yields. It can have significant impacts on soil organic carbon levels and physicochemical conditions, which consequently affect soil micro- and macro-biota. It is therefore important to understand how key biological components in the soil such as microbial and earthworm communities response to biochar application in the long-term. This study was conducted in Southern Finland in a fertile Stagnosol and a nutrient deficient Umbrisol, four and five years after biochar amendment, respectively. Biochars were produced from spruce (Picea abies (L.) H.Karst.) and pine (Pinus sylvestris L.), and applied at the rates of 10 and 30 t ha-1, respectively. Earthworms and soil samples for microbial analyses were collected in September 2015. Soil microbial communities were studied by using phospholipid fatty acid profiling and 16S rRNA gene amplicon sequencing. Casts from the sampled earthworms were collected to investigate the consumption of biochar and the potential of earthworm bioturbation to affect biochar distribution. Additionally, greenhouse gas emissions from soil were measured. Biochar and fertilizer treatments or their interaction had no statistically significant effects on the earthworm abundance, community composition or greenhouse gas emissions in either field. Earthworms had ingested biochar as earthworm casts from biochar treated-plots contained significantly more black carbon than those in the control plots, demonstrating that earthworm bioturbation is a potentially important factor in the translocation of applied biochar in the soil profile. Microbial community structure data will be presented in the final presentation.Non peer reviewe

Perennial crop growth in oil-contaminated soil in a boreal climate

Soil contamination by petroleum hydrocarbons is a global problem. Phytoremediation by plants and their associated microorganisms is a cost-effective strategy to degrade soil contaminants. In boreal regions the cool climate limits the efficiency of phytoremediation. The planting of oil-tolerant perennial crops, especially legumes, in oil-contaminated soil holds promise for great economic benefits for bioenergy and bio-fertilizer production while accelerating the oil degradation process. We established a multi-year field experiment to study the ecological and agronomic feasibility of phytoremediation by a legume (fodder galega) and a grass (smooth brome) in a boreal climate. In 40 months, soil oil content decreased by 73%–92%, depending on the crop type. The oil degradation followed first-order kinetics with the reduction rates decreasing as follows: bare fallow > galega–brome grass mixture > brome grass > galega. Surprisingly, the presence of oil enhanced crop dry matter and nitrogen yield, particularly in the fourth year. The unfertilized galega–brome grass mixture out-yielded the N-fertilized pure grass swards over years by an average of 33%. Thus, a perennial legume–grass mixture is both ecologically and agronomically sustainable as a cropping system to alleviate soil contamination in the boreal zone, with considerable potential for bioenergy and bio-fertilizer production.Soil contamination by petroleum hydrocarbons is a global problem. Phytoremediation by plants and their associated microorganisms is a cost-effective strategy to degrade soil contaminants. In boreal regions the cool climate limits the efficiency of phytoremediation. The planting of oil-tolerant perennial crops, especially legumes, in oil-contaminated soil holds promise for great economic benefits for bioenergy and bio-fertilizer production while accelerating the oil degradation process. We established a multi-year field experiment to study the ecological and agronomic feasibility of phytoremediation by a legume (fodder galega) and a grass (smooth brome) in a boreal climate. In 40 months, soil oil content decreased by 73% - 92%, depending on the crop type. The oil degradation followed first-order kinetics with the reduction rates decreasing as follows: bare fallow > galega-brome grass mixture > brome grass > galega. Surprisingly, the presence of oil enhanced crop dry matter and nitrogen yield, particularly in the fourth year. The unfertilized galega-brome grass mixture out-yielded the N-fertilized pure grass swards over years by an average of 33%. Thus, a perennial legume-grass mixture is both ecologically and agronomically sustainable as a cropping system to alleviate soil contamination in the boreal zone, with considerable potential for bioenergy and bio-fertilizer production.Peer reviewe

Impacts of lake sediment reuse on plant growth and soil properties in the field

Lake sediments are in many cases known to be rich in nutrients, organic carbon, and clay minerals. These compounds originate from eroded agricultural soils acting as primary sediment source. European countries produce about 200 million m3 y−1 of sediment removed from waterbodies which provides the potential of recycling nutrients from sediments in crop production. There are just a handful studies available exploring the potential of recycling the nutrients from sediments and none have been conducted under field conditions. Therefore, there is a need to develop efficient ways to reuse sediments on agricultural lands to preserve phosphorus and other nutrients and respond to crop demands. The aim of this research was to investigate the effects of different ways of sediments applications to soil on grass growth, soil, and environment. The study was conducted in the shore of a 1-ha heavily eutrophicated lake from which sediments were excavated. Four different sediment application methods were tested in a RCBD design with four replicates. The treatments were pure topsoil, a mixture of soil and biochar on top of the sediment, a mixture of biochar with top 20 cm of sediment, and a 75–100 cm layer of sediment directly on topsoil. In June 2017, mixture of red fescue, Kentucky bluegrass, ryegrass, and white clover was sown to all plots with meat bone meal organic fertilizer. The leaf area index, the relative leaf chlorophyll values, aboveground biomass, soil moisture content, total carbon and nitrogen, GHG emissions, and the soil penetration were measured in all plots in August 2017. The analysis of representative samples of sediments revealed that the sediments were not contaminated by heavy metals, PAHs, and PCBs. The moisture content was significantly higher in sediment plots (33±5%) than soil (19±1%). Relative leaf chlorophyll value and leaf area index were significantly 1.3 and 1.7 times greater in sediment plots than in the soil plots, respectively. Moreover, the treatments containing biochar had the highest C:N ratio. Sediment phosphorus (P) content was high, providing sufficient available P to agricultural lands. The final presentation will include data on yields of 2018, GHG emissions, and the mechanical soil resistance in different treatments. Our results emphasizes the importance of preventing the transport of nutrients to water bodies and considering the assessment of sediment nutrient contents and pollutants in the disposal of removed sediments.Peer reviewe

Sustainable phosphorus recycling from excavated sediments of a highly eutrophicated lake

We examined plant behavior and environmental sustainability factors under different ways of sediment application in 2017. In a 9-month lysimeter experiment, 1-m height columns were filled with 6 different combinations of soil, sediment, and biochar, with or without organic P fertilizer meat bone meal. The plant aboveground biomass, nutrient uptake, and N and P leaching were measured. In the field experiment, 4 different sediment application methods were tested in the shore of the lake from which sediments were excavated. The leaf area index (LAI), the relative leaf chlorophyll values, aboveground biomass, total C and N, P fractions, GHG emissions, and the soil penetration were measured. The sediments were not contaminated by heavy metals, PAHs, or PCBs. The most promising treatment of topsoil and biochar on top of the sediment column resulted in highest plant biomass and low leaching. Sediment labile P content was high, providing sufficient available P for crops. The final presentation will include data on P fractionation, plant nutrient uptake, GHG emissions, and the mechanical soil resistance in different treatments. Our small case study results will aid in reducing transformation of nutrients to water bodies and facilitate the disposal of dredged sediments in agriculture and environmental engineering.Peer reviewe

OTU table

The OTU table used in analyses (previous sequence data processing steps described in the Methods). This dataset has not been rarefied or filtered (e.g. to remove mitochondria, chloroplasts, OTUs in negative controls - see Methods). The Greengenes-assigned taxonomy strings associated with each OTU are in the right-most columns

Data from: Treating cattle with antibiotics affects greenhouse gas emissions, and microbiota in dung and dung beetles

Antibiotics are routinely used to improve livestock health and growth. However, this practice may have unintended environmental impacts mediated by interactions among the wide range of micro- and macroorganisms found in agroecosystems. For example, antibiotics may alter microbial emissions of greenhouse gases by affecting livestock gut microbiota. Furthermore, antibiotics may affect the microbiota of non-target animals that rely on dung, such as dung beetles, and the ecosystem services they provide. To examine these interactions, we treated cattle with a commonly used broad-spectrum antibiotic and assessed downstream effects on microbiota in dung and dung beetles, greenhouse gas fluxes from dung, and beetle size, survival and reproduction. We found that antibiotic treatment restructured microbiota in dung beetles, which harboured a microbial community distinct from those in the dung they were consuming. The antibiotic effect on beetle microbiota was not associated with smaller size or lower numbers. Unexpectedly, antibiotic treatment raised methane fluxes from dung, possibly by altering the interactions between methanogenic archaea and bacteria in rumen and dung environments. Our findings that antibiotics restructure dung beetle microbiota and modify greenhouse gas emissions from dung indicate that antibiotic treatment may have unintended, cascading ecological effects that extend beyond the target animal

Treating cattle with antibiotics affects greenhouse gas emissions, and microbiota in dung and dung beetles

Antibiotics are routinely used to improve livestock health and growth. However, this practice may have unintended environmental impacts mediated by interactions among the wide range of micro-and macroorganisms found in agroecosystems. For example, antibiotics may alter microbial emissions of greenhouse gases by affecting livestock gut microbiota. Furthermore, antibiotics may affect the microbiota of non-target animals that rely on dung, such as dung beetles, and the ecosystem services they provide. To examine these interactions, we treated cattle with a commonly used broad-spectrum antibiotic and assessed downstream effects on microbiota in dung and dung beetles, greenhouse gas fluxes from dung, and beetle size, survival and reproduction. We found that antibiotic treatment restructured microbiota in dung beetles, which harboured a microbial community distinct from those in the dung they were consuming. The antibiotic effect on beetle microbiota was not associated with smaller size or lower numbers. Unexpectedly, antibiotic treatment raised methane fluxes from dung, possibly by altering the interactions between methanogenic archaea and bacteria in rumen and dung environments. Our findings that antibiotics restructure dung beetle microbiota and modify greenhouse gas emissions from dung indicate that antibiotic treatment may have unintended, cascading ecological effects that extend beyond the target animal

Number of beetle offspring

The total number of dung beetle offspring collected from dung mesocosms over the course of the experiment. Each mesocosm is associated with a cow ID and treatment (antibiotic or control)

Mapping file for sequence data

The metadata associated with sequenced samples

Performance measurements of beetle offspring

The average head capsule size and fresh weight of larval dung beetle offspring collected from each dung mesocosm. Each mesocosm is associated with cow ID and treatment (antibiotic or control). No head size measurement was available for mesocosm #25