Effect of softwood biochars on earthworms in two contrasting soils in Southern Finland

Soil carbon sequestration is one of the most promising solutions to mitigate climate change. Biochar, a carbon rich solid obtained via pyrolysis and intended to be used as a soil amendment material, is currently the most efficient tool available for carbon sequestration. Further, some biochars can also improve soil properties and increase crop yield. Before the concept of using biochar as soil amendment can be implemented in a bigger scale, it is necessary to know how biochar affects soil fauna in long term. Earthworms present one of the largest animal biomass in soil. They feed on decomposed organic matter and also biochar and transfer it to pedosphere. Effect of biochars and fertilizers on earthworm abundance, biomass and community structure was studied in two field experiments, one on fertile Stagnosol and other on nutrient deficient Umbrisol. In both study sites, split-plot experiments with four replicates were arranged. The earthworms were sampled more than four and five years after the biochar have been applied to the fields on Umbrisol and Stagnosol, respectively. No significant effect of biochar or fertilizer treatments or their interactions were found on earthworms communities, suggesting biochar to be a safe method for carbon sequestration in Southern Finland conditions. The composition of earthworm species was typical for Finnish agricultural land with A. caliginosa dominating in both soils. However further research on long-term experiments are needed, in order to fully understand mechanisms of biochar effects on earthworms

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

Potential of biochar to reduce greenhouse gas emissions and increase nitrogen use efficiency in boreal arable soils in the long-term

Biochars have potential to provide agricultural and environmental benefits such as increasing soil carbon sequestration, crop yield, and soil fertility while reducing greenhouse gas (GHG) emissions and nitrogen leaching. However, whether these effects will sustain for the long-term is still unknown. Moreover, these effects were observed mostly in highly weathered (sub-) tropical soils with low pH and soil organic carbon (SOC). The soils in northern colder boreal regions have typically higher SOC and undergo continuous freeze-thaw cycles. Therefore, effects of biochars in these regions may be different from those observed in other climates. However, only a few biochar studies have been conducted in boreal regions. We aimed to assess the long-term effects of biochars on GHG emissions, yield-normalized non-CO2 GHG emissions (GHGI), and N dynamics in boreal soils. For this, we collected data from four existing Finnish biochar field experiments during 2018 growing season. The experiments were Jokioinen (Stagnosol), Qvidja (Cambisol), Viikki-1 (Stagnosol), and Viikki-2 (Umbrisol), where biochars were applied, 2, 2, 8, and 7 years before, respectively. The GHG emissions, crop yield, soil mineral N, and microbial biomass were measured from all fields, whereas, additional measurements of plant N contents and N leaching were conducted in Qvidja. Biochars increased CO2 efflux in Qvidja and Viikki-2, whereas, there were no statistically significant effects of biochars on the fluxes of N2O or CH4, but in Qvidja, biochars tended to reduce N2O fluxes at the peak emission points. The tendency of biochars to reduce N2O emissions seemed higher in soils with higher silt content and lower initial soil carbon. We demonstrated the long-term effects of biochar on increased crop yield by 65% and reduced GHGI by 43% in Viikki-2. In Qvidja, the significant increment of plant biomass, plant N uptake, nitrogen use efficiency, and crop yield, and reduction of NO3--N leaching by the spruce biochar is attributed to its ability to retain NO3--N, which could be linked to its significantly higher specific surface area. The ability of the spruce biochar to retain soil NO3--N and hence to reduce N losses, has implications for sustainable management of N fertilization.Peer reviewe

Effects of biochar on earthworms in two long-term field experiments in Finland

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Recycling eutrophic lake sediments into grass production : A four-year field experiment on agronomical and environmental implications

Inefficient use of phosphorus (P) fertilizers leads to the transfer of P into water bodies, causing their eutrophication. Sediment removal is a promising lake restoration strategy that removes nutrients including P accumulated in lake sediments, and opens the opportunity to use removed nutrients in agriculture. In the present study, we investigated the effects of using a thick layer of sediment from the eutrophic Lake Mustijarv on plant growth, and estimated the environmental impacts of different sediment application methods by analyzing greenhouse gas emissions, N and P leaching, aggregate stability, and soil biota. The field experiment (2017-2020) was established on the lake shore with the following treatments: the agricultural control soil (Soil) surrounding the lake, pure sediment (Sed), biochartreated sediment (SB), and biochar and soil mixed with sediment (SSB). The sediment-based treatments resulted in a similar grass growth performance to the Soil. The availability of most macro- and micronutrients including P (75 vs. 21 g m-3) were far greater in the Sed compared to the Soil. The sediment-based growing media emitted more CO2 than the Soil (579 vs. 400 mg CO2 - C m-2 h-1) presumably due to the high rate of organic matter decomposition. The bacterial and fungal community structures of the Sed were strongly differentiated from those of Soil. Also, Sed had lower bacterial diversity and a higher abundance of the bacterial phyla associated with solubilizing P including Proteobacteria and Chloroflexi. Sediment-based growing media increased more than seven times the risk of mineral NPeer reviewe