Special Issue "Biochar and Soil: What Is behind Its Impacts?"

A special issue of Agriculture (ISSN 2077-0472).

Deadline for manuscript submissions: closed (30 September 2018).

Special Issue Editor

Dr. Kurt A. Spokas
Website
Guest Editor
USDA-ARS: Soil and Water Management Unit, Saint Paul, MN, USA
Interests: soil; carbon cycle; nutrient transport; agrochemical; biochar

Special Issue Information

Dear Colleagues,

Despite the recent increase in biochar research, fundamental understanding of its positive agronomic alterations has remained elusive. This could suggest that a single mechanism is not behind its actions. This Special Issue will be dedicated to expand our understanding of mechanisms behind the impacts of biochar application to agricultural fields. Particularly, studies that explore innovative pathways and elucidate new insights into our understanding of biochar's effect on the soil system are particularly solicited. Field scale studies are preferred, but hypothesis driven laboratory and greenhouse studies will also be considered.

Dr. Kurt A. Spokas
Guest Editor

Manuscript Submission Information

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Keywords

  • Biochar
  • Mechanisms
  • Yield Improvement
  • Soil Fertility

Published Papers (4 papers)

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Research

Open AccessArticle
Investigating the Influence of Biochar Particle Size and Depth of Placement on Nitrous Oxide (N2O) Emissions from Simulated Urine Patches
Agriculture 2018, 8(11), 175; https://doi.org/10.3390/agriculture8110175 - 07 Nov 2018
Cited by 1
Abstract
The use of biochar reduces nitrous oxide (N2O) emissions from soils under specific conditions yet the mechanisms through which interactions occur are not fully understood. The objectives of this glasshouse study were to investigate the effect of (i) biochar particle size, [...] Read more.
The use of biochar reduces nitrous oxide (N2O) emissions from soils under specific conditions yet the mechanisms through which interactions occur are not fully understood. The objectives of this glasshouse study were to investigate the effect of (i) biochar particle size, and (ii) the impact of soil inversion—through simulated mouldboard ploughing—on N2O emissions from soils to which cattle urine was applied. Pine biochar (550 °C) with two different particle sizes (<2 mm and >4 mm) was mixed either into the top soil layer at the original 0–10 cm depth in the soil column or at 10–20 cm depth by inverting the top soil to simulate ploughing. Nitrous oxide emissions were monitored for every two to three days, up to seven weeks during the summer trial and measurements were repeated during the autumn trial. We found that the use of large particle size biochar in the inverted soil had significant impact on increasing the cumulative N2O emissions in autumn trial, possibly through changes in the water hydraulic conductivity of the soil column and increased water retention at the boundary between soil layers. This study thus highlights the importance of the role of biochar particle size and the method of biochar placement on soil physical properties and the implications of these on N2O emissions. Full article
(This article belongs to the Special Issue Biochar and Soil: What Is behind Its Impacts?)
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Open AccessArticle
Sorption to Biochar Impacts β-Glucosidase and Phosphatase Enzyme Activities
Agriculture 2018, 8(10), 158; https://doi.org/10.3390/agriculture8100158 - 10 Oct 2018
Cited by 9
Abstract
Extracellular enzymes catalyze biogeochemical reactions in soil, cycling carbon and nutrients in agricultural systems. Enzymes respond quickly to soil management, including organic amendment inputs, such as biochar, a charcoal-like solid byproduct of bioenergy production. In a previous agricultural field trial, a pine biochar [...] Read more.
Extracellular enzymes catalyze biogeochemical reactions in soil, cycling carbon and nutrients in agricultural systems. Enzymes respond quickly to soil management, including organic amendment inputs, such as biochar, a charcoal-like solid byproduct of bioenergy production. In a previous agricultural field trial, a pine biochar amendment caused an approximately 40% decrease in the enzyme activities of β-glucosidase (BG) and phosphatase (PHOS). The large surface area of the pine biochar has the potential to sorb nutrients and other organic molecules. To test if sorption caused decreased enzyme activity, we used a laboratory assay to quantify the activity of two sorbed enzymes: BG and acid PHOS, involved in the cycling of carbon and phosphorous. The enzymes were incubated with three solid phases: (1) the high surface area pine biochar, (2) the agricultural soil, and (3) a low surface area grass biochar, for an additional comparison. We quantified the sorbed enzymes at pH 6, 7, and 8, using a Bradford protein assay, and measured the immobilized enzyme activities via high-throughput fluorometric analysis. After sorption onto pine biochar, detectable BG and PHOS activity levels dropped by over 95% relative to the soil, supporting direct sorption as one mechanism that reduces enzyme activity in biochar amended soil. This laboratory assay demonstrated that sorption could account for the lack of priming of native soil organic matter and changes in soil phosphorous cycling after pine biochar addition. Full article
(This article belongs to the Special Issue Biochar and Soil: What Is behind Its Impacts?)
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Open AccessArticle
Weak Effects of Biochar and Nitrogen Fertilization on Switchgrass Photosynthesis, Biomass, and Soil Respiration
Agriculture 2018, 8(9), 143; https://doi.org/10.3390/agriculture8090143 - 14 Sep 2018
Cited by 3
Abstract
Application of nitrogen (N) fertilizer plus biochar may increase crop yield, but how biochar will interact with N fertilization to affect bioenergy crop switchgrass physiology, biomass, and soil CO2 emission (i.e., soil respiration) from switchgrass fields remains unclear. Here, we assessed this [...] Read more.
Application of nitrogen (N) fertilizer plus biochar may increase crop yield, but how biochar will interact with N fertilization to affect bioenergy crop switchgrass physiology, biomass, and soil CO2 emission (i.e., soil respiration) from switchgrass fields remains unclear. Here, we assessed this issue by conducting a field experiment near Nashville TN with two levels of biochar treatment (a control without biochar addition and biochar addition of 9 Mg ha−1), and four N fertilization levels (0 kg N ha−1, 17 kg N ha−1, 34 kg N ha−1, and 67 kg N ha−1, labeled as ON, LN, MN, and HN, respectively). Results showed that both biochar addition and N fertilization did not influence switchgrass leaf photosynthesis and biomass, but biochar addition enhanced leaf transpiration, and reduced water use efficiency. Soil respiration was reduced by biochar addition, but significantly enhanced by N fertilization. Biochar and N fertilization interactively influenced soil respiration and seasonal variation of soil respiration was mostly controlled by soil temperature. Our results indicated that switchgrass can maintain high productivity without much N input, at least for several years. The findings from this study are useful to optimize N fertilization and biochar addition in the switchgrass fields for maintaining relatively high productive switchgrass biomass while reducing soil CO2 emission. Full article
(This article belongs to the Special Issue Biochar and Soil: What Is behind Its Impacts?)
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Open AccessArticle
Determining the Stability of Sugarcane Filtercake Biochar in Soils with Contrasting Levels of Organic Matter
Agriculture 2018, 8(6), 71; https://doi.org/10.3390/agriculture8060071 - 26 May 2018
Cited by 2
Abstract
Sugarcane filtercake is a nutrient-rich residue produced prior to sugarcane distillation and is commonly disposed of by applying directly to agricultural fields, often causing high decomposition and leaching rates. Transforming this material into biochar could improve its stability in the soil. In this [...] Read more.
Sugarcane filtercake is a nutrient-rich residue produced prior to sugarcane distillation and is commonly disposed of by applying directly to agricultural fields, often causing high decomposition and leaching rates. Transforming this material into biochar could improve its stability in the soil. In this 92-day incubation study, filtercake biochar produced at 400 °C (BC400) and 600 °C (BC600) was used to trace biochar stability when mixed with two soils with different organic matter levels: an agricultural field (1.2% carbon (C)) and a forest (2.8% C) soil. Based on δ13C isotope analysis, biochar decreases in the field soil mostly occurred in the coarse silt fraction. In contrast, biochar decreases in forest soil appeared to be more equally distributed in all particle size fractions. A negative priming effect in biochar-amended soils was noticeable, mainly in the forest soil. Cumulative CO2 emissions were greater in soils with BC400 than in those with BC600 for both field and forest soils, while adding biochar increased CO2 emissions only in field soils. This increase did not appear to affect native soil organic matter pools. High-temperature filtercake biochar could thus be a more stable alternative to the current practice of raw filtercake applications. Full article
(This article belongs to the Special Issue Biochar and Soil: What Is behind Its Impacts?)
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