Browsing by Author "Shrestha, Raj K."

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    Biochar as a negative emission technology: A synthesis of field research on greenhouse gas emissions
    (Wiley, 2023-07) Shrestha, Raj K.; Jacinthe, Pierre-Andre; Lal, Rattan; Lorenz, Klaus; Singh, Maninder P.; Demyan, Scott M.; Ren, Wei; Lindsey, Laura E.; Earth and Environmental Sciences, School of Science
    Biochar is one of the few nature-based technologies with potential to help achieve net-zero emissions agriculture. Such an outcome would involve the mitigation of greenhouse gas (GHG) emission from agroecosystems and optimization of soil organic carbon sequestration. Interest in biochar application is heightened by its several co-benefits. Several reviews summarized past investigations on biochar, but these reviews mostly included laboratory, greenhouse, and mesocosm experiments. A synthesis of field studies is lacking, especially from a climate change mitigation standpoint. Our objectives are to (1) synthesize advances in field-based studies that have examined the GHG mitigation capacity of soil application of biochar and (2) identify limitations of the technology and research priorities. Field studies, published before 2022, were reviewed. Biochar has variable effects on GHG emissions, ranging from decrease, increase, to no change. Across studies, biochar reduced emissions of nitrous oxide (N2O) by 18% and methane (CH4) by 3% but increased carbon dioxide (CO2) by 1.9%. When biochar was combined with N-fertilizer, it reduced CO2, CH4, and N2O emissions in 61%, 64%, and 84% of the observations, and biochar plus other amendments reduced emissions in 78%, 92%, and 85% of the observations, respectively. Biochar has shown potential to reduce GHG emissions from soils, but long-term studies are needed to address discrepancies in emissions and identify best practices (rate, depth, and frequency) of biochar application to agricultural soils.
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    Soil organic carbon pools across paired no-till and plowed Alfisols of central Ohio
    (Wiley, 2016-12) Nakajima, Toru; Shrestha, Raj K.; Jacinthe, Pierre André; Lal, Rattan; Bilen, Serdar; Dick, Warren; Department of Earth Sciences, School of Science
    No-till (NT) farming can restore the soil organic carbon (SOC) pool of agricultural soils, but the SOC pool size and retention rate can vary with soil type and duration of NT. Therefore, the objectives of this study were to determine the effects of NT and soil drainage characteristics on SOC accumulation across a series of NT fields on Alfisols in Ohio, USA. Sites under NT for 9 (NT9), 13 (NT13), 36 (NT36), 48 (NT48) and 49 (NT49) years were selected for the study. Soil was somewhat poorly drained at the NT48 site but moderately well drained at the other sites. The NT48 and NT49 on-station sites were under continuous corn (Zea mays), while the other sites were farmers' fields in a corn–soybean (Glycine max) rotation. At each location, the SOC pool (0–30 cm) in the NT field was compared to that of an adjacent plough-till (PT) and woodlot (WL). At the NT36, NT48 and NT49 sites, the retention rate of corn-derived C was determined using stable C isotope (13C) techniques. In the 0- to 10-cm soil layer, SOC concentration was significantly larger under NT than PT, but a tillage effect was rarely detected below that depth. Across sites, the SOC pool in that layer averaged 36.4, 20 and 40.8 Mg C/ha at the NT, PT and WL sites, respectively. For the 0- to 30-cm layer, the SOC pool for NT (83.4 Mg C/ha) was still 57% greater than under PT. However, there was no consistent trend in the SOC pool with NT duration probably due to the legacy of past management practices and SOC content differences that may have existed among the study sites prior to their conversion to NT. The retention rate of corn-derived C was 524, 263 and 203 kg C/ha/yr at the NT36, NT48 and NT49 sites. In contrast, the retention rate of corn-C under PT averaged 25 and 153 kg C/ha/yr at the NT49 (moderately well-drained) and NT48 (somewhat poorly drained) sites, respectively. The conversion from PT to NT resulted in greater retention of corn-derived C. Thus, adoption of NT would be beneficial to SOC sequestration in agricultural soils of the region.