The effects of biochar-manure on crop yield, greenhouse gases, and organic matter stability in an Orthic Gray Luvisol

• Author / Creator

  Weber, Tien L.

• Cattle production contributes to the largest portion of livestock agricultural greenhouse gas (GHG) emissions in Canada, mainly in the form of methane (CH4). Therefore, there is interest in the modification of livestock diet composition to try and reduce the emission of CH4, resulting in a corresponding change in manure properties. One such modification includes using biochar, a stable carbon (C) C-rich and porous compound from thermal alteration (pyrolysis) of organic material (OM) with little or no oxygen, resulting in biochar-manure. Many report overall positive impacts on crop growth (Calvelo Pereira et al. 2014; Gomez et al. 2014; Steinbeiss et al. 2009), decreased GHG emissions (Bruun et al. 2011; Feng et al. 2012; Jeffery et al. 2016), and C sequestration (Certini 2005; Chen et al. 2020; Du et al. 2017) with biochar application due to changes in soil properties (chemical, physical, and biological) through direct and indirect impacts. Yet, information concerning the agronomic performance and long-term stability potential of biochar-manure under temperate field conditions is scarce.
  In Chapter 2, a laboratory incubation investigated the effects of biochar-manure, regular manure, and biochar by itself to a Gray Luvisol soil with loamy sand texture in a controlled environment. A 64-day incubation was used to study C and N mineralization by measuring CO2- C fluxes and inorganic N (nitrate (NO3-N) and ammonium (NH4-N)) concentrations. In Chapters 3-5, various biochar manure, regular manure, and biochar alone treatments were studied in a field trial at the Breton Research Station to examine the effect of these amendments on crop growth, fertility, GHG emissions, and C sequestration. Treatments included plots a control, (CT), biochar at 5 and 10 Mg ha-1 (BC5 and BC10), stockpiled manure (RM) at 100 kg total N ha-1, stockpiled biochar-manure (BM) (manure from cattle with biochar added at 2% of diet dry matter) at 100 kg total N ha-1, and v) BC and RM (BC + RM) or BM (BC + BM) at the aforementioned rates. Fields were planted with wheat (Triticum aestivum) in June 2020 and canola (Brassica napus) in May 2021, using a field plot seeder and harvested in September of 2020 and 2021. Soil samples were collected after amendment, pre-seeding, and post-harvest each year and analyzed for microbial biomass, microbial functioning, cations and anion concentrations, OM stability, C/N, EC, and pH. Atmospheric and soil temperature and moisture data was collected throughout the study.
  Chapter 2, the lab incubation, results showed that BM+BC lowered (P < 0.05) C mineralization relative to RM+BC, with no statistical differences in N mineralization. Chapter 3 showed that BM+BC10 had greater (P < 0.05 in wheat) grain and protein yield, as well as amino acid utilization in treatments with biochar, likely related to N use efficiency. Chapter 4, showed that BM+BC5 (133.0 kg ha-1) did not significantly impact anthropogenic emissions of N2O and CH4, while still improving grain productivity and protein content compared to BM alone, while BM+BC10 limited CH4 oxidation due to microbial community changes in the rumen. Finally, Chapter 5 findings revealed that BM+BC10 resulted in the highest (P > 0.05) organic C (OC) in aggregated (29.4 g kg-1), and non-aggregated mineral-associated organic matter (MAOM; 35.5 g kg-1). Analysis by PCA/FTIR showed higher absorbance, and hence greater long-term stability, with BM+BC10 at 2930 cm-1 and 1650 cm -1 (recalcitrant aliphatic and aromatics) than RM+BC10.
  Results from the four experiments demonstrate that various amendments and their interaction significantly (P = 0.05) affected soil properties, so further research is needed to investigate the effect of cattle fed various amounts of biochar and other soil types. Treatments were compared to the control to determine percentage of increase in GHG emissions and C stability using data from chapter 4 and 5, where RM+BC10 and BM+BC10 emitted 7% more GHG, on average; but also sequestered 43% more, compared to the control. In conclusion, combinations of BM and BC are promising means to increase C storage in soil.

• Subjects / Keywords

  • soil
  • greenhouse gases
  • crop
  • organic matter stability
  • biochar
  • manure

• Graduation date

  Spring 2023

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-zhgd-1386

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.