Influence of biochar addition to nursery container media: trace gas efflux, growth, and leachate N.

Authors: Prior, Stephen - Steve; Runion, George; MURPHY, ANNA-MARIE - Auburn University; HOFFMAN, HEATH - Auburn University; JOHNSON, MARK - Us Environmental Protection Agency (EPA); Torbert, Henry - Allen

Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2023
Publication Date: 12/18/2023
Citation: Prior, S.A., Runion, G.B., Murphy, A., Hoffman, H., Johnson, M.G., Torbert III, H.A. 2023. Influence of biochar addition to nursery container media: Trace gas efflux, growth, and leachate N. Journal of Environmental Horticulture. 41(4):141-151. https://doi.org/10.24266/0738-2898-41.4.141.
DOI: https://doi.org/10.24266/0738-2898-41.4.141

Interpretive Summary: Ornamental plant producers may be incentivized to alter production practices to reduce greenhouse gas (GHG) emissions in response to oncoming legislation, potential tax incentives or consumer demand. Since little work has examined biochar use in horticultural systems, we investigated how biochar additions to growth media affected GHG (CO2, CH4, and N2O), plant growth, and N loss (from leaching) in two separate studies: a peat-based greenhouse study using viola (80:20 peat:perlite amended with 0, 5, 10, 20, or 30% biochar) and a pinebark-based outdoor study using daylily (6:1 pinebark:sand control, or pinebark mixed with 10, 20 or 30% biochar). For viola, there were no differences in top dry weight or total plant N across biochar treatments. Loss of N2O was lowest for the 30% biochar at one sampling date with no differences in total seasonal losses of CO2, N2O or CH4. With daylily, all biochar treatments generally had lower dry weights (top and roots) and lower total plant N compared to no biochar. Early in the study, no biochar had higher N2O loss than any level of added biochar. Total losses of N2O and CO2 declined with increasing biochar suggesting that its use could help mitigate global climate change. Both studies clearly showed that N in leachate was reduced by biochar, suggesting improved N use efficiencies. The complexities of N management highlight the importance of developing biochar practices that reduce N loss for the benefit of both agriculture and the environment.

Technical Abstract: Biochar is a pyrolytic product generated by heating biomass in the absence of oxygen such as during bioergy production. Biochar can be made from various feedstocks and research into its potential use in agricultural systems has examined its effects on growth, trace gas emissions, and N loss. However, since a paucity of work has examined biochar use in horticultural container production systems, we investigated how biochar additions to growth media impacted trace gas efflux (CO2, CH4, and N2O), plant growth, and N loss via leachate in two separate experiments: a peat-based greenhouse study using viola (Viola cornuta L. ‘Sorbet® XP Deep Orange’) and a pinebark-based outdoor study using daylily (Hemerocallis x ‘EveryDaylily Cream PBR’ L.). Biochar had little effect on viola growth, but growth inhibition was noted for daylily. Both studies clearly showed that N in leachate was reduced by biochar additions, with higher biochar rates having greater effects on reducing N loss. Reductions in N loss with biochar suggest improved N use efficiencies in agricultural systems. Biochar use also decreased N2O and CO2 fluxes in daylily which suggests that biochar could help mitigate global climate change. Our results suggest that future studies should focus on testing lower rates of biochar in terms of growth and environmental impacts. The complexities of N management highlight the importance of developing biochar practices that increase N retention for the benefit of both agriculture and the environment.