A thesis submitted to the Graduate School at Tennessee State University, Funmilayo Akintunde investigated the “Effects of BiocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More Application and Nitrogen Fertilization on Microbial Community in Switchgrass ( Panicum Virgatum) Soil”. This study aimed to understand how biochar and nitrogen fertilization impact the microbial community in switchgrass soil, a critical area given switchgrass’s potential as an energy crop and the role of agricultural soils in nitrous oxide (N2​O) emissions. The research employed a two-factor randomized complete block design, incorporating three levels of nitrogen (0, 80, and 160 kgN⋅hm−2) and biochar rates (0, 20, and 40 t⋅hm−2).

The study measured various parameters, including Average Well Color Development (AWCD) and Shannon indexes using BIOLOG Eco-Plates, microbial abundance through gene sequencing, and N2​O emissions. The results from the AWCD and Shannon index showed a gradual increase in microbial metabolic activities and microbial population with nitrogen treatment compared to the control. This indicates that nitrogen fertilization generally stimulated microbial activity and diversity in the switchgrass soil.

Gene sequencing identified several bacterial genera known to be involved in the nitrogen cycle, including Nitrosomonas, Rhizobium, Nitrobacter, Nitrospira, and Nostoc. Notably, Pseudomonas constituted a significant portion, 73%, of the total bacterial population across the samples. Pseudomonas are recognized for their potential involvement in the N2​O emission process in switchgrass. Regarding N2​O emissions, the study observed that N2​O flux was lower on the 7th day and before treatment, but it tended to increase towards the 30th day, which was attributed to the longer treatment duration. This suggests a time-dependent effect of the treatments on greenhouse gas emissions.

A key finding was the notable impact on the microbial community when both nitrogen fertilizer and biochar were applied to the switchgrass soil. The interactive effect between nitrogen and biochar was particularly strong at their higher application rates. This indicates that combined application of biochar and nitrogen fertilizer can significantly influence the soil’s microbial ecosystem, offering potential for improved management strategies for switchgrass cultivation and greenhouse gas mitigation. The study’s results are crucial for understanding and controlling the microbial dynamics in switchgrass soil, especially in the context of sustainable agricultural practices and biofuel production.

Source: Akintunde, F. (2023). Biochar and Nitrogen Effects on Soil Microbes in Switchgrass (Panicum Virgatum) Soil (Master’s thesis). Tennessee State University.