The Faculty of Agriculture and Forestry has awarded PhD Subin Kalu a dissertation prize of one thousand euros for his doctoral dissertation completed in 2022. The dissertation was based on four published scientific articles focusing on an important topic related to negative emissions (C sink establishment) and sustainable agriculture – the use of biochar in agricultural soils in the boreal region. The major objective of the dissertation was on the long-term effects of biochar in soils, multiple years after its application – a topic that is rarely investigated. The dissertation evaluated long-term effects of a single application of biochar on crop yield, nutrient uptake, soil physical properties, greenhouse gas emission, N leaching and N use efficiency. In addition, a greenhouse experiment was conducted to assess biochar effects and mechanisms on soil N dynamics – including plant N uptake, N leaching and gaseous N losses using novel 15N labelled N fertilizer. The study found that even though the effects of biochar were not consistent over different years and soil types, biochar exhibited potential agricultural (increased crop yield and plant nutrient uptake) and environmental benefits (decreased N leaching and N2O emissions) several years after the soil application. Furthermore, no negative effect of biochar was observed over the long-term, hence, the soil application of biochar is the safe way to enhance soil C storage.
The grading committee stated that the topic and approach are very timely and important since few studies have been done on long-term effects of biochar applications to soils and consider both agronomic and environmental effects. Analyses showed considerable insights going beyond regular statistics, the level of detail in the published articles was extraordinary and all published papers have already been cited.
After his dissertation, Subin Kalu is working as a postdoctoral researcher at Department of Crop and Soil Sciences in North Carolina State University. His current research emphasizes the mechanism of how the incorporation of biochar in the soil alters the cycling of mineral associated soil organic carbon.
“My research interests focus on soil biogeochemistry, soil nutrient cycling, soil GHG emissions, stable isotope techniques and biochar research. In my current research project, I am studying the interactions of biochar with mineral associated soil organic carbon and exogenous carbon such as root exudates to shed light on the mechanism of complex interactions between biochar, soil organic carbon and root exudates. Understanding these interactions would be helpful in developing strategies for enhancing soil C sequestration” Subin Kalu says.