Potential of Biochar to Mitigate the Effects of Increased Precipitation Variability on Soil Greenhouse Gas Emissions and Soybean Growth
Precipitation variability has been increasing due to climate change, characterized by more frequent heavy rainfalls and more prolonged drought. The projected continuation of this trend in precipitation will likely alter soil greenhouse gas (GHG) fluxes and reduce plant growth. These impacts could be ameliorated by biochar addition in soil. Biochar has been shown to suppress soil GHG fluxes by altering microbial activity or substrate availability, and enhance plant growth by improving soil conditions. However, there have been no biochar studies to date under more variable precipitation conditions. I studied the effects of biochar on soil GHG fluxes and soybean ( Glycine max (L.) Merr.) growth in the field under ambient and variable precipitation patterns (repeated one-month droughts separated by heavy rain events), and also studied GHG emissions in the laboratory of wetted field soils. Laboratory measurements of CO2 fluxes showed that biochar decreased the cumulative fluxes from soils receiving the ambient precipitation, but increased them from soils under the variable precipitation. The field experiment found the same trend. In the field experiment, the variable precipitation treatment reduced cumulative CO2 fluxes by 29%, and biochar lowered cumulative N2O fluxes by 111% across both precipitation treatments. In the laboratory, the variable precipitation treatment decreased CH4 fluxes. The total CO2 equivalent emissions showed the same trend as CO 2 fluxes both in the field and laboratory, indicating that biochar increased total GHG emissions under the variable precipitation pattern. The variable precipitation treatment hastened the timing of seed formation; Dry soybean pods were 11% heavier in the variable precipitation treatment at the premature stage, but by full maturity seeds in the ambient precipitation treatment were 3% heavier. On average, biochar added 20 ± 9 more seeds to every plant, and increased seed weight per plant by 19%. My results showed that biochar inhibited CO2 and N2O fluxes and improved soybean yield in the ambient precipitation treatment. In the variable precipitation treatment, biochar inhibited N2O fluxes and improved soybean growth, but increased CO2 fluxes. The results indicate that biochar may be a useful tool to suppress N2O fluxes and increase soybean yield, but may increase CO2 fluxes under more variable precipitation patterns.
Dukes, Purdue University.
Off-Campus Purdue Users:
To access this dissertation, please log in to our