Modification of Surface Functionality of Biochars and Their Impact on Greenhouse Gas Emissions from Eroded Landscape.

Modification of surface functionality of biochars and their impact on greenhouse gas emissions from eroded landscape

Rajesh Chintala¹*, S. Sandhu¹, T.E. Schumacher¹, S. Kumar¹, J. Rice², D.E. Clay¹, D.D. Malo¹

¹Department of Plant Science, South Dakota State University,  

Brookings, South Dakota, USA

                     ²Department of Chemistry & Biochemistry, South Dakota State  

University, Brookings, South Dakota, USA

*Presenting Author: Rajesh Chintala, Department of Plant Science, SNP 247, Box 2140c, South Dakota State University, Brookings, SD, 57006. Email: rajesh.chintala@sdstate.edu

Pyrogenic biochars have complex composition with highly heterogeneous surface, amphilicity, and unique electrochemical properties. The incorporation of biochar as a soil amendment is hypothesized to interfere with the physical, biological, and electrochemical properties of soils thus exerting influence on carbon and nitrogen dynamics and exchange of greenhouse gases at the soil surface. The extent and nature of interference depends on the feedstock source and controlled pyrolytic processing parameters of these pyrogenic carbon materials but also on variation in soil properties. A field study was initiated in 2013 with an objective to study the effect of three biochars produced from carbon optimized gasification of corn stover (Zea mays L.), Ponderosa pine (Pinus ponderosa Lawson and C. Lawson) wood residue, and switchgrass (Panicum virgatum L.) on greenhouse gas emissions (CH₄, CO₂, and N₂O) from soils at two landscape positions. In this field study, all three biochars were incorporated at a 10 Mg ha^-1 rate (≈7.5 cm soil depth) with rototiller to a Maddock soil (Sandy, Mixed, Frigid Entic Hapludolls) located in an eroded upper landscape position and a Brookings soil (Fine-Silty, Mixed, Superactive, Frigid Pachic Hapludolls) located in a depositional landscape position. The experimental plot size was 4.5m x 6m in a corn-soybean rotation. Greenhouse gas fluxes (CO₂, CH₄, and N₂O) were measured every week during the growing season. Soil samples of two depths (0-7.5 cm and 7.5 to 15 cm) were collected twice (before planting and after harvesting) for determining C and N changes. The effect of field aging on surface characteristics of biochars were determined using N₂ dsorption BET surface analyzer and solid state ¹³C NMR. Preliminary data showed that the cumulative nitrous oxide emissions were consistently influenced by the biochar treatments in first and second crop growing seasons at both upper and depositional landscape position. N₂-BET analysis of two year field biochar showed no significant changes in surface area. But there were shifts in aliphatic, aromatic, carbonyl and carboxyl carbon distribution of two year field aged biochars demonstrated by NMR spectra.