|CHINTALA, RAJESH - University Of South Dakota|
|OWEN, RACHAEL - University Of South Dakota|
|SCHUMACHER, THOMAS - University Of South Dakota|
|MCDONALD, LOUIS - West Virginia University|
|KUMAR, SANDEEP - University Of South Dakota|
|CLAY, DAVID - University Of South Dakota|
|MALO, DOUGLAS - University Of South Dakota|
|BLEAKLEY, BRUCE - University Of South Dakota|
Submitted to: Environmental Science and Pollution Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2014
Publication Date: 11/5/2014
Publication URL: http://handle.nal.usda.gov/10113/60478
Citation: Chintala, R., Owen, R.K., Schumacher, T.E., Spokas, K.A., McDonald, L.M., Kumar, S., Clay, D.E., Malo, D.D., Bleakley, B. 2014. Denitrification kinetics in biomass and biochar amended soils of different landscape positions. Environmental Science and Pollution Research. 22:5152-5163. DOI: 10.1007/s11356-014-3762-2.
Interpretive Summary: An improved understanding of the mechanisms behind the interaction of biochar with denitrification rates in soils is needed. This research aimed to evaluate the kinetics of nitrous oxide production comparing three different types of biomass and its corresponding biochar for two different soils. Cumulative nitrous oxide emissions were reduced by 30% to 70%. However, this effect was only significiant at moisture contents >40% water filled pore space. The denitrification enzyme activity (DEA) kinetic parameters of Ks (half-saturation constant) and Vmax (maximum DEA rate) were both significantly reduced by biochar treatments. On the other hand, the activation energy (Ea) and enthalpy of activation of DEA ('H) were increased with biochar application. Therefore, this data suggests that the kinetic parameters are a good assessment tool for the nitrous oxide mitigation potential of biochar by slowing the rate of dentirification occurring in soils. These results are significant to farmers and policy makers and will assist scientists and engineers in developing improved models for net nitrous oxide exchange based on mechanistic processes, which can be used to improve soil management practices.
Technical Abstract: Knowledge of how biochar impacts soil denitrification kinetics as well as the mechanisms of interactions are essential in order to better predict the nitrous oxide (N2O) mitigation capacity of biochar additions. This study had multiple experiments in which the effect of three biochar materials produced from corn stover (Zea mays L.) - CSB, Ponderosa pine wood residue (Pinus ponderosa Douglas ex Lawson and C. Lawson) –WCB, switchgrass (Panicum virgatum L.) – SGB and their corresponding biomass materials (corn stover – CS, Ponderosa pine wood residue-WC, and switchgrass – SG) on cumulative N2O emissions and total denitrification in soils from two different landscape positions (crest and footslope) was studied under varying water filled pore space (40, 70, and 90% WFPS). Cumulative N2O emissions were reduced by 28% to 65% in footslope soil and 26 to 68% in crest soil with the incorporation of biochars during 112 days of incubation study. The effect of biochars and biomass treatments on cumulative N2O emissions and total denitrification were not observed at 40% WFPS. The denitrification enzyme activity (DEA) kinetic parameters, Ks (half-saturation constant) and Vmax (maximum DEA rate) were both significantly reduced by biochar treatments. Half-saturation constant (Ks) and Vmax were reduced with the added biochars by 72-82% and 67-78% respectively in footslope soil. In crest soil, the reductions were 81-89% in Ks and 76-80% Vmax of DEA. The activation energy (Ea) and enthalpy of activation of DEA ('H) were consistently increased with the application of biochars in both crest and footslope soils. In crest soil with the incorporation of biochars, Ea and 'H of DEA ranged from 93.5 to 103 kJ mole-1 and 91.1 to 101 kJ mole-1 respectively. Whereas in footslope soil amended with biochars, Ea and 'H of DEA ranged from 94.5 to 97.7 kJ mole-1 and 92.1 to 95.4 kJ mole-1 respectively. The trends in DEA rate constants (Ks and Vmax) were supported by the trends of thermodynamic parameters (activation energy - Ea and enthalpy of activation – 'H) for denitrifying enzyme activity (DEA). The rate constant, Vmax/Ks evaluated the capacity of biochars to mitigate the denitrification process. Denitrifying enzyme kinetic parameters can be useful in evaluating the ability of biochars to mitigate nitrogenous gas losses from soil.