Impact of biochar on plant productivity and soil properties under a maize soybean rotation on an Alfisol in Central Ohio DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Ryan Darrell Hottle Graduate Program in Environmental Science The Ohio State University 2013 Dissertation Committee: Rattan Lal, advisor Jay Martin Peter Curtis Berry Lyons Copyrighted by Ryan Darrell Hottle 2013 ABSTRACT Here we investigate the application of biochar to a maize (Zea mays)-soybeans (Glycine max L.) rotation in the U.S. Midwest in order to assess the agronomic impacts and changes to soil physical, chemical and biological properties. Biochar is a carbon- rich co-product of thermal degradation of biomass precursor material, a process called ―pyrolysis,‖ intended for the use as a soil amendment as opposed to combusted for heat or energy. Biochar could offer a sustainable means of generating energy, sequestering atmospheric CO2 (thereby mitigating climate change), and increasing agronomic productivity of crops through soil quality enhancement. At a global scale biochar could sequester >1 Pg C yr-1, thereby substantially helping to mitigate climate change. At present, the majority of long-term field trials using biochar as a soil amendemenMg have focused on highly weathered and degraded soils mainly in the tropics and subtropics. Very little long-term field trials have been conducted on agroecosystems in temperate parts of the world. Our research aimed to fill this void, by conducting a 4- year field experiment (2010-2013) with oak-derived biochar from a slow pyrolysis process at ~425⁰C at three rates (0 Mg ha-1, 5 Mg ha-1 and 25 Mg ha-1) with 100% and ii 50% of nitrogen fertilizer (146 kg ha-1 N and 72 kg ha-1 N, respectively) on a maize - soybean rotation on an Ohio alfisol soil. Variables analyzed included to total above- ground biomass, grain yield, leaf and grain nutrient uptake; soil nutrient storage, moisture capacity, aggregate stability, and greenhouse gas emissions (CO2, CH4, and N2O). Overall, our study revealed mixed results. Biochar did tend to increase above- ground biomass and grain yield in both maize and soybeans with the highest biochar treatment (25 Mg ha-1) having the greatest benefit. The results were only significant in the second year, however, although a general positive trend was found in both the first and second year. In the third year, there was a significant drought which resulted in poor stand germination and highly heterogeneous results over all plots. No significant differences in above ground biomass were detected in 2010 or 2012 when soybeans were grown, although there was a significant increase in the total above-ground biomass and grain yield from maize in 2011. In the first year, total above-ground biomass of soybeans increased 8.2% and 12.8% with application of 5 Mg ha-1 and 25 Mg ha-1 biochar, respectively, although the results were only significant (p<0.10) at the 25 Mg ha-1 level. Maize grain yield decreased by-13 and -12% for the 5 Mg ha-1 and 25 Mg ha- 1, respectively, compared with control in the plots receiving 50% of recommended N fertilizer, but increased by 1% and 18% for the 5 Mg ha-1 and 25 Mg ha-1, respectively, compared with control in plots receiving 100% N fertilizer. The specific surface area of the soil increased significantly with the application of biochar, while cation exchange capacity and pH did not significantly change. Increased available water content and increased plant uptake and assimilation of K and S are hypothesized to be contributing iii factors to observed increases in production at the 100% fertilization level. N immobilization is attributed to decreased production in the treatments receiving 50% N fertilizer. The results indicate the importance of addition of adequate levels of N fertilizer with the application of biochar and reject the hypothesis that biochar may increase nitrogen fertilizer use efficiency at 50% of recommended N levels. The flux of CO2 and CH4 did not significantly differ with application of biochar although consistent trends were found for both gases. Cumulative CO2 emissions tended to increase with the application of biochar. Within the 50% recommended N fertilizer plots, the cumulative CO2 flux over the observation period increased 3.5% and 11.1% with the application of biochar at the 5 Mg ha-1 and 25 Mg ha-1 treatments, respectively, and 8.8% and 9.3%, respectively, within the 100% N fertilizer plots. CH4 showed an opposite pattern—consumption (i.e. negative emissions) was correlated with application of biochar although the results were not significant. CH4 consumption increased by 572.5% and 951.7% from the control within the 100% N fertilizer plots. N2O emissions decreased significantly with the application of biochar (p>0.05). N2O emissions decreased by 28.2% and 35.7% with 5 Mg ha-1 and 25 Mg ha-1 biochar added, respectively, compared with the control within plots receiving 100% N fertilizer. Cumulative GWP was dominated by emissions of CO2 followed by N2O and, much less significantly, CH4. The GWP was highest for plots receiving greater quantities of biochar. In the 100% N fertilizer plots GWP was 38,203, 39,778 and 39,560 kg CO2-eq ha-1 yr-1, respectively, for the plots receiving 0, 5, and 25 Mg ha-1 biochar application. Increased CO2 emissions were hypothesized to be the result of an increase in labile C iv from biochar or an increase in microbial decomposition of native C. Decreased N2O emissions were hypothesized to be the result of increased NH4 and NO3 adsorption on biochar surfaces. The application of biochar at the highest rate decreased bulk density significantly by approximately 10% . Available water capacity also changed signficantly with the application of biochar, increasing by approximately 8%. No significant differences were found in soil texture, hydraulic saturated conductivity, penetration resistance or infiltration rate. The specific surface area of the biochar was measured to be 58 m2 g-1. When added to soil, biochar was found to increase overall specific surface area by +12% and +34% with the addition of 5 Mg ha-1 and 25 Mg ha-1 biochar, respectively. Measures of water stable aggregates were significantly different, however, such changes were likely to be the result of highly stable biochar fragments rather than actual soil aggregates although some characteristics of the biochar quasi- aggregates were likely to function much in the same way as naturally occurring soil aggregates. Generally, the results suggest that biochar may have significant benefits to soil quality particularly in regard to soil physical properties including reduced bulk density and increased moisture retention. Biochar may reduce emissions of N2O and increase the consumption of CH4, but this must be examined in terms of the entire emissions profile over time. Although not significant at a p<0.05 confidence level, there was an observed increase in CO2 emissions among plots receiving biochar. This apparent increase in CO2 emissions with biochar application offset total reductions in global warming potential (GWP) from both N2O and CH4 . v DEDICATION Dedicated to my father—scientist, soccer coach, and political thinker—who taught me to think critically and never to give up in spite of the circumstances; my mother—social worker, wonderful parent and general goofster—who would be considered for sainthood if she were only Catholic; and my brother who, in addition to being my fiercest competitor, is also my best friend and partner in all things good. I love you guys. vi ACKNOWLEDGEMENTS First and foremost, I want to extend my appreciation to my advisor, Distinguished University Professor Rattan Lal who not only expanded my knowledge and perspective on the critical issues of the day so much in so little time, but also who provided invaluable moral support. I thank my committee members Dr. Jay Martin, Dr. Peter Curtis, and Dr. Berry Lyons. I want to specifically thank Dr. Richard Moore who, as director of the Environment and Natural Resources Program, helped guide and assist me through the my time at Ohio State University. Dr. Raj Shrestra, Dr. Dr. David Ussiri, Dr. Martin Shipitalo, Dr. Brian Slater, Dr. Nick Basta, Mr. Basant Rimal, and Mr. Franklin ―Sandy‖ Jones. I thank my colleagues and classmates: Dr. Ji Young Jung, Josh Beniston, Nick Stanich, and Josh Kendell. I especially want to single out Mr. Chris Eastman who in addition to being a great research partner has also become a very good friend. vii VITA 2001 ............................................................... Granville High School 2006 ............................................................... B.A. Naropa University 2009 ............................................................... M.A. Columbia University Fields of Study Major Field: Environmental Science viii TABLE OF CONTENTS ABSTRACT ........................................................................................................................ ii DEDICATION ................................................................................................................... vi ACKNOWLEDGEMENTS .............................................................................................. vii VITA ................................................................................................................................ viii TABLE OF CONTENTS ..................................................................................................