Mulching and tillage effects on GHG emissions and properties of an Alfisol in Central Ohio THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Merrie Ann Varughese Environmental Science Graduate Program The Ohio State University 2011 Master's Examination Committee: Dr. Rattan Lal, Advisor Dr. Craig B. Davis, committee member Dr. Martin J. Shipitalo, committee member © Copyright by Merrie Ann Varughese 2011 All Rights Reserved Abstract No-tillage (NT) management in conjunction with crop residue retention on soil has been promoted as a practice capable of enhancing the soil quality as well as offsetting greenhouse gas (GHG) emissions because of its ability to sequester carbon in soils. Therefore, the objective of this study was to evaluate the long term effects of application wheat (Triticum aestivum) residue mulch under NT and conventional tillage (CT) on GHG emissions, soil physical and chemical properties in an ongoing experiment in Central Ohio. Treatments included three rates of mulch at 0 Mg ha-1 yr-1 (M0), 8 Mg ha-1 yr-1 (M8) and 16 Mg ha-1 yr-1 (M16) without crop cultivation. All treatments were replicated thrice and laid out according to a completely randomized design. The data presented showed that application of straw mulch under NT can reduce GHG emissions -2 compared to CT. The average diurnal CO2 fluxes were lower under NT (8.58g CO2-C m -1 -2 -1 d ) compared to CT (9.69g CO2-C m d ). The effects of plowing on N2O flux, although -2 -1 not significant, indicated a trend of higher N2O fluxes under NT (0.27 mg m d ) than CT (0.21 mg m-2 d-1). Similarly, there was no definite trend among tillage treatments with regards to CH4 flux. However, NT was more of a sink for CH4 while CT treatments were sources. CO2 and N2O fluxes were significantly affected by mulch treatments, but mulching did not significantly affect CH4 flux. Furthermore, the application of mulch ii directly influences chemical and physical properties of the soil. The current study shows that the application of mulch conserves soil moisture, reduces bulk density, moderates soil temperature, reduces soil salinity and enhances soil aggregation. Results suggest that mulching in conjunction with NT has positive effects on temperate agricultural soils, yet further research needs to be conducted to provide additional insight on the over-all impact and interactions between management regimes and GHG emissions, especially in relation to soil properties and climate factors. iii Dedication This document is dedicated to my beloved, George Oommen, and my family. iv Acknowledgements First and foremost, I would like to express my most sincere gratitude to my advisor Prof. Rattan Lal for giving me the opportunity to join his team. I thank him for his patience, continuous encouragement, guidance and funding to make my Masters experience productive and stimulating. I would also like to thank other members of my committee, Prof. Craig Davis and Dr. Martin Shipitalo for their insightful comments and guidance. I express my whole hearted thanks to the Carbon Management and Sequestration Centre group for their constructive criticism and excellent advice during the preparation of this I owe my gratitude to Dr. Meherban Kahlon, Senior Soil Scientist, Department of Soils, PAU, Ludhiana, India. for helping me with soil sampling and lab experiments. I am especially grateful to Basant Rimal for his constant support with lab experiments and gas sample analysis. I would also like to thank Matthew Yin of OSU‘s Statistical Consulting Service (SCS) for helping with the statistical analysis of my data. Most importantly, I would like to thank my family and my friends for all their love and support. I wish to express my deepest gratitude to my beloved, George Oommen, for always offering me a helping hand during my sampling process and for being a constant source of encouragement through-out my research and thesis work. v Vita 2001-2005 ......................................................Vidyodaya School (Higher Secondary Education) 2005-2009 ......................................................B.E. Biotechnology, Vellore Institute of Technology University Fields of Study Major Field: Environmental Science vi Table of Contents Abstract………………………………………………………………………………………….................ii Dedication………………………………………………………………………………………………...iv Acknowledgements………………………………………………………………………………………v Vita….……………………………………………………………………………………………………...vi List of Tables………………………………………………………………………………………….....ix List of Figures…………………………………………………………………………………………….x Chapter 1: Introduction .................................................................................................. 1 1.1 GHG concentrations in the atmosphere: ............................................................. 3 1.2 Factors affecting GHG emissions from agricultural soils: .................................. 6 1.2.1 Soil physical properties: ............................................................................... 6 1.2.2 Soil chemical properties:.............................................................................. 7 1.2.3 Tillage systems............................................................................................. 8 1.2.3.1 CO2 emissions ........................................................................................ 10 1.2.3.2 CH4 emissions ........................................................................................ 10 1.2.3.3 N2O emissions ........................................................................................ 11 1.2.4 Crop residue management.......................................................................... 12 1.2.4.1 Mulch amendments ................................................................................ 13 References: ........................................................................................................ 16 Chapter 2: Mulching and tillage effects on Greenhouse Gas (GHG) emissions ......... 25 2.1 Abstract ............................................................................................................. 25 2.2 Introduction: ...................................................................................................... 26 2.3 Materials and methods: ..................................................................................... 30 2.3.1 Field site and experimental design:............................................................ 30 2.3.2 Monitoring CO2, CH4 and N2O fluxes ....................................................... 31 2.3.3 Analysis of gas samples ............................................................................. 32 2.3.4 Data analysis .............................................................................................. 33 vii 2.4 Results and discussion ....................................................................................... 34 2.4.1 Diurnal CO2 fluxes ..................................................................................... 34 2.4.2 Diurnal N2O fluxes .................................................................................... 41 2.4.3 Diurnal CH4 fluxes ..................................................................................... 45 2.5 Conclusion ......................................................................................................... 49 References ......................................................................................................... 51 Chapter 3: Mulching and tillage effects on soil physical and chemical properties ..... 57 3.1 Abstract ............................................................................................................. 57 3.2 Introduction ....................................................................................................... 58 3.3 Materials and method: ....................................................................................... 62 3.3.1 Field site and experimental design:............................................................ 62 3.3.2 Determination of soil physical properties: ................................................. 63 3.3.3 Determination of chemical properties ........................................................ 64 3.3.4 Statistical analysis ...................................................................................... 65 3.4 Results and discussion:...................................................................................... 65 3.4.1 Soil physical parameters ............................................................................ 65 3.4.1.1 Soil bulk density under different mulch and tillage treatments ............. 65 3.4.1.2 Soil moisture under different mulch and tillage treatments ................... 68 3.4.1.3 Soil temperature under different mulch and tillage treatments .............. 70 3.4.2 Soil chemical parameters ........................................................................... 73 3.4.2.1 Soil pH under different mulch and tillage treatments ............................ 73 3.4.2.2 Soil EC under different mulch and tillage treatments ............................ 73 3.4.2.3 Soil macro and micro-aggregate C and N concentration under different mulch and tillage treatments ................................................................................. 75 3.5 Conclusion ......................................................................................................... 78 References