ASSESSING SOIL CARBON AND SOIL QUALITY FOR SUSTAINABLE AGRICULTURAL SYSTEMS IN TROPICAL HILLSLOPE SOILS USING SPECTROSCOPIC METHODS _______________________________________ A Dissertation presented to the Faculty of the Graduate School at the University of Missouri-Columbia _______________________________________________________ In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy _____________________________________________________ by BUNJIRTLUK JINTARIDTH Dr. Peter P. Motavalli, Dissertation Supervisor December 2017 The undersigned, appointed by the dean of the Graduate School, have examined the dissertation entitled ASSESSING SOIL CARBON AND SOIL QUALITY FOR SUSTAINABLE AGRICULTURAL SYSTEMS IN TROPICAL HILLSLOPE SOILS USING SPECTROSCOPIC METHODS presented by Bunjirtluk Jintaridth, a candidate for the degree of Doctor of Philosophy, and hereby certify that, in their opinion, it is worthy of acceptance. Dr. Peter Motavalli Dr. Keith Goyne Dr. Robert Kremer Dr. Frieda Eivazi Dr. Kelly Nelson DEDICATION This dissertation work is dedicated to my parents, Col. Bumrung and Dr. Ampai Jintaridth, for their love and support for my decisions throughout my life. I thank my sister, Dr. Pornrut Jintaridth, and my brother, Dr. Suneth Jintaridth, for their love and support during my PhD degree. ACKNOWLEDGEMENTS I deeply thank my major professor, Dr. Peter Motavalli, for providing me the opportunity to undertake this project, and for his continuous guidance, encouragement and friendship throughout my years in Columbia, Missouri. My special thanks also go to my graduate committee members, Dr. Keith Goyne, and Dr. Robert Kremer, for their time, advice, patience and critical comments on my research project. Dr. Frieda Eivazi and Dr. Kelly Nelson also provided strong support during my doctoral program. My sincerest appreciation is also for the Royal Thai Government Scholarship, USAID and Virginia Tech University for its financial support through the Sustainable Agriculture and Natural Resource Management - Collaborative Research Support Program (SANREM CRSP) project, and to the Department of Soil, Environmental and Atmospheric Sciences (SEAS) for giving me the chance to improve my graduate education. A deep appreciation to all my fellow SEAS graduate students for their kindness and support while taking classes together and working hard in the lab. I am also grateful to the undergraduate students from Bolivia, the Philippines and Indonesia, for helping me to collect valuable field information and for sending me relevant material and information during the course of my research. My sincere appreciation is also expressed to the C2 Church members for their constant support and friendship and for giving me the opportunity to worship God throughout my years in Columbia. My deep love and gratitude to my dad, mom, brother and sister and also to my host family Shirley, Bob, Rob, and Renu Olson for their constant love and emotional support from United States. - ii - TABLE OF CONTENTS ACKNOWLEDGEMENTS ................................................................................................ ii LIST OF TABLES ............................................................................................................. vi LIST OF FIGURES .......................................................................................................... vii ABSTRACT ...................................................................................................................... xii CHAPTER 1. GENERAL INTRODUCTION ................................................................... 1 Definition of Soil Quality ..............................................................................................1 Importance of Soil Quality in Developing Countries ....................................................2 Extent of Land Degradation ...........................................................................................5 Management Practices that Cause Soil Degradation .....................................................6 Measurement of Soil Quality .........................................................................................7 Soil Quality Index ..........................................................................................................8 Soil Quality Kits for Field Assessment ........................................................................10 Problems with Measurement of Soil Quality ...............................................................12 Soil Testing Constraints for Soil Quality in Asia ........................................................14 Importance of Soil Organic Carbon Fractions as the Indicators of Soil Quality ..............................................................................................................16 Separation of Soil Organic Carbon Fractions ..............................................................22 Future Challenges ........................................................................................................28 Objectives ....................................................................................................................29 Dissertation Organization ............................................................................................29 References ....................................................................................................................31 CHAPTER 2. USE OF THE POTASSIUM PERMANGANATE TEST FOR DETERMINING ACTIVE SOIL ORGANIC CARBON IN TROPICAL HILLSLOPE AGROECOSYSTEMS ..............................42 Abstract ........................................................................................................................42 Introduction ..................................................................................................................43 Materials and Methods .................................................................................................47 Study Sites .............................................................................................................47 Location #1 ........................................................................................................47 Location #2 ........................................................................................................49 Location #3 ........................................................................................................50 Location #4 ........................................................................................................51 Soil Processing .....................................................................................................51 Soil Chemical and Physical Analyses ..................................................................52 Soil Characterization ........................................................................................52 Total Organic C................................................................................................52 - iii - Particulate Organic Matter ...............................................................................52 Potassium permanganate active C (MnOxC) analysis .....................................53 Field-kit Method ..............................................................................................53 Laboratory Method ..........................................................................................54 Statistical Analysis ...............................................................................................55 Results and Discussion ................................................................................................56 Responsiveness of KMnO4-Oxidizable C Test to Differences in Management ......................................................................................................56 Comparison Between Laboratory and Field MnOxC Methods Among the Field Locations ...............................................................................62 Comparison of MnOxC with Other Indicators and SOC .......................................63 Conclusions ..................................................................................................................64 References ....................................................................................................................66 CHAPTER 3. USE OF VISIBLE NEAR INFRARED SPECTROSCOPY TO EVALUATE TOTAL SOIL ORGANIC CARBON AND SOIL CARBON FRACTIONS IN TROPICAL HILLSLOPE AGROECOSYSTEMS ........................................................79 Abstract ........................................................................................................................79 Introduction ..................................................................................................................80 Materials and Methods .................................................................................................85 Study Sites and Soil Sampling ...............................................................................85 Spectral Data Acquisition and Analysis ................................................................88 Data Collection Procedures ....................................................................................89 Data Analysis .........................................................................................................90 Soil Laboratory Analysis .......................................................................................91