Agronomic Management Practice Effects on Particulate Organic Matter and Infiltration in a Wheat-soybean, Double-crop System in Eastern Arkansas

Improving the understanding of conventional and alternative management practices and their interactions on aggregate-derived particulate organic matter (POM) fractions and soil hydraulic properties, particularly infiltration, is instrumental to soil and groundwater management and long-term sustainability in the Lower Mississippi River Delta (LMRD) region of eastern Arkansas. The objective of this long-term wheat (Triticum aestivum L.)-soybean (Glycine max [L.] Merr.), double-crop (WSDC) field study in a silt-loam soil (Glossaquic Fraglossudalf) in the LMRD region of eastern Arkansas was to evaluate the effects of conventional and alternative management practices, including wheat-residue level, residue burning, tillage and irrigation, on i) POM fractions and the distribution of C and N among POM fractions, including the total POM, light fraction (LF) and intra-POM (iPOM) fraction, in the top 10 cm of soil after 14 years of consistent management and ii) falling-head and tension infiltration after 11 and 14 years of consistent management. Long-term treatment combinations affected (P < 0.05) several macro(53-250 μm) and micro-aggregate-(<53 μm)-derived coarse and fine POM fractions. Averaged across tillage and burn treatments, the coarse LF C content was 20.3% greater (P ≤ 0.02) in the irrigated-low(107.3 g m-2) compared to the irrigated-high-residue (89.2 g m-2) and 65.4% greater than in the non-irrigated treatment combinations, which did not differ and averaged 64.8 g m-2. Adjusted for differences in initial volumetric water content (VWC) across sampling dates and averaged across burning and tillage, the falling-head overall infiltration rate in the 2012-non-irrigated-high-residue combination (8.3 cm hr-1) was 2.7 times greater (P = 0.02) than the combined average of all 2015 irrigation-residue-level combinations, which did not differ and averaged 2.2 cm hr-1. The effects of alternative management practices in a WSDC on POM fractions’ C and N contents and water infiltration can lead to greater C and N storage as well as direct and indirect improvements in soil health, aquifer recharge, and crop yields in the LMRD region. Acknowledgements I would like to thank the members of my Advisory/Thesis Committee, Dr. Kristofor R. Brye, Dr. Mary C. Savin, Dr. Edward E. Gbur, Jr. and Dr. R. Esten Mason for guiding me in my research and the preparation of this thesis. I would like to thank Dr. Kristofor R. Brye for his insightful guidance in my research and scholarly pursuits. Dr. Brye instilled a drive and passion for soil science from my undergraduate degree to now. His attention to detail and drive in his research, writing and teaching are qualities I hope to emulate and carry forward in my career. I would like to thank Dr. Mary C. Savin for her guidance throughout my undergraduate and graduate career at the University of Arkansas. Through her teachings I deepened my insight and knowledge of soil science which led me to many of the research topics in this thesis. I would like to thank Dr. Edward E. Gbur for his guidance throughout my graduate career at the University of Arkansas. Dr. Gbur helped me understand and appreciate the value of statistics, data analyses and experimental design. I would like to thank Dr. R. Esten Mason for his guidance throughout my graduate and undergraduate career at the University of Arkansas. Dr. Mason’s cereal grain production course instilled an initial appreciation for the agricultural component of soil science that later deepened. I would like to thank Dr. David M. Miller for his guidance throughout my undergraduate and graduate career. Dr. Miller introduced me to soil science and his passion for the subject was infectious. Dr. Miller and I enjoyed several long conversations together and his enthusiasm for the subject radiated onto me. I would like to thank Dr. Clifford S. Snyder for his guidance and help with understanding the possible career paths that lie ahead of me. Dr. Snyder provided invaluable insight to further my understanding of the agricultural industry. I would like to express my gratitude for the loving support of my family throughout my life. My parents, Norbert Desrochers and Line Cousineau, my uncle and aunt, Daniel Séguin and Josée Cousineau, my grandparents, Robert Cousineau and Aline Côté-Cousineau, my brothers, Lucas Desrochers and Clovis Desrochers and sister, Odelie Desrochers, have been immensely supportive of all my endeavor and have instilled in me all of their greatest qualities, words fail to express the love and gratitude I feel for them. Dedication This thesis is dedicated to my family and friends who helped motivate and inspire me throughout this undertaking. Table of