Soil-Tool-Residue Interactions: Measurements and Modelling by Zhiwei Zeng A Thesis submitted to the Faculty of Graduate Studies of The University of Manitoba in partial fulfillment of the requirements of the degree of DOCTOR OF PHILOSOPHY Department of Biosystems Engineering University of Manitoba Winnipeg Copyright © 2019 by Zhiwei Zeng Abstract Soil-tool-residue interactions are at the centre of many agricultural field operations. The study of soil-tool-residue interactions is one of the fundamental aspects of soil dynamics in agricultural engineering. The aim of this study was to investigate dynamic behaviours of soil-tool-residue interactions including soil cutting forces, soil displacement, soil loosening and furrow profile, straw displacement, residue cover and incorporation. Experimental studies of soil-tool-residue interactions were conducted for various soil-engaging tools (fluted coulter, rippled disc, and compact disc harrow) working on several field conditions (corn stubble, wheat stubble, and bare soil) at different operational parameters (working speed and depth). Numerical models of the soil-tool-residue interactions were developed for a micropenetrometer, a subsoiler, and a sweep using the discrete element method (DEM). The models were calibrated and validated by comparing simulation results with experimental data from soil bin and field tests. Field testing results of vertical tillage tools demonstrated that fluted coulters left less surface residue, incorporated more residue into the soil, created a wider furrow, and disturbed a larger area than rippled discs. The effect of working speed was more dominant than the coulter geometry on the tillage performance of the fluted coulters. Soil bin tests of a compact disc harrow indicated that disc spacing and offset had significant effects on soil disturbance characteristics, and the effects varied with the tillage depth. The DEM simulation results showed that the soil-micropenetrometer model produced comparable results to the laboratory measurements, in terms of the variation of cone index over penetration depth. The soil-subsoiler model was capable of predicting soil cutting resistance and soil disturbance characteristics with relative errors ranging from i 2.63 to 10.2%. The straw-sweep-soil model was able to simulate dynamic attributes of bulk materials and individual particles, such as straw movement, moving trajectories and velocity contours. This study embraced a broad topic of soil-tool-residue interactions. The results have advanced the science of soil dynamics and contributed to the engineering knowledge required for the development of high-performance agricultural machinery that consumes minimal tractor power and creates optimal field conditions for crop growth. ii Acknowledgements I am profoundly grateful to my advisor, Dr. Ying Chen, for her excellent supervision, invaluable mentorship, and unwavering support throughout the duration of my doctoral studies. The energy and commitment she has for research and life is contagious and motivational, which has contributed enormously to my professional development and personal growth. She was, and continues to be, an inspiration. Words could never be enough to express my appreciation. My deepest thanks go to Drs. Chen and Sylvio Tessier who changed my life. I would also like to thank my thesis advisory committee members, Drs. Claude Laguë and Marolo Alfaro, for their constructive feedback and commitment over the years. The participation of Dr. John Fielke as the external examiner is highly appreciated. Immense gratitude to the past and present members of the Soil Dynamics and Machinery Lab for their technical assistance and support. I would particularly like to thank Dr. Mohammad Sadek who helped me learn the discrete element modelling in the early days. My sincere thanks go to the teaching, administrative and technical staff of the Department of Biosystems Engineering, the University of Manitoba, especially Drs. Danny Mann and Jitendra Paliwal. A special thanks to Dr. Qiuyan Yuan for the friendship and moral support. I acknowledge the financial support received from the following sources as research grants or scholarships during the course of my studies: Natural Sciences and Engineering Research Council of Canada, Government of Manitoba, Mitacs, Faculties of Graduate Studies, Engineering, and Agricultural and Food Sciences at the University of iii Manitoba. The financial and in-kind support of industry partners including Buhler Versatile Inc. and Atom-Jet Group are also appreciated. I would like to express my deep love and appreciation to my family members for their unconditional love and support throughout my life. Especially, I would like to gratefully acknowledge the sacrifices, support, and encouragement of my loving wife Mengmeng Tian. In the course of the past four and a half years of study in Canada, there may be some individuals that I have inadvertently omitted. My humblest apologies go to those who nevertheless remain in my heart. iv 谨以此书献给我亲爱的爸妈 This thesis is dedicated to my beloved parents v Table of Contents Abstract….. .......................................................................................................................... i Acknowledgements ............................................................................................................ iii Table of Contents ............................................................................................................... vi List of Tables .................................................................................................................... xii List of Figures .................................................................................................................. xiii Chapter 1: General Introduction ......................................................................................... 1 1.1. Introduction .............................................................................................................. 1 1.2. Objectives ................................................................................................................. 4 1.3. Thesis structure ........................................................................................................ 5 1.4. References ................................................................................................................ 7 Chapter 2: General Literature Review ................................................................................ 9 2.1. Soil-engaging tools ................................................................................................... 9 2.2. Soil-tool-residue interactions ................................................................................... 9 2.2.1. Soil-tool interaction ......................................................................................... 10 2.2.2. Role of residue ................................................................................................. 11 2.3. New tillage tools ..................................................................................................... 12 2.3.1. Vertical tillage ................................................................................................. 13 2.3.2. Compact disc harrow ....................................................................................... 14 2.4. Experimental studies .............................................................................................. 15 2.4.1. Soil bin testing ................................................................................................. 16 2.4.2. Field testing ..................................................................................................... 16 2.5. Modelling studies ................................................................................................... 17 2.5.1. Analytical modelling ....................................................................................... 18 2.5.2. Numerical modelling ....................................................................................... 19 2.6. References .............................................................................................................. 22 Chapter 3: Performance Evaluation of Fluted Coulters and Rippled Discs for Vertical Tillage ............................................................................................................ 31 3.1. Abstract .................................................................................................................. 31 3.2. Introduction ............................................................................................................ 32 vi 3.3. Material and methods ............................................................................................. 35 3.3.1. Site description ................................................................................................ 35 3.3.2. Description of the VT tools ............................................................................. 36 3.3.3. Experimental design ........................................................................................ 39 3.3.4. Measurements .................................................................................................. 39 3.3.4.1. Soil cutting forces .................................................................................... 40 3.3.4.2. Residue cover and incorporation ............................................................. 40