Research Paper Effect of velocity ratio on performance characteristics of an active-passive combination tillage implement Ganesh Upadhyay a,b , Hifjur Raheman a,b,* a Department of Farm Machinery and Power Engineering, College of Agricultural Engineering and Technology, CCS Haryana Agricultural University, Hisar, Haryana, 125 004, India b Department of Agricultural & Food Engineering, Indian Institute of Technology Kharagpur, West Bengal, 721302, India article info Article history: Received 26 August 2019 Received in revised form 11 December 2019 Accepted 20 December 2019 Published online 11 January 2020 Keywords: Combined offset disc harrow Draught Torque Specific energy requirement Tillage performance index A study was conducted to investigate the effect of velocity ratio (ratio of peripheral velocity to the forward velocity of tillage tool) on the performance of an active-passive combined offset disc harrow. This implement unites the benefits of powered discs and combination tillage to reduce draft requirements, wheel slip, and gross fuel consumption. The test parameters consisted of forward velocities (3.46, 4.55, and 6.82 km h 1 ) and rotational velocities of front gang axle, N FGA (95, 133, and 150 rpm) to ultimately vary the velocity ratio from 1.48 to 4.59. Tests were conducted in freshly harvested paddy fields with sandy clay loam soil having moisture content and cone index of 11 ± 0.75% (dry basis) and 975 ± 50 kPa, respectively. The results indicate that increase in velocity ratio from 1.48 to 3.49 helped to reduce both draught and torque requirement with negligible reduction observed when velocity ratio was increased beyond 3.49. At a velocity ratio of 2.91, the specific energy consumption was minimum. Attempts were made to select a suitable velocity ratio based on tillage perfor- mance index considering both fuel energy input and tillage effectiveness parameters such as crop residue burial efficiency and soil pulverization. It is suggested to operate this type of implement at velocity ratio of 3.09 (forward velocity 4.55 km h 1 , N FGA 133 rpm) and 4.06 (forward velocity 3.46 km h 1 ,N FGA 133 rpm) during the first pass and the second pass, respectively to obtain maximum tillage performance with minimum energy consumption. © 2020 IAgrE. Published by Elsevier Ltd. All rights reserved. 1. Introduction In combination tillage, active and passive or passive and passive tillage tools are combined to reduce the number of passes required for seedbed preparation with increased effi- ciency and lower costs without sacrificing the work quality of tillage. In an active-passive combination tillage implement, the forward thrust generated by its active element helps to * Corresponding author. E-mail addresses: ganesh.upadhyay0@iitkgp.ac.in, showkat@agfe.iitkgp.ernet.in (G. Upadhyay), hifjur@agfe.iitkgp.ernet.in (H. Raheman). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/issn/15375110 biosystems engineering 191 (2020) 1 e12 https://doi.org/10.1016/j.biosystemseng.2019.12.010 1537-5110/© 2020 IAgrE. Published by Elsevier Ltd. All rights reserved.