Review Current and emerging methodologies for estimating carbon sequestration in agricultural soils: A review A.K. Nayak a,b, ⁎, Mohammad Mahmudur Rahman b,c , Ravi Naidu b,c , B. Dhal a , C.K. Swain a , A.D. Nayak a , R. Tripathi a , Mohammad Shahid a , Mohammad Rafiqul Islam b,d , H. Pathak a a ICAR-National Rice Research Institute, Cuttack, Odisha 753006, India b Global Centre for Environmental Remediation (GCER), Faculty of Science and Information Technology, The University of Newcastle, Callaghan, NSW 2308, Australia c Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), The University of Newcastle, Callaghan, NSW 2308, Australia d Department of Soil Science, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh HIGHLIGHTS • Methodologies for the measurement of soil carbon sequestration at point, field, ecosystem and regional level reviewed. • Recent developments in spectroscopic techniques are discussed. • Eddy-covariance and indirectly LCA methodological approaches are reviewed. • Methodological potentials and uncer- tainties of soil carbon research seques- tration are highlighted. GRAPHICAL ABSTRACT abstract article info Article history: Received 19 September 2018 Received in revised form 13 January 2019 Accepted 8 February 2019 Available online 11 February 2019 Editor: Deyi Hou This review covers the current and emerging analytical methods used in laboratory, field, landscape and regional contexts for measuring soil organic carbon (SOC) sequestration in agricultural soil. Soil depth plays an important role in estimating SOC sequestration. Selecting appropriate sampling design, depth of soil, use of proper analytical methods and base line selection are prerequisites for estimating accurately the soil carbon stocks. Traditional methods of wet digestion and dry combustion (DC) are extensively used for routine laboratory analysis; the latter is considered to be the “gold standard” and superior to the former for routine laboratory analysis. Recent spectro- scopic techniques can measure SOC stocks in laboratory and in-situ even up to a deeper depth. Aerial spectros- copy using multispectral and/or hyperspectral sensors located on aircraft, unmanned aerial vehicles (UAVs) or satellite platforms can measure surface soil organic carbon. Although these techniques' current precision is low, the next generation hyperspectral sensor with improved signal noise ratio will further improve the accuracy of prediction. At the ecosystem level, carbon balance can be estimated directly using the eddy-covariance ap- proach and indirectly by employing agricultural life cycle analysis (LCA). These methods have tremendous poten- tial for estimating SOC. Irrespective of old or new approaches, depending on the resources and research needed, they occupy a unique place in soil carbon and climate research. This paper highlights the overview, potential lim- itations of various scale-dependent techniques for measuring SOC sequestration in agricultural soil. © 2019 Elsevier B.V. All rights reserved. Keywords: Sampling design and depth SOC measurement Spectroscopic methods Wet digestion Dry combustion Life cycle analysis Science of the Total Environment 665 (2019) 890–912 ⁎ Corresponding author at: ICAR-National Rice Research Institute, Cuttack, Odisha 753006, India. E-mail address: aknayak20@yahoo.com (A.K. Nayak). https://doi.org/10.1016/j.scitotenv.2019.02.125 0048-9697/© 2019 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv