Soil organic matter doubles the cation exchange capacity of tropical soil under no-till farming in Brazil 1 Running title: Effect of organic matter on soil cation exchange capacity Fabricio T Ramos 1 *; Eliana F G de Carvalho Dores 1 ; Oscarlina L dos Santos Weber 2 ; Daniel C Beber 3 ; José H Campelo Jr 2 ; João C de Souza Maia 2 *Corresponding author. E-mail: fabriciotomazramos@gmail.com 2 Post-graduation Program on Water Resources, Federal University of Mato Grosso, 2367 Fernando Corrêa da Costa Ave., Cuiabá, MT, 78060-900, Brazil 3 Postgraduation Program on Tropical Agriculture, Federal University of Mato Grosso, 2367 Fernando Corrêa da Costa Ave., Cuiabá, MT, 78060-900, Brazil 4 Faculty of Agronomy and Zootechnics, Federal University of Mato Grosso, 2367 Fernando Corrêa da Costa Ave., Cuiabá, MT, 78060-900, Brazil ABSTRACT BACKGROUND: Conservation agricultural practices increase total organic carbon storage in soil (T OCS ), a factor that is correlated with the physical and chemical qualities of highly weathered soils. In this study, we investigated the effects of T OCS on the physicochemical attributes of a Latosol after 10 years of no-till management in Mato Grosso State, Brazil. RESULTS: T COS was highly correlated (r = 0.92) with cation exchange capacity (CEC, pH = 7) and soil density. In the top 0.2 m soil layer, CEC increased by 25% with every 1.8 kg m -2 of stored organic carbon. Eliminating soil organic matter reduced CEC from an already low value of 8.40 cmol c kg -1 to 4.82 cmol c 1 Excerpt from the first author's doctoral thesis, funded by CAPES - Brazilian Federal Agency for Support and Evaluation of Graduate Education. This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/jsfa.8881 This article is protected by copyright. All rights reserved. Accepted Article