Carbon input and the structural quality of soil organic matter as a function of agricultural management in a tropical climate region of Brazil

Shirlei Almeida Assunção; Marcos Gervasio Pereira; Jean Sérgio Rosset; Ricardo Luiz Louro Berbara; Andrés Calderín García

doi:10.1016/j.scitotenv.2018.12.271

Carbon input and the structural quality of soil organic matter as a function of agricultural management in a tropical climate region of Brazil

Sci Total Environ. 2019 Mar 25:658:901-911. doi: 10.1016/j.scitotenv.2018.12.271. Epub 2018 Dec 19.

Authors

Shirlei Almeida Assunção¹, Marcos Gervasio Pereira², Jean Sérgio Rosset³, Ricardo Luiz Louro Berbara⁴, Andrés Calderín García⁴

Affiliations

¹ Federal Rural University of Rio de Janeiro, Institute of Agronomy, Department of Soil, Laboratory of Soil Genesis and Classification and Laboratory of Soil Biological Chemistry, Brazil. Electronic address: shirleiaassuncao@gmail.com.
² Federal Rural University of Rio de Janeiro, Institute of Agronomy, Department of Soil, Laboratory of Soil Genesis and Classification and Laboratory of Soil Biological Chemistry, Brazil.
³ Sate University of Mato Grosso do Sul (UEMS), BR 163, Km 20,2, 79980-000 Mundo Novo, MS, Brazil.
⁴ Federal Rural University of Rio de Janeiro, Institute of Agronomy, Department of Soil, Chemical Biological Soil Laboratory, Brazil.

PMID: 30583185
DOI: 10.1016/j.scitotenv.2018.12.271

Abstract

Carbon (C) stabilization and the quality of soil organic matter (SOM) in a tropical climate are key aspects regulating carbon dioxide emissions and maintaining the C cycle. Soil management influences the accumulation of C, regulating the balance between mineralization and/or the humification of SOM. This study aimed to quantify inputs of different chemical forms of C into soil and to evaluate the structural chemical characteristics of humified SOM. Four management systems were established: Forest (F), Pasture (P), Conventional tillage (T), and No-tillage (NT). Total organic carbon (TOC) and nitrogen (TN) by depth, chemical forms of organic matter input, and spectroscopic characterization of SOM in the form of humic acids (HA) were analyzed. The results obtaining by PCA-¹³C NMR show that the forest accumulated a high amount of C on the surface (surpassing 20 Mg ha^-1), favoring the formation of aliphatic HA (C_Alkyl-H,R; C_Alkyl-O,N; C_Alkyl-O). In the NT management that increases biomass in the soil (14 Mg ha^-1), the mineralization process occurred to a greater extent, allowing HA to form with a predominance of aromatic structures (C_Arm-H,R and C_Arm-O,N). The PCA-FTIR analysis showed that the P system contributed to the formation of similar HA to those under F management. The T management system incorporated the least TOC and TN, with different HA types being formed in these soils than what was found in other managements. Thus, minimally managed and more stabilized systems in tropical climates form HA of structural and compositional similarity, regardless of the nature of C (C3 or C4). In contrast, soils subjected to agricultural uses that promote higher or lower C inputs, form HA that are structurally different from P and F. This study demonstrates the need for developing experiments for model building to elucidate the relationships among C input, management type, and the formation of humic substances.

Keywords: (13)C NMR; Carbon balance; Humic substances; Soil organic matter; Spectroscopy characterization.

MeSH terms

Agriculture / methods*
Brazil
Carbon / analysis*
Environmental Monitoring*
Humic Substances / analysis*
Organic Chemicals / analysis
Soil / chemistry*
Tropical Climate

Substances

Humic Substances
Organic Chemicals
Soil
Carbon