Mineral vs. organic matter supply as a limiting factor for the formation of mineral-associated organic matter in forest and agricultural soils

Xiang Wang; Brandy M Toner; Kyungsoo Yoo

doi:10.1016/j.scitotenv.2019.07.219

Mineral vs. organic matter supply as a limiting factor for the formation of mineral-associated organic matter in forest and agricultural soils

Sci Total Environ. 2019 Nov 20:692:344-353. doi: 10.1016/j.scitotenv.2019.07.219. Epub 2019 Jul 17.

Authors

Xiang Wang¹, Brandy M Toner², Kyungsoo Yoo³

Affiliations

¹ College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China; Department of Soil, Water, and Climate, University of Minnesota-Twin Cities, Saint Paul, MN 55108, USA.
² Department of Soil, Water, and Climate, University of Minnesota-Twin Cities, Saint Paul, MN 55108, USA.
³ Department of Soil, Water, and Climate, University of Minnesota-Twin Cities, Saint Paul, MN 55108, USA. Electronic address: kyoo@umn.edu.

PMID: 31351278
DOI: 10.1016/j.scitotenv.2019.07.219

Abstract

Physical and chemical interactions between soil organic matter (OM) and minerals is one of the primary mechanisms for stabilizing OM in terrestrial ecosystems. Focusing on OM association with mineral surfaces, this study sought to examine mineral-associated OM from the perspectives of both mineral surface characteristics and organic matter chemistry. The research was conducted at paired-sites under North American Mid-Atlantic Coastal forest and crop production with shared environmental factors. Using carbon (C) and nitrogen (N) 1s micro- X-ray absorption near-edge fine structure (XANES) spectroscopy, we investigated the amounts and types of mineral-associated OM. Mineral specific surface area (SSA) of bulk soil was determined for three conditions: untreated, post OM removal and post iron (Fe) (oxyhydr)oxides removal. Amounts of mineral-associated OM were smaller in the agricultural soil, where greater SSA sourced from clay-sized phyllosilicates and Fe (oxyhydr)oxide minerals did not result in greater OM coverage of the mineral surface area. Although agricultural surface soil showed less abundance of phenolic C, speciation of mineral-associated OM did not differ between comparable horizons. Our results suggest that despite the plow-derived mixing of soil, which increased SSA and secondary minerals available to interact physically and chemically with OM in the plowed layer, the formation of mineral-associated OM in agricultural soil is ultimately limited by available OM.

Keywords: Agricultural management; Chemical composition; Iron oxides; Mineral-associated organic carbon; Specific mineral surface area; XANES.