Abstract
The interaction of organic carbon (OC) with clay minerals and amorphous iron and aluminum oxides, especially in the finest soil fractions (<20 μm), represents a good method for its stabilization, and different tillage practices can improve or reduce the persistence of OC in soils. This study investigates the effects of conventional (CT) and no (NT) tillage and soil depth (0–30, 30–60, and 60–90 cm) on the soil organic carbon (SOC) in four soil size fractions and its interactions with clay minerals and amorphous oxides. To identify the mineralogical composition of the four soil size fractions isolated from each soil, the X-ray powder diffraction (XRPD) technique was used with near infrared (NIR) spectroscopy, while the X-ray fluorescence (XRF) technique was used to determine the chemical composition of soil fractions. The higher OC content found in the finest soil fraction is related to its higher content of clay minerals and amorphous oxides. The SOC content is similar among CT and NT treatments as well as the mineralogical composition and the amount of amorphous oxides, suggesting that more than ten years of different tillage did not influence those parameters.
Highlights
Soil organic matter (SOM) consists of a heterogeneous mixture of organic compounds with highly variable composition, different inherent stabilities and turnover rates [1]
Kaiser and Guggenberger [3] and Kögel-Knabner et al [4] showed that the stability of organic matter (OM) in soils can be affected by the formation of various organo-mineral associations between
A large proportion of OM is entrapped among clay layers, and the soils dominated by 2:1 phyllosilicates are more efficient in stabilizing organic carbon (OC) than those dominated by 1:1
Summary
Soil organic matter (SOM) consists of a heterogeneous mixture of organic compounds with highly variable composition, different inherent stabilities and turnover rates [1]. SOM provides a reservoir of nutrients such as N, P and S, improves soil structural stability, influences the retention of water and thermal properties, modifies the cation exchange capacity, reduces the change of soil pH through buffering capacity, complexes cations and reduces the availability of toxic compounds [2]. SOM particles and the surfaces of clay minerals, i.e., phyllosilicates [5] and metallic oxides [6], especially the amorphous ones [7]. The effects of these interactions are an increased carbon (C) mean residence time, up to millennial time periods [8]. A large proportion of OM is entrapped among clay layers, and the soils dominated by 2:1 phyllosilicates are more efficient in stabilizing OC than those dominated by 1:1
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