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Soil, the largest terrestrial carbon reservoir, is central to climate change and relevant feedback to environmental health. Minerals are the essential components that contribute to over 60% of soil carbon storage. However, how the interactions between minerals and organic carbon shape the carbon transformation and stability remains poorly understood. Herein, we critically review the primary interactions between organic carbon and soil minerals and the relevant mechanisms, including sorption, redox reaction, co-precipitation, dissolution, polymerization, and catalytic reaction. These interactions, highly complex with the combination of multiple processes, greatly affect the stability of organic carbon through the following processes: (1) formation or deconstruction of the mineral–organic carbon association; (2) oxidative transformation of the organic carbon with minerals; (3) catalytic polymerization of organic carbon with minerals; and (4) varying association stability of organic carbon according to the mineral transformation. Several pieces of evidence related to the carbon turnover and stability during the interaction with soil minerals in the real eco-environment are then demonstrated. We also highlight the current research gaps and outline research priorities, which may map future directions for a deeper mechanisms-based understanding of the soil carbon storage capacity considering its interactions with minerals.

Abstract Background Land use and land cover changes have a significant impact on the dynamics of soil organic matter (SOM) and its fractions, as well as on overall soil health. This study conducted in Bharatpur Catchment, Chitwan District, Nepal, aimed to assess and quantify variations in total soil organic matter (TSOMC), labile organic matter fraction (CL), stable organic matter fraction (CS), stability ratio (SR), and carbon management index (CMI) across seven land use types: pastureland, forestland, fruit orchards, small-scale conventional agricultural land, large-scale conventional agricultural land, large-scale alternative fallow and conventional agricultural land, and organic farming agricultural land. The study also explored the potential use of the Carbon Management Index (CMI) and stability ratio (SR) as indicators of soil degradation or improvement in response to land use changes. Results The findings revealed significant differences in mean values of TSOMC, CL, and CS among the different land use types. Forestland and organic farming exhibited significantly higher TSOMC (3.24%, 3.12%) compared to fruit orchard lands (2.62%), small scale conventional farming (2.22%), alternative fallow and conventional farming (2.06%), large scale conventional farming (1.84%) and pastureland (1.20%). Organic farming and Forestland also had significantly higher CL (1.85%, 1.84%) and CS (1.27%, 1.39%) compared to all other land use types. Forest and organic farming lands showed higher CMI values, while pastures and forests exhibited higher SR values compared to the rest of the land use types. Conclusions This study highlights the influence of various land use types on soil organic matter pools and demonstrates the potential of CMI and SR as indicators for assessing soil degradation or improvement in response to land use and land cover changes.

Background: Land use and land cover changes have a significant impact on the dynamics of soil organic matter (SOM) and its fractions, as well as on overall soil health. This study conducted in Bharatpur Catchment, Chitwan District, Nepal, aimed to assess and quantify variations in total soil organic matter (TSOMC), labile organic matter fraction (CL), stable organic matter fraction (CS), stability ratio (SR), and carbon management index (CMI) across seven land use types: pastureland, forestland, fruit orchards, small-scale conventional agricultural land, large-scale conventional agricultural land, large-scale alternative fallow and conventional agricultural land, and organic farming agricultural land. The study also explored the potential use of the Carbon Management Index (CMI) and stability ratio (SR) as indicators of soil degradation or improvement in response to land use changes. Results: The findings revealed significant differences in mean values of TSOMC, CL, and CS among the different land use types. Forestland and organic farming exhibited significantly higher TSOMC (3.24%, 3.12%) compared to fruit orchard lands (2.62%), small scale conventional farming (2.22%), alternative fallow and conventional farming (2.06%), large scale conventional farming (1.84%) and pastureland (1.20%). Organic farming and Forestland also had significantly higher CL (1.85%, 1.84%) and CS (1.27%, 1.39%) compared to all other land use types. Forest and organic farming lands showed higher CMI values, while pastures and forests exhibited higher SR values compared to the rest of the land use types. Conclusions: This study highlights the influence of various land use types on soil organic matter pools and demonstrates the potential of CMI and SR as indicators for assessing soil degradation or improvement in response to land use and land cover changes. [ABSTRACT FROM AUTHOR]

Soil, the largest terrestrial carbon reservoir, is central to climate change and relevant feedback to environmental health. Minerals are the essential components that contribute to over 60% of soil carbon storage. However, how the interactions between minerals and organic carbon shape the carbon transformation and stability remains poorly understood. Herein, we critically review the primary interactions between organic carbon and soil minerals and the relevant mechanisms, including sorption, redox reaction, co-precipitation, dissolution, polymerization, and catalytic reaction. These interactions, highly complex with the combination of multiple processes, greatly affect the stability of organic carbon through the following processes: (1) formation or deconstruction of the mineral-organic carbon association; (2) oxidative transformation of the organic carbon with minerals; (3) catalytic polymerization of organic carbon with minerals; and (4) varying association stability of organic carbon according to the mineral transformation. Several pieces of evidence related to the carbon turnover and stability during the interaction with soil minerals in the real eco-environment are then demonstrated. We also highlight the current research gaps and outline research priorities, which may map future directions for a deeper mechanisms-based understanding of the soil carbon storage capacity considering its interactions with minerals., Competing Interests: The authors declare no conflicts of interest., (© 2024 The Author(s).)

Cropping systems and fertilization have important effects on soil organic carbon (OC) and nitrogen (N) turnover and availability; however, little information exists about the interaction of cropping system and fertilization. Herein, we analyzed the dynamics of soil OC and N in a 31-year experiment in a highland agroecosystem to understand how the effects of fertilization vary with cropping systems. The experiment included different cropping systems, and each system included various fertilization treatments. The cropping systems were continuous alfalfa (Medicago sativa L.), continuous winter wheat (Triticum aestivum L.), and grain-legume rotation of winter wheat + millet (Panicum miliaceum L.) - pea (Pisum sativum L.) - winter wheat. The fertilization treatments were the control (CK), phosphorous (P), P and nitrogen (NP) and NP and manure (NPM). A bare fallow treatment that did not receive any crop and fertilizer was designed to compare the effects of the cropping systems. The soil samples were collected at different times of the experiment. The contents of OC, N, and labile OC were measured, and the carbon management index was calculated. When averaged across the experimental periods, soil OC, N, labile OC and carbon management index were significantly higher in the pure legume (i.e., continuous alfalfa) system than in the bare fallow and nonlegume system (i.e., continuous winter wheat) due to the higher C and N inputs from root biomass. The NP and NPM significantly increased these soil variables, and the effects of NPM were greater than those of NP due to the higher supplying of C and N in NPM treatment than NP treatment. However, the effects of NP or NPM on soil OC and N contents were similar among the cropping systems. The effects of P were greater in the continuous alfalfa system but smaller in the continuous winter wheat system in comparison with those in the grain-legume rotation system. Therefore, at the conditions of our study, legume-included cropping systems with large root biomass and manure combined with chemical fertilizers have the potential to increase OC and N and their availability in highland soils, which could be important strategies for improving soil fertility and quality and sequestrating C in soils. Moreover, P fertilizer was recommended for the legume-included cropping systems. • We studied the effects of fertilization on soil OC and N in three cropping systems. • Continuous legume, continuous winter wheat and a grain-legume rotation were tested. • Legume increase soil OC and N and their availability. • Effects of NP or NP combined with manure were similar among cropping systems. • Effects of chemical P fertilizer on soil OC and N varied with cropping systems. [ABSTRACT FROM AUTHOR]