Feinan Hu

Degradation of soil structure and function is a significant obstacle to sustainable agriculture, yet using biochar is known to be an effective way of increasing soil organic carbon and boosting structure. Aggregate stability is greatly influenced by soil internal forces (SIFs), such as van der Waals, hydration, and electrostatic forces. However, it is still not clear which specific organic carbon components play a significant role in the stability of aggregates and the action of soil internal forces. In this study, a field simulation experiment was conducted using maize straw and wheat straw biochars to investigate how biochar addition affects soil aggregate stability. The findings showed that as the rate of biochar application increased from 0 % to 10 % over 180 and 365 d, the contents of soil light fraction organic carbon (LFOC), particulate organic carbon (POC), dissolved organic carbon (DOC), readily oxidized organic carbon (ROC), as well as soil specific surface area and surface charge number, increased. The content of different carbon fractions decreased with prolonged incubation time, while soil electrochemical parameters continued to increase throughout the incubation period. Pearson correlation and redundancy analyses showed that soil active organic carbon fractions were strongly correlated with soil surface electrochemical properties, with ROC and POC being the primary factors. Soil aggregate stability increased with higher biochar application rates, and the beneficial effect of biochar on aggregate stability became increasingly pronounced over time. Based on the quantitative estimates of SIFs, the addition of biochar facilitated soil aggregate stability by increasing van der Waals attractive pressure and decreasing electrostatic repulsive pressure, and finally lowering net repulsive pressure between soil particles. The soil aggregate breaking strength increased rapidly initially and then leveled out as the electrolyte content decreased; 10 ⁻² mol L ⁻¹ marked the tipping point. The study identified the active organic carbon (ROC and POC) fractions which could mediate the soil surface electrochemical properties and soil internal forces, thereby enhancing soil aggregate stability. Our research provides a theoretical basis for the targeted use and modification of biochar to efficiently improve soil structure.

Degradation of soil structure and function is a significant obstacle to sustainable agriculture, yet using biochar is known to be an effective way of increasing soil organic carbon and boosting structure. Aggregate stability is greatly influenced by soil internal forces (SIFs), such as van der Waals, hydration, and electrostatic forces. However, it is still not clear which specific organic carbon components play a significant role in the stability of aggregates and the action of soil internal forces. In this study, a field simulation experiment was conducted using maize straw and wheat straw biochars to investigate how biochar addtion affect soil aggregate stability. The findings showed that as the rate of biochar application increased from 0 % to 10 % over 180 day and 365 days, the contents of soil light fraction organic carbon (LFOC), particulate organic carbon (POC), dissolved organic carbon (DOC), readily oxidized organic carbon (ROC), as well as soil specific surface area and surface charge number, increased. The content of different carbon fractions decreased with prolonged incubation time, while soil electrochemical parameters continued to increase throughout the incubation period. Pearson correlation and redundancy analyses showed that soil active organic carbon fractions were strongly correlated with soil surface electrochemical properties, with ROC and POC being the primary factors. Soil aggregate stability increased with higher biochar application rates, and the beneficial effect of biochar on aggregate stability became increasingly pronounced over time. Based on the quantitative estimates of SIFs, the addition of biochar facilitated soil aggregates stability by increasing van der Waals attractive pressure and decreasing electrostatic repulsive pressure, and finally lowering net repulsive pressure between soil particles. The soil aggregate breaking strength increased quickly at initially and then leveled out as the electrolyte content decreased; 10⁻² mol L⁻¹ marked the tipping point. The study identified the active organic carbon (ROC and POC) fractions which could mediate the soil surface electrochemical properties and soil internal forces, finally enhance soil aggregate stability. Our research provides a theoretical basis for the targeted use and modifying of biochar to efficiently improve soil structure.

Degradation of soil structure and function is a significant obstacle to sustainable agriculture, yet using biochar is known to be an effective way of increasing soil organic carbon and boosting structure. Aggregate stability is greatly influenced by soil internal forces (SIFs), such as van der Waals, hydration, and electrostatic forces. However, it is still not clear which specific organic carbon components play a significant role in the stability of aggregates and the action of soil internal forces. In this study, a field simulation experiment was conducted using maize straw and wheat straw biochars to investigate how biochar addtion affect soil aggregate stability. The findings showed that as the rate of biochar application increased from 0 % to 10 % over 180 day and 365 days, the contents of soil light fraction organic carbon (LFOC), particulate organic carbon (POC), dissolved organic carbon (DOC), readily oxidized organic carbon (ROC), as well as soil specific surface area and surface charge number, increased. The content of different carbon fractions decreased with prolonged incubation time, while soil electrochemical parameters continued to increase throughout the incubation period. Pearson correlation and redundancy analyses showed that soil active organic carbon fractions were strongly correlated with soil surface electrochemical properties, with ROC and POC being the primary factors. Soil aggregate stability increased with higher biochar application rates, and the beneficial effect of biochar on aggregate stability became increasingly pronounced over time. Based on the quantitative estimates of SIFs, the addition of biochar facilitated soil aggregates stability by increasing van der Waals attractive pressure and decreasing electrostatic repulsive pressure, and finally lowering net repulsive pressure between soil particles. The soil aggregate breaking strength increased quickly at initially and then leveled out as the electrolyte content decreased; 10⁻² mol L⁻¹ marked the tipping point. The study identified the active organic carbon (ROC and POC) fractions which could mediate the soil surface electrochemical properties and soil internal forces, finally enhance soil aggregate stability. Our research provides a theoretical basis for the targeted use and modifying of biochar to efficiently improve soil structure.

Degradation of soil structure and function is a significant obstacle to sustainable agriculture, yet using biochar is known to be an effective way of increasing soil organic carbon and boosting structure. Aggregate stability is greatly influenced by soil internal forces (SIFs), such as van der Waals, hydration, and electrostatic forces. However, it is still not clear which specific organic carbon components play a significant role in the stability of aggregates and the action of soil internal forces. In this study, a field simulation experiment was conducted using maize straw and wheat straw biochars to investigate how biochar addtion affect soil aggregate stability. The findings showed that as the rate of biochar application increased from 0 % to 10 % over 180 day and 365 days, the contents of soil light fraction organic carbon (LFOC), particulate organic carbon (POC), dissolved organic carbon (DOC), readily oxidized organic carbon (ROC), as well as soil specific surface area and surface charge number, increased. The content of different carbon fractions decreased with prolonged incubation time, while soil electrochemical parameters continued to increase throughout the incubation period. Pearson correlation and redundancy analyses showed that soil active organic carbon fractions were strongly correlated with soil surface electrochemical properties, with ROC and POC being the primary factors. Soil aggregate stability increased with higher biochar application rates, and the beneficial effect of biochar on aggregate stability became increasingly pronounced over time. Based on the quantitative estimates of SIFs, the addition of biochar facilitated soil aggregates stability by increasing van der Waals attractive pressure and decreasing electrostatic repulsive pressure, and finally lowering net repulsive pressure between soil particles. The soil aggregate breaking strength increased quickly at initially and then leveled out as the electrolyte content decreased; 10⁻² mol L⁻¹ marked the tipping point. The study identified the active organic carbon (ROC and POC) fractions which could mediate the soil surface electrochemical properties and soil internal forces, finally enhance soil aggregate stability. Our research provides a theoretical basis for the targeted use and modifying of biochar to efficiently improve soil structure.

Degradation of soil structure and function is a significant obstacle to sustainable agriculture, yet using biochar is known to be an effective way of increasing soil organic carbon and boosting structure. Aggregate stability is greatly influenced by soil internal forces (SIFs), such as van der Waals, hydration, and electrostatic forces. However, it is still not clear which specific organic carbon components play a significant role in the stability of aggregates and the action of soil internal forces. In this study, a field simulation experiment was conducted using maize straw and wheat straw biochars to investigate how biochar addtion affect soil aggregate stability. The findings showed that as the rate of biochar application increased from 0 % to 10 % over 180 day and 365 days, the contents of soil light fraction organic carbon (LFOC), particulate organic carbon (POC), dissolved organic carbon (DOC), readily oxidized organic carbon (ROC), as well as soil specific surface area and surface charge number, increased. The content of different carbon fractions decreased with prolonged incubation time, while soil electrochemical parameters continued to increase throughout the incubation period. Pearson correlation and redundancy analyses showed that soil active organic carbon fractions were strongly correlated with soil surface electrochemical properties, with ROC and POC being the primary factors. Soil aggregate stability increased with higher biochar application rates, and the beneficial effect of biochar on aggregate stability became increasingly pronounced over time. Based on the quantitative estimates of SIFs, the addition of biochar facilitated soil aggregates stability by increasing van der Waals attractive pressure and decreasing electrostatic repulsive pressure, and finally lowering net repulsive pressure between soil particles. The soil aggregate breaking strength increased quickly at initially and then leveled out as the electrolyte content decreased; 10⁻² mol L⁻¹ marked the tipping point. The study identified the active organic carbon (ROC and POC) fractions which could mediate the soil surface electrochemical properties and soil internal forces, finally enhance soil aggregate stability. Our research provides a theoretical basis for the targeted use and modifying of biochar to efficiently improve soil structure.

In the fragile Loess Plateau ecosystem, straw return is a key measure to improve its low soil organic matter. However, the short-term carbon retention efficacy of straw return, which depends on the initial balance between carbon mineralization and sequestration, remains unclear across different soil textures. This study investigated the short-term impacts of straw return on organic carbon fractions in three soils with varying textures via laboratory incubation. Results showed that while straw return universally increased active organic carbon pools, its accumulation in the mineral-associated organic carbon (MAOC) pool was texture-dependent. Straw incorporation, especially maize straw, effectively promoted MAOC formation in clayey soils (Phaeozems and Anthrosols) with large specific surface areas. Conversely, in Arenosols, carbon was retained in active pools, limiting long-term retention potential. The mechanism involves a combined regulation by soil physicochemical properties, where clay content and specific surface area are fundamental physical drivers for MAOC accumulation, synergistically influenced by chemical factors like pH and electrical conductivity through processes such as cation bridging. These findings provide critical scientific evidence for developing texture-specific straw return management strategies for the Loess Plateau.

Vegetation restoration can improve soil structural stability and erosion resistance, However, the effects of forest composition on the rheology-based stability of soil microstructure and its relationship with erosion are still unclear. Therefore, this study investigated typical plantation soils on the Loess Plateau to explore differences in soil rheological properties and their stratification under different afforestation models. Our results show that: (1) Afforestation significantly altered soil physicochemical properties. Mixed forests of Robinia pseudoacacia (RP) and Platycladus orientalis (PO) (1:1) notably enhanced the accumulation of organic carbon in the surface layer (0–20 cm). (2) PO plantations promoted the retention of water-stable macro-aggregates (> 0.25 mm). Despite mechanical and water-induced disruption, these soils maintained a higher proportion of macro-aggregates, with significantly greater mean weight diameter and lower aggregate disruption rates (p < 0.05). (3) With increasing strain, soil structure progressively approached its shear strength limit until failure occurred. Mixed forest soils exhibited both a wider linear viscoelastic region (γLVR) and higher integral Z (Iz), suggesting an elastic and tough structure. In contrast, PO soils showed the highest γLVR but the lowest Iz, indicating structural rigidity with weak internal cohesion. (4) Modeled soil erodibility (K) was lowest in mixed forests and highest in PO soils. In fine-textured, low-organic-matter soils, high mean weight diameter may accompany high rigidity and brittleness, resulting in poor erosion resistance. Overall, high aggregate stability does not invariably indicate strong erosion resistance. Through rheological analysis can identify healthy soil structures that combine strength and resilience. This study elucidates the intrinsic relationships among soil rheological properties, aggregate stability, and soil erodibility, providing new insights into the soil conservation functions of forests from a mechanical perspective.

The Maowusu Desert is still suffering from serious ecological and environmental security issues such as wind erosion and desertification, influenced by both natural and human factors. The amendment of aeolian sandy soil with soft rock material presents an effective erosion control strategy, leveraging the complementary structural and compositional properties of both materials to enhance soil stability and rehabilitate degraded environments. However, there are few studies that investigate the effect of soil surface electrochemical properties and particle interaction forces on the structural stability of compound soils with soft rock and sandy soil. This decade-long field study quantified the electrochemical properties and interparticle forces and their synergistic effects on structural stability across five soft rock-to-aeolian sandy soil blend volume ratios (0:1, 1:5, 1:2, 1:1, 1:0) within the 0–30 cm soil profile. The results showed that the soil organic matter (SOM), specific surface area (SSA), and cation exchange capacity (CEC) significantly increased with the incorporation of soft rock material. For five different proportions, with the addition of soft rock and the extension of planting years, the content of SOM increased from 5.65 g·kg⁻¹ to 11.36 g·kg⁻¹, the CEC varied from 4.68 cmol kg⁻¹ to 17.91 cmol kg⁻¹, while the σ₀ importantly decreased from 1.8 to 0.47 c m⁻² (p < 0.05). For the interaction force at 2.4 nm between soil particles, the absolute value of van der Waals attractive force increased from 0.10 atm to 0.38 atm, and the net force decreased from 0.09 atm to −0.30 atm after the incorporation ratios of soft rock from 0:1 to 1:1. There was a significant negative correlation between the resultant net force between the particles of compound soil and the SSA and CEC. These results indicate that the addition of soft rock material positively improves the surface electrochemical properties and internal forces between aeolian sandy soil particles, further enhancing its structural stability. This study establishes a foundational theoretical framework for advancing our mechanistic understanding of aeolian sand stabilization and ecosystem rehabilitation in the Mu Us Desert.

Soil structural stability is fundamentally linked to soil functionality and sustainable productivity. Rheological properties describe the deformation and flow behavior of soil under external stress, playing a crucial role in understanding soil structure stability. Despite their importance, the studies about rheological properties of black soils in Northeast China remain limited. This study aims to assess the rheological properties of two kinds of black soil with different degrees of degradation in Northeast China. The rheological parameters of these soils under various water contents and shearing were quantified by conducting Amplitude Sweep Tests (ASTs) and Rotational Sweep Tests (RSTs). Both AST and RST results showed that as soil water content and shear rate increased, shear strength, viscosity, and hysteresis area all decreased in Keshan and Binxian black soils. The increase in soil water content reduces the friction between soil particles, leading to a decrease in soil structure stability. Additionally, the viscosity and hysteresis area of the two soils decreased with the increase in water content, making it more flowable and exhibiting shear-thinning behavior. Keshan black soil exhibited stronger recovery and shear strength compared to Binxian black soil; this is mainly due to the higher organic matter content in Keshan soil, which could increase structural stability by bonding the soil particles at the micro-level. These findings enhance our understanding about the structure stability of the black soils based on the rheological parameters via rheometer.

Wide application of biochar and subsequent release of biochar nanoparticles (NPs) significantly impact the stability of natural clay minerals and soil NPs, which are crucial for soil quality and play a vital role in determining the fate of nutrients and contaminants in the environment. Soil is a naturally occurring complex system composed of multiple components. Existing research on soil particle aggregation has predominantly focused on homo‐aggregation. However, the addition of biochar to soil inevitably induces hetero‐aggregation with soil components. In this study, the effects of biochar NPs on the aggregation of representative clay minerals (hematite and illite) and natural soil NPs from Luvisol, Phaeozem and Ferralsol under various solution chemistry were studied. The mechanisms were further elucidated by adopting the Derjaguin‐Landau‐Verwey‐Overbeek (DLVO) theory. The results indicated that the addition of negatively charged biochar NPs significantly altered the aggregation behaviours of positively charged hematite NPs through charge neutralisation. The aggregation of negatively charged illite particles was inhibited by the generating H‐bonding and steric repulsion. Biochar NPs significantly increased the colloidal stability of Luvisol (from 343.82 to 382.96 mM) and Ferralsol NPs (from 28.39 to 215.35 mM) by increasing the net DLVO repulsive forces. Nevertheless, the stability of Phaeozem NPs, containing higher organic matter, decreased with increasing biochar NP concentrations due to electrostatic shielding. In conclusion, for complicated natural soil systems with significant differences between organic and inorganic components, the application of biochar NPs has a profound impact on colloidal particle interactions, particularly affecting positively‐charged mineral colloids and soils with low soil organic matter content.