The degradation of soil structure in sandy regions undermines soil functionality and poses a significant threat to environmental sustainability. The incorporation of Pisha sandstone, a natural soil amendment, has been recognized as an effective intervention to reduce soil erosion and expand arable land in the Mu Us Sandy Land, China. However, the microstructural stability and resilience of amended sandy soil formed by mixing Pisha sandstone with sandy soils remain inadequately understood. This study aims to evaluate the effects of Pisha sandstone addition on the microstructural stability of sandy soils. Four amendment rates of Pisha sandstone (16.7 %, 33.3 %, 50 %, and 100 % w/w) and five water content levels (40 %-80 %) were tested. Key parameters related to microstructural stability and structural resilience were assessed using amplitude sweep and rotational shear tests via a rheometer. Results indicated that soil shear resistance (tau LVR, tau max, tau y), storage modulus (G'YP) and viscosity (eta 0) decreased with the addition of Pisha sandstone, attributed to its lubricating effect and swelling properties. Additionally, Pisha sandstone enhanced physical elasticity (gamma LVR) and structural recovery of sandy soil under conditions of low disturbance. However, when water content exceeded 50 %, the fluidity of the amended sandy soil increased with Pisha sandstone addition. The sandy soil with a Pisha sandstone addition rate of 16.7 % exhibited optimal structural elasticity, shear resistance, and stiffness. These findings provide valuable insights into the enhancement of sandy soil structural stability using Pisha sandstone, offering a scientific foundation for refining amendment ratios and advancing agricultural management practices.

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.