Objective This paper investigated the effect of nano-mineral allophane on soil aggregate stability through the overlapping of positive and negative double electric layers.

Method Yellow-brown earth was collected from the hilly region of Ningzhengyang, Jiangsu Province, and the nano-mineral allophane was synthesized using the hydrothermal synthesis method. The influences of varying amount of allophane (0, 0.1 wt.%, 0.5 wt.% and 1wt.%) on the soil surface charge number, zeta potential, and water-stable aggregates were evaluated to explore the effect and mechanism of nano-mineral allophane on soil aggregate stability.

Result The isoelectric point (IEP) of the allophane was approximately 9.2, allowing it to carry more than 120 mmol kg⁻¹ positive charges in the yellow-brown soil, resulting in the coexistence of positively and negatively charged electrical double layers (EDLs) after application of allophane. The addition of allophane led to a significant reduction in net negative charges, resulting in a shift towards net positive charge, as evidenced by the gradual increase in zeta potential. Furthermore, the application of allophane substantially increased the mass percentage of large (> 2 mm) and small (2–0.25 mm) macroaggregates, as well as the mean weight diameter (MWD), geometric mean diameter (GMD) and mass percentage of macroaggregates (> 0.25 mm, denoted as R_0.25). Correlation analysis revealed positive relationships between the mass percentages of large and small macroaggregates, MWD, GMD and R_0.25, and zeta potential, as well as surface charge number.

Conclusion The addition of nano-mineral allophane proves to be an effective approach to improve soil aggregate stability through the overlapping of oppositely charged EDLs. The results highlights the potential of nano-mineral allophane as a promising amendment for the middle-low yield cultivated land or newly reclaimed soils.