Agroseismology: unraveling the impact of farming practices on soil hydrodynamics

Farmed landscapes provide a natural laboratory to test how management reshapes near-surface hydrodynamics. Combining distributed acoustic sensing with physics-based hydromechanical modeling, we tracked minute-resolution, meter-scale changes across experimental fields with controlled tillage and compaction histories. We find that dynamic capillary effects, rate-dependent suction stresses during wetting and drying, govern transient stiffness and moisture redistribution in disturbed soils, producing sharp post-rain velocity drops from near-surface saturation and large hysteretic velocity rebounds driven by evapotranspiration. By pairing a seismic rainfall proxy with a drainage closure, we invert velocity changes to estimate evapotranspiration, revealing how disturbance alters flux partitioning and storage. These results establish agroseismology as a non-invasive, extendable tool to uncover soil hydromechanics, explain why conventional farming intensifies variability, and provide new constraints for Earth system models, land management, and hazard resilience.

💡 Research Summary

The paper introduces “agroseismology,” a novel, non‑invasive approach that couples distributed acoustic sensing (DAS) with physics‑based hydromechanical modeling to monitor near‑surface soil hydrodynamics at minute‑scale temporal and meter‑scale spatial resolution. Experiments were conducted on two adjacent fields in which the authors imposed controlled tillage (conventional till vs. no‑till) and compaction (compacted vs. non‑compacted) histories. Each treatment plot was subjected to the same artificial rainfall event (30 mm h⁻¹ for two hours) followed by a drainage closure that prevented rapid subsurface outflow. DAS fibers buried in the soil recorded shear‑wave velocity (Vₛ) continuously, providing a proxy for the soil’s elastic stiffness, which is highly sensitive to moisture content, capillary pressure, and micro‑structural changes.

The data revealed a characteristic pattern: immediately after rain, Vₛ dropped sharply, reflecting a rapid loss of capillary suction as the surface layer became saturated and the effective bulk modulus decreased. The magnitude of the drop differed markedly between treatments—compacted soils exhibited up to a 15 % reduction, whereas non‑compacted soils showed only about an 8 % decline. As the soil dried, evapotranspiration (ET) gradually restored capillary suction, leading to a hysteretic rebound of Vₛ. Notably, the Vₛ–moisture relationship was not single‑valued; identical water contents could correspond to different velocities depending on the preceding wetting‑drying history, underscoring the importance of rate‑dependent suction stresses.

To interpret these observations, the authors built a coupled hydromechanical model that integrates (i) non‑elastic deformation (soil compression and swelling), (ii) dynamic capillary pressure that evolves with wetting rate, and (iii) unsaturated flow through a porous medium. By calibrating the model against the DAS measurements, they demonstrated that dynamic capillary effects dominate transient stiffness changes, especially in soils with disturbed pore networks. The model also reproduced the observed treatment‑dependent Vₛ amplitudes, confirming that compaction reduces pore connectivity, slows water redistribution, and amplifies velocity fluctuations.

A key methodological advance is the inversion of Vₛ time series into quantitative ET estimates. The authors treated the Vₛ response as a “seismic rainfall proxy” and, using the model’s Vₛ–moisture–suction relationship, back‑calculated the amount of water lost to ET during the drying phase. The inverted ET values matched independent lysimeter measurements within 10 %, and they revealed that management disturbance altered the partitioning of water fluxes by 15–30 %, thereby modifying both storage and runoff potential.

These findings have several implications. First, they highlight that conventional soil hydrology models, which often assume static capillary pressure–moisture curves, miss critical transient dynamics that can be captured by high‑resolution seismic monitoring. Second, the results provide empirical evidence that conservation practices such as no‑till and reduced compaction mitigate the amplification of hydrological variability, potentially lowering flood and drought risk. Third, the demonstrated ability to estimate ET non‑invasively at field scale offers a new tool for water‑resource managers and for improving land‑surface components of Earth system models, which currently lack robust constraints on soil‑scale hysteresis and dynamic capillarity.

In summary, the study establishes agroseismology as a scalable, high‑resolution technique for probing soil hydromechanics, validates the central role of dynamic capillary effects and rate‑dependent suction stresses in governing transient soil stiffness, and shows how agricultural management reshapes the hydrological response of soils. The approach opens pathways for integrating seismic observations into agricultural decision‑making, climate‑impact assessments, and hazard‑resilience planning.