Soil compaction : Regeneration of compacted soils

Stresses induced by agricultural machinery that exceed the soil strength can cause soil compaction and damage a number of soil functions. Soil compaction is a growing concern because of the increasing weight of agricultural vehicles. The ecological and economic costs of compaction are dependent on the time it takes the soil to recover from compaction. However, little is known about the recovery rates of compacted soils.

The “Soil compaction” project aimed at elucidating mechanisms and quantifying soil structure recovery rates after compaction. A long-term soil structure observatory (SSO) was established to monitor the post-compaction recovery of soil functions under different management scenarios. This was combined with detailed studies of root-soil interactions and of the reworking of soils by earthworms (bioturbation).

Compacted soil recovers only very slowly. Field observations in the SSO show that many soil functions had not developed substantially during the first 18 months after compaction. Compaction modified the architecture and anatomy of roots and reduced plant productivity. The project team also determined energy requirements and mechanical limits for root penetration and earthworm burrowing.

The SSO provides unique insights into processes governing post-compaction soil structure recovery under various management scenarios. In associated experiments, the project team was able to show that roots actively grow towards spots of least resistance and high oxygen concentration. Physically based modelling combined with lab experiments enabled the researchers to define the limits of earthworm activity based on the mechanical strength and the water and organic carbon content of soil.

It takes a few seconds to compact a soil, but it may take decades for the soil to recover from the damage and regain its full functionality and productivity.

Biophysical processes controlling restoration of compacted soil structure – long-term soil structure observatory and mechanistic studies