Temporal changes in soil physical properties following reclamation of underground natural gas pipeline rights-of-way on cropland

Abstract

Underground oil and natural gas pipeline rights-of-way (ROWs) sometimes traverse croplands, leaving behind tracts of disturbed land characterized by poor productivity even after reclamation. This study investigated temporal post-reclamation changes in soil penetration resistance (PR), field saturated hydraulic conductivity (Kfs), near-saturated hydraulic conductivity (KΨ), soil pore indices, and wet aggregate stability (WAS) on natural gas pipeline ROWs on cropland. These attributes were measured in two fields in late summer of 2021 and 2022. Across the two fields, three ROWs that had been reclaimed four to thirteen years prior (i.e., time since reclamation (TSR) of 4 to 13 yr) were assessed along with adjacent undisturbed (off-ROW) transects located 50 m from the ROWs. Measurement locations on each ROW and on off-ROW were 25 m apart. Samples for WAS were collected from the 0–15 cm layer. The results showed a significant (p < 0.05) TSR by soil depth interaction for PR. Treatments were not significantly different in the 0- to 20-cm and 40- to 60-cm layers, but in the 20- to 40-cm depth interval, PR was 57.7–64.2 % greater on the 4.5-yr ROW than on off-ROW. Saturated hydraulic conductivity was three to four times lower on the 4.5- and 6.5-yr ROWs than on the off-ROW. Near-saturated hydraulic conductivity on the 4.5-yr ROW was 61.6 % lower than that on the off-ROW, while no significant differences were detected between the 6.5-yr and 12.5-yr ROWs and the off-ROW. Effective water conductive macroporosity was 72.5 % lower on the 4.5-yr ROW than on the off-ROW. All measured physical properties improved with increasing TSR. These results indicate a significant but slow recovery in soil physical attributes with increasing TSR of ROWs on cropland. This has implications on the productivity of these ROWs as crop yields, which depend on these soil physical properties, are also expected to recover slowly.