Revegetation of Oil Well Reserve Pits in West Texas

Abstract

On-site disposal of drilling fluids frequently causes severe, longterm disturbance of rangeland soils. The effects of mulch on establishment and standing crops of seeded kochia [Kochia scoparia (L.) Schrad.], King Ranch bluestem [Bothriochloa ischaemum (L.) Keng], Lehmann lovegrass (Eragrostis lehmanniana Nees), kleingrass 'Selection 75' (Panicum coloratum L.), alkali sacaton [Sporobolus airoides (Torr.) Torr.], and fourwing saltbush [Atriplex canescens (Pursh) Nutt], and transplanted fourwing saltbush were evaluated on 4, recently covered oil well reserve pits in Reagan County Texas, in 1981 and 1982. On-site disposal of drilling fluids resulted in substantial to large increases in sodium adsorption ratios (SAR) and concentrations of soluble salts, primarily sodium chloride, in reserve pit soils. Mulching with 4,500 kg/ha of weathered hay had no effect, but irrigation was essential for establishment and growth of the seeded species on severely contaminated soils (ECe 71 to 114 dS m-1, SAR 33 to 127). Mulching improved establishment and yields of seeded King Ranch bluestem and kleingrass on reserve pit soils with ECe values of 9 to 11 dS m-1 and SAR values of 12 to 16. Application of 5.1 cm of supplemental water and mulching reserve pit soils with Ece values of 3 to 7 and SAR values of 5 to 9 stimulated establishment of competing vegetation, which tended to decrease establishment and yields of seeded and transplanted species. Establishment and yields of transplanted fourwing saltbush were acceptable with or without mulching or irrigation. Survival of fourwing saltbush transplants was near 100% on moderately contaminated soils and 26 to 30% on severely contaminated soils.