Revegetation of saline oil well reserve pits using grasses and shrubs with or without mulching and irrigation, near Big Lake, Texas, USA

  • Published source details McFarland M.L., Ueckert D.N. & Hartmann S. (1987) Revegetation of oil well reserve pits in west Texas. Journal of Range Management, 40, 122-127


On-site disposal of drilling fluids resulted in substantial increases in sodium adsorption ratios (SAR) and concentrations of soluble salts (primarily sodium chloride) in oil well reserve pit soils on rangeland in the semi-arid Edwards Plateau area near the town of Big Lake, Texas (southwest USA). This study evaluated planting of four grasses and two shrubs, with or without mulching and irrigation, for vegetation restoration.

Experiments were undertaken on two reserve pits 10 km east of Big Lake (Ferguson sites) and two 32 km to the west (Jackson sites). Each pit was covered 1 month prior to seedbed preparation (standard procedure: crawler-tractor then disked). Each was divided into 6 blocks containing 6.1 x 6.1 m plots. Treatments (3 replicates of each) were randomly assigned within each block (applied on 28 April 1981 at Ferguson and 17 March 1982 at Jackson):

1. King Ranchbluestem Bothriochloa ischaemum (non-native) - broadcast at 3.4 kg pure live seed (PLS)/ha;
2. Kleingrass Panicum coloratum (non-native) - 2.2 kg PLS/ha;
3. Lehmann lovegrass Erogrostis lehmanniana (non-native) - 1.1 kg PLS/ha;
4. Alkali sacaton Sporobolus airoides (native) - 1.1 kg PLS/ha (Jackson only);
5. Kochia Kochia scoparia (non-native)- 2.2 kg PLS/ha;
6. Fourwing saltbush Atriplex canescens (native) - 13.9 kg PLS/ha;
7. Fourwing saltbush - seedlings grown for 3 months; pruned to 10 cm prior to planting out; 36/plot.
Sorghum (Ferguson) or wheat straw (Jackson) mulch was then applied at 4,500 kg/ha to half the blocks on each pit. One pit at each location was irrigated for 1-2 months after planting.

Seedlings were counted in 10 (0.25-m²) quadrats/plot 2 months after planting, and also 6 and 16 months after planting (Ferguson) and after 7 months (Jackson) when standing crop was also estimated. Soil samples were collected on each pit and from adjacent uncontaminated areas for analysis.

Severely contaminated soils, primarily due to salt (ECo 71 to 114 dS/m, SAR 33 to 127; about 1 dS/m in adjacent, uncontaminated soils) were present at the Jackson sites; mulching did no improve seeded species establishment, and in the non-irrigated plots they failed.
Mulching improved establishment and yields of bluestem and kleingrass on less saline soils (ECo 9-11 dS/m; SAR 12-16) of the Ferguson sites. However, irrigation plus mulch enhanced establishment of other vegetation, tending to decrease establishment and yields of seeded species and transplants. Of the seeded grasses, Kleingrass and alkali sacaton faired better than bluestem and lovegrass.
Saltbush transplants did well (survival 99% on moderately contaminated soils and 26-39% on severely contaminated soils). Establishment and yields were acceptable with or without mulching or irrigation. Plantings of native shrubs such as fourwing saltbush may also benefit wildlife.
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