Study

Revegetation of a salt water blowout site

Summary

In western North Dakota (USA), a salt water blowout at an oil drilling site during 6-14 April 1982 killed most vegetation within a 30 ha area. The plant community included Rocky Mountain juniper Juniperus scopulorum, many graminoids (primarily western wheatgrass Agropyron smithii, blue grama Bouteloua gracilis, sideoats grama B.curtipendula, inland saltgrass Distichlis stricta, green needlegrass Stipa viridula, needle-and-thread S.comata and sedges Carex spp.), forbs, and shrubs (e.g. sagebrush Artemisia spp.). This study assessed the effectiveness of soil reclamation and vegetation recovery.

A contaminated area of about 1 ha alongside the western well edge and a nearby 1 ha reference site with no salt damage, were selected. Vegetation was surveyed (species basal cover estimated in quadrats) in July 1982. The contaminated area was then split into two: soil in the west half was not subject to reclamation; soil in the east half was ‘reclaimed’ by adding CaCl2 (a highly soluble form of calcium) at a rate of 1,200 kg/ha to irrigation water sufficient to leach at least the upper 15 cm of the soil.

In autumn 1982 following irrigation, the 1 ha contaminated area was broadcast with a native grass seed mix (7 kg/ha western wheatgrass, 3 kg/ha blue grama, 8 kg/ha sideoats grama, 12 kg/ha green needlegrass, 18 kg/ha needle-and-thread).
 
Surveys were repeated in July 1984. Soil samples (to 15 cm depth) were taken periodically from 39 locations within the entire contaminated area (27 subject to reclamation treatment).

In July 1982 on the contaminated area, inland saltgrass (basal cover 0.8% vs. 0.2% on reference site) was the only plant persisting. A few prickly pear Opuntia polycantha (0.2%) and Atriplex nuttali (0.1%) plants were just alive but subsequently died.

Reclamation efforts reduced sodium adsorption ratio values in the surface 15 cm of the soil to more acceptable levels for vegetation recovery.
 
In July 1984, species with the highest percent basal cover on the reclaimed half were western wheatgrass (2%; reference site 5%), blue grama (4.8%; reference site 8.2%)and saltgrass (6.4%; reference site 0.8%). Those with highest cover on the unreclaimed half were wheatgrass (2.9%), saltgrass (0.8%), pepperweed Lepidium densiflorum (2.2%) and prickly pear (0.8%).
 
In 1984, total grass basal cover on the reference site was 21.4%, on the reclaimed site 14.2%, and on the unreclaimed site 3.7%. Forbs contributed basal cover values of: reference site 0.6% (2 species); reclaimed site 1.4% (6 species); and unreclaimed site 3.8% (4 species).
 
In 1982, percent bare ground at the reference site was 8.4% (5.2 in 1984) and 25.2% at the contaminated site (the major cover component being dead litter 64%). In 1984, bare cover was still 25.2% on the reclaimed half, whilst increasing on the unreclaimed half to 43.1%, thus leaving it open to erosion.
 

Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: https://www.uair.arizona.edu/holdings/journal/issue?r=http://jrm.library.arizona.edu/Volume42/Number1/

 

Output references
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