Emergence and Height of Plants Seeded in Crude Oil Contaminated Soil

Abstract

Accidental contamination of soils with petroleum hydrocarbons results from oil production and shipping. Growing plants in these soils may enhance the rate and extent of remediation of these soils reducing their potential to contaminate surface and ground water. The objective of this study was to identify plants that are native, naturalized, or that have been successfully introduced to North Central Texas which will emerge and grow in crude oil contaminated soil. A greenhouse study was conducted in seed flats with the dimensions of 55 x 28 x 3.2 cm (L x W x H) containing 20 individual rows. Rows were filled with a Windthorst sandy clay loam soil amended with 0 (control), 0.5, 5, or 10% unweathered crude oil (soil dry weight basis). Soil moisture was maintained near-30kPa. Nineteen plant varieties were seeded in separate rows at a rate of 10 seeds per row. Treatments were conducted in triplicate in a completely randomized design. Emergence and plant height were measured on days 7, 14, 21, and 28. After 28 days, emergence had decreased by 79%, 90%, and 98% in soils with 0.5%, 5%, and 10% respectively when compared to controls. Decreases in plant height were 72%, 86%, and 96% in soils with 0.5%, 5%, and 10% crude oil respectively. Plant species with the greatest emergence and plant height in soil with crude oil were Kenaf#2 (Hisbiscus cannabinus var. tainvng #2) and Kenaf#3 (Hisbiscus cannabinus var. sf459), which were the only seedlings that emerged in the treatment with 10% crude oil. These two varieties are recommended for use on crude oil spills of 10% or less (soil dry weight basis) in North Central Texas. Delaying seeding for a few days following a spill and tilling the contaminated soil may remove toxic volatile components of the crude oil from soil and improve seedling emergence, plant growth, and enhance phytoremediation.