Improvement in ryegrass seed germination for diesel contaminated soils by PEG treatment technology

Phytoremediation of petroleum contaminated soils has been recognized as a p otentially cost effective treatment technology and has gained much attentio n recently. Because grasses have fibrous root systems which can provide hig h surface areas for the soil microbial population to increase bioremediatio n in the rhizosphere, many researchers choose grass species as plants with great potential in the phytoremediation of petroleum contaminated soils. Th e presence of Volatile petroleum hydrocarbons in soils at relatively low co ncentration (4000-8000 mg kg(-1) dry soil) could severely hinder seed germi nation resulting in poor plant establishment. In this study, we evaluate th e feasibility of using polyethylene glycol (PEG) seed pre sowing treatment technology to solve the problem. Experiments were conducted with 15g of die sel contaminated soils. The results show that PEG seed pre-sowing treatment successfully avoided the phytotoxicity effects of volatile petroleum compo unds on seed germination. The seed germination percentage as well as the un iformity of germination were significantly increased by PEG seed pre-sowing treatment. In one of the germination tests, ryegrass seed germination perc entage was significantly increased from 60% (untreated dry seed) to 80% in dean soil samples and from 20% (untreated dry seed) to 90% in 3% (fresh con taminated) diesel soil samples with 20 degrees C/20% PEG treatment. Short-t erm phytotoxicity effects of petroleum compounds on early seeding growth we re observed.