Greenberg, B; Huang, XD; Yu, XM; Chang, PC; Wu, SS; Gerhardt, K; Nykamp, J; Yu, X; Glick, B; Gerwing, P
Globally, almost 1 billion ha of land is affected by soil salinity. This has a negative impact on one-third of world's food production. Salt in the environment can occur naturally, or they can be discharged into the environment from anthropogenic activities (e.g. up-stream petroleum production and irrigation). Much effort has been put into developing economical and effective methods to reclaim salt impacted soils. In western Canada, brine water associated with upstream oil and gas production can result in salt impacted soils. High soil salinity inhibits plant growth and negatively affects land reclamation. Phytoremediation holds great promise for removing salt from soils, if salt phytotoxicity can be overcome. Some plants can, or can be induced to, tolerate high salinity and accumulate salt to levels that make phytoremediation feasible. The efficiency of salt removal is usually proportional to plant biomass production. The objectives of our studies were to achieve vigorous plant growth and salt phytoaccumulation on salt impacted soils from upstream oil and gas sites. One means by which high salinity can inhibit plant growth is via production of the plant stress hormone ethylene. Because many plant growth promoting rhizobacteria (PGPR) can lower stress ethylene in plants, we tested PGPR for their ability to improve plant growth on salt impacted soils. We used several PGPRs, some of which were isolated from the saline impacted sites in SK, AB and the NWT. Plants tested included barley, oats, wheat, blue gramma, buffalo grass, creeping red fescue, tall fescue, alfalfa and perennial ryegrass. PGPR treated seeds were sown in soils from SK, AB and the NWT with levels of salinity ranging from an ECe of 4 dS/m to an ECe of 30 dS/m (SARs ranged from 8 to 15). In the greenhouse, PGPR treatment significantly improved plant growth of all plants tested; the PGPR typically improved plant growth by ∼100 %. Salt accumulation by the plants tested was excellent; salt bioconcentrations in the foliage were ∼60 g NaCl per kg leaf dry weight. Field work was initiated in 2007 at three sites in SK. One site was moderately saline (ECe ∼8 dS/m) and the other two sites were highly saline (ECe > 20 dS/m). In the field trials, foliar salt uptake and improved plant growth due to PGPR treatment were on par with our observations from the greenhouse research. Based on the levels of salt accumulation achieved in the greenhouse and the field, we can predict that saline soils with an ECe of ∼ 15 dS/m can be remediated by approximately 50 % in about 5 years. Thus, PGPR treated plants have the potential to be an effective phytoremediation strategy for highly saline soils.
