Submitted to: Plant and Soil
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/12/2003
Publication Date: 10/1/2003
Citation: Angle, J.S., Baker, A.J., Whiting, S.N., Chaney, R.L. 2003. Soil moisture effects on uptake of metals by thlaspi, alyssum, and berkheya. Plant and Soil Journal. 256(2):325-332. Interpretive Summary: Phytoextraction is a new soil remediation technology which uses growth of hyperaccumulator plants to remove metals from a contaminated or mineralized soil. Development of commercial technologies requires testing of many aspects of the agronomic management needed to achieve cost-effective phytoextraction. In this paper, the effect of soil water content management on growth and metal accumulation by three metal hyperaccumulator plant species was tested, as well as the extractability of soil metals before and after plant growth. All three hyperaccumulator species are known to be well adapted to low soil water status periodically during their growth because the mine wastes or serpentine soils that the plants naturally occur on are coarse-textured and seasonally dry. Interestingly, maximum yield occurred when soil moisture was maintained near 100% of the soil water holding capacity, and declined when water holding capacity was less than 80% filled. Further, concentration of metals in the plants was not reduced by higher water supply, so the maximum annual soil depletion of metal occurred at the 100% of water holding capacity. These results provide guidance for irrigation management of Alyssum murale, Berkheya coddii and Thlaspi caerulescens production to phytoextract soil metals.
Technical Abstract: Most commonly used hyperaccumulator plants for phytoextraction of metals evolved on soils where moisture is limited throughout much of the year. As these plant species are commercialized for use, they are frequently moved from the point of evolution to locations where environmental conditions may be significantly different. Greatest among these potential differences is soil moisture. The objective of this study was therefore to determine whether these plants could grow in soils with much higher soil moisture and whether they would continue to hyperaccumulate metals as soils approach saturation. We examined extractable soil metal concentrations, plant growth, and metal accumulation for the Ni hyperaccumulators, Alyssum murale and Berkheya coddii and the Zn hyperaccumulators Thlaspi caerulescens cultivars AB300 and AB336. Non-hyperaccumulating control species for each were also examined. In general, extractable soil concentrations of Ni decreased with increasing soil moisture content. Few significant effects related to Zn extractability were observed for any of the soil moisture treatments. The biomass of all tested species was generally greater at higher soil moisture and inhibited at low soil moisture. Further, plants accumulated large amounts of metals from soil at higher soil moisture. Highest foliar concentrations of Zn or Ni were found at the two highest WHCs of 80 and 100%. These results show that hyperaccumulators grow well under conditions of high soil moisture content and that they continue to hyperaccumulate metals. Thus, growing Thlaspi, Alyssum, and Berkheya for commercial phytoextraction under nonnative conditions is appropriate and suggests that this technology may be applied to a wide and diverse range of soil types, climatic conditions, and irrigation regimes.