Large ultramafic areas exist in Albania, which could be suitable for phytomining with native Alyssum murale. We undertook a five-year field experiment on an ultramafic Vertisol, aimed at optimizing a low-cost Ni-phytoextraction crop of A. murale which is adapted to the Balkans. The following aspects were studied on 18-m2 plots in natural conditions: the effect of (i) plant phenology and element distribution, (ii) plant nutrition and fertilization, (iii) plant cover and weed control and (iv), planting technique (natural cover vs. sown crop). The optimal harvest time was set at the mid-flowering stage when Ni concentration and biomass yield were highest. The application of N, P, and K fertilizers, and especially a split 100-kg ha(-1) N application, increased the density of A. murale against all other species. It significantly increased shoot yield, without reducing Ni concentration. In natural stands, the control of graminaceous weeds required the use of an anti-monocots herbicide. However, after the optimization of fertilization and harvest time, weed control procured little benefit. Finally, cropping sown A. murale was more efficient than enhancing native stands and gave higher biomass and phytoextraction yields; biomass yields progressively improved from 0.3 to 9.0 t ha(-1) and phytoextracted Ni increased from 1.7 to 105 kg ha(-1).
UltramaWc outcrops are widespread in Albania and host several Ni hyperaccumulators (e.g., Alyssum murale Waldst. & Kit.). A Weld experiment was conducted in Pojske (Eastern Albania), a large ultramaWc area in which native A. murale was cultivated. The experiment consisted in testing the phytoextraction potential of already installed natural vegetation (including A. murale) on crop Welds with or without suitable fertilisation. The area was divided into six 36-m 2 plots, three of which were fertilised in April 2005 with (NPK + S). The soil (Magnesic Hypereutric Vertisol) was fully described as well as the mineralogy of horizons and the localisation of Ni bearing phases (TEM-EDX and XRD). Ni availability was also characterised by Isotopic Exchange Kinetics (IEK). The Xora was fully described on both fertilised and unfertilised plots and the plant composition (major and trace elements) and biomass (shoots) harvested individually were recorded.The soil had mainly two Ni-bearing phases: highMg smectite (1.3% Ni) and serpentine (0.7% Ni), the Wrst one being the source of available Ni. Ni availability was extremely high according to IEK and conWrmed by Ni contents in Trifolium nigriscens Viv. reaching 1,442 mg kg ¡1 (A new hyperaccumulator?). Total biomass yields were 6.3 t ha ¡1 in fertilised plots and 3.2 t ha ¡1 in unfertilised plots with a highly signiWcant eVect: fertilisation increased dramatically the proportion of A. murale in the plots (2.6 t ha ¡1 vs. 0.2 t ha ¡1 ). Ni content in the shoots of A. murale reached 9,129 mg kg ¡1 but metal concentration was not signiWcantly aVected by fertilisation. Phytoextracted Ni in total harvest reached 25 kg Ni ha ¡1 on the fertilised plots. It was signiWcantly lower in unfertilised plots (3 kg Ni ha ¡1 ). Extensive phytomining on such sites could be promising in the Albanian context by domesticating already installed natural populations with fertilisation.
This study aimed at relating the variability of Ni biogeochemistry along the ultramafic toposequence to pedogenesis and soil mineralogy. Hypereutric Cambisols dominate upslope; Cambic Vertisols and Fluvic Cambisols occur downslope. The soil mineralogy showed abundance of primary serpentine all over the sequence. It is predominant upslope but secondary smectites dominate in the Vertisols. Free Fe-oxides are abundant in all soils but slightly more abundant in the upslope soils. Whereas serpentines hold Ni in a similar and restricted range in every soil (approx. 0.3 %), Ni contents in smectites may vary a lot and Mg-rich and Al-poor smectites in the Vertisol could hold up to 4.9 % Ni. Ni was probably adsorbed onto amorphous Fe-oxides and was also exchangeable in secondary smectites. High availability of Ni in soils was confirmed by DTPA extractions. However, it varied significantly along the toposequence, being higher in upslope soils, where Ni-bearing amorphous Fe-oxides were abundant and total organic carbon higher and sensibly lower downslope on the Vertisols: NiDTPA varied from 285 mg kg(-1) in the surface of soil I (upslope) to 95.9 mg kg(-1) in the surface of Fluvic Cambisols. Concentration of Ni in Alyssum murale shoots varied from 0.7 % (Hypereutric Cambisols) to 1.4 % (Hypereutric Vertisol). Amazingly, Ni uptake by A. murale was not correlated to NiDTPA, suggesting the existence of specific edaphic conditions that affect the ecophysiology of A. murale upslope.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.