Assessing soil characteristics and potentially toxic elements (Fe, Mn, Ni, Cu, Cr, Pb, Zn) in the topsoil and the vine leaves (Vitis vinifera) in a sloping vineyard (Tállya, NE Hungary)

Intense soil erosion in sloping vineyards can substantially change the spatial quality patterns of soil that may ultimately affect plant nutrition. Our study aimed to assess spatial patterns of topsoil quality and evaluate if the topsoil-bound potentially toxic element (PTE) contents are linked with those in vine leaves. The study was conducted at a 0.4 ha plot in Tállya (in Tokaj-Hegyalja, NE Hungary), where Cambisol is the main soil type. Ploughing is regularly practiced in the vineyard, while no cover-crops are used, and sedimented soil material from the footslope area is occasionally redistributed on the hillslope. A total of 20 topsoil samples (0-10 cm) and 11 vine leaf (Vitis vinifera) samples were collected in May 2020. The moderately acidic soil (pH(d.w.): 6.12-6.92) developed on a magmatic base rock (rhyolite) showed high gravel contents ranging from 31% to 48%, a low to moderate soil organic matter (SOM) content with a mean of 1.49%, low carbonate contents (0.4-2.01%), and clay loam texture at the hillslope, while sandy clay loam at the footslope. The concentrations of bioavailable  Fe, Mn, and Cu (extracted in 0.05 M NH₄-EDTA) showed high ranges in the soil: 62–258 mg kg⁻¹, 40-114 mg kg⁻¹ and 46-110 mg kg⁻¹, respectively. On the other hand, Zn, Pb, Ni, and Cr concentrations were low with mean±stdev: 6±4 mg kg⁻¹ for Zn, 4±1 mg kg⁻¹ for Pb, 1.5±0.5 mg kg⁻¹ for Ni, and 0.1±0.1 mg kg^-1 for Cr. Increased Cu bioavailability can be explained by the regular use of Cu-based pesticides. The highest total PTE contents in vine leaves were observed for those PTE that are important micronutrients for vine plants (mean±stdev): 90±13 mg kg⁻¹ of Fe, 167±88 mg kg⁻¹ of Mn, 15±15 mg kg⁻¹ of Cu and 31±6 mg kg⁻¹ of Zn.  Zinc and Mn concentrations in leaf samples were markedly greater than their bioavailable contents in the topsoil. In contrast, lower levels of Fe and Cu prevailed in the leaves compared to their topsoil-bound bioavailable contents. Only Mn showed a significant correlation in the vine leaves and the topsoil (r=0.62).

Spatial distribution maps of the measured basic soil parameters and the bioavailable PTE contents were prepared by inverse distance weighting and ordinary kriging methods. The maps showed higher concentrations of PTEs at the summit and the shoulder of the hillslope, while lower concentrations were found at the backslope and footslope zones. The SOM showed the highest loads at the summit and the toeslope zones, while increased gravel contents were found at the backslope, confirming the effects of soil erosion dynamics and cultural practices. Our study shows that cultural practices and the lack of erosion control measures in the vineyard significantly influenced the spatial variability of topsoil characteristics and bioavailable PTEs. 

• I. B. is grateful for the support of the Premium Postdoctoral Research Program of the Hungarian Academy of Sciences. The research received funds from the OTKA 1K 116981.