Riolittufa mállásának hatása a talajok vízvezeto képességére

Translated title of the contribution: Effects of rhyolite tuff weathering on soil water conductivity

Zsófia Bakacsi, Koós Sándor, András Nagymarosy, László Péter

Research output: Contribution to journalArticle

Abstract

The Tokaj Wine Region is situated in northwestern Hungary and has been known as a significant production area of the sweet botritized dessert wine known as "Aszú" since the Middle Ages. Its reputation can be attributed to the geological and pedological features of the area, the special microclimate and the unique mould infection, combined with long years of experience. In 2013 the Hungarian Government set up a programme of sustainable quality wine production in the Tokaj region, coordinated by the Tokaj Kereskedoház Ltd, the biggest wine producer. To achieve this target it was indispensable to assess the potential of the vineyard soil. The viticultural characterization of the land was carried out during two main surveying phases (2013-2015). The primary objective of the present work was to contribute to terroir zoning by examining how the weathering of rhyolite tuff, the most common parent material in this region, influences soil water management, with special emphasis on saturated hydraulic conductivity, one of the characteristic factors. The conductivity values were calculated at four locations, based on borehole infiltration tests, which proved to be a feasible insitu measuring technique. The textural composition (Figure 1) of the excavated soil layers and the calculated conductivity values were used to determine the conductivity of rhyolite tuff detritus. Rhyolite tuff was excavated from three boreholes (Nos. 3, 4, 6), while borehole No. 5 consisted of only rock debris (Figure 3). During the measurements the boreholes were filled up with water several times, the time dependence of the water level changes was recorded, and the standard Hungarian protocol (MÉM NAK, Table 1) was used to calculate the hydraulic conductivity, based on linear trend lines fitted to the water level data with the highest R-squared values, considered to represent the steady state. Relatively fresh, hard, silicified, unaltered, but strongly fractured rhyolite tuff was reached at a shallow depth (50 cm) in borehole No. 6. At this site the initial drop in the water level was very fast. Boreholes Nos. 3 and 4 contained only slightly different, strongly weathered, "sand-like" rhyolite tuff, in which feldspar minerals, which are easily modified, had been entirely transformed into clay, while some of the mafic minerals remained observable in the samples (mostly biotite). The hydraulic conductivity values of the strongly weathered, sand-like rhyolite tuff were lower than expected in the field, being several orders of magnitude lower than the conductivity of "true" sand and close to the values recorded for clayey loam. The results show that the presence of this kind of volcanic detritus in the soil profile leads to greater water retention, while silicified, fractured rhyolite that has undergone little or no alteration does not prevent the vertical movement of water. This means that terroir evaluation should take into account not only the nature of the underlying rock, but also to what extent it has been altered.

Translated title of the contributionEffects of rhyolite tuff weathering on soil water conductivity
Original languageHungarian
Pages (from-to)5-15
Number of pages11
JournalAgrokemia es Talajtan
Volume65
Issue number1
DOIs
Publication statusPublished - Jun 2016

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Soil Science

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