Changes in Norisoprenoid Levels with Long-term Nitrogen Fertilisation in Different Vintages of Vitis vinifera var. Riesling Wines

C13-norisoprenoids were measured in Riesling wines produced from the 1996, 1997 and 2003 vintages within thescope of a long-term nitrogen (N) fertilisation experiment. The wines were made from treatments of 0, 60 and 150kg N/ha; each treatment was repeated four times and arranged in a completely randomised design. N fertilisationled to lower TDN (1,1,6-trimethyl-1,2-dihydronaphthalene) concentrations, whereas the trend was for actinidol andß-damascenone to increase with increasing fertilisation and vitispirane was not affected by fertilisation. Yield,which was affected by N fertilisation, showed negative correlations with norisoprenoids in 1996 and 1997.Vitispirane, actinidol and TDN increased with storage time. The colder year, 1996, which had fewer sunshine hours,resulted in higher concentrations of ß-damascenone and lower concentrations of the norisoprenoids vitispirane,actinidol and TDN compared with 1997

Geostatistical Analysis and Scaling of Grapevine Root Distribution

Geostatistical analysis was conducted for the root distribution of Vitis berlandieri x Vitis riparia using dispersionindex, fractal dimension, autocorrelation and semivariance. The data were derived from the observation of rootsof six 12-year old Riesling/5C vine plants in a field experiment using minirhizothron technique. The dispersionindex (DI) indicated the clustering of roots. Autocorrelation as a function of the distance lag showed that a higherDI was related to higher autocorrelation at small lags. Small scale (< 3cm) spatial analysis using variograms,showed a clustering of roots at short distances (< 6cm), but also a periodicity at greater distances (16cm) with holeeffects in the variograms. The spatial variance for small scale was 60-85% within a range of 5-8cm. At mediumscale (5-10cm) the spatial variance decreased to 0-20%. Geostatistical analysis is a useful tool to demonstratevariation in root distribution at plant level and to improve root sampling. Although the different geostatisticaltools were related, it was not possible to deduce one result from the other quantitatively

Effect of different N fertilization of vine on the tryptophan, free and total indole-3-acetic acid concentrations

The compound responsible for UTA (untypical ageing off-flavour) in wines is o-AAP (o-amino acetophenone). It is formed from IAA (indole-3-acetic acid), triggered by sulfurylation. The aim of this study was to evaluate the effect of different N fertilizer supply on this precursor in must and wine, making use of a long-term nitrogen fertilization experiment. Trp (Tryptophan) as well as free and conjugated IAA were determined in musts and wines produced from grapevines supplied with 0, 30, 60, 90 or 150 kg N ha-1 year-1. IAA concentrations in musts and wines varied highly over years (1994-1999), wines containing about half of the total IAA of musts. The IAA concentration in must was positively correlated with the concentration of amino acids in must, however, nitrogen supply did not have any effect, neither on Trp nor on IAA concentrations

Investigation of grapevine root distribution by in situ minirhizotron observation

Root observations of Vitis berlandieri x Vitis riparia were conducted in two experimental sets using minirhizotron technique. Experiment 1 was a field experiment carried out on a 12 years old Riesling/5C vineyard. On six plants three minirhizotrons were installed at different angles (90°, 60°, 45°) and two directions per tube were used for observation. The maximum of root length density (RLD) was found in soil depths of 600-800 mm with high variation mainly due to plant x angle interaction. Observation direction did not influence the estimates of RLD. The installation angle of the tubes did not lead to any consistent effect on root observation. Experiment 2 was a pot trial of six pots with four vines each. Tubes were installed horizontally. RLD in the pot experiment according to the monolith method and the estimated RLD according to the minirhizotron method did not correlate, so the quantification of Vitis RLD distribution using minirhizotron is difficult.

Root dynamics and pattern of 'Riesling' on 5C rootstock using minirhizotrons

Root length density (RLD) in the years from 1994-1997 was estimated using minirhizotrons. The field experiment was conducted on six 'Riesling' vines in Rheingau (Germany). The majority of root distribution was found in soil depths of 60-100 cm with considerable variations between the plants. Roots dynamics showed a periodicity with one or two maxima, depending on year and vine plant. The first peak of RLD was observed around veraison, the second peak appeared after harvest. The rate of root length death was estimated. In the deeper layer the turnover of roots was 60% of the total RLD every year.

Ambivalence of the influence of nitrogen supply on o-aminoacetophenone in 'Riesling' wine

AAP (o-aminoacetophenone) is the aroma substance responsible for the untypical ageing off-flavour (UTA). The impact of nitrogen supply on the formation of AAP was investigated between 1994 and 1999. The experiment was carried out in the Rheingau (Germany) with six fertigation treatments of annual quantities of N (0, 30, 60, 90, 150 kg·N·ha-1). Results indicated that the long-term varied N fertilization affected AAP concentration in wine as much as the year. Whereas a better N supply of the grapes due to effects of the year coincided with lower AAP values, the fertilization effect was reversal: higher N fertilization increased the concentrations of AAP. AAP did not correlate with its precursor IAA and only slightly with antioxidative capacity. Neither varying yield nor soluble solids could explain the high variance of AAP. An indicator for potential AAP formation could not be found, neither in must nor in wine.

Untypical ageing off-flavour and masking effects due to long-term nitrogen fertilization

The off-flavour UTA (untypical ageing) of wines produced from the vintages 1996-1999 within the scope of a long-term N fertilization experiment was compared to the o-aminoacetophenone (AAP) concentrations found in these wines. The wines were made of plants treated with 0, 60 and 150 kg N ha-1·N fertilization led to higher UTA intensities and AAP concentrations in aged wines; due to stronger fruity aromas with increasing N fertilization, young wines were able to mask AAP. Controls had a stronger masking effect in older wines, caused by antioxidants (phenols) and possibly higher alcohols. Moreover, at the same AAP level, wines from the vintages 1996 and 1998 exhibited lower UTA intensity than wines from 1997 and 1999. This is influenced by N supply, yield and time of harvest which can not be separated from each other.

Erratum

Untypical ageing off-ßavour and masking effects due to long-term nitrogen fertilizationVitis 46 (1), 33-38 (2007

Untersuchungen des BÖL-Verbundprojektes zur Kupferminimierung im ökologischen Weinbau

The development of sustainable and economically feasible strategies to get an effec-tual control of downy mildew on grapes (Plasmopara viticola) with less than 3 kg/(ha*a) of copper to avoid further environmental risks is the intention of this project. Due to harmful effects on the natural environment, copper applications are under considera-tion. Therefore, in this four-year-project first of all test products are screened under greenhouse conditions on potted vines. Thereafter the best test agents are studied in organically managed test vineyards. Finally the selected strategies are tested under practical conditions on organically managed vineyards. Beyond these examinations a close link between wineries and research is given by SME and consultant partners. The results indicate that plant extracts, finely ground stones and new copper formula-tions could probably serve as plant resistance improvers and plant protection prod-ucts, respectively, to prevent attacks of P. viticola. Moreover, it was possible to select prosperous agents and strategies for the growing period 2007. These were agents of the substance categories “new copper formulations”, “plant extracts” and “finely ground stones”. Regarding the results of three growing periods, the project will provide effective and economically feasible alternatives for copper applications in order to deliver sustainable approaches for P. viticola control in practise

Is grape composition affected by current levels of UV-B radiation?

Research Not