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Case Study

Final report of the test on vine (2002-2004) with the GOBBI products in collaboration with S.Michele all’Adige

L. Gobbi Sri, Italy.
Dott. Duilio Porro.
Agricultural Production Department – S.Michele all’Adige (TN).

November 2005

Key words
Grapes, Foliacin, Mycorrcin, Cabernet Sauvignon, Italy.


Overview

  • The test was performed on the Cabernet Sauvignon cultivar in the Sormi area during the 2002-2004 period. The influence of the leaf and/or root fertilizers of the GOBBI line on the nutritional performance and the quantitative-qualitative behaviour of the plants was observed.

Results:

  • The experimental groups compared were 7, repeated three times according to an experimental model with randomized units. In the previous years the experimental model had already been detailed, therefore, to facilitate the data reading and understanding, only the compared groups are mentioned:
TreatmentsApplicationTiming
TestNo fertiliser
G1LG 71 2,5 l/haSeparate bunches Initial blossom Full blossom Fruit set
G2LG 91 3 l/ha10 days after fruit set 15 days after 1st treatment
G3LG 75 750 g/ha + LG 62 2 l/ha + LG 74 3 l/haBy closing of bunch Onset of ripening
G4Mycorrcin 5 l/ha Mycorrcin 2 l/ha Mycorrcin 2 l/haEarly spring 10 cm shoot 10 days before bunch closing
G5Foliacin 750 ml/haBreaking open of leaf buds By end of bloom By closing of bunch
G6Combined application G4 + G5
  • The root fertiliser [Nitrophoska blu spezial, ternary complex made by Compo (12-12-17)] had been spread on the plots of the different experimental groups (G1, G2,G3, G4, G5 e G6) in April for a total contribution of 50 units of nitrogen.
  • Implementing the treatment was an heavy duty that necessitated several and varied interventions; the controls have addressed:

1. Nutritional status valuation with SPAD (Soil and Plant Analysis Development) on fruit set
and ripening onset. The sampling has been implemented by measure of the depth of the
green colour of the leaves for a total of 30 leaves per plot.

2. Nutritional status valuation through leaf diagnosis (nitrogen, phosphorus, potassium,
calcium, magnesium, sulphur, iron, boron, manganese, zinc and copper content analysis)
was performed in the two given phenologic phases. Each sample corresponds to each
plot, for a total of 3 samples for each different group.

3. Quantitative data of harvest. From each plot 6 plants have been harvested, from which
the number of shoots, the number of bunches and the yield expressed in weight were
obtained; from these primary data, the secondary values of real fertility and average
bunch weight were obtained.

4. Quantitative data of harvest. From each plot, on three homogenous plants well
representative of it, 3 samples have been collected for sugar content, titratable acidity,
pH, malic acid, tartaric acid, potassium ion analysis and finally the weight of 100 grape
berries was established.

5. Micro-vinification of harvest. About 35 kg grapes have been collected from each
experimental group for the purpose of micro-vinification, polyphenols and total
anthocyanins analysis. APA (Readily Assimilable Nitrogen) was also measured on the
wines. These wines were then evaluated by a taste panel.

6. In wintertime, data about the robustness of the plant were collected, expressed in terms
of weight of pruning wood.

  • Data gathered during the three years of survey have been submitted to ANOVA (Analysis of Variance), including among the variables year, experimental group and year x group interaction (table 1).
  • Nutritional data and data relative to the SPAD (Soil and Plant Analysis Development) values measured during the separate phenological phases and been added for a better understanding of the results.

Table 1

ANOVA applied to the vegetal production, qualitative and nutritional parameters during the three year survey period. F values and F probability values are included: significant average differences for each variable are indicated in bold print.

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As documented in Table 2, the data relative to the three year survey period relative to the group are discussed, showing that the year influence has been significant for all researched parameters, with exception of the leaf manganese, while the year x group interaction has never been significant.

After the three year survey period significant differences between the groups are demonstrated in the number of shoots, productivity, weight of 100 grape berries, sugar content, robustness of the plant (expressed in terms of weight of pruning wood and SPAD [Soil and Plant Analysis Development] values), and also in the leaf values of potassium and magnesium.

More specifically:

  • Exp. group G5 is producing a higher number of shoots than exp. group G2;
  • Exp. group G4 is more productive than any other; the reference group and exp. group G1, on the contrary, are the less productive and are significantly separated also from exp. group G3 and G6; intermediate values, not statistically different from each other, are found in exp.group G2 and G5;
  • The weight of 100 grape berries, in other words their size, varies in the different exp.groups showing the lowest values in exp.group G5, intermediate in the reference group and exp.group G1 and G2, and the highest in exp.group G3; exp.groups G4 and G6 are not demarcated either from G3 or from the intermediate exp.groups;


Table 2

Vegetal production, qualitative and nutritional parameters during the three year survey period; separation of the averages of the different groups has been done by Tukey test; significantly different values have been marked by different letters.

table_2.jpg

  • The sugar content appears significantly raised in exp.groups G1, G2 and G5 in comparison with the reference group and exp.group G6;
  • The degrees of robustness of the plant expressed in terms of weight of pruning wood, also demonstrate that exp.group G1, G4 and G6 are clearly higher than those of the reference plants;
  • In a parallel way, the SPAD values show the same tendency, albeit without difference, with exp.group G1; even if the average values are not statistically different, the nitrogen leaf levels show the same tendency;
  • The leaf potassium levels are significantly lower in exp.groups G2 and G6 when compared to G6, while the magnesium levels show higher levels in G2 and G5 when compared to G3;
  • Wines and musts have not shown statistically significant variations for polyphenol, anthocyanin and readily assimilable nitrogen levels; 
  • Similarly, the yearly analysis of the produced wines (Table 3) does not show marked variations, with the exception of a tendency to a higher alcohol content in exp.groups G1, G5 and G2 and lower content in the reference group;
  • The tasting profiles of the wine produced (figure 1) demonstrate, albeit with differences in the different years, that fertilisation can contribute to change some factors of the tasting profile; more specifically, the non fertilised exp.group scores a very low aromatic and tasting score, clearly separating it from all other wines, even without taking into account the spiced, herbal, bitter, phenolic and citric caracters. This confirms what had already been observed after the first year of the survey period.
  • The G5 wine proves to be the most appreciated for its rich floral, tobacco and sour cherry taste. The G1 and G3 wines were also very much appreciated, particularly the abundance of red fruit taste in G3. G4 and G6 wines, in general, have shown in the years average to low tasting profiles with limited sour cherry and red fruit taste, comparable to the non fertilised group.

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Figure 1

Tasting profile analysis of the wines in the different experimental groups.
Average values of the three years ± standard error.

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Table 3: Wines and musts analysis of the three years, comparing the experimental groups.

2002

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2003

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2004

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  •  The data obtained from tasting confirm in any case what had been observed from the average values in terms of sugar gain and plant productivity in the different groups. This shows that, according to the model of this survey, even minimal production gains compatible with the fertilising effect, can contribute to the shifting of the intrinsic balance of the plant. 
  • Such data prove that the different fertilisation strategies, either trough the roots or the leaves, can influence the plant quantitative –qualitative performance and that an adequate management of the time of intervention can be of strategic importance to obtain better plants that will produce more enjoyable wines better appreciated by the consumer.

Conclusion:

  • The data obtained from tasting confirm in any case what had been observed from the average values in terms of sugar gain and plant productivity in the different groups. This shows that, according to the model of this survey, even minimal production gains compatible with the fertilising effect, can contribute to the shifting of the intrinsic balance of the plant.
  • Such data proves that the different fertilisation strategies, either through the roots or the leaves, can influence the plant quantitative –qualitative performance and that an adequate management of the time of intervention can be of strategic importance to obtain better plants that will produce more enjoyable wines better appreciated by the consumer.

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