| Abstract |
- This study investigated how manipulating vineyard nitrogen status, irrigation
levels and cultivation practices would effect nutrient composition, and anthocyanin
and phenolic accumulation in Pinot noir juice and wine from a commercial
Willamette Valley Oregon vineyard.
Pinot noir fruit was sourced from a vineyard trial in the Benton Lane
Vineyard, located in the Southern Willamette Valley in 1999 and 2000. Treatments
were applied in a factorial design varying irrigation, cultivation, and nitrogen
applications. Irrigation was applied in both years post lag phase. Tilling was carried
out early spring in alternate rows to promote nitrogen utilisation and reduce water
and nutrient competition from vineyard grasses. Three nitrogen treatments were
applied: zero nitrogen, soil nitrogen applied early spring both years at 39.2kg N/ha as
urea, foliar nitrogen applied both years at the onset of ripening, and at verasion at
2.98 kg N/ha as wettable urea.
Dry treatments in 1999, and 2000 had lower yields (kg/vine), smaller berry
weights, higher seed weights, and greater seed weight to berry weight ratios compared to Irrigated treatments. I hypothesised that wine made from Dry
treatments would have higher anthocyanins and phenolics. Ammonia (mg N/L),
nitrogen from alpha amino acids (mg N/L), and yeast assimilable nitrogen content
(mg N/L) were consistently higher in Dry treatments throughout the trial. No
differences in pH and titratable acidity were observed in either year between
Irrigated and Dry treatments. Skin anthocyanin and total phenols were found to be
higher in Dry treatment berries both years, as were wine anthocyanins, colour
intensity, and hue. Analysis using HPLC of 1999 wines made from the trial
indicated Dry treatments had significantly higher malvidin and polymeric
anthocyanin when compared to Irrigated treatments supporting our hypothesis.
Berry dehydration and concentration in Dry treatments were attributed to smaller
berry weights concentrating nutrients and anthocyanins.
In 1999, Tilling had lower yield (kg/vine) than No-Till treatments. A delayed
effect occurred in the second year and yield was higher in Tilled treatments in 2000.
In both years, Tilling treatments had higher berry weights, seed weights and greater
percentage seed weight per berry compared to No-Till treatments. Total soluble
solids (0Brix), ammonia, nitrogen from alpha amino acids, and yeast assimilable
nitrogen were higher in Till treatments in both years. No significant differences or
trends between cultivation treatments were observed for titratable acidity, pH, malic
acid concentration, alcohol, anthocyanins, phenolics, colour intensity and hue in
either year. Soil Nitrogen (SN) treatments in 1999 and 2000 had significantly lower
yields, seed weights, and a higher percentage seed weight per berry due to small
berries compared to Zero Nitrogen (ZN) and Foliar Nitrogen (FN) treatments. It was
hypothesised that wines made from SN treatments would have greater colour
intensity and anthocyanins than ZN and FN treatments. Ammonia levels were lower
in SN treatments, however, nitrogen from alpha amino acids (NOPA) was higher in
SN treatments yielding higher net yeast assimilable nitrogen content (YANC) in both
years. The ZN treatments had lower juice pH, higher titratable acidity and malate
concentration compared to FN and SN treatments in 1999 and 2000. No significant
difference was observed in soluble solids or alcohol content in any treatment. Soil
Nitrogen treatments both years had significantly higher skin anthocyanins and
phenolics. Wines from SN treatments tended to have higher anthocyanins,
phenolics, colour intensity and hue in both years compared to ZN and FN wines.
Analysis by HPLC in 1999 indicated SN wines were significantly higher in
polyphenols and polymeric anthocyanins supporting our hypothesis. These results
indicate that irrigation and soil nitrogen treatments had positive effects on wine
quality.
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