Viticulture 3 Site Selection.txt
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Define Macro-, meso-, and micro- climate
- Macroclimate: regional,up to hundreds of km, e.g., Bordeaux
- Mesoclimate: a vineyard to a sub-region, up to a few km, e.g., Pomerol
- Microclimate: an individual vine
Name some factors that affect the microclimate
- Relationship with its neighboring vines
- row width
- planting distances
- trellising and training type
- height of trellis
- methods of canopy management
Grapevines respond to differences in climate more than an other fruit crop. T or F?
The sugar level in grapes at harvest is directly related to site quality. T or F?
True. In many instances the financial value of the grapes will depend entirely on the sugar level at harvest.
What is the effect on wine of sugar and acid levels?
- Sugar: if low, thin and unripe; if high, alcoholic, warm and unbalanced
- Acid: if low, flabby and short-lived; if high, acidic and aggressive
Name the 3 most important factors of site selection in growing grapes
- Latitude (location)
Name 15 fixed factors of site selection in growing grapes
- Length of the growing season
- Number of sunshine hours
- Diurnal temperature range (affects speed of ripening and acid reduction)
- Site's relationship to prevailing winds
- Proximity of large bodies of water
- Humidity and the evapotranspiration (ET) rate
- Type and depth of soil
- Management of the vineyard floor (cultivated, bare earth, or grassed down)
- Layout of the vineyard (direction of rows)
- Trellising and training system
- Choice of rootstock
- Type and clone of grape variety
- Cropping level
- Wine type and quality level to be produced
Name 3 variable factors of site selection in growing grapes
- Weather (most important)
- Pest & disease control
- Canopy management
- Irrigation regime
Name 4 methods to measure the macroclimate
- Heat Summation (aka Degree Days, Winkler Scale, Regions I-V, Heat Units): Maynard A. Amerine and Albert J. Winkler, UC Davis, 1944
- Latitude Temperature Index (LTI): David Jackson and Danny Schuster, New Zealand, 1994
- MTWM - MTCM: difference between mean temperatures of warmest and coldest months;
- MTWM alone: Richard Smart and Peter Dry, Australia, 1980; good corrleation to degree days for wamer sites
- (10 year average of number of) days over 30°C: good for cooler regions
Name the issues associated with the Heat Summation, LTI, and MTWM-MTCM methods
- Heat Summation: OK for California but not appropriate for cooler, less continental regions
- LTI: factors in latitude (length of the day); appropriate for cooler, less continental, more maritime regions
- MTWM - MTCM: factors in continentality of the site (length of growing season impacted by proximity to water bodies)
What is the theory behind the Winkler Scale?
No shoot growth occurs below 50°F
What is a degree day?
- Average daily temperature above 50°F
- Example calculation: (81°F + 57°F)/2 - 50°F = 19 degree days
- Heat Summation scale is the sum of all degree days between April 1 and October 31 (7 months = 213 days)
What is the daily average degree days per climate region?
- Climate Region I: up to 11.7
- Climate Region II: from 11.7 to 14
- Climate Region III: from 14 to 16.4
- Climate Region IV: 16.4 to 18.8
- Climate Region V: more than 18.8
- Note: each region adds about 2.3°F to next cooler region
Define the Winkler Scale and what grapes grow best in each region
- Climate Region I: up to 2,500 degree days; CS, CH, PN, Riesling, SB
- Climate Region II: from 2,500 to 3,000 degree days; same varieties as Region I plus merlot
- Climate Region III: from 3,000 to 3,500 degree days; Carignan, Ruby Cabernet, SB, Semillon, Zinfandel
- Climate Region IV: 3,500 to 4,000 degree days; Barbera, Ruby Cabernet, Emerald Riesling, port-style wine grapes
- Climate Region V: more than 4,000 degree days; Souzao, Tinta madera and Verdelho
Define the Winkler Scale and name example areas for each region
- Climate Region I: up to 2,500 degree days; Champagne, Côte d'Or, Rhine
- Climate Region II: from 2,500 to 3,000 degree days; Bordeaux
- Climate Region III: from 3,000 to 3,500 degree days; Rhone
- Climate Region IV: 3,500 to 4,000 degree days; Southern Spain
- Climate Region V: more than 4,000 degree days; North Africa
Name 2 ways to measure the length of the growing season
- Number of days between the last spring frost and the first winter frost (e.g., at least 180 frost-free days needed to ripen grapes)
- Number of days between start of flowering and start of harvest (e.g., Bordeaux usually 110, Central Otago up to 145)
Best sites are those with what macroclimate measurements?
- Growing season of 180+ frost-free days
- Summer rainfall around 500 mm (19.7 in)
- LTI of 200+
- Degree Days of 1000+
- Sheltered from cooling winds
- Slope towards the sun
Name 3 negative effects of global warming (e.g., 2°C rise in mean annual temperature)
- Need to switch varieties
- Need to learn about acidification and alcohol reduction techniques
- Change in the spectrum of pests and diseases
What other factors might account for higher sugars attributed to global warming?
- Improved plant material (clones)
- Better canopy management
- Much better (chemical and viticultural) Botrytis control which allows for a longer ripening period
- Temperature control
- More alcohol-productive yeast strains
Name an insect that has found its way to Europe, once considered too cool for it
- Multicolored Asian Lady Beetle (aka Harlequin Ladybird Harmonia axyridis)
- Exudes "reflex blood" from its legs which has a fould odor and taste (taints grapes and wine made from them)
Name the world's coolest winegrowing region by far
U.K.; Cropping levels, at around 50-60 hl/ha, are lower than those in vineyards in Champagne
Name 3 varieties for cool climates
- Seyval Blanc
Has global warming changed the timing of bud-burst, flowering, veraison, or harvest?
As you rise above sea-level, how does the annual mean temperature change?
- Temperature falls by around 0.5-0.6°C per 100 m rise (1.8°F per 109 yards)
- Sites also become more exposed to prevailing winds
What is the effect of altitude on site selection?
- The higher the altitude, the shorter the growing season and ripening will occur later.
- This increases the dangers of frosts and disease.
At what altitude are the most suitable sites in cooler and warmer regions?
- Cooler: below 300 m
- Warmer: up to 1000 m
- Hot: 1000+ m
At what altitude is the highest vineyard in the world?
- Bodega Colome vineyards sit between 2300 and 3111 meters above sea level
- Located in Argentina, in the Upper Calchaqui Valleys in Salta, latitude 26°S
What aspects are preferred?
Sites that slope towards the sun (to the south in the northern hemisphere, to the north in the southern hemisphere)
What aspect catches the morning sun? What is the effect of this?
- SSE or SE in the northern hemisphere
- Site warms up more quickly after night cooling; may also be more sheltered from prevailing winds
Sites with what aspect stays warmer into the evening?
- SSW or SW in the northern hemisphere (slopes that face east are favored over those that face west in the southern hemisphere)
- Dark or stone rich soils benefit from this but in many regions the cooling prevailing wind comes from this direction.
What is insolation?
Incoming solar radiation
When is incoming solar radiation the greatest?
- Insolation is greater the more the site is angled to the sun (up to a slope of about 40°)
- The effect is more significant at the end of the growing season
Define "thermal zone"
- Slopes are warmer because air (as it is cooled by the land) travels down the slope to be replaced by warmer air from above.
- Example slopes with thermal zones are Corton hill in ALoxe-Corton and Kaiserstuhl in Baden.
Name 3 advantages growing grapes on slopes have over flat sites
- Thermal zone (warmer)
- Thinner topsoil (less vigorous)
- Better drainage (dry out and warm up better)
Does water or land store heat more effectively?
How are air temperatures equalized between land and water?
Warm air on the land rises and is replaced by cool air from the water.
What is the Gulf Stream?
- A powerful, warm, and swift Atlantic ocean current, about 100 km wide X 1 km deep.
- Ocean currents are mainly caused by wind that forces the water to move in the same direction.
How much does the Gulf Stream warm the land it touches?
About 9°C (16.2°F) above that for the latitude
Are regions with small or large diurnal temperature swings preferred for grape growing?
- Small, in (cooler) old world, since they heat up more quickly in the day, thus advancing maturity.
- Large, in (warmer) new world, since cool nights aids in the retention of acids.
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