D1: Water (growing environment) 5 Flashcards
Vine needs water to survive and adequate water availability is vital for healthy vine growth and grape ripening
generally vine needs a min of 500mm or rainfall per year in cool climates and at least 750 in warm regions
The vine needs water for turgidty (so that it doesnt wilt) , photosynthesis and regulating its temperature
water also act as a solvents for nutrients in the soil which is important for their uptake by the vine
- ** and is the medium in which all of the vines biochemical and physiological mechanisms take place
- ** too little or too much can also have negative influence
transpiration:
1) water vapour diffuses out of the stomata (tiny pores on the underside of vine leaves
2) the loss of water from the cells in the leaves causes water to be pulled upwards from the soil through the roots and the above ground parts of the vine
open stomata allow the free exchange of water vapour out of the vine and also let co2 and oxygen diffuse in and out of the leaves.
1) if the vine has suff water it can leave its stomata open all day
2) lack of water causes leave to close it stomata fully or particularly
* can help to conserve water
* * also can stop photosynthesis due no entrance of co2
* ** so the vine growth will be stunted and ripening slows down
3) extreme water stress causes leaf loss and death of vine so irrigation can be needed
A plenty supply of water in spring encourages the growth of lots of leaves and hence the establishment of a large leaf surface area to support the growth of the vine and ripening of grapes.
however if water is too easily available into late spring, this lead to excessive vegative growth in the stage f grape ripening which acts as a competitive source for the vines sugars, delaying and compromising ripening
Mild water stress before veraison can be benefical because it inhibits further vegative growth:
1) too many shoots is too big canopy
* shading of grapes and bunches
* reducing formation of anthocyannins, tannins and aroma compounds
- - less tannin polymerisation and higher levels of methoxypyrazines
2) also dense canopy: poor ventilation: fungal diseases
Severe water stress or plentyfull water during veraison and ripening:
1) too much water: sugar in the grapes can dilute and the grapes can burst (so vulnurable for botrytis)
2) water deficit: grape shriveling and may not reach the desired level of ripeness
Damp soils are often cold, especially early in growing season:
1) this can delay budburst
2) shortens the season
Warm soils promote budburst and root growth, so
more ability to take up water and nutrients
Hail can cause mayor damage to green parts of the vine at any point of the season:
reducing yields and quality of the remaining fruit
rainfall at polination and fruit set can also be negative:
resulting in uneven ripeness or lower yields
rain creates humid conditions:
fungal diseases
Air that is low in humid:
Can provide evapotranspiration and therefore the potental of water stress
* associated with increased grape transpiration (more sugar accumulation)
The presence of water can moderate both diurnal and seasonal temp:
1) ocean currents can also incr or decr the average temp in the growing season
2) a lake or river can encourage breezes that are good against frost
3) proximity of water highers humidity level: so risk of fungal diseases (can also be benefical in some regions for wines made by grapes affected of noble rot)
Natural factors that effect water availability:
1) rainfall
2) characteistics of soil and land
3) evapotranspiration rate
Rainfall:
1) natural source of water for the vine
* amount and timing important
2) waterholding capacity of soil is important
Rainfall is caused by water vapour condensing and precipitating:
1) warm temp cause moisture from the land to evaporate rise
2) it cools and condense in the air and eventually raiin
** hail and snow can also be natural sources of water when they melt
Topography can have influence on patterns of rainfall:
1) mountain ranges can force winds of warm moist air upwards over high altitudes
2) this causes tha water vapour to cool, condense and precipitate
3) washington state: west of cascade mountains (Puget sound) is cooler and much wetter than the east of the mountains (columbia valley).
* plentifull rainfall in winter and dry early spring means that puget sound can dry farm
Characteristics of the soil can have a sign influence on the availability of water for the vines roots:
it depends on how easily the water drains, the waterholding properties (the function of the soils texture and organic matter content and the soils depth
Hawkes bay gravel soil:
1) hawkes bay receives around 800mm
- - extremely free draining nature of gravel soil causes the region to the need of irrigation
Jerez albariza soil:
1) 650 mm and virtually no rain in summer
2) clay soil that has good waterholding capacity and slowly release to the vine
3) also forms a crust when dry, reducing evaporation
Soils that retain some water can be advantageous, especially in areas of low rainfall.
Water logged soil (poor drainage) are harmfull to the vine
** reducing the amount of oxygen available to the roots, which slows their growth and eventually killing the vine
Topography also has an influence for water availability:
1) greater surface run off in veneyards on slopes
2) less water penetration: can be advantageous in regions with lot of rainfall
3) water run of causes soil erosion hence also nutrients
4) generally due erosion the soil on the slopes are very thin, limiting the area over which vines can obtain water and nutrients
Evapotranspiration rate is the amount of transpiration from the vine, combined with the evaporation of water from the soil surface
1) The rate at which water is no longer available
* either it has been taken up by the vine or lost to atmosphere
2) evapotranspration rate depends on temp, humidity and wine
- - hot dry windy weather leading to a greater evapo
* high evapo means the vine needs more water
* * therefore vines in dry, hot windy conditions needs more water
