Agriculture Reference
In-Depth Information
Grapevines also have specific temperature requirements. Grapes do not grow in the
desert because temperatures above 95°F (35°C) shut down the photosynthetic process. If
temperatures are less than 50°F (10°C), photosynthesis will also be inhibited. Somewhere
between these two extremes is the place to be. However, warm winters are not necessary
to have a vineyard. Grapevines are deciduous plants that go dormant in the winter. Cold
weather, ice, and snow do not have a negative effect on vines, except in cases of extreme
winter lows.
Grapevines also need water. As the roots absorb water, the moisture is drawn into the
leaves where it evaporates in a process known as transpiration. On the underside of each
leaf, there are microscopic pores called stomata, which evaporate the water drawn up from
the root system. Daytime sunlight induces the pores to open; at night they are closed. The
rate of transpiration is closely linked to the process of sugar production.
Interior leaves in dense canopies may be exposed to such low light levels that their
stomata do not completely open. So it stands to reason that leaves that are shaded have
lower rates of transpiration, less photosynthesis, and thus less sugar production. Exterior
leaves on a grapevine canopy are exposed to higher sunlight levels and temperature, and
thus transpire more than shaded interior leaves.
Maintenance of the vineyard is primary in order to encourage photosynthesis. I will
give you practical steps to take to allow the photosynthetic process to continue at the
highest possible rate. Remember, maximum photosynthesis creates maximum sugar, the
best fruit, and thus the best wine.
THE ORGANIC VINEYARD
An organic vineyard is one that is grown without the use of any synthetic fertilizers,
weed killers, insecticides, or other chemically manufactured products. To be able to sell
your grapes as organic, the vineyard must be certified by an organic organization such as
the National Organic Program (NOP), the National Sustainable Agriculture Information
Service (ATTRA), or the Canada Organic Regime. In addition to these federal organiza-
tions, there are organic and sustainable farming organizations at the state and provincial
levels.
Sustainability is a process of growing crops using practices that do not use up the nat-
ural resources of the land, but rather enhance and improve them. A sustainable farmer or
grower aims to prevent soil depletion and erosion, water pollution, loss of biodiversity, and
ecological impacts from crops. That means improving the texture and fertility of the soil
