Irrigation (viticulture)

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inflorescence

In the case of irrigation in viticulture , an unusually large number of flowers or small berries are repelled from the stem. Normally the proportion of flowers that develop into berries is only 30 to 60 percent (= flow rate), depending on the grape variety. This is normal as there is no way the vine would be able to fully ripen all of the fruit. Irrigation is a fertilization disorder and belongs to the family of physiological disorders of the grapevine. The fertilization disorder can occur up to 3 weeks after flowering. The climatic conditions often play an important role during this time. As a result of the trickling, there is small berries and thus a reduction in yield. Some grape varieties such as Grenache , Malbec , Merlot, but also Ortega and Muscat Ottonel tend to trickle.

cause and effect

For the vines to bloom (stage 61 according to the BBCH scale for grapevines ), the mean daytime temperature must be at least 15 ° C, but preferably 20-25 ° C. When blooming, the flowers are pollinated . A berry set occurs when at least one ovule in an ovary is fertilized. Without fertilization through the pollen tube , only small, seedless berries (virgin berries) can form. In particular, the Huxelrebe and Gewürztraminer grape varieties tend to form virgin berries.

The trickling, i.e. the shedding of flowers or small berries, can have many causes. Common to all causes is a disruption of the carbohydrate supply in plant tissue:

  • Climatic conditions: Rain, cold, but also extreme heat during flowering can disrupt the development of the egg cell, pollination or fertilization.
  • Lack of light, strong defoliation of the vine, chlorosis or hailstorms during the flowering affect the supply of Gescheine with assimilates .
  • Nutrient deficiency or excess can lead to impaired fertilization. The boron plays an important role in fertilization. But a deficiency in the elements molybdenum , zinc or phosphorus also lowers the blood flow rate.
  • Unadjusted vigor (excessive or low growth) due to poor pruning , an unadjusted vine training or the wrong rootstock can lead to coulure.
  • The improper use of herbicides , too high a proportion of harmful gases such as sulfur dioxide , but also various harmful organisms such as the red burner or eutypiosis can be the cause.
  • Infestation by a viral disease such as B. the sticks disease .

activities

The Malbec grape variety is susceptible to trickling. The clone selection provides a partial remedy.

The winemaker's influence is limited. It is usually difficult to do without grape varieties such as Gewürztraminer , Merlot or Malbec . In the context of clone selection, however, it is possible to filter out less susceptible varieties of the grape varieties mentioned. Thinning out excess shoots can reduce the nutrient deficiency per grape. The tip of the shoots is a tried and tested means of shifting the carbohydrate competition from the tip of the shoot to the shell.

By choosing suitable rootstock varieties, the vigor of the vine can be adapted to the local conditions.

literature