The supply of water in the right quantity and at the best possible time is an important prerequisite for the growth of the vines and is indispensable for photosynthesis. This takes place naturally through precipitation (rain), the required amount is usually between 500 and 750 mm per year (depending on climate, soil type and grape variety). With ideal soil conditions, however, larger amounts of precipitation can also be absorbed. In Portuguese Vinho Verde, the amount of precipitation is around 1,500 mm. In addition to the quantity, the timing also plays a major role in the course of the annual vegetation cycle. The "right" amount of water is important; too little moisture can lead to water stress or drought stress, while excessive rain can lead to excessive vegetation (foliage growth).
Rain is particularly undesirable during the grape harvest and leads to poor wine quality due to the dilution of the grape must. In extreme cases, moisture stress occurs, in which the berries swell or even burst open, causing the grape must to oxidise or, in extreme cases, ferment. A similar phenomenon is berry splitting, which presumably occurs due to excessive alternation between too much and too little water supply. In addition, too much moisture promotes infestation by microorganisms such as fungi or bacteria. The soil moisture is measured using a tensiometer in order to take any necessary measures. In agriculture and horticulture, tensiometers are used in the automation of irrigation systems. The amount of water can be controlled in such a way that the plants are optimally supplied with water without water and nutrients...
