How and when to fertilize grapes – fertilization requirements for vineyards.

In general, at the beginning of the growing season, plants need more nitrogen to promote foliar growth and for photosynthesis. During fruit growth, plants need potassium to produce well-shaped grapes. Phosphorus is always needed, as it plays an important role in the transport of nutrients. In addition, in the first few years after planting, phosphorus helps the plant to develop a healthy root system. In many cases, young plants established on acidic soils are unable to use phosphorus effectively. For this reason, many farmers apply P2O5 before sowing. calcium controls the ripening process and colouring of the fruit and is very important for producing uniform grapes.

The first fertiliser application is made at the end of winter (February). Many farmers apply well-rotted manure and plough with a furrow opener. A few weeks later, farmers may apply urea at the beginning of the growing season to help the plants develop larger foliage. Other producers use a foliar application method based on nitrogen. Other farmers also apply a balanced slow release granular fertiliser (12-10-20 (+28) + 2MgO + ΤΕ - 500 kg per hectare - 12 weeks release) at the start of the growing season to allow the plants the right amount of time to gradually absorb the nutrients. In many cases, producers apply KNO3 at ripening. potassium is also thought to help grapes achieve an intense red colour. (Please note that 1 hectare = 2,47 acres = 10.000 m2 and 1 tonne = 1,000 kg = 2,200 lbs.)

Some farmers use seaweed extracts (brown algae), while others apply nano-sized calcium-based fertilisers, especially on alkaline soils. A study showed that the application of nano-sized calcium-based fertilisers led to a significant increase in leaf development and chlorophyll concentration in vines cultivated on alkaline soils. The application of seaweed extract also increased the zinc chlorophyll content of grape leaves. You can read more about this here.

The type and amount of fertiliser required for a vineyard depends on many different factors. The type of soil, the age of the plant, the training system, the environmental conditions, the variety, and the type of vineyard, are all key factors. Plants have different nutritional requirements at different stages of development.

As the plant reaches maturity, the demand for potassium is increasing, while the demand for nitrogen is minimal. At this stage, the plant channels its nutrients to the fruit to increase its sugar, phenolic and aromatic content.

The timing of fertilisation varies from vineyard to vineyard. For example, in wine vineyards without irrigation, some producers prefer to apply the full portion of fertiliser as a slow-release top dressing during the winter. In irrigated vineyards, they use 50% N and K and 75% P and M as top dressing. They apply the rest of the nitrogen and phosphorus after the fruiting stage and the rest of the potassium in 3-4 applications. In areas with soils containing high levels of calcium carbonate, there is a risk of iron deficiency. Producers can therefore provide chelated iron by applying fertiliser or by using foliar sprays. Foliar fertilisation can help us to address short-term iron deficiencies very quickly. However, it is not usually a substitute for other types of fertilisation. Soil fertilisation usually has a more lasting effect.