Growing grapevines requires regular fertilization by which the grapevine is compensated for nutrients removed by yields or grape harvest, but it is also the source of supplies of all those nutrients lacking in the soil in order to ensure regular yields of good quality. The basic fertilization of vineyards with NPK fertilizers is best done in autumn after the harvest, due to the deeper treating of vineyard in the autumn so the nutrients from mineral fertilizers penetrate deeper into the soil. During the autumn and winter, the applied nutrients dissolve through the entire treated soil layer and are thus closer to the roots of the grapevine. The grapevine root grows during the winter, it absorbs nutrients from the soil that produce supplies in the root and overhead parts of the grapevine. In the spring when the vegetation starts, this reserve feed, collected from autumn to spring, is used for growth and development of green shoots and formation of buds on the shoots. If the fertilization of the vines was postponed for spring, the effect would only be to increase the size of the berry and the weight of the bunch; the number of shoots and the number of bunches of grapes would not be greatly affected.
Grapevine is a major consumer of potassium that positively influences the accumulation of sugar in grape berries, increased resistance to drought, fungal infections, mechanical pressure, and winter exposure. Phosphorus is important in the initial stages of growth and development because it stimulates root development, thus strengthening the root and overall vine, reflecting on the condition and increased resistance to high and low temperatures. Good nutrition with phosphorus has a beneficial effect on the formation of flowers in buds, early ripening of grapes and more complete ripening of the vine. When lacking, the yield and quality of the grapes are reduced and in the spring the vegetation is late. However, very often in vineyard soils, phosphorus is blocked and unavailable to plants due to the extreme acidity of the soil. In such soils it is necessary first to solve the acidity problem, i.e. to perform soil liming.
For basic fertilization of vines NPK fertilizers are used with a lower nitrogen content, and a pronounced phosphorus and potassium content, such as NPK 7-20-30 or NPK (MgO, SO3) 7-14-21 (2, 18), whose ratio of nutrients meets the needs of grapevines.
For a medium yield of grapes of 10 t / ha it is necessary to apply 100-120 kg / ha of nitrogen (N), 50-100 kg / ha of phosphorus (P2O5) and 85-170 kg / ha of potassium (K2O) into the soil. So on soils moderately well-supplied with phosphorus and potassium, 500 kg / ha NPK 7-20-30 or 700 kg / ha NPK (MgO, SO3) 7-14-21 (2, 18) is applied. This amount of fertilizer meets the annual needs of grapevines for phosphorus and potassium. A smaller amount of nitrogen that is introduced will be used by the vine for growth and development of the root during the winter period.
Along with regular fertilization with mineral fertilizers, account should be taken of the content of organic matter in the soil. That is why vineyard should be fertilized with mature manure fertilizer once in three or four years, in the amount of 30-40 t / ha. Another organic fertilizer can be applied instead. This has favorable impact on the stability of the soil structure, microbiological activity, water-air and heat conditions in the soil, i.e. on the total fertility of the soil.
If basic fertilization is not done in the autumn, it should be done in winter when the weather permits, but it should certainly be done before the vegetation starts in the spring.