Estratégias de fornecimento de nitrogênio em videiras em produção

Abstract

Soils with sandy texture and low organic matter have low nitrogen (N) availability, it is necessary supplemental applications to the vines. N is applied on the soil surface without incorporation, which potentiates losses by volatilization. Thus, it is necessary to use of alternative modes of N supply, such as fertigation or application of N followed by irrigation, which may increase N utilization by vines. However, it is not sufficiently knoSN the impact of N doses supply modes on grapevine growth parameters, nutritional status, production and grape composition. The work aimed to define N doses supply modes more suitable to be applied in vines at the beginning of production. Two studies were conducted in vineyards in groSN under the cordon training method of ‘Alicante Bouschet’ cultivar, grafted on Paulsen 1103 rootstock. The studies were located in Santana do Livramento (RS), Campanha Gaúcha region. Study 1 evaluated growth, yield, must composition and N losses by leaching, in a vineyard submitted to N application of recommended doses for the vine with different supply modes. The treatments were without N application (SN), application of 20 kg N ha-1 + 20 kg N ha-1 without irrigation (NSI), application of 20 kg N ha-1 + 20 kg N ha-1 followed by irrigation (NCI), application of 20 kg N ha-1 + 20 kg N ha-1 via fertigation (NF) and application of 20 kg N ha-1 via fertigation (½ NF). Leaves were collected at flowering and at veraison phenological stages, and determined to N concentration. Plants stem diameter was measured. Grape production and your components (number of clusters per plant, mass of 100 berries and number of berries) were determined. Total soluble solids (SST), pH, total titratable acidity (ATT) and total anthocyanins (AT) were evaluated in the must. Lysimeters with porous capsule were installed at 0.20 m a depth for the collect of soil solution and determination the ammonium and nitrate. Study 2 evaluated growth, yield and must composition in vines submitted to applications of N dose supply modes. The experiment was a two-factorial (dose x mode). N doses (0, 20, 40, 60, 80 and 100 kg N ha-1 year-1) were applied in three supply modes (application of N without irrigation - NSI, N followed by irrigation - NCI and N via fertigation - NF). The evaluations of this study were the same as those performed in Study 1, besides the cluster length and width, and total polyphenols (PT) in the must. In Study 1, vines submitted to NF and NCI modes were more advantageous to the N provided, because they presented higher N concentrations in leaves, higher stem diameter and yield, due to higher concentration of nitrate in the soil solution. However, the must had lower values of SST, TA and higher values of ATT. In Study 2, vines that had N concentrations greater than 2.75% in leaves at flowering and greater than 2.25% in the veraison presented 99% of probability to reach maximum grape production. The application of 35 kg N ha-1 was the dose that allowed the maximum technical efficiency, associated with the adequate concentrations of TA, PT and SST in the must.