Proposição de doses e níveis críticos de nitrogênio e potássio em videiras

Abstract

When the soil does not have the capacity to supply enough nutrients to supplement the demand of the grapevines, it becomes necessary to carry out fertilization. However, it is not sufficiently known which the critical levels of nitrogen (N) and potassium (K) in leaves, and of K available in the soil, which may assist in defining the real need for application. But, it is also not known the best doses of N and K to be applied, aiming at high productivity, but also must with adequate oenological characteristics. The present study aimed to establish the best doses of maximum technical efficiency (MTE) and critical levels (NC) of N, in grapevine cultivars, aiming at maximum productivity and must with appreciated oenological variables, in sandy soils and subtropical climate. Two studies were carried out with Chardonnay and Pinot Noir cultivars, in scattered vineyards, in the municipality of Santana do Livramento (RS), region of Campanha Gaúcha. Study 1 addressed “Doses and critical levels of N in leaves of Chardonnay and Pinot Noir grapevines to obtain yields and must with desired chemical variables”. The treatments were 0, 10, 20, 40, 60 and 80 kg N ha-1. Study 2 dealt with the “Use of Bayesian hierarchical models to determine critical levels of K in leaves of Chardonnay and Pinot Noir grapevines and in the soil”. The treatments were 0, 20, 40, 60 and 80 kg K2O ha-1. In both studies, evaluations occur in the 2016/17, 2017/18 and 2018/19 crop seasons. Leaves were collected at flowering and veraison, to determine total N and K. Grape production and its components were determined. Total soluble solids (TSS), total titratable acidity (TTA) and total anthocyanins (TA) were evaluated in the must. In Study 1, the NC of N in the leaves during flowering to increase productivity were 21.35 g N kg-1 and 23.93 g N kg-1, for Chardonnay and Pinot Noir, respectively. While the veraison was 19.78 g N kg-1 for Chardonnay and 20.62 g N kg-1 for Pinot Noir. The MTE for Chardonnay was 49 kg N ha-1 in the 2016/17 season and 80 kg N ha-1 in the 2017/18 and 2018/19 crop seasons. Meanwhile, at Pinot Noir it was not possible to adjust the MTE. In Study 2, the NC of K in leaves during flowering and veraison did not differ between cultivars. While in the soil, the NC in the 0-10 cm layer were 41.4 and 44.9 mg K dm-3 and, 33.5 and 30.1 mg K dm-3, in the 0-20 layer, for Chardonnay and Pinot Noir, respectively. Could not adjust MTE for Chardonnay. For Pinot Noir, the adjustment for production was possible in the 2017/18 crop season, with a dose of 38.3 kg K2O ha-1.