Análise foliar de diferentes combinações enxêrto-cavalo, para dez variedades de videira

No presente trabalho é feito um estudo comparativo do porta-enxêrto e da variedade através de seus efeitos na composição das fôlhas de videira, cultivada em canteiros sob condições comparáveis de solo, tratamento cultural e clima da Estação Experimental de São Roque, do Instituto Agronômico. Amostras de fôlhas de idade definida (a primeira madura, a contar da ponta) foram colhidas à época do florescimento, e analisadas para nitrogênio total, fósforo total, potássio, cálcio, magnésio e boro. Os dados obtidos permitem distinguir as variações de composição das fôlhas determinadas pela variedade-enxêrto e variedade-cavalo e o uso desta informação como base nos pesquisas para o estabelecimento dos índices de nutrição para a videira, pela análise foliar. A diferença encontrada nos teores dos elementos nutritivos nas fôlhas foi maior entre porta-enxertos do que entre variedades. Determinations of total nitrogen, phosphorus, potassium, calcium, magnesium, and boron were made on leaves of ten grape varieties on different rootstocks, growing in experimental plots under comparable soil, cultural, and climatic conditions. The youngest fully matured leaf was sampled at booming time. The influence of rootstock and scion on the principal nutrient elements in grape leaves could be summarized as follows: a) Rootstocks induced larger variations in the concentrations of nutrient elements in the leaves than did the scion varieties, b) Some of the rootstock differences were similar from one scion variety to another. This is illustrated for the highest levels of nitrogen and phosphorus on nearly all scion over the rootstock Rupestris du Lot, and for high calcium increases in leaves for most varieties grafted on the Riparia x Rupestris 101-14 rootstock. c) At least for potassium, the scion does have some influence on the composition of the leaves. The varieties Diamante Negro, Itália e Moscatel de Hamburgo had more potassium present in their leaves, regardless of the rootstock. d) Some characteristics are peculiar to some rootstock-scion combinations only, e) The range in leaf content of the various nutrient elements showed that potassium had the least variation and calcium had most variation among the macro-nutrient elements. Boron had more variation between samples than all macro-nutrient elements. f) The results suggested the need for different "optimum" values for certain mineral constituents when rootstocks and varieties are considered.