Doctoral Degrees (Institute for Wine Biotechnology)

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Browsing Doctoral Degrees (Institute for Wine Biotechnology) by Subject "Dissertations -- Agriculture"

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    Espacement studies on unirrigated grafted Pinot noir (Vitis vinifera L.)
    (Stellenbosch : Stellenbosch University, 1990) Archer, Eben; Goussard, P. G.; Stellenbosch University. Faculty of AgriSciences. Department of Viticulture and Oenology and Institute for Wine Biotechnology.
    ENGLISH ABSTRACT: The effect of vine spacing on root distribution, plant and soil water status, some physiological aspects as well as vegetative and reproductive growth of Vitis vinifera L. cv. Pinot noir, grafted onto 99 Richter (Vitis Berandieri var. Las Sorres x Vitis rupestris var. du Lot) was investigated. Vine spacings used were 1,0 m x 0 .5 m, 1,0 m x 1,0 m, 2,0 m x 1,0 m, 2,0 m x 2,0 m, 3,0 m x 1,5 m, and 3,0 m x 3,0 m. This trial was conducted on a medium potential soil without irrigation in the Stellenbosch district. Root density was directly affected by vine spacing and it increased and decreased with closer and wider spacing respectively. The larger contact surface between roots and soil in the case of closer spaced vines, increased the utilization of soil water and nutrients. This increased depletion of soil water, induced water stress earlier in the growth season with the result of a timely arrestment of shoot growth. This phenomenon brought about advantageous characteristious in canopy density and canopy microclimate. Vine spacing also affected cordon length per vine as well as total cordon length per hectare, thus affecting the distribution and orientation of the canopy. Closely spaced vines induced shorter cordons per vine, but the total cordon length per hectare was higher than that of widely spaced vines. Although a smaller crop was produced per vine in the case of closer spacings, the total yield per hectare was higher than in the case of wider spewed vines. In addition, a better potential for bunch nutrition was ensured by a higher leaf surface : fruit mass ratio in the case of closer spaced vines. The low canopy densities of closer spaced vines, together with a better water-supply early in the season (bud break to pea size) ensured a higher physiological activity than in the case of wider spaced vines. As the season progressed, however, this situation was reversed so that the shoot elongation of closer spaced vines ceased before that of wider spaced vines. This phenomenon was advantageous for bunch nutrition, affecting both grape composition and wine quality. The subterranean and above-ground changes brought about by closer vine spacing augmented both yield and quality. A better wine quality was obtained through a higher sugar concentration, lower acid concentration and better colour of the grapes. A higher yield per hectare stemmed from an increase in total cordon length per hectare. These results were realized for a medium potential soil without irrigation. More luxurious conditions will probably induce more vegetative growth, necessitating wider in-row vine spacing for the best yield and quality. The ideal vine spacing for a given locality is dictated by soil potential, rootstock and scion cultivar and cultivation practices such as irrigation and fertilization. It is probably wrong to standardise vine spacing for all vineyards on a specific farm.