Viticultural experimentation using whole blocks: evaluation of three floor management options

Abstract

Background and Aims: Vineyard floor cover crops can affect vine vigour because of their requirement for soil, water and nutrients, as well as their interactions with pests and diseases. An on-farm trial was established to identify the best floor cover management for an organically certified vineyard in the Clare Valley, South Australia, which was characterised by low vine vigour and yield. In establishing this trial, we also sought to evaluate a new approach to field experimentation in which the entire management unit is used for the experiment rather than small plots. Methods and Results: Three different floor covers were compared: the existing ryegrass cover crop with compost under the vine (control), ryegrass with mulch under the vine, and a replacement of the ryegrass with alternating mid-rows planted to either cereal (Triticum triticosecale) or legume (Vicia faba), in both cases reverting to bare soil during summer. Spatially variable treatment differences were evident in the second and third year of the trial. The greatest benefits, in terms of enhanced yield and vine vigour, were induced by the cereal/legume treatment, although it was shown that only about half of the experimental area (i.e. only half of the entire vineyard) would have increased yields with the adoption of such a floor management strategy. Conclusions: The whole-of-block approach offers both researchers and vineyard managers a means of acquiring considerably more useful information than would be obtained from a conventional plot-based experiment. In this particular vineyard, differential management with ryegrass retained in the southern part, but with the cereal/legume cover crop used in the northern part, is the ideal management practice. Significance of the Study: This study provides a novel demonstration of an approach that makes use of spatial variability as an experimental tool, and which enables experimental results to be acted upon in a way that recognises and exploits the underlying spatial variability of the vineyard.