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ISHS Acta Horticulturae 1136: I International Symposium on Grapevine Roots

The effects of sustained deficit irrigation and re-watering on root production and turnover in warm climate viticulture

Authors:   E.J. Edwards, A. Pearce, A.F. Lawlor, J. Pech, M.G. McCarthy, S.D. Tyerman
Keywords:   roots, minirhizotrons, soil cores, sustained deficit irrigation
DOI:   10.17660/ActaHortic.2016.1136.13
A five-year collaborative project by the Wine Innovation Cluster in South Australia was established to determine the effects of sustained deficit irrigation (SDI) on the carbon allocation in wine grapes and integrate this with water use. An area of particular focus was to understand the root system response to water availability in a whole vine context. 'Chardonnay' vines on Ramsey rootstock in an existing warm climate commercial vineyard were assigned to one of six irrigation treatments, each sustained for 1-4 seasons before being returned to full irrigation for 1-4 seasons. Minirhizotron tubes were installed in three of these, the 30, 50% and full irrigation treatments. Imaging of minirhizotron tubes was undertaken for the final three years of the five, providing data for a) the third year of SDI, b) the first year of full irrigation following three years of SDI, c) a fourth year of SDI, d) the second year of full irrigation following three years of SDI and e) the first year of full irrigation following four years of SDI. Minirhizotron imaging was matched with bi-annual soil coring, from which roots were extracted and root length and dry mass determined. Fine root dry mass demonstrated intra- and inter-seasonal differences, with 0.6-0.8 kg m-3. Root length density was not significantly different between seasons, averaging 4.5 km m-3 at veraison from the same samples. Over-wintering fine root length and biomass were reduced in the deficit irrigated treatments, with the effect increasing with increasing deficit. The impact at veraison was less, with reductions not significant. The minirhizotron data were surprising in that the lifespan of a given new fine root was generally greater than a single season, with many surviving for the duration of the experiment. The data also indicated that the rate of root deaths, relative to births, was lower under SDI than under control irrigation and that SDI effects on root length, observed in data from coring, were present in winter, but not during the growing season.

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