By Bart Arnst, Viticultural Consultant
The third set of Focus Vineyard field days has recently been completed, with the variation between regions and sites becoming clearer.
All regions had approximately 50 attendees, with both Marlborough and Central Otago dodging showers as a cool weather front moved up the country.
Wither Hills was fortunate that members of the Organic Winegrowers executive committee (James Millton, Jonathan Hamlet, Colin Ross, Rebecca Reider) were able to participate in the early part of the field day. They took questions from the floor, with undervine weed control options and the conventional vineyard’s use of systemic fungicides discussed.
At this point there appeared to be little difference between the organic and conventional treatments in the Sauvignon Blanc; however, in contrast, the Pinot Noir shows obvious differences. Vine vigour and leaf colour are markedly different in the Pinot Noir comparison blocks. (For more details and photos, see Jacqueline’s blog here.)
The conventional vines are more vigorous and have a much darker leaf colour, contrasting with the less vigour and lighter leaf colour of the organic block. It created an interesting conversation piece amongst the attendees on which block looked best for high end Pinot Noir production.
Mission Estate’s Mere Road block still shows no visible difference in treatments at this stage. Hawkes Bay turned on the best of the field days’ weather.
One interesting observation was made by Caine and myself whilst walking the organic section of Mere Road. Some reasonably sized roots which had been exposed by the undervine cultivator showed a distinct change in angle of growth (often an elbow of 90 degrees) where the root would have been meeting the wheel tracks in the mid-row. It’s often thought that because there is stone in the soil profile (in this case Gimblett Gravels) that compaction is not or is less of an issue; however all soils are susceptible in varying degrees. To check your compaction level, have a dig around with a spade, in the undervine, wheel tracks and mid-row; you’ll soon feel the difference.
Over time, increased soil biological activity in association with a lift in organic matter will alleviate the issues caused by compaction, however a ripper that breaks through the pan (compacted layer) will give a quicker result.
Gibbston Valley’s site on Bendigo Station is now fully netted with the multi-row system. Rainfall the evening and morning prior to the field day gave the visitors an appreciation of the erosion that can be caused by undervine herbicide. Many worms (dead) were observed on the headland tracks. Tim Jenkins, who is monitoring earthworms in the focus vineyards, theorised (via phone, email and photos) that these were “the grey field worm which were flushed out by the rain and perhaps drowned rather than dried out (given that they’ve retained shape). Exposure to light isn’t great for them either.”
Veraison was taking its time throughout Central Otago. The weather in February hadn’t been as consistently warm as the earlier months. Most bunches observed had a mixture of black, red and green berries, however in general the berry size within the bunch was consistent. In this situation if the berry size was inconsistent (hen and chicken) then there is the likelihood of the smallest berries splitting prior to harvest; this can lead on to botrytis issues and/or extreme brix variation within the bunch.