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February (No. 493)

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Grapegrowing Q&A: Real Viticulture with Ben Rose

Ben Rose , Performance Viticulture 1944 Kinglake Rd Toolangi, Victoria 3777

Real Viticulture is a regular column written exclusively for Grapegrower & Winemaker by Ben Rose, principal consultant of Performance Viticulture. This month, Ben responds to questions about increasing quality, and whether young Riesling vines should be allowed to carry fruit up to harvest.

I have a number of blocks of vines in which there is some vigorous growth but also some weaker growth near the tops of the hills. Many of the rows have both vigorous and weaker vines in them. How should I manage the block for the remainder of this season to get the best quality at harvest?

In a previous article I have mentioned my thoughts on “quality” versus “composition” and “style”. So to answer your question I will assume that you are referring to “composition” (the factors within the grapes as measured at harvest). The aim of all viticultural practices is to reduce the variation between vines within each block. In some blocks this is difficult as soil types and climatic factors differ along the rows.

The first element to look at is water management. Do all the vines need the same amount of water during the season and do they require it delivered in the same way? For example, a heavy clay soil may require fewer, longer irrigations, than a sandy or gravely soil that may require less water more often. Vines in high wind run areas (ie. hill tops) may require more-frequent irrigations. If your irrigation system is not configured to deliver water to each variation in soil and elemental conditions along each row then can it be modified to do so? In an ideal situation each variant would have its own irrigation valve so that it can be managed independently (or even better, original block design would take this into account), but this may lead to a large, unwieldy irrigation system.

Nutrition may also play a role in vigour and selective plant tissue analysis is a good way to begin (although this is better undertaken earlier in the season when results can be turned into corrective action). Soil analysis of different areas may also prove beneficial. Soil pathogens can also be analysed.
At this stage of the year a good way to reduce the variation within blocks of grapes is to split the block into two different sections. Mark out the weaker areas from the stronger areas and sample them separately. Estimate crop loads according to this division.
Continue to sample these separately, and discuss the option of harvesting them separately with your winery. At harvest, if there is a difference between the samples, harvest the parcels in the same pass, but keep the two areas separate and well identified. Deliver them to the winery separately and you should find that one parcel is significantly better than the other, and better than the sum of the two parcels if they were combined.

I planted grafted Riesling vines in November 2002 and developed a single trunk in that year (in a similar manner to your description in your first article). This year I have wrapped down some green shoots that will become my cordons for next year. All the Riesling vines have at least two inflorescences showing and quite a lot have 6-8 or more. Should the vines be allowed to carry fruit up to harvest? If so, how much? If some is to be removed, when should I do it? (ps. Given that I'm impatient to get some Riesling made into wine, I'm going to leave some fruit on whatever you say!)

Historically, viticulturists have insisted that young vines should not carry any crop until their third season, and then only a small proportion of their fully-mature crop load. Modern viticulturists have taken an economic look at things and have brought into practice new management techniques that allow a crop to be successfully produced in the second year, and a full crop in the third, without detrimental effects on the vines.

The amount that the young vines can carry will depend entirely on the vine balance, that is, the leaf area to crop-load ratio. In this second year, however, always remember that you are still trying to establish a framework and the production of strong shoots for pruning should be the main aim.

Provided that you have adequate leaves (12-16 per shoot) and good shoot lengths, I cannot see why you should not carry 1-2 bunches per shoot up to harvest.

If you were to remove crop the best time is dependant on what result you require. If you do not have enough shoot length then the earlier that you remove the crop the better, to allow the shoots to develop for winter pruning.

In a mature-vine situation crop removal should be undertaken prior to or at veraison to improve ripening characteristics (crop removal later than veraison may have little effect on ripening characteristics).

However, as it is often difficult to source enough labour to undertake crop thinning quickly at veraison, in my opinion it is better to begin a few weeks prior to veraison occurring.

Disclaimer:
Information in this article is general in nature and should not be construed as provision of comprehensive advice. Each vineyard site and management situation is different. Qualified, specific advice should be sought prior to implementation of any of the ideas discussed in this column.

Ben Rose is the principal advisor of Performance Viticulture. Ben has always been involved in wine and viticulture, growing up on the family’s Rising Vineyard in the Yarra Valley outside Melbourne. He graduated with first class honours in Agricultural Science at Melbourne University and spent four years with Yalumba Wines, as technical officer at Oxford Landing Estate and then as company grower services and nursery manager. Ben established Performance Viticulture seven years ago. He can be contacted on phone: 0500 836 773, fax (03) 8660 2238 or email: performanceviticulture@netspace.net.au



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