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Variability in a vineyard is inherent. Best case scenario the variability was accounted for at planting, and the right varieties and rootstock combos were planted in a manner that takes advantage of the site. Worst case scenario – we’re not going to go there, but it’s not pretty. Regardless, even when a site is planted with the best of intentions, how you manage site variability, but especially intra-block variability, can make or break your fruit quality goals.
Fortunately, we live in an age of technological advancements in the agricultural space, and tools to help us understand variability are readily available. Now, if you have the budget to buy the flash new product that promises the moon, go forth and buy the Cadillac of tech. But there are affordable resources, that have equal if not better ROI, and in my opinion can provide growers with a clearer game plan for managing their site.
Playing the Hand You’re Dealt
When you inherit a vineyard, you’re forced to play the hand you get, but having a few cards up your sleeve can be a game changer. First things first, identify the things you cannot readily change – soils, variety, rootstocks, spacing, trellis, irrigation infrastructure, climate, et cetera. While these can weigh heavily on vine performance, there are still management practices that can push the dial in a direction that improves vine growth and wine quality.
If we ignore the qualitative benefits for a second, it can also be significantly less efficient to run a vineyard with variable vigour. For example, the vineyard may require an additional wire lifting passes to ensure vigorous shoots are contained, even though most of the shoots are not quite tall enough. This trend can continue with trimming (hedging) for those few vigorous hollows running across a block, when the majority of the block is not ready, to avoid disease pressure. Both of these “manage” the vines appropriately, but there are other/better methods that could reduce labour and tractor passes and increase fruit quality.
NDVI – Needs (some) Damn Vigour Intervention?
NDVI stands for Normalised Difference Vegetative Index. NDVI maps are a simple and accessible tool, regardless of budget, and are a real game changer for identifying zones. Keeping the poker analogy from earlier, it’s hard to play your hand when you can’t see your cards. NDVI, or other measures that visualise vigour potential, such as EM38, show you your hand so you can figure out how to best play it.
NDVI maps can be made with no specialised equipment, so they are my standard starting points when assessing a vineyard. Even a relatively uniform vineyard will still have small variations which can be picked up in an NDVI image. And while there are other mapping tools such as modern barrel pruning kit that can measure cane diameter (a good proxy for vigour), or mountable cameras that count canes or buds, these maps generally look very similar to an NDVI map of the block, but can be cost prohibitive, and require driving the vineyard to create a map.
Once an NDVI map is made, one can see how the various vigour zones of a vineyard (or future vineyard site) are laid out. This map becomes a powerful guide showing you:
Where to dig soil pits and sample soils for nutritional/textural analysis
Locations likely to be disease hot spots
Areas where fruit ripening will likely be more advanced or less advanced
And more
It’s important to keep in mind that these NDVI maps are a comparison of vigour between areas, and a tool to delineate zones, which needs to be put into context at the vineyard. “Low vigour” as represented on an NDVI may very well be the ideal growth for the fruit you’re wanting to farm, if the rest of the block is overly vigourous. Same with “high vigour” zones, if growth in the rest of the block is restricted for some reason be it nutritional, water, or rooting capacity. However, one thing holds true regardless – treating all areas the same will almost certainly guarantee that the variability will remain, just at a different level.
Tools to Smooth the Edges
Once you’ve decided what your ideal vigour zone is, it’s time to start thinking about ways to obtain the growth you want. Some remedies are easier than others, pans can be ripped, acid soils can be limed, deficient soils can be supplemented, etc. However, in alluvial soils, like many of those around NZ, the vigour differences are generally due to differences in silt deposition, leading to more topsoil in some areas than others over the river stones. Hillside often have lower vigour at the top and higher vigour at the bottom because of soil erosion down the slope, and water holding capacity differences. In these cases, it’s easier to manage areas differently in the vineyard than to try to even out the soil differences.
So what tools area there? Once the vineyard is set up and planted, you’re essentially limited to irrigation (if you have it), fertilisation, floor management, canopy/crop management.
Irrigation
The first lever I generally see managers reach for is irrigation. It’s a powerful tool, but a blunt one. When you turn on the tap, all the vines get the same water, unless your system is old and stuffed. This is only of use if water stress is limiting growth. It does not, in any way, even out variation, and generally the variation in growth is apparent well before vines need supplemental water.
Fertilisers
In my experience, especially in the early season, sluggish vine growth in specific areas of the vineyard is driven by differences in nutrition, not water status. Fert, depending on how it is applied, can be a tool to even out vigour. Fertigation has the same issue as irrigation though, with all the vines getting the same, so does not do anything to even out vigour. However, solid fert (including compost) or foliar fert can be applied in specific regions of need, and not across the vineyard as a whole. This can dramatically affect growth if increasing vigour is the intended goal. Given the skyrocketing costs of fertilisers and compost, being more efficient with their use by only applying where needed, will only become more important moving forward.
Vineyard Floor Management
Undervine and midrow management is something folks might not think of in terms of being vine vigour management tools, but they can have dramatic effects on vines. Allowing undervine competition, even just for the first few weeks of the season, can reduce vine vigour and pull an overly vigourous area back, making it easier to manage. In the Eastern US, much has been done on undervine cover crops as vigour management tools (Vanden Huvel and Centinari, 2021). Deep rooted and competitive midrow cover crops (such as chicory), have been shown to reduce vigour and improve wine quality in Cabernet Sauvignon in New Zealand (Wheeler et al, 2005).
And while I am a proponent of low till/no till when it comes to vineyard management, in extreme cases, ripping/discing/tilling, can be used as a tool to improve nutrient availability for a brief point in time, which can help in those extreme cases.
Pruning to Capacity
Pruning can be another way to modulate early season growth by leaving more or fewer buds into which the vine’s energy is divided. Here in New Zealand we cane prune most vineyards, but how many canes we lay down for next year can vary. By laying different cane/bud numbers (or even a “kicker cane” you’ll remove later) based in the vigour potential of the area of the vineyard, early shoot growth can be evened out, making operations like trimming and wire lifting more efficient.
It's also important to note that balanced pruning for the vigour potential of your site, in the absence of other inputs, can both increase crop load and fruit quality. Laying 3 or 4 canes at pruning in weak area of a block can produce less crop than a vine with 2 canes in that same area due to proper balance of vegetative demand and available resources.
Crop load Management
Finally canopy management and crop manipulation in specific areas can be used to make sure you get optimum ripeness and quality; however, these can require hand labour that is increasingly more expensive, and in some cases, in short supply. Ideally, by managing vigour earlier in the season using some of the other levers I’ve described here, the need for these “band-aid” remedial actions can be minimised.
While zonally managing crop load may be too extreme for some. Zonal sampling is easily implemented, and can help vineyard managers and winemakers accurately sample to ensure the fruit across all zones averages to the desired spec at harvest when the block is picked.
What does it all mean?
Making educated management decisions and practicing thoughtful viticulture does not need to be time and/or cost prohibitive. As many of you have experienced, management changes can take time to show their full effects, and even then, what is readily visible is not the whole story. But even small changes can have a big impact, and even if you don’t have the cool new shiny tech at your disposal you can still make educated decisions and grow great wine.
If you’re interested in having NDVI images made of your blocks, or to discuss zonal management strategies based on them, please reach out.
Cited Works
Bramley, R. G. V., Trought, M. C., & Praat, J. P. (2011). Vineyard variability in Marlborough, New Zealand: characterising variation in vineyard performance and options for the implementation of Precision Viticulture. Australian Journal of Grape and Wine Research, 17(1), 72-78.
Vanden Heuvel, J., & Centinari, M. (2021). Under-vine vegetation mitigates the impacts of excessive precipitation in vineyards. Frontiers in Plant Science, 12, 713135.
Wheeler, S. J., Black, A. S., & Pickering, G. J. (2005). Vineyard floor management improves wine quality in highly vigorous Vitis vinifera’Cabernet Sauvignon’in New Zealand. New Zealand journal of Crop and Horticultural Science, Vol. 33. 317-328.
Other Helpful Resources:
Harvard Business Review. 01 April 2024. https://hbr.org/2024/04/are-you-a-micromanager
Harvard Business Review. 11 Nov 2014 https://hbr.org/2014/11/signs-that-youre-a-micromanager?ab=at_art_art_1x4_s02
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