Water into Wine

Jesus made it seem easy – but he wasn’t dealing with a rapidly changing climate!  In this post I will discuss a project on optimizing irrigation efficiency in the Coonawarra region.  Located 4 hours southeast of Adelaide, Coonawarra is primarily known for producing quality Cabernet sauvignon, but it has much more to offer than just cab (as I quickly discovered by sneaking in a few tastings after field work).

Spatial variability is inherent in vineyards, which can be attributed to differences in soil type, variety, rootstock, disease, etc.  This means that the vines won’t all grow the same or be equally healthy across any given vineyard.  Technology that reveals vineyard variability can allow growers to allocate their resources more efficiently by adjusting inputs like water and nutrients.  Additionally, technology that provides continuous data on the vines’ physiological status is useful in making well-timed irrigation decisions.  The goal of this project is to characterize the spatial variability and provide growers with continuous information. Such monitoring capabilities are incredibly valuable to any viticulturist, especially given the increased likelihood of severe droughts and extreme temperature events due to climate change.

We visited the site twice in February – the first time we installed infrared canopy temperature sensors (prototypes built from scratch by Joe Hu, one of Vinay’s masters students) and the second time we went to troubleshoot the sensors and take physiological measurements.  Simultaneously, a plane flew overhead capturing NDVI (normalized differential vegetation index, essentially a measure of “greenness” that can indicate vine health) and thermal images of entire vineyard blocks.  The basic idea is that the infrared canopy temperature sensors will provide similar data to that of the plane, except it will be continuous (recording temperature every 10 minutes) and less expensive than flying a plane.  Also, the plane gave us an initial idea of each vineyard’s variability, so we installed some canopy temperature sensors in areas of interest where the vines looked particularly stressed.  We also performed Vinay’s classic suite of field measurements: gas exchange, pre-dawn and midday water potential, chlorophyll content, and FLIR thermal imaging.  We are now completely drowning in data!  But it’s great, we are learning so much about what’s going on at a macro and micro level in Coonawarra.

 

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Joe took a very artsy shot of one of his canopy temperature sensors, complete with its solar panel

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Me measuring stomatal conductance with the porometer

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Vinay having success with something – sometimes all you need is a little duct tape

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Joe hard at work fixing one of the more stubborn sensors

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A picture of the airplane taking pictures of us
 

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Alien signs in the backyard?

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Nope, just reflective crosses to mark reference points on the images from the plane
Aside from the Coonawarra project, we are very busy.  We harvested the Sauvignon blanc from Riverland (that in-canopy mist experiment was discussed in my prior post) and made the wine.  Vinay has also gotten me started on my own small experiment in which I will compare how certain varieties respond to high temperatures in different ways.  This involves a lot of stem water potentials and gas exchange.  I was initially intimidated by the LICOR (gas exchange machine) with its millions of buttons and settings, but it is quickly becoming my best friend in the field.  I have to forget that it is more expensive than a Ferrari, though, or I get all nervous about touching it.

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Sauvignon blanc harvest

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Fran celebrating the last pressing of Sauvignon blanc
In other news, the Adelaide Fringe Festival has just kicked off – this is the biggest arts festival in the southern hemisphere and apparently the second biggest in the world.  I attended the opening parade and an acrobatics show so far, both were pretty cool.  I’m going to try to go to as much of it as I can in between all the harvesting, winemaking, field measurements, and data analysis.

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The Fringe Festival opening parade

Oh, and spiders here are huge.  And they’re all over my house, and I don’t know if I will ever be ok with it.

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I caught this one trying to sneak under my bed, then played digital dress up with it in revenge
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I hope I explained everything clearly in this post, but please let me know in the comments if you have any questions!

 

 

Greetings from Oz

It has been one month since I arrived in Australia! I enjoyed a few weeks of travel before I began research (Taiwan → Sydney → Tasmania → Melbourne → Great Ocean Road → Adelaide) and now we are in a frenzy of data collection.

First, I’ll give a little background as to why I’m here and what I’m doing:  I am one of the lucky recipients of the Fredrick Dreer Award, an incredible opportunity granted to me by the Horticulture Section at Cornell.  I am working with Dr. Vinay Pagay at the University of Adelaide, Waite Campus.  His lab is on the cutting edge of vineyard technologies that will allow us to better understand and manage the effects of climate change on vines and wine quality.

Some of the projects Vinay’s lab is working on include:

  • Detection of biotic and abiotic stresses in grapevines using proximal and remote sensing techniques
    • The effect of heatwaves on aroma compounds in Sauvignon blanc
    • The effect of heatwaves on phenolic compounds in Cabernet sauvignon
    • Continuous in situ measurements of plant water status using a micro-tensiometer

I’ve had the opportunity to help with most of the experiments already.  I’ll explain a few of them to the best of my understanding so far.  It is also worth noting that this has been an incredibly wet year for South Australia and so while the vines are experiencing some degree of heat stress, this is by no means the normal amount of precipitation received during the summer months.  Growers are hedging vines multiple times this season and battling outbreaks of powdery mildew and downy mildew (the latter is rarely encountered here).  The climate is becoming predictably unpredictable, that is for sure.

The Sauvignon blanc trial is located at a commercial site in the Riverland, a region 2 hours north of Adelaide and mostly known for bulk production.  Wen-Ching Huang, one of Vinay’s masters students, is leading this trial.  The experiment uses in-canopy misters to cool the leaves and bunches during high temperatures.  The misters turn on for 15 seconds every 10 minutes when ambient temperature is above 35°C.  We installed thermocouples (temperature sensors) on the leaf blades and inside bunches to monitor changes in temperature that occur when the misters turn on and off.  Basically, the thought is that the water from the mist will create an evaporative cooling effect in the canopy during high temperature events.  We know that temperature indirectly affects the production of secondary metabolites (C-6 alcohols, pyrazines, thiol precursors, etc, all important to the varietal character of quality Sauvignon blanc wine) by directly affecting primary metabolites.  So far, data is showing an 8-10 °C temperature drop on leaves and bunches immediately after misting!  The next step to see if these desired compounds are present will be berry and juice analysis with gas chromatography.  We also collect data on midday stem water potential, predawn leaf water potential, and leaf gas exchange with an Infrared Gas Analyzer (IRGA).  The IRGA data gives us a measure of the stomatal conductance – this is important to consider alongside water potential measurements because it can indicate if the vine is actually respiring or not, providing a realistic assessment of stress.

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Measuring midday water potential during a heatwave last week (it was 40 degrees C!)
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Measuring predawn water potential at 3am on a Saturday morning – nights are chilly!
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The thermocouple data logger box.  The thermocouples themselves are just very small wires run through the canopy.
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The LI-COR infrared gas analyzer (IRGA).  A leaf is clamped into the front.

Phew!  That was just the description of one experiment!  I guess I’ll save the others for future blog posts – there is no shortage of information to share.  I’ll briefly discuss a protocol I learned to assess berry cell death (because I have a cool picture of that), then save the rest for next time.

Berry cell death is being looked at intensively by one of the other labs here, the Tyerman lab.  It results in decreased fruit quality and yield loss (up to 30% in some cases).  Ideally, it can be mitigated by increasing irrigation during times of vine stress.  There are two ways to measure berry cell death (or berry cell viability, if you want to look at it glass half full!).  You can use electrical impedence and/or cell staining with a fluorescent dye.  I learned how to do both, and hopefully we will incorporate this data into the findings of the Sauvignon blanc and Cabernet sauvignon experiments.  Impedance works by measuring electrical current through a berry – low impedance indicates high cell death, while relatively high impedance indicates low cell death.  Staining the mesocarp with FDA (fluorescent diacetate) and putting it under UV light gives a visual of berry cell death.  We can input this image into a computer program that will measure the area of green (live cells) vs black (dead cells).  It is important to exclude the seeds from the measured area (they show up as the large kidney-bean shaped black masses).  It’s kind of like doing a berry xray!

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Measuring impedance.  Yep, those are legos!
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FDA stained berry under UV light