The effects of water on tannin levels in grape development - Part three: Irrigation

In February I had the pleasure of speaking at the Oregon Wine Industry Symposium on a panel talking about grape and wine tannins. Anna Matzinger, Steve Price and I wanted to clarify what tannins are, how their levels in wine affect texture and structure of the wine, where tannins come from, the role of soil moisture on grape tannin levels and how harvest date affects quality of tannins.

I was tasked with talking about the relationship between soil water status and grape tannin levels. It was a great opportunity to improve my understanding of the relationship, and helped me come to terms with the difference between dry farming here in the Willamette Valley and the irrigated vineyards in Southern Oregon. On dry farmed sites factors like soil type, depth and texture, along with the seasonal rainfall have a profound effect on tannin level. In vineyards where there isn’t enough soil moisture to sustain the vines for the entire season, supplementary irrigation is needed. In those vineyards you have more control over the tannin levels of the grapes. To understand this topic and prep for my panel discussion, I studied three key disciplines: 1) soil science; 2) plant physiology; and 3) irrigation management.

Before I get into this I will say that I think the Internet is great for researching topics but I really like books.

PART THREE: IRRIGATION

By controlling the water applied to plants through irrigation you can study its effects on the growth of the vines, yield and also the fruit chemistry. In dry farmed situations it’s very hard to control the water therefore it is harder to study the effects of water on the vines and fruit.

There have been a lot of studies on irrigation management all over the world and the effects of varying irrigation levels at different points throughout the season. What researchers have found is that by applying less water than the vines are losing to ET between fruit set and veraison, you can control the vine growth and vigor, increase the exposure of the fruit and reduce the berry size. All of these factors help to increase the concentration of tannins and other phenolic compounds in the grapes, desirable in red grapes but less desirable in white grapes.

This understanding has led to wide spread adoption of the irrigation practice called Regulated Deficit Irrigation (RDI) and it is used to improve the quality of red wine grapes. To learn more about RDI visit this site: http://cru.cahe.wsu.edu/CEPublications/EM061E/EM061E.pdf.

Apr 22, 2016 at 3:26 PM Permalink

The effects of water on tannin levels in grape development - Part two: Plant physiology

In February I had the pleasure of speaking at the Oregon Wine Industry Symposium on a panel talking about grape and wine tannins. Anna Matzinger, Steve Price and I wanted to clarify what tannins are, how their levels in wine affect texture and structure of the wine, where tannins come from, the role of soil moisture on grape tannin levels and how harvest date affects quality of tannins.

I was tasked with talking about the relationship between soil water status and grape tannin levels. It was a great opportunity to improve my understanding of the relationship, and helped me come to terms with the difference between dry farming here in the Willamette Valley and the irrigated vineyards in Southern Oregon. On dry farmed sites factors like soil type, depth and texture, along with the seasonal rainfall have a profound effect on tannin level. In vineyards where there isn’t enough soil moisture to sustain the vines for the entire season, supplementary irrigation is needed. In those vineyards you have more control over the tannin levels of the grapes. To understand this topic and prep for my panel discussion, I studied three key disciplines: 1) soil science; 2) plant physiology; and 3) irrigation management.

Before I get into this I will say that I think the Internet is great for researching topics but I really like books.

PART TWO: PLANT PHYSIOLOGY

No one has written a better book on grapevine anatomy and physiology than Markus Keller: The Science of Grapevines, 2010. This was my go to resource for trying to understand how the plant responds to water.

Plants uptake water though their roots via osmosis. It is transported up the xylem to the leaves and out through the stomata. The negative pressure (tension) in the stomata pulls the water from the roots to the leaves. The tension in the leaves has to be greater that the tension in the xylem and the soil to effectively move the water. Therefore the tension in the soil affects the tension in the plant.

An increase in soil tension due to evaporation and transpiration (evapotranspiration or ET) causes a higher increase in xylem tension which, in turn, slows shoot growth and can stop shoot growth all together.

The drying of the soil also causes abscisic acid to be produced (ABA) in the roots. ABA is then transported around the plant where it has many effects.

1. ABA helps regulate stomatal conductance. An increase in ABA closes the stomata so the plant loses less water.
2. ABA works against Auxins which stimulate cell elongation and apical dominance. ABA production, like xylem tension helps to slow and stop shoot growth.

Apr 15, 2016 at 2:25 AM Permalink

Learning to Prune

I don’t have a green thumb. Far from it. I’ve been known to kill cactus. So you might imagine my apprehension when Karen, our Viticulturist, handed me her pruning shears as we stood in the REX HILL Vineyard this misty February morning. I didn’t anticipate our morning field trip and lesson in vineyard maintenance would involve hands-on practice.

Of course, I needn’t have worried. Karen showed us how she and our vineyard team prune back last year’s growth leaving behind a few select canes that will become the backbone for this year’s crop. The process is critical for regulating the number of shoots that will grow this coming season and for keeping excellent fruit quality. Winter pruning kicks off the year for the vineyard team and they work through the cold and the wet to ready the vines for another growing season.

Several factors are taken into consideration including cane thickness, location relative to the guidewires, and number of buds in order to decide what to cut, where to cut, and what to leave alone. Experienced workers can assess and prune a vine in a minute or two. I, on the other hand, took ten minutes just to confirm with Karen (twice) that I was cutting correctly. I didn’t want to add Pinot Noir to the list of plants that perished at my hand.

Thankfully, my vine is in good health (even after I was through with it) and has three healthy canes through which it will produce fruit this year. Is it Spring yet?

Feb 4, 2016 at 1:35 PM Permalink

Soils!

In celebration of the UN naming 2015 the International Year of Soils (IYS), I think it is only fair to write about soils; however, there is only one way to do it justice...a SOIL SERIES! So, we will be bringing a series of soil related blog postings that will hopefully get everyone just as excited as we are about soils.

To kick off the series, I'll share with you an epiphany I had while reminiscing about the soil classes I took during my undergrad: When describing a wine, many of the terms used to identify specific qualitites of that wine are shared by soil scientists when describing soils. Our Tasting Room Manager, my fellow Karen at REX HILL, and I have put together a table of descriptors for your enjoyment.

Jun 12, 2015 at 1:48 PM Permalink

Counting sheep at the Jacob-Hart Estate Vineyard

One hundred sheep joined our vineyard crew this spring to pitch in and graze the cover crop at our certified Biodynamic, estate vineyard, Jacob-Hart. They save on tractor work and naturally fertilize the vineyard but move on in the next few weeks as budbreak gets closer.

Mar 13, 2015 at 5:07 PM Permalink

Don't be afraid. It's SkySquirrel NOT Skynet.

The use of military drones has led to many a heated discussion of military ethics; however, as these devices make their way into agricultural industries, the only appropriate response is, "AWESOME."

Aerial imaging has been used in vineyards for many years to give growers an overview of the general health of their vineyard. Now you may be thinking, "Can't you just walk the vineyard and see weak areas?" Yes, but consider a vineyard like Jacob-Hart, with approximately 34 vineyard acres planted to 5x8 spacing. There are about 37,000 vines and aerial imaging allows us to see them all at once. Even better, companies specializing in scientific aerial imaging offer many imaging options including thermal imaging which identifies areas under stress as hotter than areas that are healthy (see image to the left). With basic knowledge of the site, you can often locate changes in soil type, location of recently planted blocks, disease hot-spots, drainage issues, and many other aspects that influence vine performance.

As you might imagine, this is neither an inexpensive nor quick service. So how does such a company make their services more available? Drones.

VineView, a scientific aerial imaging company based out of St. Helena, California, joined forces with SkySquirrel Technologies, a Canadian unmanned aerial system company, to bring drones to the agricultural community. The name of this joint effort is Aqweo, and it made its first appearance at the Napa Valley Grapegrowers' first ever ROOTSTOCK conference on November 13th. This marks an impressive step in the precision agriculture movement and, while there are currently some FAA restrictions that will delay commercial drone use in vineyards, I cannot help but get excited about where this technology will be in the next few years.

Dec 15, 2014 at 4:59 PM Permalink

Crop Load Study

We are currently participating in a state-wide crop load trial in collaboration with Patricia Skinkis at Oregon State University. It's a five year study that looks into the effects of yield, pruning weight and the Ravaz index on fruit quality (Pinot Noir). We are crop thinning to three different treatments:

1. Two clusters per shoot
2. One cluster per shoot
3. One cluster every other shoot

Crop thinning is performed 55 days post bloom.

At veraison, leaf blades are sampled to monitor plant nutrient status and to see if the crop load is affecting vine nutrient partitioning. The reference vines are all harvested at the same time, the fruit is weighed and the samples are collected for fruit analysis. Yields in each treatment vary from year to year and depend mostly on fruit set. We have found that there are some interesting correlations between yield and fruit chemistry, but we need another three years of results to draw strong conclusion.

Aug 19, 2014 at 3:30 PM Permalink

April First, Bud Burst

We’re off to a good start this season with a nice warm and dry spring.

No joke, the buds burst on the 1st of April, about 2-3 weeks earlier than average.

Apr 1, 2014 at 11:55 AM Permalink

Recycling Sprayer

REX HILL purchased the first recycling sprayer in Oregon and only the second on the West coast. This cutting-edge equipment is the most environmentally friendly sprayer available and will be used in the Biodynamically farmed, owned and long leased vineyards. It will reduce spray drift by 95% and cut pesticide use by 40%, which means less spray per application, less time filling up the holding tank, and less fuel usage.

REX HILL's new Recycling Sprayer at Biodynamic, Jacob-Hart Vineyard

GRAPE DISEASES

Wine grapes are unfortunately very susceptible to a number of diseases. This is our fault, as humans, for propagating them for thousands of years through mass selection and for transporting them around the world carrying diseases with them along the way. The main diseases that challenge us in Oregon are Powdery mildew (Erysiphe necator) and Botrytis bunch rot (Botrytis cinerea). The climate in California is favorable for these same diseases and others like Downy mildew, Pierce's disease and Phomopsis. There are many things we can do as farmers to reduce the impact of these diseases through cultural practices like canopy management. However, Powdery mildew, in particular, will destroy a crop if not controlled using pesticides.

WHAT WE DO ABOUT IT

It is important to understand that using the term 'pesticide' includes many categories like insecticide, fungicide, bactericide, rodenticide, and herbicide. These are named based on the target organism and not because they are organic or inorganic chemicals. In the case of Powdery mildew, we need to spray fungicides to control it. Fungicides are products or substances that help control fungal pathogens. Typically fungicides are sprayed by a machine that is towed behind a tractor. It has a tank, pump and nozzles that apply the fungicides to the canopy. Most sprayers use air to transport the liquid to the canopy. Unfortunately the air often carries a percentage of fungicides past the target which is wasteful and not great for the environment.

HOW WE DO IT

We have recently purchased a sprayer manufactured by LIPCO that is a recycling tunnel sprayer. This is the first unit to be sold here in Oregon. It sprays two rows of vines at once within a tunnel (so wind doesn't affect the coverage). A tunnel sprayer has walls that surround the vine on both sides of the trellis. Attached to the wall are the nozzles that spray the vine. The spray that travels past the target hits the other side of the tunnel, runs down to a sump and is pumped back to the tank. This collected fungicide is then applied again. Essentially the sprayer is a precision sprayer. The application rates vary with the canopy size and 95% of the liquid that doesn't stay on the vines' canopy is recycled. There is next to no drift of pesticides to neighboring properties, waterways or any other sensitive areas. Because we are spraying two rows at once we are now using less diesel, compacting the soil less and we are getting more coverage with less fungicide. We should reduce the amount of fungicides used by approximately 35% and our diesel cost for spraying should go down by 50%. These sprayers are not cheap but we are committed to environmental stewardship and want to be leaders in sustainability.

Apr 10, 2013 at 10:27 AM Permalink Comments (2)

Jacob-Hart Vineyard: Planting Out the Rocky Block

REX HILL’s Jacob-Hart Vineyard was planted in 1988 during the early years of the Oregon wine industry.  Situated on a southeast facing slope in the Chehalem Mountains AVA, the vineyard is certified Organic & Biodynamic and in a rare geological feat--it has every major soil type found in the Willamette Valley.

The unfortunate thing about Oregon’s old plantings is that they are self rooted Vitis vinifera. Now, there is nothing wrong with self rooted vines, in fact, many winemakers are convinced they produce better fruit. The problem with self rooted vines is that they are susceptible to phylloxera: a grapevine root aphid that causes vines to die. The only solution for a vineyard that is struggling with phylloxera is to replant it on a rootstock that can tolerate this pest. 

At our Jacob Hart Vineyard phylloxera was found in 1996 and ever since then it’s been slowly replanted. Martin Loeza, one of our Vineyard Managers, has worked at Jacob Hart since the beginning. He was there when the vineyard was planted in 1988. He has planted every block, some of them twice. He remembers planting 5E ‘the rocky block’ back in 1989. 5E was the hardest to plant and the hardest to farm but has consistently grown the best fruit in the vineyard.

In 2010 we got less than a ton per acre from this block and it was time to talk about replanting. I was discussing with Martin the replanting program, “I think 5E is going to be next.”   Martin didn’t like that idea, you could see the pain on his face just thinking about planting it again, he replied, “Oh no; maybe one more year.”

We wanted to retain the heritage of the block and use the clonal material (most likely Pommard)  that performed so well in that site. Before we pulled out the original Pinot Noir vines we took thousands of cuttings to be grafted onto a phylloxera tolerant rootstock called 3309. When it came to planting, we couldn’t use the typical augers because they only work in soil. We had to dig the holes by hand with shovels, picks, hammers and metal bars.  Putting in the line posts was worse.

Once the vines and posts were in it was up to Mother Nature to do the rest. There were nice bursts of sunshine and warmth in early spring to break the vines out of dormancy. We also had a couple of weeks of rain in early June to really water the vines in and keep them growing longer into summer. The summer however was extremely dry, with one of the longest dry spells in over 50 years. Thankfully we put in a temporary drip irrigation system to keep the soil around the vines from completely drying out and the vines from shutting down. We achieved great uniform growth across the block despite the rocky conditions and dry summer. All the credit goes to our great vineyard crew and the nursery for supplying us great vines. I’m looking forward to seeing some great growth next year!

Nov 30, 2012 at 11:03 AM Permalink Comments (2)