Things that change fruit ripening

I've talked about fruit thinning before, and here's another missive.

Common in commercial practice is to do thinning at colour change, so that you can remove the fruit that is less-advanced in ripening - i.e. the stuff that hasn't gone through veraison as soon as the bulk of it.

When you do this, you're advancing the maturty of the harvested fruit. However, this is only so because you have removed that tail end of the fruit -all the stuff that's less ripe, so that the average brix is higher, and that carries on through to harvest.

But, what if you remove fruit randomly at that point in the season? I don't believe you will see much of an effect on Brix at harvest, if at all.

I think this is because regardless of how much fruit is on the vine (within reason!), the rate at which it will accumulate brix won't change much. The conduit for the sugars to pass through is the phloem, and under the conditions in the vine during ripening, sugars are already moving through and into the berry as fast as they can. Removing fruit might mean the vine has more carbohydrates available, but that doesn't mean that the pipes (phloem) leading to the berries can push more sugar into the berry. There is a limit!

In fact, there is evidence that the size of fruit is related to the diameter of the stem that leads to that fruit (i.e. a larger number of pipes leads to a larger fruit), such as this paper working with citrus. This doesn't necessarily mean cause and effect, but it is a logical conclusion.

It might also mean that if you think the fruit early enough (within a couple of weeks post-fruit set), you might be able to enhance the ripening of the fruit because the pedicels can grow larger due to the greater amount of carbohydrate available? I wish I knew the answer to that question!!

Water footprints - another eco-measure

Radio New Zealand had an article about water footprints a while ago, which stated that 109 litres of water is used to produce the average glass (125ml) of wine (see the article that prompted it all here). This is not the first time this has been in the news - I found this article in the Economist from back in Feb 2009 and a column from The Wine Economist from late 2008, which cites a special issue (December 2008) of the Wine Business Monthly on the topic...

Water use is a hot topic, both in terms of how much is used, but also what to do with the water afterwards. In fact, there is an internationally focussed meeting about this, specifically aimed at the wine industry, being held in Blenheim later this year (6th International Specialised Conference on Sustainable Viticulture: Winery Waste and Ecologic Impacts Management)

The Radio NZ article was brief, and I didn't hear the audio version of it, but I was intrigued, as figures like this are hard to interpret without knowing what goes into calculating it. So I wrote to Dr. Ranvir Singh, who is a Senior Lecturer in Environmental Hydrology and Soil Science at the Institute Of Natural Resources, Massey University to see if more information was available.

He very kindly replied and pointed me toward reports from the Water Footprint Network, who have published reports on global average values for water "use" for various crops and for animal farming. They were also the organisation behind the 2009 article, which quoted the values as coming from a report by Peter Gleick, who got his data (Table 19) from Waterfootprint.org.

So what is a water footprint? From the Water Footprint Network, it is "a spatially and temporally explicit indicator of direct and indirect water use of consumers and producers."

What does this mean? Similar in concept to the Ecological Footprint, and its sub-category the Carbon Footprint, the Water Footprint attempts to track all actual and "virtual" water use in the production and life of a item.

It's pretty easy to calculate the amount of water that is applied to grapevines, for example, and then set that against the tonnage of grapes harvested and the amount of wine subsequently made. And it's also reasonably straightforward to estimate the amount of water used in the winery through processing of the grapes into wine. There's even the opportunity to take into account the water used in the production of the labels, corks/caps, cardboard boxes etc. and add that to the total.

However, what is virtual water? Well gracious me, Wikipedia has an entry on that, too! The definition they quote there is “the volume of freshwater used to produce the product, measured at the place where the product was actually produced”

Getting back to our 109L per glass, that equates to about 870L of water per litre of wine. Let's look at what the vine contributes to that total.

Grapevines can typically use a couple of litres of water per day during the peak of the growing season, but use less in the Spring and Autumn as the temperatures decrease. So to allow some fudge-factor room, figure maybe 5 months of using 2L per day on average (either water in the soil or water applied through rain or irrigation). That's about 360L per season for the vine.

The amount of fruit a vine will produce varies a lot, but if we look at a typical Sauvignon blanc vine it might produce 4.5kg of fruit (this value varies a lot with vine spacing and other factors, but let's keep it simple...). In the winery this will probably equate to almost 3 litres of juice, which most likely will turn into about 2.9L of wine. So the vine itself is using about 124L of water to produce a litre of wine.

So that's about 14% of the total suggested by the report. The other 76% must come about from the winemaking process, packaging and other items used during the growing of the grapes and production of the wine.

 Flood irrigation has a low capital cost to install, but is not suited to all areas, and quite a bit of water can be lost to evaporation, rather than getting to the vine roots.

However, some studies suggest that daily vine water usage can be upwards of 60 litres per day (e.g. here)! Yes, this is not the average over a season, but in a dry area with vines having a high crop load, the daily average might be quite a bit higher. All of a sudden, the vine is contributing a lot more to the total virtual water use, maybe doubling, tripling the value, or even more.

In-line drippers deliver the water to vines much more efficiently than flood irrigation

So what should we make of all this? With any model system, such as what they are doing with the water use studies, there are a lot of assumptions that need to be made - if there weren't the models would be far too complex to actually use. We've demonstrated with relatively simple calculations that there can be wide variation in the final number depending on the numbers going in.

So taking a value you might hear somewhere doesn't really mean an awful lot until you start investigating what went into the calculation of that number, and understanding how it comes about.

That is, with thy wine, take a grain of salt.... :-)


Here are some links of potential interest on the topic of water use:

Sonoma Wine Company, Graton Facility - A winery that was successful in reducing their water use

New Recycling Technology Turns Winery into Water Saver
A winery re-using water that has come from the winery


Wine Business Monthly article on winery water use

Sustainable Farming Fund project looking at benchmarking water use in the vineyard

Water use efficiency of table and wine grapes in Western Cape

Frosts in California (and elsewhere!)

I have mentioned frosts before (August 14 and October 17, 2009), but some recent news brings this subject up again.

Early season frost is a big problem in New Zealand, but also in a lot of other growing regions around the world, such as in Ontario, which I've talked about before. The latest news from California, in an article from Western Farm Press, details the aftermath of a couple of frost events on April 8-10 in areas south of San Francisco. Damage estimates suggested that about one-quarter of the 10,500 hectares of grapes in the Paso Robles area will have a crop that won't be commercially worth harvesting.

Any grower worth his weight in quality secateurs should know what the frost risk is when looking to develop a vineyard, and if the risk is perceived as being great enough, some sort of management system will be planned for the development

Results of a severe spring frost - all green tissues of the vine are completely decimated

If the frosts are mild, then passive means, such as having bare soil between the rows in the spring, which will maximise heat accumulation during the day and release at night, can give from 0.5 to 1.0°C protection (of course, careful decision making in site selection is the best means of passive management!).

Active means of management include such things as taking advantage of an inversion layer (where a layer of warm air sits above the cold air at vine level, and which tend to form on still nights with clear skies) and sending up a helicopter to push the warm air down to mix with the cold.

However, if the frosts are very frequent, then installing a permanent system becomes cost effective, such as the wind machines I've already written about, or using water sprinkled over the vines.

A frost fan installed in Central Otago. Plenty of snow-capped mountains around the area!

There are some big differences between the wind and water methods. The movement of air method relies on mixing the warmer air in an inversion layer with the cold air on the ground. This works great unless 1) the inversion layer doesn't have enough warm air to raise the temperature of the cold air to above freezing or 2) there is no inversion layer.

The former is heartbreaking, as you might be successfully fighting off the freezing temperatures, then just before dawn and the temperature rise that comes with it, the inversion layer is all used up and the grape buds freeze.

The latter has the same outcome, but then you don't have to spend all night running around trying to combat the frost!!

In some cases, the conditions are not right for an inversion layer to form, or the cold might be coming in as a mass of freezing air, for example, from nearby hills or mountains that have recently been covered by snow (this appears to be what happened in California recently). In this case, since there is no warm air around, fans and helicopters won't help. However, the application of water to the plants will work for all types of frost events.

The idea behind the application of water is that as water goes from liquid to solid form (freezes) it releases heat (heat of fusion).

So as long as water is freezing on the plants, heat is being released, effectively keeping the temperature at 0°C. Plant tissues can survive this temperature and even a bit lower without damage, so as long as enough water is supplied to always have some in the process of crystallising, the ice, and grape buds or shoots inside, will be kept from temperatures that might damage them.

Two types of post-mounted micro-sprinklers - these use quite a bit less water than the traditional impact-type overhead sprinklers

The down side is that if enough water is not applied, the temperature can continue to decrease, so if the application system breaks, or the water runs out, before the air temperature rises sufficiently, you can lose the new growth.

In the foreground row visible in this picture there is a number of vines where less growth is visible. This is because the sprinkler at the top of the post (centre left in the photo) failed during a frost event, meaning that the vines were not continuously covered with water - thus once the freezing stopped, the temperature of the ice and tissues within dropped to damaging levels. Note that there is a frost fan in the background - the fan isn't able to cover the area that these vines are in, so the sprinklers were put in to provide protection there.

My preference, if I were to plant in an area that was prone to frost events, would be to use water sprinklers. However, in some cases there wouldn't be enough water available for this. Large dams can be build to provide a source of water, but sprinkling even a hectare of ground with water for a decent frost can require up to 40 cubic metres of water per hour depending on the system used!

The concerning thing is that with global changes to climate, we should be prepared for more extreme weather events - in this context, we need to be ready for more severe frosts later in the season. Seeing as how some grape growing regions in New Zealand can have a potentially damaging frost in almost every month of the year (historically, anyway), this isn't good news!!!

Hands up those who thought being a viticulturist was a cushy job!!

Thoughts on vine density

A student asked this question today, and I spent some time on a reply. A good topic for discussion (and final exam questions??? :-)

"Can you explain why low potential soils need closer vine spacing to optimize the yield and quality and soils with higher potential need wider vine spacing?"

"My understanding is that higher soil potential leads to high vigour of the vine and should increase the density of the vine to manage that right? So therefore high potential soil should have closer spacing than the low potential soil."

My answer:

Vine spacing is one of those things that you should really try to get right when you're planning the vineyard. It's one of the reasons why detailed soil surveys are done before vineyards (incorporating variety, trellis, rootstock etc.) are designed. Get the spacing too tight, and the vines will outgrow the volume of space available to them. Get it too sparse, and the vines may not be able to take advantage of the volume allocated to them, leading to unused cropping potential.

To begin this discussion, we should first define what we are talking about. There are two types of spacing: within row (between vine) and between row.

Generally speaking, as you decrease the between row spacing, you also decrease the between vine spacing. However, there is room to move, so to speak, when practicing this.

Firstly, let me tackle the question of soil qualities and appropriate vine density (which, through altering between row and within row spacing, is what we are mostly talking about here).

If a soil is fertile, then there are two trains of thought. One is to give the vine a lot of space to express its high capacity for growth - therefore, low vine density or wide spacings.

The other is to plant with high density to get the vines competing with each other for nutrients and water.

If the soil is not very vigorous, then there are the same trains of thought. Have wide spacings and low vine densities because the vines will then have little competition (assuming weeds are kept under control) and therefore access to the most water and nutrients that they can.

This sort of spacing is used in dryland farmed areas, where irrigation not feasible. The vines are trained as bushes, with perhaps only a stake for support. Because of this, yields per hectare are low, but then at least you can get something off the land - it's just not an intensive producing area (the most planted vine data I showed in my cultivars lecture demonstrated this - Arién has the most area planted to it, but the vine density, and therefore yields, would be very low compared to some other varieties).

Or, if you can add water to the equation, you can plant them closer together so that you can get a continuous canopy and therefore more productivity per unit area of land.

So determining the appropriate vine density depends not just on the soil, but also how it's going to be managed. The question referred to this as optimising the yield, which is the key.

So, with that out of the way, let's talk about vine spacing in terms of what is practiced in the Old World versus the New World (using gross generalisations here, so please bear with me...)

In the Old World, some of the best wines come out of vineyards that are planted at around 1mx1m, or 10,000 vines per hectare. This compares to the usual 3mx2m spacings (1667 vines per hectare) in most of the early New World plantings, including a lot of Marlborough Sauvignon blanc (I assume everyone is familiar with how those spacings came about??).

The reasoning used by some is that because great wines come off of vineyards with close spacing that it must be the close spacing that contributes to that wine quality. Therefore, if we replicate that spacing in another place, we will get better wines.

However, as reasoned above, it's actually a balance of the soil and overall management that really results in achieving vine balance (open canopies and an appropriate ratio between fruiting and vegetative growth), where it's easiest to get the most quality out of your fruit. What often happens when close spacings are transplanted to another area is that the vines end up being vigorous and turn into a mess of shoots and canes that would send Richard Smart into conniptions!

Why does this happen? Well, in many New World areas, the soils are a lot more fertile and deeper than soils in the Old World, where they have been farmed for centuries (and are often on hillsides). It's true that close vine planting will result in root competition to the sides, but what if the soil is deep? The roots can grow down and away from competing roots and fine plentiful nutrients and water. Therefore, they grow like triffids, and viticulturists may resort to pulling out rows and vines to get it into balance. We just can't control growth of roots down into the soil - unless rainfall is low, and irrigation is used...

And that last point is really the crux to the discussion: viticultural management can alter what might not be the best vine spacing into a system that still produces optimum fruit. If the spacing is too tight and vines are growing out of the volume allocated to them, we can reduce irrigation, or plant a more competitive cover crop, make the weed-free strip under the vines narrower, change the training system, or, if it's dire, rip out some of the vines...

In practice, this happens all the time - though we try to get as much information as possible pre-planting, we are still just making a best-guess as to the vineyard setup - the best way to know how vines will perform in an area is to plant some and see how they go over a 10-15 year period. This is why vineyard redevelopment, as we have see in many areas due to phylloxera, for example, is really an opportunity.

Significant advances in grape processing

I recently came back from helping take Lincoln University's HORT212 (Viticulture I) class around Marlborough for two and a half days, looking mostly at vineyards, but also including a very good tour through the Brancott Winery.

I think this was my 10^th time on the tour, but in any case, it's always interesting to go, as you learn new things every time, and it's also fascinating to see how the wine business changes from year to year to year.

We were given a very good talk about the future by Dr Michael Trought of the Marlborough Wine Research Centre, who mentioned new harvesting technology that is being developed as I type.

This was in the news a little while ago and has created a bit of a stir. It isn't actually all that new an idea, as this article from 2008 can confirm, but it is, as far as I'm aware, the first time the technology has actually been seen working in New Zealand.

On what is a fairly ordinary machine harvester, built by ERO, is added the innovation of on-board grape processing.

Not only does the machine harvest the grapes, but it also crushes and extracts the juice out of them them (using a centrifuge), so that instead of a mix of grape skins, seeds, pulp and material other than grape (e.g. leaves, petioles and other things that get collected by the harvester) being discharged into a bin being towed in an adjacent row, clear grape juice comes out. The grape skins and seeds are discharged to the ground in the vineyard.

As Dr Trought demonstrated to us, the juice coming out of this machine was very clear, having only a small amount of solids suspended in it (after juice is pressed from the grapes, it is normally put into a tank and allowed time for the bits of grape that came out with it to settle to the bottom of the tank - the clear juice off the top is then the premium stuff). This is desirable because there is less loss of good juice during the settling process, which probably makes up for the slightly lower litres of juice recovered per tonne of grapes that the machine juicer gets compared to the conventional press.

So what this technology can deliver is pretty clear juice straight from the vineyard.

What does this mean? Well, it means that about 20% of the weight of the fruit (skins and seeds) doesn't have to be carted to the winery, only to have to be carted back out again. There's a savings here in the number of trucks/drivers/amount of fuel needed to move the grapes to the winery and then the grape solids back to a composting facility.

It means that for those varieties that can be harvested in this way, a press is not needed back at the winery. This leads to lower capital expenditure to establish a winery.

It means that fewer people will be needed to process the grapes. A plus for the winery, but not so good for those wanting to work in wineries!

Potentially it could mean that lesser amounts of processing aids are needed to recover top-quality clear juice, leading to cost savings and more efficient use of tank space.

There are disadvantages, though. Grape waste, which is normally collected from the winery and distributed back into the vineyards, cattle yards or the composting facility, are now returned in raw form to the vineyard floor. Grape skins and seed waste has a high carbon to nitrogen ratio (C:N) of about 27:1 (Ferrer et al.2001), so leaving it out in the vineyard as it is can result in a loss of root-available nitrogen to the vines. That's not to mention that it's a bit of a slippery mess!

As well, it's pretty much useless for red wine, as the colour and mouth feel properties of the wine are tied up in the seeds and skins. If you juice the grapes in the vineyard, there is no chance for these things to be extracted into the wine.

And, as well, many white wines are made using a bit of skin contact time. That is, after the grapes are crushed, the skins are left to stew in the juice for a while. This allows flavour and aroma compounds to be extracted, as well as tannins and other compounds from the skin that can have an effect on the way the wine smells and tastes. This isn't feasible with the current machine.

A significant point for New Zealand when considering this technology is that the country's most famous wine, the Marlborough-style Sauvignon blanc, actually relies on some post-crushing skin contact time to lend it some of the aroma characteristics that it's so well known for.

It's highly likely that this time and effort-saving machine may not be able to be used with the grape that makes up almost 50% of the grape area planted.

Bummer!

Biodynamics - a viticulturist's view

We have a V&O student forum at Lincoln University, where posts about tastings, announcements, and other tidbits can be seen by all. One student just put up a, shall we say, "incite"-ful post about Biodynamics. That is to say, they were attempting to stir the pot...


I thought I would put in my two cents worth, from my view as a viticulturist, so I've repeated it here:

My experiences with Biodynamics goes back to when I first visited James Millton up in Gisborne more than 10 years ago. He makes fantastic wines, and in one of the more difficult places to grow grapes in NZ due to the increased disease pressure there.

Some of my research dealt with maximising vines' natural resistance to fungal diseases through phytoalexins, so he invited me up there to have a chat and see what they were doing.

As a viticulturist, I came away from it not really wondering what the effects of the Biodynamic preparations were, but rather being impressed with the amount of attention paid to the soil, the vines and the grapes.

Growing organically or Biodynamically means that the viticulturist has to be much more "in tune" with the grapes and the environment. In order to manage diseases, and since they don't have fungicides as effective as synthetic ones, they need to be much more aware of what the canopies are like, and manage them more actively. This means they are out looking at the vines more often and putting into effect management decisions in a timely fashion: staying ahead of the problems.

So my take on this topic is that it isn't necessarily the preparations or ethos of Biodynamics and the Steiner principles that are at work, but rather viticulturists that are much more aware of what is going on in their vineyards, and anticipating problems rather than reacting to them.

Anything that gets people into their vineyards more and looking critically and thoughtfully about their vines has got to be better for the health of the vineyard and the quality of the grapes, regardless if it comes about through a belief in anthroposophism, the principles of organic farming, or an obsessive-compulsive disorder relating to lianas...  :-)

Climate change and eco-mindedness

TizWine recently sent out a link to an article about climate change in California and its effects on the wine industry (Napa Valley Register).

It's not really focused on climate change in terms of  global warming, but more the climate of perception and ideas about vineyard management.

There is beginning to be more emphasis on looking at more than just dollars in the bottom line. The article describes how some parts of vineyards that were prone to flooding were ripped out to improve flow through it for wet times of the year. Native plants are being planted near vineyards to encourage native fauna (much like the Greening Waipara programme here in Canterbury) and increase biodiversity.

Then, the use of solar panels to generate electricity, the excess of which can be fed back into the grid (There are reasonably good rebate programmes in the States that assist companies to put in alternative energy generations - would that New Zealand had a similar stance), is described - these are sitting on the surface of a pond, which can have multiple benefits in that it would also reduce evaporation from the pond's surface.

Napa is cooler than one might expect from its latitude, primarily because fogs roll in off the ocean during the night, and don't burn off until later in the day. The change in climate will affect this, and I think it would be rather sensitive, too. If the fogs burned off a couple of hours earlier each day, there could be significant effects on the number of heat units gained in those areas. Likewise, if the fogs hang around for longer, things could be a bit cooler. On reflection, that could be a good thing - maybe the alcohol levels in the wines won't get so high! :-)

So to combat this, they're changing the orientation of the vine rows (typically they run north-south, so there is sun on the east side in the morning and on the west side in the afternoon) to more northwest-southeast, so that in the hotter parts of the day the sun-side of the vines don't get the full brunt of the light and heat.

As well, more leaf cover also can reduce fruit temperature and minimise the amount of berry burn:

In this picture, the leaves were removed over a shaded cluster and shoot, and the resulting exposure to the sun has done considerable damage to parts of the berries but also the shoot and rachis!

So keeping some leaves on to get dappled light on the clusters can be a good thing if you are growing in a hot area. Trellising choice also has an influence, as those systems where the fruit is below the canopy (e.g. pergola (overhead) or T-trellis)are better off in those conditions.

 A Parronal vineyard in Chile. Also called a pergola or overhead trellis system. Here shoots have recently been thinned from the vines to create a more dappled light effect on the grapes and ground beneath.

A T-trellis system in Australia. Here the grapes hang beneath the canopy, too, but there doesn't need to be an elaborate overhead wire system to support the vines.

Trellis systems like there are more commonly used for table grapes, where the appearance of the fruit is especially important.

There is no doubt in my mind that we will need to alter management of our vines to suit changes in climate over the next 40 years - as with all things viticulture, planning for it beforehand is the best approach. So read through the climate projections for your area, and make a plan to deal with the possible changes - before they happen and its too late!!!