March 2012 Douro Insider

Hopes were raised on the first day of the month that this year’s hideous climatic patterns might finally be changing for the better (i.e. worse) when we enjoyed the very lightest speckling of drizzle during the afternoon, but it was so little that at several of the weather stations the amount wasn’t even enough to register.  Some more odd drops fell over the first weekend of the month but, as they say in these parts, it was barely enough to settle the dust.  And then it got worse (or better?) as temperatures began to warm up considerably to the extent that we were into the high 20ºs C in some parts of the country by the middle of the next week.  The heat, combined with the ongoing drought, was a recipe for wild fires with a number burning around the Vila Real area on the 15th.  By this date, according to the Met Office, a huge 53 % of continental Portugal was under ‘extreme’ drought conditions, and the remaining 47 % was merely ‘severe’.

The sudden onset of this warm weather made quite a change since figures released by the Instituto de Meteorologia had just confirmed that on a national scale this winter (December to February) was the third coldest since records began in 1931, as well as the driest, needless to say.  But the first hot spell was well and truly over by the 20th and we then had about a week of much cooler, cloudier days.  But no more than that.  Temperatures climbed back into the high 20ºs again by the end of the month and there was a definite summery feel in the air – which was the last thing that anyone wanted.

This second hot period appeared to be associated with the start of the warm evening winds that so characterise summer in the Douro but, like everything else climatic in recent months, they were going the wrong way – blowing down-river.  And whilst we were desperate for winds of change, it wasn’t this sort: dragging in hot air from central Iberia, rather than nice cool and moist air from over the Atlantic.  Round about this time the house martins arrived back from their winter break in warmer climes, only to fly about bemusedly, looking in vain for mud with which to build their nests.

It then stayed consistently hot right through to the end of March, meaning that another rash of forest fires broke out across the country on the 29th, including one in the hills just inland from Porto.  For several hours a yellowish cloud of pine and eucalypt scented smoke hung heavily over the city.  The air did generally appear to be getting heavier though, as if the humidity was building up.  These thundery conditions gave the impression that the weather might finally break in time for the end of the month, but an area of low pressure in the southeast brought only some minor changes.  The skies were slightly threatening, there was a bit more wind and even the occasional localised shower.  Nevertheless, it was clear that the effects of this instability were more keenly felt in the south of the country and any impact that they might have had on the dire viticultural situation in the Douro was negligible.

A look at the data above reveals that the month turned out to be just over one degree warmer than average on balance, at 13.4º (compared with 12.3º).  This makes it the first month since October with above-average temperatures; we saw earlier that it was indeed a particularly cold winter.  But spring can set in very fast.  It is worth noting that one property came within a whisker of hitting 30º, whilst at the other end of the scale another still had two freezing nights.  Once the buds burst we will obviously hope to escape any further frosts.

As we are all well aware, precipitation was yet again hugely disappointing with a feeble total of just 7 mm falling in Pinhão, and this was immediately followed by a week of hot weather which almost certainly evaporated much of it away again. This is not even 15 % of the average for the month (52 mm). To put things in proportion, rainfall in the heart of the Douro has averaged just 13.6 mm per month over the last four months. The average rainfall for July, the driest month of the year in the Douro, is higher than that, at 14.0 mm. Predictably therefore our cumulative graph continues showing a line which has run almost flat since November. So far this year we have had only 16 mm of rain. The benchmark for this stage would more than thirteen times greater, at 215 mm. And all this coming on top of last year’s 34 % shortfall.

The result of this is that soil moisture keeps on dropping, as it has been since before the start of this year.  It should, of course, have been rising steeply all the time, indicating a replenishment of the water table.  It is also worth mentioning that during the course of the month the soil temperature rose dramatically from around 11º to about 18º.  Whilst this is perfectly normal (and indeed this sudden and sharp increase in soil temperature will be a major factor in the timing of budburst) the problem is that a warmer soil is likely to lose more water by evaporation.  On the other hand the ground is so dry that it is hard to imagine that there is anything still left there to evaporate…

Almost without exception March marks the start of the real viticultural year, although this event is something of a moveable feast.  I refer, of course, to budburst.  Our average date for this over the past decade or so is the 23rd, and we were expecting things to be quite delayed this year as a result of the very cold winter.  That turned out not really to be the case, however, and in fact the phenological cycle started just three days late, on the 26th.  Or possibly four days, since it is a leap year, but in any case the delay was less than expected.  Probably the unseasonably high temperatures in the middle of the month awoke the vines a little earlier than was good for them.

Unfortunately things did not look particularly promising right from the start because the whole of the budburst period was markedly heterogeneous – both between vines within the same block, and within the same plant.  It was quite odd to see many cases where one cordon of the vine was green with well-developed shoot tips, whilst the other cordon remained completely dormant.  More worryingly still was the lack of sap rising in last year’s canes and spurs – cutting into them clearly revealed that many of the pores in the xylem contained nothing but air.  Since this tissue is supposed to supply water to the leaves it should obviously not be hollow.

What this meant in practice was that initial shoot growth was very slow indeed, as even adult plants simply did not have enough water to get off to a normal start.  Quite how unwell this bodes for the rest of the year is not clear but it surely won’t be pretty.  This situation led in turn to unprecedented activity in the vineyards when it was considered necessary in many cases to water the rootlings that were planted last year yet again.  In all but the most extreme circumstances they are only ever watered in the first year of planting, and certainly it has never been necessary to start as early as March in the unlikely event that they should need watery help in the second year.

The grafting procedure that has been described over the course of the last two reports was coming to an end by the second half of the month.  This is later than normal, but then we had made a conscious decision to hold off as long as possible in the hope of getting some rain.  The reason for this is that the sap (what sap?) needs to rise to start the healing process at the graft union, and as we have already seen this is certainly a slow sap season.  It is quite possible, perhaps even probable, that the take rate of the grafts (which is usually close to 100 %) will suffer as a result.

After pruning, but before budburst, is really the only window available to us for trellis maintenance.  We systematically go through all the vineyards replacing damaged posts, lost staples and mending broken wires.  The end assemblies are particularly vulnerable to accidental tractor damage as the topography of the Douro means that often the turning headlands at the ends of the rows are quite narrow.  Only after all this is done can all the wires be properly tensioned.  Given the solidity of the soil at the moment replacing damaged posts was especially hard work.  This is even more so in the case of the now obsolete blue schist (stone) vineyard posts since the brittle nature of this material means that they cannot be hammered into the ground.  Instead a hole must be dug to receive the post and then backfilled and packed down hard to anchor it firmly in place.  Although aesthetic, the stone posts are not used in modern mechanised plantations.  In the older vineyards, however, there are always a certain number of breakages every year due to their lack of affinity with tractors.

The vineyard weed control that was touched upon last month also continued in March.  This activity, much like trellis maintenance, is best carried out before budburst so as to avoid damaging the delicate first leaves as they emerge.  It is a time-consuming business and actually took up the majority of the working month.  Often shoot growth just after budburst is so fast (particularly if the spring is warm) that is seems as if we have to start worrying about getting on a first dose of sulphur almost immediately.  This year we clearly have plenty of time on our hands, some of which we decided to spend on despedrega, or stone clearing.  Any time we need to plough the vineyards (after fertilisations, for instance, or sowing cover crops) we inevitably end up bringing a certain number of rocks to the surface.  These need to be cleared away, by hand unfortunately, to stop them getting in the way of machinery and this kept us busy until the end of the month.

5 thoughts on “March 2012 Douro Insider”

    1. Hi Augusto, no, sadly not enough rain and water yet – although it has been showery here in Gaia, Alexandre Mariz tells us very little of it has gotten up to the Douro – so still nowhere near “enough”, though every drop we do get is welcome and useful!

  1. At the beginning of last week in Sao Joao da Pesqueira, the month’s cumulative rainfall was close to the long term average, but with no catch-up for the months of preceding drought. More rain has since fallen, and things were looking much greener when I drove back home on Friday.

    More rain is forecast for later this week, so hopefully there will be some good news in the next report!

    1. Hi Tom, There has been some rain indeed, but you and I have had this conversation before about micro-climatisation, and the differences between locations, and between what falls on the altos (the highlands), such as São João de Pesqueira, and properties near the river. You may be interested in the stats in our latest Tracking the Season article. Yes, we are hoping for good news! Always!

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