January 2011 Douro Insider

For those strong enough to venture outside on the first two or three days of the year, 2011 seemed to have got off to a reasonably good start, with the weather generally sunny and dry.  This being January, however, inevitably meant that not long would pass before it turned rather damp again.  Indeed, an area of low pressure over the UK obliged almost immediately, and started to suck in wet air off the Atlantic that passed right over northern Portugal.  All of a sudden it seemed like December again, but with added windiness.  It was certainly not as cold though (neither here, nor in the rest of Europe) as maritime-driven weather replaced the continental freeze.  In Germany the winter thaw caused serious flooding as the Rhine overflowed, whilst in the Douro temperatures approached 20º C.  More to the point, the minimum temperatures dropped little at night due to the insulating effects of a more or less permanent cloud blanket, so it actually felt unseasonably mild around the middle of the month.  This was accompanied by a steady trickle of rain, making sure that the soil was kept very damp.

The 21st brought a dramatic change as the incoming weather front reverted to continental.  With the skies suddenly clear again it turned seriously cold and the winds picked up with renewed vim after what had been a relatively still period.  There were gusts strong enough to judder the cars around on motorways, especially going over the Marão, and of course a significant wind chill factor meant that it felt even colder than the few negative degrees shown by thermometers.  Needless to say, the frosts returned to the vineyards and were occasionally accompanied by morning fogs.  These days were even worse, as all the fogs did was keep the sun off the frozen ground for longer.  On the morning of the 27th there was a very light frosting of snow in the highest parts of the Douro, and the month continued in a similar vein to finish cold and clear.

After both wet and dry periods, the total precipitation for the month was very close to average, with the final value of 84 mm coming in just a little under the long-term mean of 89 mm.  This means that our cumulative total at the start of this year (the lone yellow dot on the first graph) is obviously almost exactly on the average for this stage, showing (almost imperceptibly) just five irrelevant millimetres less than would be expected.

The other graph indicates that this month’s mean temperature was 0.7º warmer than the average January, these figures being 8.6º and 7.9º respectively.  Perhaps the surprisingly low number of frosts contributed to this; in Pinhão there were just three freezing nights.  It also meant that after three notably cold months, each at least 1.3º C colder than the mean, January of 2011 finally produced an average temperature warmer than the long-term value.  Although not especially remarkable in itself, it was actually the warmest January for seven years.

By the end of the month the vast majority of the pruning should be wrapped up.  Normally, by this stage, we have moved into the younger vineyards, by which I mean the ones that are not yet in full production (i.e.  less than four years old, according to local convention).  We always leave these vineyards until the end as pruning them is more labour-intensive and time-consuming than it is in a well-trained mature vineyard.  This is because suitable canes have to be chosen to lay down and wrap around the fruiting wire.  We then choose five or six well-positioned buds to keep, and carefully remove the rest with pruning secateurs.  Correct spacing of the buds is very important, as the shoots which burst from them will form the permanent pruning spurs a year later.  Some of the older vineyards are not spur-pruned, and in this case the canes will need to be tied down to the bottom wire of the trellis as well.  In practice this means that pruning the last few hectares of vineyard takes a disproportionate amount of time to finish, but the slightly more interesting process makes a welcome change after the tedium of the last few months.

Once the pruning is over, and the cut canes have all been stripped off the wires, it is the perfect time for trellis maintenance, a job which obviously needs to be carried out before budburst to avoid damaging the new shoots.  Slack wires will be tightened (we use a clever little pair of ratcheted pliers) and any damaged posts are replaced.  If the soil isn’t too damp, the strainers of the end assemblies can also be tightened up.  It is important to keep the wires strictly horizontal (or rather, parallel to the ground) or they might snag in the machinery.  The prepruner is particularly destructive if it catches a loose wire as it spins at a high rate and it can therefore do considerable damage in the couple of seconds it takes to stop.  For this reason it is clear that the disks of the prepruner also need to work parallel to the ground so the wires can pass between them without snagging.

All of which brings us onto another problem: we plant our vineyards on steep hillsides, and as a result most of our tractors run on caterpillar tracks rather than wheels.  We also have very stony soils and this can be awkward for a number of reasons.  In this case, when a tracked tractor comes across a large stone, even if working on the flat, it rises at the front and climbs up the stone until it reaches a tipping point and then see-saws down again on the other side.  This movement is not conducive to maintaining the aforementioned parallelism of prepruner disks so it is important that regular stone clearing (or smashing) is carried out in the worst parcelas.

Fertilisations are not especially time-critical, although it is obviously beneficial that they are followed by some rain to help dissolve the granules.  In other words, they should be carried out before the end of winter, so after the pruning is not a bad time.  This means that the nutrients should start to become available to the vines before the first flush of root growth in the spring.  The truth of the matter is that different elements have varying mobility in the soil solution anyway, so nutrient uptake will continue over several months, or even years.  As we saw in December’s Insider, it’s not all high-tech if the vine spacing is too narrow for a tractor.

Last of all, for those properties that were really ahead of the game, mid-winter is perfect for pruning olive trees (should one be so inclined in these belt-tightening times).  Fortunately olive trees only really need to be trimmed back every four or five years perhaps, but there is always the aesthetic aspect to consider.