February 2009 Douro Insider

Global scale climatic aberrations meant that February got off to a very bad start in Europe, although the ill-effects of this strange weather system were felt far more keenly in the north of the continent than down here in the south. Unusual disturbances in the stratosphere resulted in strong easterly winds bringing cold Arctic air into the UK over the North Sea, and London experienced its heaviest snowfall for 18 years. At over a foot deep, the snow was sufficient to put planes, tubes and buses all out of action, close roads and schools and effectively paralyse the city. Whilst many there enjoyed a ‘mass skive’ (in the words of the Mayor) we also had one or two unofficial ‘feriados’ in the vineyards of northern Portugal. In this case they were due to rain however, not snow, which on some mornings fell with such intensity as to make working outside quite impossible. The rain was by no means unique to Portugal, and London’s snow was immediately followed by torrential rainfall leading to widespread flooding in southern England around the 10th of the month.

Meteorologists from the World Meteorological Organization explained that the icy conditions which have blighted us since November are caused by La Niña, which is itself produced by cooler surface water temperatures in the Pacific Ocean. They then comfortingly reassured us that this meant that their predictions for the rest of the year were ‘very uncertain’, but claimed that the chilling effect was diminishing. In other words, they think that the spring will be warmer than the winter.

Out here, on the fringes of this violent weather system, the start of a new month did not actually herald any particular change in weather patterns. The terrible conditions from the end of January just kept up, at least for the first week of February. It stayed very wet, and the wind was strong enough to prune the occasional old or rotten branch from the trees in the Douro. Thankfully we are still a few weeks away from budburst as high winds are the sworn enemy of tender vine shoots. Yet more snow was threatened but didn’t in fact materialise in any significant amounts. Nevertheless, it was clearly cold enough to have done so across much of the north of Portugal, with the mean monthly temperature well below average. And pleasingly, for the first time in ages, the level of the water in the river Douro rose visibly.

Things finally got better around the middle of the month with an abrupt turnaround. The rain cleared up, the wind stilled, temperatures stabilised and the sun came out. Although the nights remained very cold, it suddenly seemed warm again during daylight hours, with the skies overhead finally turning blue. Almost immediately the almond trees came into flower, for many people signifying the end of winter. It is also a timely reminder that it will not be long until the viticultural cycle starts again; after the almond trees bloom, their leaves come out. And the first green tips will emerge in the vineyard not long afterwards.

In Pinhão the overall average temperature for the month was a full degree below the mean, at just 8.7º C. This makes February the eighth consecutive month of colder-than-expected temperatures, in spite of the fact that from the 11th onwards it actually climbed above 15º every day. But as has been mentioned, the lack of clouds at night meant that much of this warmth was radiated back into the starry sky, and sub-3º minimums were the norm. The absolute maximum temperature was a perfectly acceptable 21.5º (quite warm enough to go outside without a jumper) but it still dropped to a minimum of 0.6º.

In terms of precipitation the first 10 days brought plenty of welcome water, but this pattern was not sustained and nothing else of any consequence came for the rest of the month. This left us looking at a total of just 50 mm, which is about 30 % off the long-term average of 73 mm. As the figure below shows we are still just a little over the cumulative mean for this time of year, for what it is worth at this early stage, due entirely to the fact that February’s shortfall was smaller than January’s bonus. Nevertheless this is coming in on the back of a very dry year in 2008, so we still need plenty more rainfall to replenish the water tables. There is no cause for concern yet as historically April and May are both wetter than March in the Douro.

Viticulture in February is always a slightly fragmented business, and any number of ‘winter jobs’ (i.e. pre-budburst) could be going on simultaneously, especially since the main activity of the season (pruning) is coming to an end almost everywhere. What this means in practice is that there are fewer incidences of the sort of activities that tend to precede pruning (such as pre-pruning) and more occasions on which we find the workers involved in post-pruning jobs, such as cane destruction or tying down the canes. Of course to some degree all of these pruning-related jobs occur at once, carried out by different teams of people who work their way through a property rather than by a single team making several passes through the same vineyard. Whilst on the subject of related practices, training the young vines onto the wire also features strongly at this time of year.

Once the pruning is wrapped up we are provided with an excellent opportunity to make sure that all the vineyard trellises are in a good state of repair. This needs to be done with some sense of urgency as obviously replacing any wires or posts once there are shoots and leaves on the vines could be extremely damaging to the structure of the plant and this year’s crop of fruit. Trellis maintenance was therefore a major concern at a significant number of properties, whilst others of course had already begun last month. After that the general trend is to start thinking about clearing away the weeds that have emerged during the supposedly wetter months. Thus three main activities start appearing on the roster with more frequency – ploughing, cleaning up the taludes (terrace banks) and herbicide applications.

Whilst we can control weeds growing in the entrelinhas (the space between the rows) by ploughing, the under-vine strip (preferentially) and the banks (obligatorily) are best treated with herbicide sprays. Although the green movement abhors the use of weedkillers there is a growing backlash that they might in fact be preferable to supposedly more ecological methods of weed destruction. Biologically very sophisticated chemicals have been developed recently with extremely low animal toxicity and no detectable negative impacts on the environment in the long term. Alternatives such as soil mobilisation are criticised for a number of reasons, however. Firstly, cultivation brings organic matter to the surface of the soil where it is exposed to sunlight, thereby causing its degradation which is in turn detrimental to microbial life. Furthermore, ploughing destroys soil structure and accelerates erosion. It has also been claimed that unnecessary passes through the vineyard cause compaction of a strip of earth under the wheels of the tractors, right next to the rows of vines. This then leads to a reduction in the volume of soil that the vines’ roots are able to exploit for water and nutrients.

In any case, steps are being taken to reduce both ploughing and herbicide application. Our dependence on ploughing can be reduced by dominating spontaneous weed growth through the use of cover crops (which can then be mown and left on the soil surface as an organic mulch). Herbicide applications are also being scaled down to those areas only where it is strictly necessary, such as the taludes within a vineyard. Where earth banks are doing nothing more than supporting a road, for instance, natural vegetation can be allowed to appear since there are no vines nearby with which it might compete. Likewise, the traditional Douro mindset that herbicides need to be applied to the tracks and roads within a quinta is both costly, outdated and unnecessary. No significant vegetation will ever grow on a track due to compaction from the wheels of the vehicles and the physical effects of their constant passage. We can even cut out herbicide use in some of the olive groves too since the mowers being used to cut the cover crops can be hydraulically offset to the left or right, meaning that they can cut spontaneous vegetation right up to the trunks of the oliveiras (olive trees).

Once the herbicides have been applied it is a good time to move on to replanting falhas (missing vines) often using American rootstocks (especially in older vineyards) but ready-grafted vines may still be considered in the first or second years after plantation. Most properties were involved with this and some had already progressed to grafting the vinifera scions onto the rootstocks planted last year to fill in gaps in the vineyards.

This year’s new plantations pressed on with the usual sequence of terrain shaping, soil preparation and corrections, stone removal or destruction, marking out, planting and trellising and so on. In general all properties are close to planting if they haven’t already started. Some of the smaller projects are practically finished. On a similar subject grow-tubes were put in one or two of last year’s plantations. Their principal benefit is protection of the young vines against careless herbicide application or rabbit attacks rather than any special improvement in take rate or growth.