Distance between vineyard rows: when quality is a question of space

The density of vineyard planting is one of the most important factors for achieving high quality production. The emissions norm applied to narrowtrack tractors carries the risk of required changes of vineyard training systems which would harm the quality of wine production

A glass of fine wine is born from the earth, the sun which warms it, the work in the vineyard and making selections in the field and in the wine cellar. Agronomists and enologists are called on to decide the destiny of a vineyard. The current widespread view among operators in the sector is that a wine of quality is achieved in the vineyard; that careful attention must be devoted to correctly working the grapes selected according to the environment and what a sound agronomic technique has produced. This means that the grapes correctly produced and harvested already contain within the potential to become a quality wine which wine making techniques and refining must be able to bring out. Quality and other characteristics of the product are planned in the field, beginning with the choice of terrain and the planting of the vineyard. In this setting, agronomic practices must be capable of enhancing the terroir, that is, the characteristics that the geography, geology and microclimate of a determined location can offer for high quality production.

Among the requirements the agronomist is called on to deal with in creating a vineyard, the main ones are settling on the rootstock to use and the choice of the variety, the suitable layout of the terrain and the correct location of the plants in their spaces, that is, the density of planting, form of vine training and pruning system as well as suitable crop techniques. Taken together, these factors are acknowledged as making up the keystone for high quality production and the financial advantageous agronomic management of the vineyard.

The choice of the density of planting is the crucial one among these decisions; density, other than being influenced by the vigor of the rootstock, depends on the fertility of the soil and whether water for irrigation is available or not. Finding the right compromise among these factors means determining that, with full development, the plants are not in competition and that their planting spacing is not excessive. Basic for the practice of thickening the density of planting are several purely natural physiological factors; the objective is to achieve an ideal vegetative-productive balance throughout the entire vineyard. With spacing between the plants between 0.50-0.60 and 1 meter, the root apparatus of the plants enter into competition and are required to send their roots deeper to explore the soil rather than grow laterally. This development increases resistance to water stress and improves interaction between the vine and soil to enhance the terroir effect associated with the rocky matrix. Moreover, competition among the root systems is a cause of a lowered level of vegetation vigor which results in limiting the number of buds per plant, greater uniformity in developing germination and thus the contemporary maturation of the grapes to hasten full production for the vineyard and enhancing longevity. Also, for reasons cited above, high density planting leads to lower grape production per plant and smaller grapes which are, however, of superior quality because the timely slowing and arrest of vegetative activities in the phase leading to véraison (a French phenological term meaning the onset of ripening when the grape berries change color) works to increase the accumulation of sugar and tannins in the bunch resulting in greater alcohol content and better wine structure and color.

Thus the choice of planting density raises a fundamental point for achieving high quality production and this parameter refers to the combination of two variables: the spacing of the plants and the distance between rows. The former can be easily dealt with by applying the agronomic findings considered above and the second must be in line with technical and operational requirements. In fact – aside from reciprocal shading of the vines in contiguous rows, which can be easily avoided by paying attention to the correct relationship between spacing and the height of the foliage wall –  with the hypothetical Guyot single curtain vine training system, the distance between rows is conditioned by the width of the machinery to provide a safe distance between machines and the plants and the average reach of their foliage wall.

This consideration makes clear the importance of the machinery manufacturers’ role in this field. In fact, the evolution of these machines has led the way to the important changes in viticulture and the vineyards landscapes in Italy moving away from traditional vine training to give way to new planting systems and more rational vine training which facilitate the mechanization of crop operations. These developments involve not only specific machinery for performing the work, vine shoot liming, topping, leaf removing, for example, but also tractors for powering the equipment. The transformation of tractors has involved, on the one hand, big machines for straddling rows, implement carriers and multi-purpose work capable of performing various operations, from topping to harvesting and ideal for large areas and very thick plantings. On the other are small tractors, especially narrow, with capabilities of operating in restricted spaces and more suitable for work on the small-medium size areas which account for the majority of farming enterprises on Italian territory. 

At this point, in light of the fact that from the financial point of view very few viticulture operators can afford to make a substantial investment for a straddle row machine it is easy to understand their need for one which can work with agility between rows with spacing which conforms to the width of the tractor. Row distances must be between 1.60 and 2 meters, a distance which nullifies the root system competition referred to above. The possibility of tightening the distances between rows would have positive repercussions on the quantity of grapes produced per hectare rather than on quality, which is correlated to spacing along the row.

The mechanization of caring for crops and quality production is a present and future consideration for winning viticulture which can complete on European markets and those beyond the continent. The directions taken by the European Union Common Agriculture Policy (CAP) include incentives for this path in the framework of the Common Market Organization (CMO) now brin­ging the wi­ne sector into the Agriculture Single CMO Regulation (EC) No 1234/2007. Mentioned in Council Regulation (EC) No 479/2008 article 11 is the eligibility of “restructuring of vineyards” for support progra­ms and Regulation (EC) No 555/2008 also covers support programs in articles 6, 7, 8 and 9. These incentives, already written into Commission Regulation (EC) No 1493/1999, were again proposed by the Commission in connection with structural support measures.

Regional commissioners responsible for agriculture are given a mandate for posting notices and identifying specific parameters for the assignment of points for the purpose of creating classifications for the award of aid for which the Regulation provides the guidelines. In this connection, an example is the Veneto Region statement that viticulture operators in conformity with EU norms can restructure existing vineyards to make use of mechanization for achieving an improvement of quality in production and many other regions have acted in the same way by singling out the feasible instruments for “the transformation of vineyards from existing training systems to one more suitable for quality of production and possible greater density in the rows and between rows,” (Regional restructuring and conversion of vineyards, Veneto Region – 2011).

Thus there is recognition of the worth of thickening plantings and expanding aid for viticulture operators who lessen distances between the plants, in the row as well as between rows, but this is sharply opposed to the consequences regulation emission produced by “Non Road Mobile Machinery” could bring in for the size of vineyard tractors built in sizes, and especially in widths, which could be enlarged with the installation of after treatment systems. What would be witnessed amounts to unprecedented nonsense. On one hand, the EU is enlarging funds for lessening the distances between rows while on the other, viticulture operators would be denied the possibility of deploying machines of the correct size for working with agility in those vineyards which the EU itself has contributed to for arranging them in the field.

The hope is that the European Commission grants the manufacturers of these narrow-track tractors a delay for the application of the norm because it would increase not only the size of these tractors but also the price of the machines. In light of the indications provided by the CAP, and much more so for reasons of economic sustainable, it would be wrong to ask viticulture operators to go ahead with modifications of the density of plants in their vineyards to wind up with a double defeat: operators keeping in their inventories obsolete tractors but of the correct size with the result that the very purpose of the engine exhaust norm to lower emissions would be nullified.