Sustainable viticulture’ the “semi‐minimal” pruned “hedge” system for grape vines long term experience on cv. Sangiovese (Vitis vinifera L.)

Abstract

Context and purpose of the study ‐ In previous experiments carried out in Bologna on Sangiovese grapevines raised with the Australian “Minimal Pruning” system, it has been shown that this system left an excessive burden of buds on the vine (650/meter of row) and inhibited the plant from correctly activating its physiologic self‐regulating mechanisms, thus causing alternancy and drops in the sugar content. However, “Minimal Pruning” also reduced labor time and resulted in loose grape bunches on the vine, which are less prone to fungal diseases. Considering the importance of these last results, the University of Bologna has experimented with a cultivation method based on the Australian technique, but modified so as to reduce the bud load and regulate production without losing the advantages of low cost and healthier grapes. The new system, trained to a “Hedge” form with “Semi‐Minimal” mechanical pruning, has been tested on Sangiovese grapevines since 1990 and has undergone important structural modifications, which might also make it suitable for other grape varieties.

Material and methods ‐ The initial research on the Sangiovese grapevine trained as a Hedge compared it to the classic Spur‐Pruned Cordon (SPC). The Hedge productive surface was 1.2 meters tall and was managed with mechanical “Semi‐Minimal” pruning (400 buds/m of row, i.e. 40% less than Australian “Minimal Pruning”), while the classic SPC was managed with traditional manual pruning (18‐buds/meter of row). Between 2000 and 2008, the main growth, production and quality characteristics of SPC and Hedge were identified and an assessment was made of the likelihood of shoot density in the lower areas of the Hedge (as already mentioned, 1.2 m tall) to verify the acrotony effect.Moreover from 2013 to 2018 a second model of Hedge, 0.8 m tall (“Shorter Hedge”) was used on Sangiovese grapevines (235 buds/meter of row, i.e. 65% less than Australian “Minimal Pruning”). For the “Shorter Hedge” the principal 2013‐2018 behavioral parameters were identified and the spatial distribution of shoots and bunches along the productive Hedge wall was also verified.

Results ‐ The results of the first investigation (2000‐2008) showed that in respect to the SPC (18‐buds/m), the 1.2 m tall Hedge (400 buds/m) gave rise to a larger crop of similar quality to that of the SPC, with a greater number of bunches that were smaller, looser and completely free from botrytis. Nevertheless, in the lower part of the 1.2 m tall Hedge, a small drop in the number of shoots produced was observed after few years.In the second investigation, carried out between 2013 and 2018 on the Sangiovese “Shorter Hedge”, with a 0.8 m tall productive surface (235 buds/m), the data confirmed that the lesser height of the yield wall and the relate lower bud number improved the self‐regulation and equilibrium of the vines, markedly reducing the annual variability of the different grape parameters. Overall, the vines always produced quantitatively and qualitatively to satisfaction, with many small bunches free from rot. During the trial, a decreasing of shoot and cluster density was not observed in the lower parts of the 0.8 m tall Hedge.Today, after almost 20 years of research, the Hedge system has shown itself to be capable of being practically applied to other grape varieties thanks to its reduced management costs, complete adaptability to integrated mechanization and the positive results regarding the yield and grape quality.