The "semi-minimal pruned hedge (SMPH)", a novel grapevine training system, tested on cv. Sangiovese (V. vinifera L.)

In a previous three-year study on cv. Sangiovese (V. vinifera L.), the degree of adaptation to minimal pruning (MP) compared with conventional spur-pruning (CSP) was investigated in the Central Po Valley in northern Italy (Intrieri et al., 2001). Despite a marked reduction in bud sprouting, shoot fruitfulness and cluster weight, the MP vines, in which more than 600 nodes per m of row were left, showed an alternate bearing pattern coupled with large crop-linked variation of grape quality. However, the clusters of MP vines were distinctly less compact than those produced by CSP and this feature was crucial in preventing massive bunch rot even in wet season. Since all Sangiovese clones are currently characterized by dense or very dense clusters, the MP looks like an effective tool to induce looser clusters, but it was clear that future work will have to assess to counterbalance the drawbacks related to alternate bearing pattern and the delayed or incomplete ripening without loosing the feature of less compact clusters. According to this principle, a novel grapevine training system featuring a hedge-wall 120 high x 20 cm in depth was tested on cv. Sangiovese. Designed for integral mechanised pruning and harvesting as the classic MP, but also for a more severe winter pruning, the new system was called the ‘semi-minimal pruned hedge’ (SMPH) and was shaped since 1998 starting from a spur-pruned cordon vines, by attaching a few of the preceding year’s canes to the horizontal trellis wires. The hedge shape was maintained over time by pruning the sides and top with mechanical cutter bars. Three years after the first pruning a specific study was performed, in which SMPH was compared against CSP featuring 18 count nodes per vine and per meter of row. Over the period 2000-2002, the nodes left on SMPH were 320 per m of row. As expected, the hedged vines showed a consistently earlier leaf-area expansion in spring and a larger leaf area per vine at the end of shoot growth. Measurements of single-leaf photosynthetic capacity evinced no significant differences between the two systems, thereby indicating a greater take-up potential of the SMPH vines. Accordingly, the average yield of the SMPH vines was about 30% higher than the CSP’s, but no differences in final ripening were found. These results were confirmed during the 2002 season, in a parallel work (Filippetti et al., 2004), in which photosynthesis and dry matter production of the SMPH and of the CSP were modelled by the software Stella (High Performance System Inc. USA) and showed that SMPH had an higher dry matter accumulation compared to CSP all along the season. Overall, the SMPH clusters appeared smaller over the trial years, with less compact berries and free of botrytis (bunch rot) attacks with respect to CSP’s. In addition, a preliminary experiment on mechanical harvesting of the SMPH with an over-row horizontal shaking unit was successfully performed at the end of 2002 season. All the above data suggest interesting practical application for the SMPH system, because of its adaptability to full mechanization and for the positive findings in regard to vine physiology and grape yield and quality, as well as to lower susceptibility to bunch rot.