Multidisciplinary assessment of selective harvesting in the Colli Piacentini wine district

Abstract

Within-field variability can be managed through Precision Viticulture (PV) protocols aiming at identifying homogeneous zones and addressing site-specific operations including selective harvesting (SH). Several authors demonstrated SH profitability in extensive viticulture while few information is available within the Italian context. Based on a NDVI-derived vigor map (5 m resolution), a 3-year study was performed in a mature Barbera vineyard from Colli Piacentini. Ground-truthing of 3 vigor zones encompassed soil properties, canopy growth, yield and fruit composition. Experimental wines were made and sensory analysis performed for comparing vigor classes. A professional-targeted survey aimed at explaining technical and economic potential of SH. Results show higher soil fertility and water holding capacity in high vigor (HV) leading to higher leaf area (3.99 vs 2.67 m2/vine recorded in low vigor (LV)), excessive crop load (6.99 vs 3.37 kg/vine) and incomplete ripening (TSS: 20.7 vs 24.9 °Brix; TA: 9.72 vs 7.71 g/L; anthocyanins: 0.82 vs 1.60 g/kg). When compared to HV, LV wines showed higher color and purple hues, full body, more balance and, occasionally, higher astringency. More than 70% of the professionals asserted within-field variability can affect economic performance of the wineries demonstrating “high” or “very high” interest on SH. SH might be very profitable for growers and even more for wine producers, however the majority of the interviewed estimated wineries will be much less inclined to differentiate fruit pricing depending on different enological potential at the field scale. SH can boost exploitation of vineyard variability in the Colli Piacentini area and grapes from the same parcel used for producing young sparkling as well as barrel-aged still wines.