Novel termination techniques of winter cover crops in the vineyard: Effects on physiology and performance of Pinot Noir and Malvasia di Candia aromatica grapevines

A current significant vineyard challenge is how other-than tillage soil management solutions can be implemented without incurring in major competition for water and nutrients with the consociated grapevines. Therefore, a three-year study was carried at two hilly sites (Sartori and Ottina) in Northern Italy to evaluate the impact of two novel winter cover crop terminations (interrow rolling, R, and sub-row mulching, SRM) on vine physiology and performance as compared to standard practice, either alternate tilled-grassed interrow and/or green manuring (GM). Moreover, at the Ottina site, cover crop sowing used two different seed mixtures: the cereal based Humusfert (HF) and the legume based Nitrofert (NF). Each season, in summer, soil and vine water status were measured as soil saturation degree (theta s/theta sat), pre-dawn (Psi PD) and midday leaf water potential (Psi MD), whereas gas exchange was monitored as leaf assimilation (A) and stomatal conductance (gs). At both sites, for data pooled over years, the amount of rolled dry biomass was lower than 650 g m-2 and R did not result in any significant variation of water status, gas exchange and vine performance versus the standard practice. Vice versa, at the Sartori site, the amount of mulched biomass under the row was quite abundant (1.517 g m-2 dry weight) and effective for weed suppression. SRM also maintained less negative Psi PD in the warmest part of 2022 and 2023 seasons without, however, greatly impacting leaf water status, gas exchange and vine performances. At Ottina, SRM assured, for data pooled over years, higher total soluble solids (TSS) and malic acid and lower pH than R suggesting that sugar accumulation and acid degradation were partially decoupled. At the same site, NF allowed to increase yield without any concurrent change in vigor with a consequent ripening delay in terms of lower TSS, pH and anthocyanins, and higher tartaric acid at harvest, a sought effects under a global warming scenario. It is also practically relevant that HF lowered berry [K] significantly vs. NF suggesting that it might be used as an additional control tool to limit K accumulation into the berries and, eventually, wine pH. Overall, while SRM had better performance than R in terms of weed suppression, soil water status and berry ripening, results can vary as a function of the type of seed mixture which, in turn, closely interacts with specific environmental conditions.