Soil Functional Responses to Sheep Wool and Alfalfa Hay Mulching Across Contrasting Terroirs of the Tokaj Wine Region

Under changing environmental conditions, soil buffering capacity is a key soil-related component of terroir functional stability and vineyard resilience. We assessed the effects of sheep wool and alfalfa hay under-vine mulches during the first two years after treatment establishment in four vineyards with contrasting volcanic and loess-derived soil in the Tokaj Wine Region. Soil responses were evaluated using soil organic carbon (SOC), permanganate oxidizable carbon (POXC), fluorescein diacetate (FDA) hydrolytic activity, easily extractable glomalin-related soil protein (EE-GRSP), and the relationships of EE-GRSP with SOC and clay fraction. Mulch effects were site-specific rather than uniform. SOC values remained close to or above baseline levels in several vineyard–treatment combinations. POXC relative variability decreased in mulch-treated plots, with the proportion of highly variable units declining from 75% to 25% in both mulch treatments by autumn 2025, while this category remained dominant in the control. FDA activity was mainly associated with soil depth and vineyard-specific conditions. EE-GRSP showed positive relationships with both SOC and clay fraction. Neither mulch material showed consistent superiority across all indicators during the first two years. These findings suggest that soil buffering capacity was best interpreted as the outcome of multiple biological, organic matter-related, and mineral-associated processes operating at different temporal scales. Natural under-vine mulches may support soil stability, although longer-term monitoring is needed to assess the persistence of these responses.