From doom to bloom: unravelling soil – vine nutrient pathways across land-use legacies in BC vineyards

Abstract

Reducing synthetic fertilizer inputs without compromising yield remains a central challenge for viticulture under climatic and economic pressures. Biological nutrient management offers a promising alternative, yet the mechanisms linking soil microbial function with nutrient cycling and vine establishment are not fully resolved. These uncertainties are particularly important in newly planted vineyards established on contrasting land-use legacies, where inherited microbial communities, soil structure, and nutrient availability can influence early vine performance and shape the emergence of terroir expression. This study evaluates the efficacy of biological nutrient amendments, including mature compost and microbial extracts, in improving soil function and vine establishment relative to synthetic fertilizer across two former land uses, forest and forage, in a newly planted Pinot Noir block in the Cowichan Valley, Vancouver Island, Canada.

Fieldwork was conducted from 2023 to 2025 in a commercial vineyard situated within a cool-summer Mediterranean climate characterized by glacial-fluvial soils moderated by marine conditions. The experimental layout consisted of eight rows of Pinot Noir (990 vines), with paired biological-treatment and fertilizer-control rows replicated across forest- and forage-derived soils. Soil properties were assessed biweekly throughout each growing season, including pH, carbon, compaction, aggregate stability, and microbial functional groups using shadowing microscopy. Litter decomposition was quantified using three-month incubations in spring and fall, and phospholipid fatty acid analysis (PLFA) profiling characterized microbial community structure and functional guilds. Vine performance was evaluated annually using pruning biomass.

Generalized linear mixed models (GLMMs) and structural equation modelling (SEM) resolved direct and mediated pathways linking microbial biomass and guilds, decomposition, soil physical condition, and vine biomass. Ordination analyses were used to visualize legacy- and treatment-driven differences in microbial community structure.

Biologically managed vines achieved comparable or higher vigor than synthetic-fertilizer controls, with the strongest responses occurring in the former forest soils. Biological treatments reduced compaction, increased aggregate stability, and elevated fungal biomass, particularly in legacy forest soils where fungi were already more abundant. Forage soils began with lower fungal biomass, organic matter and aggregation, and exhibited more gradual shifts. Decomposition rates and microbial activity were closely aligned with shifts in soil structure and nutrient availability, indicating that microbial networks mediate amendment effects through their influence on nutrient-cycling pathways. These findings demonstrate that biological nutrient management can accelerate early vine establishment, enhance soil functional resilience, and reinforce the ecological underpinnings of terroir in newly established vineyards across heterogeneous legacy soils.

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Acknowledgments

– Mathematics of Information Technology and Complex Systems (MITACS), Miraterra Inc.

– Stephens Family Research Awards in Organic & Sustainable Food Systems

– Jackson Family Wines