Phosphorus fractionation in vineyard soils: Influence of cover crops and duration of cultivation

Phosphate fertilizers are typically applied to the surface of vineyard soils in subtropical regions, leading to phosphorus (P) accumulation in the uppermost layers due to the soil's high nutrient adsorption capacity. This scenario often reduces nutrient use efficiency and increases the risk of environmental contamination. The use of cover crops represents a promising strategy to enhance P cycling and redistribution throughout the soil profile via root uptake and subsequent nutrient release at different depths. This study aimed to evaluate: (i) whether cover crop species can redistribute and alter P fractions in the soil profile, and (ii) the vertical distribution of P fractions in vineyards cultivated for 14 and 23 years under cover crop management. Two experiments were conducted to assess the presence of cover crops and the effect of cultivation duration on soil P dynamics. Soil samples were collected from five layers (0.00–0.05, 0.05–0.10, 0.10–0.20, 0.20–0.40, and 0.40–0.60 m) and subjected to sequential chemical P fractionation. The absence of cover crops promoted the accumulation of labile P fractions in the surface layer. In contrast, cover crops favored vertical P redistribution, reducing surface concentrations and increasing P availability in subsurface layers. The 23-year-old vineyard exhibited the highest P concentrations and stocks across all fractions, with a predominance of non-labile forms, reflecting a significant “Legacy P" effect over time.