Abstract
<title>Abstract</title> <p>Organic viticulture in semi-arid regions depends on organic fertilizer sources, but their effectiveness on calcareous, phosphorus-deficient soils needs further field quantification. Six organic fertilizer sources (bacterial biofertilizer, bat manure, farmyard manure, compost and vermicompost in solid and liquid forms, and a commercial organic fertilizer applied to soil or foliage), each at three rates, together with an untreated control, were compared on seven-year-old own-rooted 'Boğazkere' vines grown in a slightly alkaline (pH 7.6–7.7), calcareous (13.0–16.7% CaCO₃) vineyard soil in Diyarbakır, Türkiye, during the 2021 growing season. The 28 treatments were arranged in a randomized complete block design with three replicates of three vines each. Yield, cluster and berry traits showed no significant differences among treatments (p > 0.05); vine yield ranged from 7.07 to 15.22 kg vine⁻¹, the highest under the bacterial biofertilizer at 100 mL. Must total soluble solids was the only must trait that differed among treatments, increasing from 18.10% in the control to 19.43% under the bacterial biofertilizer at 100 mL (+ 7.3%), while foliar commercial fertilizer at 10 g and liquid compost at 75 mL gave the lowest values (16.87% and 16.63%). Leaf nitrogen remained within the sufficiency range, whereas leaf zinc stayed below the sufficiency threshold in every treatment, including the control. The bacterial biofertilizer at 100 mL vine⁻¹ was the treatment most consistently associated with improved must soluble solids, whereas organic matter-based amendments had no detectable effect on yield or berry composition; the site-wide zinc deficit calls for a separate foliar Zn programme.</p>