Micronized Calcite Foliar Treatments as an Approach to Enhancing Yield and Quality Parameters of Red Globe Grape (Vitis vinifera L.) Under Semi-Arid Conditions

Background: Foliar fertilization is a crucial practice in modern viticulture to enhance grape yield and fruit quality. Micronized calcite is a fine-particle mineral fertilizer that potentially improves vine performance; however, its treatment timing and optimal dosage require further scientific validation under field conditions. Methods: This study investigated the effects of the use of micronized calcite as a foliar biostimulant on the Red Globe grape variety. Control and three treatments were compared: a control (no treatment), a single treatment (pre-bloom, 0.5%), two treatments (pre- and post-bloom, 0.5% + 0.5%), and three treatments (pre-bloom, post-bloom, and véraison, 0.5% + 0.5% + 0.5%). The evaluation encompassed phenological stages, total effective temperature, yield components, cluster and berry characteristics, and must composition. This was a single-season trial (2022) conducted at a single location with three replicates per treatment (n = 3); multi-year, multi-location validation is therefore required before the findings can be generalized. Results: All micronized calcite treatments slightly shortened the vegetation period compared to the control. Under the conditions of this single-season trial, the single pre-bloom treatment was associated with the highest yield parameters, with the average number of clusters per vine, cluster weight, and total grape yield per vine being higher than the control by 48.67%, 51.16%, and 121%, respectively. For must composition, only must yield differed significantly (between the 1st and 3rd treatments; p < 0.05); soluble solids content (+5.64%) and ripening index (+16.99%) were numerically higher but not statistically significant (p ≥ 0.05) and are therefore reported as trends rather than improvements. By contrast, the two-treatment (pre- and post-bloom) showed the highest values for physical berry traits, with cluster width and 100-berry weight exceeding the control by 35.03% and 11.11%, respectively. Conclusion: Under the semi-arid conditions of this single-season trial, foliar treatments of micronized calcite, particularly a single pre-bloom application, were associated with notable improvements in yield and must quality of Red Globe grapevines. These preliminary findings suggest that finely milled calcite may serve as a promising supplementary foliar fertilizer in viticulture; however, the results are context-specific, and multi-year, multi-location trials are required before broader recommendations can be made.