Table grape harvested sequentially twice a year in a subtropical climate

Harvesting table grapes twice yearly presents a viable opportunity for winegrowers seeking to increase profitability and extend fruit availability in the market. In this study, we aimed to assess the production and quality of the seeded grape Niagara Rosada, a table grape resulting from a natural mutation of Niagara with red fruit. The vineyard was 14 years old and not irrigated; the soil is classified as dystrophic Tb Haplic Cambisol, and the climate is humid subtropical with dry winter and warm summer. Vines were pruned twice a year, leading to harvests in 2015 and 2016 in both summer and winter (a total of 760 days). Throughout the experiment, we monitored various climatic conditions, such as rainfall, air temperature, photosynthetically active radiation (PAR), temperature range, degree-day accumulation, and Huglin index values. We evaluated yield and fruit quality, including the number of branches and bunches, as well as the weight and size of the bunches and berries. Additionally, we assessed the quality of the must, examining soluble solids, acidity, and the maturation index for each harvest. We observed that higher rainfall and PAR during the summer harvest resulted in increased grape production compared to winter harvest. Niagara Rosada produced two branches and four bunches more per plant during the summer than in the winter crop, increasing by 71.2% of grape production. Interestingly, however, fruit harvested in winter displayed better quality with a higher maturation index. Despite these differences, both summer and winter harvests met the quality standards for commercialization. In conclusion, our findings suggest that winegrowers can successfully harvest Niagara Rosada grapes twice a year under subtropical conditions, offering a feasible approach for increasing productivity and fruit availability within the market.