Impact of Subsurface Localized Irrigation on Physicochemical Quality and Postharvest Stability of Table Grapes

The quality of table grapes at the consumer level depends on both cultivation conditions and their behaviour during the cold chain. This study evaluates how a new subsurface irrigation system (DRS) affects fruit quality attributes at harvest and during storage at 1 ºC for three weeks. The DRS irrigation system draws water directly from the surface tube drip system and delivers it directly to the crop root zone, thereby minimizing water losses due to evaporation, typically associated with conventional drip irrigation, where surface-level wetting bulbs are directly exposed to the atmosphere, reducing water availability to the root zone. Grapes from ‘Regal’ cultivar grown under DRS were compared with those from a conventional drip irrigation system. At harvest, DRS-grown grapes showed greater firmness and more intense green coloration, along with an improved mineral profile (higher calcium, magnesium, and sodium in the pulp, and calcium and sodium in the skin). Fruit also showed a lower ripening index, with reduced sugar content (glucose and fructose) and higher retention of organic acids (citric, malic), as well as lower total polyphenol levels and their subfamilies (hydroxycinnamic acids, flavan-3-ols, and flavonols), suggesting lower physiological stress during development. After storage, DRS clusters retained better physical integrity, with reduced berry drop and less rachis browning and dehydration. In conclusion, field irrigation management is not only relevant to agricultural yield but also determines fruit chemical composition and cold storage capacity. Optimizing production systems such as DRS can improve produce stability, representing a key strategy to reduce food waste caused by inadequate management during cultivation and postharvest stages.