Orchard cooling with overtree microsprinkler irrigation to improve fruit colour and quality of 'Topred Delicious' apples

The influence of supplemental microsprinkler irrigation on fruit colour of 'Topred Delicious' apples (Malus domestica Borkh.) was evaluated in the area of Lleida (NE Spain) over a 3-year period. Cooling irrigation was applied for 2 h daily for 25-30 days preceding the harvest. Three treatments were evaluated: (1) control without overtree microsprinkler irrigation; (2) microsprinkler irrigation applied at sunset; (3) microsprinkler irrigation applied at mid-day (year 2) or at sunrise (year 3). Fruit colour, measured with a Minolta CR-200 portable triestimulus colourimeter using the CIE 11976] L*a*b* system, and anthocyanin concentration were significantly affected by the cooling irrigation and also by the weather of the particular year. While in 1997, low temperatures and rainfall prior to harvest masked the effects of cooling irrigation on fruit colour, 1998 and 1999 were average warm years, and cooled fruits had better colour. Increased red colour, and higher anthocyanin content resulted from microsprinkler irrigation especially when applied at sunset and at sunrise. Fruit firmness, fruit size, and soluble solids concentration (SSC) were significantly higher in cooled fruits than the control, whereas titratable acidity (TA) was not influenced consistently by the evaporative cooling. (C) 2002 Elsevier Science B.V. All rights reserved.