PHENOLOGY AND GROWING DEGREE DAYS OF FESTIVAL STRAWBERRY GROWN ON RED VOLCANIC ROCK AT TWO PLANT DENSITIES

Abstract

Due to their correlation with temperature, growing degree days (GDD) allow to analyze the effect of climate change on plant phenology, while being also useful for scheduling activities in a cultivation system. Fruit cropping systems in general lack enough information in this regard. This research aimed to determine GDD during the phenology of Festival strawberry (Fragaria × ananassa Duch.) grown on two substrates at two plant densities under a macro-tunnel. Previously chilled (4 o C/720 h), one-leaf plants were grown from August 2016 to March 2017 either in hydroponics on red volcanic rock or in soil with fertigation at 10 or 15 plants m^-2. A Steiner nutrient solution reduced to 50% of its original concentration was used. GDD were counted daily after planting using the single sine curve method with a base temperature of 3 o C. A high correlation coefficient (r > 0.964) was found between GDD and days after planting (DAP) for the phenological stages studied. The phyllochron was not affected by treatments, and 597 GDD were required as an average for the onset of leafing and a high correlation between air temperature and the emission of leaves number 2 to 10 (r = 0.9754; P ≤ 0.0001). The substrate did not affect the chronology of the reproductive phenological stages. The onset of anthesis was delayed by 17 days in plants grown at 15 plants m^-2 (2039.4 GDD) compared to those grown at 10 plants m-2 (1829.7 GDD), but there was no effect of plant density for the sequent phenological stages. It is concluded that GDD have a high predictive value in Festival strawberry for DAP of the phenological stages studied; likewise, the phyllochron and reproductive phenology were not affected by substrate cultivation; however, planting at high densities could delay the onset of anthesis.