Abstract

The highbush blueberry (Vaccinium corymbosum L.) develops naturally under storey of deciduous forests. In Chile, there is a need to produce fruit earlier in the season, which has forced growers to plant under greater environmental stresses (temperature, radiation, and relative humidity). In this context, colored shading nets can alleviate stresses and affect yield and fruit quality. This research was set up to study the effects of shading nets (color, shading degrees) on environmental conditions faced by plants, as well as vegetative growth, yield and quality of fruit produced, as well as economical performance in highbush blueberries. The experiment started in 2003 in an orchard cv. Berkeley planted in Miraflores, Chile (Lat. 36°04'S; Long. 72°47'E) in 1994 at 3 x 1 m. Black, white, gray and red nets and 35 and 50% shading plus a control treatment (no net) were tested. Nets were set each season at 3.5 m height at fruit set and remained until early leaf fall. With respect to control, white 35 and 50, gray 35 and 50 and red 35%, decreased PAR radiation in 29%; while red 50, black 35 and black 50 decreased PAR in 41, 47 and 53% respectively. Colored nets did not consistently affect air temperature, soil moisture and relative humidity. Yields (wt/plant) over control were increased in year 1 and 2 by 90.5 and 44.6% respectively for white 50%, 59.6 and 24.9% (gray 35%) and 84.2 and 31.9% (red 50%). Black net, commonly used by growers, had long term negative effects on yield; thus for black 35%, yields were 37.2 and -8.3, while for black 50%, yields were -3.2 and -28% of control, respectively. Higher yields were due to greater fruit number, since nets did not affect fruit size or soluble solids. In season 1, black nets increased shoot and internode length, and leaf size, while shoot number and leaf length/width ratio were unchanged.