Effect of shade cloth on fruit and leaf nutritional concentration and bitter pit incidence in 'Fuji' apples

Juan Hirzel1*, Ernesto Moya-Elizondo2, Macarena Hernández3, Pedro Guzmán3, and Dagoberto González3
Shade cloth is commonly used to reduce incident light in apple (Malus domestica [Suckow] Borkh.) orchards. Nevertheless, this technology can generate changes in plant physiology that affect tissue nutritional composition and cause fruit nutritional disorders. The effect of shade cloth on the nutritional concentration of six macroelements and six microelements on leaves, six macronutrients in the fruits of 'Fuji' apples, and bitter pit incidence was assessed in a study conducted in a commercial orchard in south-central Chile for three seasons. Two treatments (control without shade cloth and 30% shade cloth cover) were evaluated with five replicates in a split plot design. Averaged results for the three seasons showed that shade cloth increased Mg, Mn, and Zn concentrations in leaves by 0.02%, 40 mg kg-1, and 5.5 mg kg-1, respectively, and decreased K, Mg, and S concentrations in fruits by 12, 0.35, and 0.38 mg 100 g-1 fresh fruit, respectively. Bitter pit incidence was not affected by shade cloth (values between 0.3% and 6.6%), but seasonal conditions did affect this abiotic disorder. In conclusion, the use of shade cloth in apples did not affect bitter pit incidence, but it caused some changes in leaf and fruit nutritional concentration.
Keywords: Bitter pit, Malus domestica, nutrients, shade cloth.
1Instituto de Investigaciones Agropecuarias, INIA Quilamapu, Av. Vicente Méndez 515, Chillán, Chile.*Corresponding author (jhirzel@inia.cl). 2Universidad de Concepción, Facultad de Agronomía, Av. Vicente Méndez 595, Chillán, Chile.3Exportadora UNIFRUTTI Traders Ltda., Longitudinal Sur km 300, Linares, Chile.