Foliar fertilization in ‘Nocellara del Belice’ olive trees

Abstract

Eight-year-old olive trees of ‘Nocellara del Belice’ grown in central Sicily were treated with five different types/combinations of organic and mineral foliar fertilizers. Floral 20-20-20 (mineral N, P, K, and microelements; FLO), Alga (extract of brown algae; ALG), FLO+ALG, Azomin (organic N, amino acids and peptides; AZO), Supernat93 (organic N and K, distillation residue; SUP), and water (CONTROL) were applied four times during summer and fall 2002. Yield and trunk circumference were measured during fall 2002, whereas other vegetative and reproductive parameters were measured during spring-fall 2003. AZO and SUP trees produced more than CONTROL and ALG ones, whereas only AZO trees showed higher yield efficiency than CONTROL. The number of inflorescences per shoot was greatest in FLO and ALG trees and smallest in CONTROL trees. Percentage of ovary abortion and June drop were lowest in AZO trees and highest in FLO+ALG and ALG trees, whereas ALG was the only fertilizer that caused a greater fruit drop at harvest. Shoot growth was significantly reduced in ALG and FLO trees, and AZO trees presented leaves with reduced specific weight. Organic foliar fertilization with AZO and SUP generally induced better productive and vegetative performances in ‘Nocellara del Belice’ olive trees than CONTROL or mineral foliar fertilizers by reducing ovary abortion and June drop and increasing shoot growth.