Response of `Nocellara del Belice' Olive Trees to Organic Foliar Fertilization

Abstract

Five different types/combinations of foliar fertilizers were tested on eight-year-old trees of `Nocellara del Belice' olive grown in central Sicily. Trees were sprayed four times during Summer and Fall 2002 with Floral 20-20-20 (mineral N, P, K, and microelements; FLO) in combination with Alga Cifo (extract of brown algae; ALG), Floral 20-20-20 alone, Alga Cifo alone, Azomin (organic N, amino acids and peptides; AZO), Supernat93 (organic N and K, distillation residue; SUP), and water (control). 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 trees, 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 improved yield and growth of `Nocellara del Belice' olive trees by reducing ovary abortion and June drop and increasing shoot growth.