TISSUES ALTERNATIVE TO LEAF TO ASSESS THE RESPONSE TO FERTILIZATION WITH ZN OR B IN HASS AVOCADO

Abstract

Symptoms of zinc (Zn) or boron (B) deficiencies in fruit and leaves are common in the Hass avocado (Persea americana Mill.) producing region AT the State of Nayarit, México. Monitoring foliar concentrations of these micronutrients in response to fertilization does not always provide an accurate diagnosis. This research evaluated the effect of soil fertilization with Zn or B on the concentration of these nutrients in the tissue of different plant structures of Hass avocado. The study was conducted in a commercial Hass avocado orchard grown without irrigation under the sub-humid semi-warm climate of Tepic, Nayarit. Treatments were applied to the soil during the 2001 to 2005 rainy seasons (July and September) and consisted of (g per tree per year): (T1) two applications of 750 g ZnSO₄ (35.5 % Zn); (T-2) two applications of 29.5 g Boronat® (32 % B); and (T-3) control without Zn or B applications. Sampled tissues were floral buds at “cauliflower” stage, complete inflorescences at anthesis, flowers at anthesis, rachis of inflorescences at anthesis, fruit peduncle + pedicel at physiological maturity, fruit pulp, and 6-month old leaves from the winter vegetative flush. Tissues that showed the best response to fertilization with Zn were the rachis of inflorescences at anthesis and the fruit pulp at physiological maturity. For B, the best tissues were complete inflorescences at anthesis and the peduncle + pedicel of fruit at physiological maturity.