Fontes de adubos foliares na produção de mudas enxertadas de cajueiro-anão

Abstract

The increase in the dwarf cashew tree plantation area to replace the common cashew tree has required a growing demand for quality seedlings. The use of superior clones, in addition to the practice of foliar fertilization in the seedling production phase, can be essential to improve the development and vigor of seedlings, producing better quality plants and, consequently, more productive cashew trees and resistant to pest attack, diseases and environmental stresses. The objective was to evaluate the application of foliar fertilizers in dwarf cashew tree clones in the seedling production phase. The experiment was carried out in two locations, the rootstock production stage and grafting being carried out in the Experimental Field of Embrapa Agroindústria Tropical, during the first 135 days, located in Pacajus - CE and the second stage corresponding to the application phase of the foliar fertilizers and evaluations, carried out in a greenhouse at the Federal University of Ceará, in the last 60 days. A completely randomized experimental design was used, in a split-plot scheme, with three sources of foliar fertilizers (Mega 10®, FH Attivus® and Master®) being evaluated, in addition to the control (without foliar fertilizer) as main treatments and five clones of dwarf cashew tree ('BRS 265', 'BRS 189', 'BRS 226', 'CCP 76' and 'Embrapa 51') in the subplots, with five replications. Each experimental unit consisted of three plants, totaling 300 seedlings. The following biometric components were evaluated: seedling height, stem diameter, number of leaves, leaf area and dry mass of leaves, roots and stem; the physiological variables evaluated were: net photosynthetic rate, leaf transpiration rate and stomatal conductance to water vapor; photosynthetic pigments and SPAD index; and the levels of macro and micronutrients in the leaves. The foliar fertilizers did not promote improvements in the biometric characteristics and in the dry matter biomass of the seedlings of the dwarf cashew tree clones, but an increase in the relative and absolute growth rates was observed. Foliar fertilization provided an increase in SPAD index, total chlorophyll content, gas exchange and micronutrient levels. It is recommended to use the Master® foliar fertilizer for the 'BRS 189' and 'CCP 76' clones, the Fh Attivus® and Master® foliar fertilizers for the 'BRS 265' and 'Embrapa 51' clones and the Mega 10® foliar fertilize for the 'BRS 265' clone.