Tolerância de genótipos de maracujazeiro-azedo a salinidade da água de irrigação sob adubação potássica.

Abstract

The semi-arid region of Brazil stands out in the production of passion fruit, however, in these areas it is common to use water with high salt content in irrigation, which is a factor responsible for limiting the growth, development and production of crops. In this sense, the use of management strategies, such as supplementing potassium fertilization and the use of salinity-tolerant genotypes, are techniques that can optimize crop production in these regions. Therefore, the objective was to evaluate the tolerance of passion fruit genotypes to the salinity of irrigation water under potassium fertilization in semi-arid conditions in Paraíba. The research consisted of two stages, developed in vessels adapted as drainage lysimeters under field conditions, at the experimental farm of the Center for Agro-Food Science and Technology of the Federal University of Campina Grande, São Domingos, Paraíba. A randomized block design was used in both experiments. In the first stage, the 5 × 3 factorial scheme was adopted, with five levels of electrical conductivity of irrigation water - ECw (0.3; 1.1; 1.9; 2.7 and 3.5 dS m-1) and three genotypes of sour passion fruit (Gigante Amarelo - ‘BRS GA1’; Sol do Cerrado - ‘BRS SCS1’ and Catarina - ‘SCS 437 Catarina’). In the second stage, the BRS Sol do cerrado genotype was used (as it was the one that showed the greatest tolerance to saline stress in the first stage), adopting the 5 × 4 factorial scheme, with the same irrigation ECw levels as in stage I, and four doses of potassium - KD (60; 80; 100 and 120% of the K2O recommendation). The data allowed us to conclude that water salinity from 0.3 dS m-1 reduced the relative water content, gas exchanges and increased electrolyte extravasation in the leaf blade, 154 days after transplanting. The genotypes ‘BRS Gigante Amarelo’, ‘BRS Sol do Cerrado’, and ‘SCS 437 Catarina’ were classified as sensitive to saline stress, with threshold water salinity levels of 0.3, 1.0, and 0.3 dSm-1, respectively. Increasing the salinity of irrigation water reduced the number and production of fruits per plant of the genotypes. The genotype ‘BRS Sol do Cerrado’ showed the smallest reduction in relative production due to the increase in salinity levels of the irrigation water. An increase in sodium and chloride levels was also observed in the stem and leaves of the sour passion fruit plants with the increase in ECw levels. Furthermore, the nutrient contents in the leaves and stems varied xix following the same order of concentration N>Cl>P>Na>K, depending on the increase in the electrical conductivity of the irrigation water, at 160 days after transplanting. Regarding post-harvest quality, irrigation with water with electrical conductivity of 2.7 dS m-1 associated with fertilization of 60 and 80% K2O increased the total soluble solids content and the ascorbic acid content in the sour passion fruit ‘BRS Sol do Cerrado’.