Cultivo de maracujazeiro-amarelo sob estratégias de irrigação com água salobra e potássio.

Abstract

The use of brackish water in irrigated areas in the Brazilian semiarid region has intensified, mainly due to the long periods of drought. However, excess salts in water can cause stress in plants, depending on the species, genotype or stage of development. In this context, the use of strategies with brackish water and potassium fertilization have stood out as promising alternatives for the cultivation of yellow passion fruit in the semi-arid conditions of Northeast Brazil. Thus, this research aimed to evaluate the physiology, production and postharvest quality of yellow passion fruit fruits submitted to irrigation strategies with brackish water and potassium doses. The research was carried out in two cultivation cycles under field conditions at the Experimental Farm 'Rolando Enrique Rivas Castellón', belonging to the Agro-Food Technology Science Center - CCTA of the Federal University of Campina Grande - UFCG, in São Domingos - PB. A randomized block design was used, in a 6 × 2 factorial scheme, whose treatments were constituted by the combination of two factors: irrigation strategies with brackish water (irrigation with low salinity water during the entire crop cycle - SE; irrigation with of high salinity only in the following phases: vegetative - VE; flowering - FL; fruiting - FR; successive phases vegetative/flowering VE/FL; vegetative/fruiting - VE/FR and two doses of potassium (60 and 100% of K2O of the recommendation of fertilization for the culture), with four replications, with each plot consisting of 3 plants, making a total of 144 experimental units. The 100% dose corresponded to 345 g of K2O per plant per year. In the establishment of management strategies, two salinity levels were used, one with low salinity (ECa=1.3 dS m-1) and the other with high CEa (4.0 dS m-1). The first productive cycle was carried out from transplanting the seedlings to the field until the end of the fruiting phase (1- 253 DAT). The second production cycle corresponded to the period of 254 – 445 DAT. In both production cycles, gas exchange, photosynthetic pigments, chlorophyll a fluorescence, water status, production and post-harvest quality of the fruits were evaluated. In the first production cycle, in general, the saline stress imposed on the different phenological phases xiv caused reductions in the fluorescence of chlorophyll a, photosynthetic pigments, and the water status of passion fruit plants, however, in general, passion fruit plants cultivated under saline stress successively in the vegetative and flowering phases showed significant reductions in gas exchange, in the number of fruits, productivity, and polar and equatorial diameters of the fruits, and between the doses of potassium, the dose of 60% favored greater photosynthetic efficiency, resulting in greater number of fruits and productivity, increasing the polar and equatorial diameters and the post-harvest quality of the fruits. For the second production cycle, in general, the saline stress imposed in the different phenological phases caused significant reductions in photosynthetic pigments and in the water status of passion fruit plants, however, commonly when saline stress was imposed in the vegetative and flowering phases successively. , passion fruit plants were more sensitive, showing significant reductions in gas exchange and chlorophyll a fluorescence, resulting in a decrease in the number of fruits, productivity, and polar diameter of the fruits, and between potassium doses, the dose of 60 %, caused greater synthesis of chlorophyll a, and in general, favored an improvement in the water status of the leaves and in the post-harvest quality of the fruits.