Cultivo de aceroleira irrigada com águas salinas sob combinações de adubação nitrogenada e potássica.

Abstract

The West Indian cherry stands out among the fruit trees with potential for cultivation in the semiarid region of the Brazilian Northeast. In this region, the use of saline water for irrigation has intensified during the long periods of water scarcity; however, the use of water with high concentrations of salts can affect the nutritional balance, growth and crop production. Under these conditions, the management of a combination of nitrogen and potassium fertilization can be an alternative to mitigate these effects caused by salt stress. Thus, this research aimed to study the effect of different salinities on irrigation water on the physiology, growth, production components and postharvest quality of West Indian cherry fruits, fertilized with combinations of nitrogen and potassium doses in the first and second year of cultivation. The research was carried out in the field, with plants grown in pots adapted as 60-L lysimeters, in an experimental area belonging to the Center for Agrifood Science and Technology of the Federal University of Campina Grande, located in the municipality of Pombal-PB, in a randomized block design, with treatments arranged in a 5 x 4 factorial scheme, referring to five levels of irrigation water salinities (ECw): 0.3, 1.3, 2.3, 3.3 and 4.3 dS m-1 and four combinations of doses of nitrogen and potassium: 70% N + 50% K2O; 100% N + 75% K2O; 130% N + 100% K2O and 160% N + 125% K2O, of the recommended dose for irrigated West Indian cherry, with three replicates and experimental plot consisting of a lysimeter, containing one plant, totaling 60 experimental units. Graft West Indian cherry fruits seedlings were used, having as rootstock the cultivar Junco, and graft to cultivar Flor Branca. The application of fertilizer combinations and saline water started at 20 and 41 days after transplanting, respectively, in which they were applied until the end of the experiment. Growth, physiological, production and post-harvest quality variables were evaluated up to 550 days after transplanting. Irrigation water salinity compromised plant growth after 230 days, with a decrease in stem diameter below, at the point, above the grafting and primary branches above ECw of 2.32 dS m-1, while gas exchange was not affected during this period. Between 260 and 330 days after transplanting, the negative effects of increasing salinity to ECw of 4.3 dS m-1 were intensified in the plant stem diameters and reduced fruit size, weight and vitamin C content. However, did not affect canopy diameter and volume, vegetative vigor index, fruit number, yield per plant, anthocyanin, carotenoid content, pH, titratable acidity and total soluble solids and fruit flavor. In the second year of cultivation, between 420 and 550 days after transplanting, the increase in salinity of irrigation water from 0.3 dS m-1 decreased the content of photosynthetic pigments in leaves, photochemical efficiency, gas exchange, the water potential in the plants, intensified the damage to the membranes and reduced the length, diameter and mass of fruits, number of fruits and production per plant. The combination of 70% N + 50% K2O of the recommended dose favored higher plant growth, physiological activities and production components in the first and second year of cultivation, although it did not affect the physicochemical attributes of the fruits in the first year, at 295 days after transplanting. In addition, this combination of N and K2O mitigated the effect of salinity on the average fruit size in the first year of cultivation (between 260 and 295 days after transplanting) and production per plant in the second year (between 420 and 550 days after transplantation), up to water salinity levels of 1.3 and 2.3 dS m-1, respectively, making it the most suitable fertilizer combination for fertilizing irrigated aceroleira with saline water. Fertilization with nitrogen and potassium above the recommended dose intensified the salt stress and nutritional imbalance in the plants, compromising the growth, physiology and production components of the West Indian cherry in the first and second year of cultivation.