HIGHLIGHTS
Electrical conductivity of water of 3.0 dS m-1 reduces the chlorophyll synthesis and production of custard-apple.
NPK recommendation of 100-125-125, 125-125-100 and 125-125-125% cause more damage to the cell membrane.
Reduction in the quantum efficiency of custard-apple under salt stress is indicative of photoinhi-bitory damage.
Key words:
water scarcity; salt stress; mineral nutrition; custard-apple
ABSTRACT
In the semi-arid region of Northeastern Brazil, the high concentration of salts found in the waters stands out as a limiting factor for irrigated agriculture. Thus, fertilization with nitrogen (N), phosphorus (P) and potassium (K) is a strategy capable of alleviating the effects of salt stress on plants. In this context, the objective of this study was to evaluate the concentrations of chloroplast pigments, chlorophyll fluorescence, cell membrane damage and the production of custard-apple irrigated using water with different electrical conductivities and fertilized with nitrogen, phosphorus and potassium. The treatments were distributed in randomized blocks, with three replicates, in a 2 × 8 factorial scheme, corresponding to two levels of electrical conductivity of irrigation water - ECw (0.8 and 3.0 dS m-1) and eight combinations of NPK fertilization (100-100-100; 100-100-125; 100-125-100; 100-125-125; 125-100-100; 125-100-125; 125-125-100 and 125-125-125% of the recommended doses of N-P2O5-K2O). ECw of 3.0 dS m-1 reduced chlorophyll a and total chlorophyll concentrations, number of fruits per plant, photochemical efficiency, and increased carotenoid concentration and cell membrane damage in custard-apple. Fertilization with 100-125-125, 125-125-100 and 125-125-125% of the recommended doses of N-P2O5-K2O resulted in greater cell membrane damage in custard-apple.
Key words:
water scarcity; salt stress; mineral nutrition; custard-apple
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Means followed by the same letters did not differ significantly by Tukey test (p ≤ 0.05); Vertical bars represent the standard error of the mean (n = 3)
C1 = 100-100-100; C2 = 100-100-125; C3 = 100-125-100; C4 = 100-125-125; C5 = 125-100-100; C6 = 125-100-125; C7 = 125-125-100 and C8 = 125-125-125% of the recommended dose of N-P2O5-K2O; Means followed by the same letter do not differ significantly for irrigation water salinity and different combinations of fertilization with N-P2O5-K2O, respectively, by Tukey test and Scott-Knott test at p ≤ 0.05, respectively; Vertical bars represent the standard error of the mean (n = 3)
Means followed by the same letter do not present significant differences between each other by the Tukey test (p ≤ 0.05); Vertical bars represent the standard error of the mean (n = 3)