Photosynthetic efficiency and production of Annona squamosa L. under salt stress and fertilization with NPK

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-(KO)-O-2 resulted in greater cell membrane damage in custard-apple.