Photochemical efficiency and growth of sugar apple under irrigation with saline water and foliar nitrogen

Salt stress has compromised the worldwide expansion of fruit farming by causing damage to light energy regulation and crop growth, which can be mitigated by applying foliar nitrogen (N). From this perspective, this study aimed to evaluate the chlorophyll contents, fluorescence, and the growth of sugar apple seedlings under irrigation with saline water and foliar N fertilisation. The experiment was conducted in a plant nursery and following a randomized block design referring to five electrical conductivity levels of irrigation water (0.5, 1.15, 2.75, 4.35, and 5.0 dS m-1) and five foliar N levels (0.0, 0.33, 1.15, 1.97, and 2.3 g L-1), with four replications and two plants per plot, totaling nine combinations generated by the Box central composite design. Irrigation water salinity reduces the growth of sugar apple seedlings irrigated with conductivity levels over 1.7 dS m-1 at 90 days after emergence. Foliar N fertilisation increased the photochemical efficiency and growth of sugar apple seedlings. The foliar application of 1.93 g L-1 mitigate the deleterious effects of water salinity on the photochemical efficiency and growth of sugar apple seedlings.