Morphophysiology and quality of custard apple seedlings irrigated with saline water and foliar nitrogen

The establishment of quality seedlings when irrigated with water with a high saline index has become a challenge for fruit growers in arid and semi-arid regions, requiring the adoption of techniques that will mitigate such effects. In this scenario, this study aimed to evaluate the effects of irrigation with saline water and foliar nitrogen fertilization on the formation of custard apple seedlings. The experiment was conducted in a randomized block design and arranged in a 5 x 5 factorial corresponding to five electrical conductivity levels of irrigation water-ECiw (0.5, 1.15, 2.75, 4.35, and 5.0 dS m(-1)) and five nitrogen levels applied on the leaves (0, 0.33, 1.15, 1.97, and 2.3 g L-1), with four replicates and two plants per plot, totaling nine combinations generated by Box's central composite design. Irrigation with the electrical conductivity level of 1.33 dS m(-1) caused acceptable losses of up to 10% in the net photosynthesis rate, phytomass accumulation, and quality of custard apple seedlings. Nitrogen fertilization at the level of 1.45 g L-1 mitigated the effects of salt stress on the morphophysiology and quality of custard apple seedlings. The N level of 1.59 g L-1 associated with the ECiw of 0.5 dS m(-1) increased the gas exchange, phytomass accumulation, and Dickson Quality Index of custard apple seedlings 90 days after emergence. The application N level from 0.95 ml L-1 maintains the acceptable quality of custard apple seedlings under irrigation conditions with water of 5.0 dS m(-1).

Automated summary

The establishment of quality seedlings in arid and semi-arid regions is challenging when irrigated with high salinity water. This study evaluated the effects of saline water irrigation and foliar nitrogen fertilization on the formation of custard apple seedlings. The results showed that an electrical conductivity level of 1.33 dS m(-1) caused acceptable losses in net photosynthesis rate, biomass accumulation, and seedling quality. Nitrogen fertilization at 1.45 g L-1 mitigated the effects of salt stress on morphophysiology and seedling quality. Additionally, a nitrogen level of 1.59 g L-1 combined with an ECiw of 0.5 dS m(-1) improved gas exchange, biomass accumulation, and Dickson Quality Index of custard apple seedlings. An application of 0.95 ml L-1 of nitrogen maintained acceptable seedling quality under irrigation conditions with water of 5.0 dS m(-1).