Physiological alterations and production of guava under water salinity and nitrogen fertilizer application

Adequate management of saline water irrigation and nitrogen (N) fertilizer application in agriculture can contribute substantially to expanding guava cultivation in the semi-arid region of Northeast Brazil. This study aimed to evaluate gas exchange and production of ‘Paluma’ guava cultivated with different levels of water salinity and N. The experiment was carried out in drainage lysimeters under field conditions in an experimental area of the Federal University of Campina Grande (UFCG), Campus of Pombal, PB, Brazil. The experimental design was randomized blocks, in a 5 × 4 factorial scheme, with five levels of water salinity – ECw (0.3, 1.1, 1.9, 2.7 and 3.5 dS m-1) and four doses of N (70, 100, 130 and 160% of the recommendation) with three replicates. The dose relative to 100% corresponded to 541.1 mg of N dm-3 of soil. The following production components were evaluated: number of fruits, mean fruit weight, polar and equatorial diameter of fruits, and polar diameter/equatorial diameter ratio. In addition, the following physiological variables were evaluated at 180 days after fruit pruning: stomatal conductance, CO2 assimilation rate, internal CO2 concentration and transpiration rate. CO2 assimilation and transpiration rate were used to calculate instantaneous water use efficiency. The interaction between water salinity and N doses did not cause significant effects on any variable studied. Irrigation water salinity above 0.3 dS m-1 hampered gas exchange at 180 days after fruit pruning and negatively affected production components.