IMPACT OF SALINE CONDITIONS AND NITROGEN FERTILIZATION ON CITRUS PRODUCTION AND GAS EXCHANGES

In two simultaneous experiments, we evaluated the impact of brackish irrigation water and nitrogen (N) fertilization on the production of citrus (scion-rootstock combinations) and its associated gas exchanges. These experiments were conducted at the Campus of Federal University of Campina Grande, Brazil in a protected environment (shade screens on the sides) using drainage lysimeters. Experiment I used a randomized block design (3 replicates), in a 5 x 3 factorial arrangement, corresponding to five water salinity levels (0.6, 1.2, 1.8, 2.4, and 3.0 dS m(-1)) and three scion-rootstock combinations: RS1-Common Sunki mandarin (TSKC) x Poncirus trifoliata English (TRENG) -256; RS2- Common Rangpur lime (LCRSTC); and RS3-TSKC x (Rangpur lime (LCR) x P. trifoliata (TR)) -059; with Mimo do Ceu orange as the scion variety. Experiment II used a randomized block design (3 replicates), in a 3 x 2 factorial arrangement, corresponding to the three scion/rootstock combinations and two nitrogen (N) doses (100 and 200 mg kg(-1) of soil). Plants were irrigated with water of 3.0 dS m(-1). For both experiments, gas exchanges and mean mass of fruits were evaluated at harvest. Gas exchanges were inhibited in plants under saline stress. Plants grafted with Common Rangpur lime showed greater production potential than did the other genotypes studied, even under brackish water conditions.