Crescimento, fisiologia e produção de citros sob águas salinizadas e adubação nitrogenada.

Abstract

In semiarid regions the use of brackish water in irrigation has become a frequent practice may compromise the physiological indices and yield of crops, such as in citrus; however, this can be minimized by the use of tolerant rootstocks and suitable nitrogen source. Thus, the objective of this study was to evaluate the growth, physiological indices and yield of combinations scion/rootstock of citrus irrigated with saline water and nitrogen. Two concurrent experiments were conducted in lysimeters with capacity of 200 L installed in UFCG campus of Campina Grande-PB, exposed condition with only screen protection in a greenhouse. In the first experiment randomized complete block design we used with three replications studying, factorial (5 x 3), five levels of water salinity - CEa (0.6, 1.2, 1.8, 2.4, and 3.0 dS m-1) applied to three combinations of scion/rootstock (PE1 – TSKC x TRENG – 256; PE2 – LCRC e o PE3 – TSKC x [LCR x TR] – 059) and the canopy formed by orange ‘mime of heaven’. In experiment II the treatment of CEa of 3.0 dS m-1 was replicated, applying a dose of 200% of recommendation for tests in a controlled environment and compared with the results of the first experiment, forming a factorial (3 x 2) three combinations of scion/rootstock x two doses of nitrogen, with three replications each. After 150 days of flowering, were evaluated in both experiments, growth rates, biochemical, physiological and production. Data were subjected to analysis of variance by F test comparing the means by Tukey test (p < 0.05). Irrigation with saline water reduces stem diameters. The PE1 (TSKC x TRENG – 256) is more tolerant to salinity in the relative water content and electrolyte extravasation. Salt stress reduces gas exchange and levels of chlorophyllian pigments of citrus plants. The quantum efficiency of photosystem II is inhibited in citrus plants under salt stress. The increase in the salt content of the irrigation water promotes the number of fruits per plant, but reduces the size, mean weight and total fruit production. The highest yield was observed in the grafted plants lemon (cravo comum), as well as minor reductions in fruit size with increasing salinity. In the experiment with nitrogen less cell damage was observed when higher dose of N was applied. The transpiration rates, stomatal conductance and photosynthesis are high under higher dose of nitrogen. The increase in nitrogen fertilization increased fruit production.