Crescimento de cinco espécies florestais cultivadas em diferentes níveis de salinidade da água.

Abstract

An experiment was undertaken in Campina Grande (Paraiba State, Northeastern Brazil) to evaluate the effect of different levels of salinity of the irrigation water on chemical properties of soil and on the growth of different wood species. The experiment was carried out under greenhouse condition, using a sand-loam soil from Sao Jose do Bonfim, Paraiba State, as substrate. Five wood species such as craibeira (Tabebuia caraiba Bur.), favela (Cnidosculus phyllacanthus Pax. & K. Hoffm), jurema-preta (Mimosa hostilis Benth), pauferro (Caesalpinia ferrea Benth - Ducke), and sabia (Caesalpiniaefolia Mimosa Benth)], six levels of salinity of the water (1, 2, 3, 4, 5 and 6 dS m"1) and three independent replicates, in a randomized design, were utilized. The water of a dam was used by adding Na+, Ca2+ and Mg2+ chloride salts at rates of 70, 20 and 10%, respectively, to achieve the desirable electric conductivity (EC) values, what led to increases on Na+, Ca2+ + Mg2 \ K+ soil concentrations and, as consequence, in the EC values of saturation extract, but pH was not affected. Some studied species had been affected in their growth by the salinity, but for some other this was not seen by analyzing the height of shoot and/or the diameter. After 120 days of treatment there was an significant reduction in the growth of the craibeira, jurema-preta and pau-ferro (61.10, 24.37 and 35.46%) in the highest level of salinity, while the height of favela and sabia species was similar to that of control. Similarly, the diameter of the craibeira, pau-ferro and sabia were significantly smaller in the higher levels of salinity of water (41.40, 22.01 and 26.42% smaller). Craibeira and sabia had presented the biggest reductions in the accumulation rates of dry mass of the shoot, which had reached, respectively, 82 and 86%. In the case of the species favela and jurema-preta the effect of salinity of irrigation water was sharper in the dry mass of the roots, while in the specie pauferro the accumulation of dry mass in the shoot and the roots similarly was affected by the salinity. It is concluded, that the production of dry mass of the aerial part was the best indicator of salt tolerance and the favela and the jurema-preta species showed better growth in soils with high concentrations of salt.