Produção de mudas de gravioleira irrigadas com águas de distintas salinidades e doses de nitrogênio.

Abstract

The cultivation of soursop (Anonna muricata L.) in the irrigated areas of the Brazilian northeast has great socioeconomic importance. However, due to the limitation of water of low electrical conductivity for irrigation in this region, it is necessary to carry out the study of techniques that make possible the use of saline water in the cultivation of the species. In this sense, the aim of this work was to evaluate the tolerance of soursop seedlings to the increase of salinity of irrigation water, under fertilization with different nitrogen doses. The experiment was carried out in a greenhouse at the Federal University of Campina Grande at the Agro-Food Science and Technology Center, Pombal campus, PB. The experimental design was a randomized block design in a 5 x 4 factorial scheme, with four replications and two plants per plot. The treatments were related to the five levels of electrical conductivity of the irrigation water (0.3, 1.1, 1 , 9, 2.7 and 3.5 dS m-1) in combination with four nitrogen doses (70, 100, 130 and 160% N of the recommended dose for soursop seedlings), in which the cultivar Morada Nova was evaluated. The plant height, stem diameter, leaf number, leaf area, leaf area ratio, specific leaf area, and physiological variables were evaluated at 45 and 90 days after application of the treatments, with respect to the absolute and relative growth rate of the leaf diameter. Stem in the periods of 15-45 and 45-90 DAT. On the other hand, the variables of fresh and dry phytomass of stem and leaves, root dry matter, shoot and total, as well as Dickson quality index were evaluated at 90 days after application of the treatments. The growth of soursop seedlings cv. Morada Nova, submitted to different levels of salinity of water was less affected in the initial phase (45 DAT). In the production of soursop seedlings, CEa water of 2.1 dS m-1 can be used as it provides an acceptable average reduction of 10% in growth. Doses of N higher than 70 mg of N dm-³ soil do not attenuate saline stress or promote greater growth of soursop seedlings cv. New address. The interaction between the factors nitrogen doses and water salinity levels did not affect the production stage of saplings cv. New address.