Biometria em plantas de noni sob irriga??o com águas salinas e lixivia??o dos sais do solo

摘要

The use of water with a high salt content is seen as an alternative in global agricultural production; but there is a need for technologies that reduce the impact on soil and crop yields, such as employing leaching of salts from the soil or the use of salt-tolerant species. With this in mind, the aim of this work was to evaluate the growth of the noni plant (Morinda citrifolia L.) when submitted to irrigation and washing the soil with water of increasing salinity. The experiment was carried out in a greenhouse environment of the Centre for Agricultural Science, at the Federal University of Paraiba in Areia, in the State of Paraiba, Brazil. The design was of randomised blocks, with four replications and two plants per lot, using a 5×2 factorial arrangement, representing the five values for electrical conductivity of the irrigation water (0.5, 1.5, 3.0, 4.5, 6.0 dS m-1), with and without drainage for washing the soil and leaching the salts. Increases in the electrical conductivity of the irrigation water raised the saline character of the soil to values that compromised biometric growth and the total biomass production of the noni plants, whether with or without the leaching of salts; this was more severe for all variables in the soil with no drainage. The plants in soil where there was no leaching, did not survive irrigation with water at an estimated salinity of 5.28 dS m-1, displayed less than adequate growth in height, stem diameter, leaf emission and leaf area, and produced low levels of biomass under irrigation with water at an electrical conductivity of 4.5 dS m-1.