PERFORMANCE OF LETTUCE SEEDLINGS UNDER DOSES OF PHOSPHORUS SOLUBILIZING BIOLOGICAL INOCULANT

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Abstract

The development of cropping systems with vegetables aiming at the optimization of productivity has made efforts to reduce or even eliminate deficiencies of the productive sector, such as nutritional and phytosanitary problems of the seedlings. The objective of this study was to evaluate the ability of the Streptomyces isolate

to promote the growth of two lettuce cultivars in different doses on commercial substrates. For in vitro phosphate solubilization assay PCA medium added with K₂HPO₄ and CaCl₂ solution was used. The statistical design was a completely randomized design, with a 2x5 two-factor scheme, totaling 10 treatments with 4 replicates, cultivars were Great Lakes Americana and Crespa Grand Rapids and five doses 0, 75, 150, 225, 300 g kg^-1 of product, being the experimental unit constituted by ten plants. The evaluated variables were: seedling height, fresh aerial mass, fresh root mass, aerial dry mass and root dry mass and root system length. As for the phosphate solubilization test, only one isolate UFT-St07 presented solubilization index. The best doses were 75 and 150 g kg^-1 of product substrate for all variables analyzed in American lettuce (Crespa Grand Rapids). It is concluded that the genus Streptomyces is a promising agent to be used as a biofertilizer in order to promote the growth of lettuce plants.