Efeitos da adubação nitrogenada e fontes de fósforo em sabiá (Mimosa caesalpiniaefolia Benth.), submetido ao estresse hídrico

Abstract

Due to the social accountability demanded from university research, this study is related to the challenge of making available development strategies for regionssuch as the semi-arid northeastern regions, which is characterized mainly by its limited soil and climate conditions. The purpose of this work was to assess the behavior of “sabiá” seedlings (Mimosa caesalpiniaefolia Benth.), subjected to a experimental outlining fully randomized in the factorial arrangement of: 2 X 3 X 3, two N levels (fertilized or not with nitrogen) three P levels (nonfertilized; fertilized with SFT or B20, which is composed of natural phosphate and sulfur inoculated with Acidithiobacillus spp.), and three watering cycles (daily watering, a five-andten days interval between watering), with four repetitions in greenhouses, where soil of low fertility inoculated with Rhizobium was utilized. At 12 weeks after application of hydric treatments, growth through height, stem diameter, number of leaves, total dry matter and the root : ratio / aerial part and hydric relations through transpiration, diffusive resistance and foliar hydric potential were all evaluated. Data were submitted to variance analysis and the means compared through Tukey’s test at 5% and 1% probability levels. Data growth and hydric relations showed that although there was no lethal effect in plants subjected to up to ten days of interruption of watering, the Sabiá seedlings (M. caesalpiniaefolia Benth.) present alterations in their physiological behavior already in the seedlings submitted five days of watering interruption. These alterations were: reduction of water potential in the leaf, increase of diffusive resistance and decrease in water vapor transpiration, as well as decrease in height, stem diameter, number of leaves, total dry matter and increase of root:ratio/ aerial part. Phosphorous and nitrogen fertilization solely increased the aerial part development (height, number of leaves), total dry matter and decrease of root:ratio/ aerial part. The results indicate that the species studied (M. caesalpiniaefolia), shows favorable characteristics for growing in regions such as the semi-arid. Taking into account economical and ecological factors, the results suggest that fertilization with B20 is on optimum strategy to provide for the lack of phosphorus, as well as to help the biological fixation of nitrogen.