CYANOBACTERIA IN THE DEVELOPMENT AND PRODUCTIVE PERFORMANCE OF MAIZE CULTIVATED UNDER NITROGEN DOSES

Nitrogen (N) is one of the most required nutrient by the maize crop being associated with its production, however, subject to losses in the soil by leaching, and runoff volatilization, causing environmental damage. The application of plant growth promoting bacteria (PGPB) to increase agricultural production is one of the most important alternatives for relying less on chemical fertilizers. (PGPB) stimulate biological nitrogen fixation (BNF). Some species of cyanobacteria have this ability in addition to producing growth promoting hormones favoring different cultures. The cyanobacteria, photosynthetic prokaryotic microorganisms, have the capacity to fix the atmospheric N2 by the process of biological fixation, however, have been little studied as inoculant. The objective of this work was to evaluate the development and productive performance of maize grown at different rates of nitrogen in topdress in response to inoculation with cyanobacteria (Anabaena cylindrica and Nostoc muscorum) in two crop seasons. The experiments were carried out in two agricultural crops (second harvest in 2016 and first harvest in 2016/17, at the Agronomic Institute of Paraná (810 g kg-1 clay), located in the municipality of Londrina (PR), geographical coordinates 23º23 'S and 51º11' W, average altitude 566 m and climate, according to classification of Köppen, Cfa - subtropical humid type. The maize cultivar was IPR164 variety. Sixteen treatments were tested using a randomized complete block design with four replications, in a 4x4 factorial arrangement, corresponding to four levels of topdress N fertilization (0, 30, 80 and 130 kg ha-1) with 20 kg ha-1 N at sowing, totaling 20, 50,100 and 150 kg ha-1 N and four levels of inoculation (without inoculation, Anabaena cylindrica, Nostoc muscorum, and commercial inoculant based on Azospirillum brasilense). Plant height, stem insertion height, stem diameter, leaf area index, leaf chlorophyll, leaf content of N, P and K, number of rows per ear, number of grains per row, number of grains per ear, number of ear per plant, N content in the grain, mass of 1000 grains and grain yield were assessed. The phytometric characteristics and yield of maize were not altered by the interaction between N doses and inoculants, demonstrating that N doses do not interfere with cyanobacteria performance. The inoculation with Anabaena cylindrica favored the development and yield performance of maize and resulted in an increase in grain yield of 912 kg ha-1 (20.46%) in the season 1 and 1020 kg ha-1 (21.11 %) in season 2, in relation to the control.