Resposta de cultivares de arroz irrigado à inoculação de bactérias diazotróficas

Abstract

The selection of strains of diazotrophic bacteria for use in rice culture by flooding is important for the reduction of production costs and the potential for contamination of the environment by excessive use of nitrogen (N). The present study aimed to select and evaluate the effect of diazotrophic bacteria on biological fixation of N (FBN) and productivity of two varieties of rice. The study was carried out in the field, during cultivation of rice by flooding, in the experimental area belonging to the Department of plant science at the Federal University of Santa Maria-RS. The experimental design used was the random blocks with four replications in a factorial 2 x 4 x 3, being two irrigated rice cultivars (IRGA-409 and Puitá Inta-CL), four inoculation conditions (without inoculation-SI, strain UFSM-11 strain UFSM-13 and Azospirillum brasiliense present in commercial inoculant Masterfix grasses, Stoller-IC) and three doses of N (0 , 50 and 100 of the recommended dosage for culture). The evaluations performed were: production of dry matter (DM) and N accumulated in the rice plants, FBN by the technique of natural abundance and productivity of grain. Inoculation of diazotrophic bacteria increased the production of MS and the accumulation of N in rice physiological maturation, especially strains UFSM-13 and the IC. The combined use of inoculation and nitrogen fertilization promoted increase in production of MS and accumulation of N, however this did not result in higher productivity of grain. The BNF occurred naturally in varieties of rice BR-409 and Puitá Inta IRGA-CL and was increased in those varieties with the inoculation of strain UFSM-13 and of Azospirillum brasiliense of IC. Grain productivity increased only using strain UFSM-13. The positive effect of inoculation of this bacteria occurred in two rice varieties evaluated (BR IRGA-409 and Puitá Inta-CL).