Resposta do feijão-vagem de crescimento determinado à inoculação com Rhizobium tropici

Abstract

The snap bean is a vegetable legume with high nutritional value and of great agricultural importance, handling around 2.8 thousand tons, equivalent to $ 3.37 million, at CEASA-GO in 2017. However, in order to maintain good productivity requires applications of nitrogenous fertilizers, a practice that increases production costs and generates negative impact on the environment. In view of this, we are looking for sustainable alternatives to the use of fertilizers, highlighting the biological nitrogen fixation (BNF), a process that occurs in the soil through specialized bacteria. However, FBN in snap bean is still not efficient, and selection of cultivars and study of the effects of nitrogen fertilizer use may be a way to increase BNF efficiency. The objective of this work was to evaluate the behavior of bean cultivars of determined growth and the influence of nitrogen fertilization rates and inoculation with Rhizobium tropici on snap bean. Two experiments were carried out, both in the greenhouse of the State University of Goiás, Câmpus Ipameri. The first experiment was conducted in a completely randomized design, with four replications, in the 7x2 factorial scheme corresponding to seven cultivars (Commodore Improved, Contender, Delinel, Jade, Strike, Stringless Green and Provider), in the presence and absence of rhizobial inoculant (R. tropici). The second experiment was completely randomized, with four replicates and a 5x2 factorial scheme, corresponding to five doses of N in coverage (0, 30, 60, 90 and 120 kg ha-1 ), respectively, at 15 days after emergence, at absence and presence of rhizobial inoculant. In both, a 9-liter pot was used, and planting fertilization with 50 kg ha-1 de N, 300 kg ha-1 de P2O5 e 100 kg ha-1 de K2O. The inoculant used was Nitro1000 Feijão, from Nitro1000, in the form of liquid fluid containing 3.0 x 109 viable cells per mL of R. tropici Semia 4077 and Semia 4088 at a dose of 100 mL to 40 kg of seeds. The height, diameter, number of leaves, leaf area, shoot dry mass, root length, root area, root dry mass, number of nodules, leaf nitrogen content, accumulated nitrogen in the aerial part were evaluated at the flowering stage, nitrogen utilization efficiency, specific nodulation and relative efficiency. There is a difference between bean pod cultivars for aerial part, root system and nitrogen accumulation, with Delinel, Jade and Stringless Green being the most promising for biological nitrogen fixation studies. Inoculation is able to increase the number of nodules, specific nodulation efficiency of nitrogen utilization. Nitrogen fertilization coverage has negative effects on biological nitrogen fixation, reducing the number of nodules, specific nodulation and efficiency of nitrogen utilization.