ADUBAÇÃO NITROGENADA NA SOJA INIBE A NODULAÇÃO E NÃO MELHORA O CRESCIMENTO INICIAL DAS PLANTAS

Abstract

Nitrogen fertilization may affect soybean symbiosis process with bacteria of the genus Bradyrhizobium (ryzobium), changing the efficiency of the biological fixation of nitrogen (BFN) and plants´ growth. Current study evaluates the effect of doses and application periods of nitrogen associated with the inoculation of Bradyrhizobium japonicum bacteria, in nodulation and initial growth of two soybean cultivars. Assay was performed in a vegetation house in Cassilândia MS Brazil, during the 2016-2017 harvest. Experimental design comprised randomized blocks, within a 2 x 3 x 4 factorial scheme, with four replications. Treatments consisted of two soybean cultivars (BRS 1074 IPRO and ST 797 IPRO), three application periods (seeding; 30 DAE and 50 DAE) and four N doses (0, 20, 40, 60 kg ha–1 N). After 65 days of plant emergence, the number of nodules, volume, dry matter, density, dry matter of aerial section, dry matter of roots and radicular volume were evaluated. Regardless of application period and cultivar, nitrogen fertilization in soybean culture inhibits the number, volume and dry matter of nodules. It does not increase radicular volume, dry matter of aerial section and radicular system.