Características biométricas, produtivas e fisiológicas da soja submetida a inoculação e co-inoculação com Bradyrhizobium japonicum e Azospirillum brasilense

Abstract

Soy demands a large amount of nitrogen since the element constitutes amino acids, proteins and lipids. In addition to the high demand for nitrogen, soybeans also need good water availability, since they have a low efficiency in the use of water because it is a plant with C3 metabolism. In view of the demand for nitrogen and water, practices that increase efficiency in the use of these resources are studied, including nitrogen-fixing bacteria and plant growth promoters, with Bradyrhizobium japonicum and Azospirillum brasilense being the most studied. Thus, the study aimed to evaluate the behavior of the biometric, productive and physiological characteristics of soybean as a function of inoculation and co-inoculation with Bradyrhizobium japonicum and Azospirillum brasilense. A randomized block design was used, with 04 treatments (Control; B. japonicum inoculation via seeds; Inoculation with Azospirillum brasilense via seeds and co-inoculation of B. japonicum + A. brasilense via seeds) and 06 repetitions. In protected cultivation at the R3 stage, biometric characteristics and production components and productivity per pot were evaluated. In the field, production components and crop productivity were evaluated. In R3 and R6, gas exchange analyzes of soybean submitted to water deficit were performed, in R3 the relative water content (TRA) was determined, the analysis of the leaf nutrient content and the SPAD index. In the pot experiment, differences were observed for inoculation and co-inoculation for the stem diameter, number of nodules per plant, root dry matter and total dry matter. The bacteria B. japonicum and A. brasilense increased the TRA and the photosynthetic rate of soy in R3. The inoculation with A. brasilense proved to be able to increase the efficiency of CO2 assimilation. In R6, inoculation with A. brasilense also promoted gains in photosynthesis. In the field, plant height and productivity were positively affected by the use of B. japonicum, A. brasilense and co-inoculation. In view of the observed results, it can be concluded that inoculation with B. japonicum and A. brasilense and co-inoculation, positively affect biometric characteristics in pot condition, but do not affect the components of soybean production and productivity, on the other hand. On the other hand, treatments with B. japonicum and co-inoculation influence the productivity of the culture in the field conditions with an increase of 31%. Inoculation with B. japonicum, A. brasilense and co-inoculation increase the relative water content in the phenological stage R3 of soybeans by 13.58, 22.19 and 18% respectively. The inoculation of seeds with B. japonicum results in a greater leaf accumulation of N and Mg, with increments of 47.6 and 42.78% respectively, increasing the chlorophyll content of the soybean by 6.51%. The use of the bacteria B. japonicum and A. brasilense in inoculation or co-inoculation promoted an increase in photosynthetic rates of soybean under the condition of water deficit.