Reinoculação em cobertura de Rhizobium tropici, Azospirilum brasilense e os micronutrientes Mo/Co no feijão comum

Abstract

Biological nitrogen fixation (BNF) can provide the nitrogen needed for the common bean crop, but for this to occur, important limitations involving the inoculant application technology need to be overcome. In this sense, the use of co-inoculation is a management technique used to obtain benefits and increase the potential of BNF from the association between bacteria of the rhizobia group, such as Rhizobium tropici, and plant growth-promoting bacteria, such as Azospirilum brasilense, in association with the addition of nutrients that allow greater efficiency of atmospheric N2 fixing bacteria. This study aimed to evaluate the common bean response to the re-inoculation of R. tropici in co-inoculation with A. brasilense, mixed with the micronutrients Co/Mo, in the 2021 winter season, in Anápolis-GO. The randomized block design with four replications was used. The following treatments were studied: TR1 – Re-inoculation of R. tropici; TR2 – Re-inoculation with co-inoculation of R. tropici + A. brasilense; TR3 – Re-inoculation of R. tropici + Mo/Co micronutrients; TR4 – Re-inoculation with co-inoculation of R. tropici + A. brasilense + micronutrients Mo/Co; TR5 – Inoculation via seed, without re-inoculation; TR6 – Fertilization with N mineral in the sowing furrow and at topdressing; TR7 – Control, without any source of N. The topdressing treatment applications were carried out at the R4 stage, using the doses recommended by the manufacturers of the studied products. At the R6 stage, the nodulation (number and dry mass of nodules) and morphophysiological characteristics of the plants (taproot length, root dry mass, leaf area index, plant height, shoot dry mass, and N accumulation in the shoot) were evaluated. At the time of harvest, the final stand of plants, yield components (the number of pods per plant, number of grains per pod, and 100-grain weight), and grain yield were determined. It is concluded that inoculation followed by re-inoculation in topdressing with R. tropici in co-inoculation with A. brasilense + Mo/Co, compared to mineral nitrogen fertilization, improves the efficiency of the nodulation process and the morphophysiological characteristics of common bean plants. Seed inoculation and topdressing application with R. tropici, associated with co-inoculation with A. brasilense + Mo and Co, has the potential to replace mineral nitrogen fertilization in common beans.