Effect of Azospirillum brasilense in gas exchanges and production of soybean

Abstract

The present study aimed to verify the photosynthetic responses and yield of soybean cultivars in relation to foliar inoculation with Azospirillum brasilense at different sowing dates. For this, three field experiments were carried out at the Federal University of Tocantins, Palmas campus, Brazil. Consecutive seasons were carried out on three sowing dates, November 15th, 2019, December 2nd, 2019 and December 20th, 2019. The experiment was conducted in a randomized block design with four replicates, in a 2 × 5 factorial scheme, represented by two soybean cultivars (M9144RR and TMG1188RR) and five doses of Azospirillum brasilense (0, 100, 200, 300 and 400 mL), applied via foliar at the stage of growth V5. Stomatal conductance rate (gs), internal CO2 concentration (iC), transpiration rate (E), net photosynthetic rate (A) and grain yield were evaluated. The cultivars showed different responses to sowing dates and to doses of A. brasilense in all evaluated parameters. The cultivar TMG1188RR showed higher yield (3,450 kg·ha−1) and gs (4.89 µmol CO2 m−2·s−1) at the lowest dose applied, while the cultivar M9144RR showed higher yield (3,441 kg·ha−1), gs (3.35 µmol CO2 m−2·s−1) and A (17.32 µmol CO2 m−2·s−1) at highest dose applied. The leaf inoculation with A. brasilense was more responsive in periods in which there were unfavorable environmental conditions for soybean cultivation and can be recommended as complementary management in these conditions.

Keywords

• azospirillum brasilense
• exchanges
• production
• soybeans
• glycine max (l.) merrill
• rhizobacteria
• drought stress