Water use efficiency in soybean crop after inoculation with Azospirillum brasiliense in the Cerrado of Tocantins State, Brazil

Abstract

Crops in the Cerrado experience short drought stress periods that affect cultivation development, especially the water use efficiency (WUE), which can be modified by the use of Azospirillum brasiliense bacteria. In this sense, this study evaluated soybean plants' response to A. brasiliense inoculation, in relation to WUE, in the Cerrado of Tocantins State. During the growing season of 2015/2016, three experiments were conducted in Palmas municipality, with analyses in the phenological stages: R3 for the first planting and R2 for the second and third plantings. The experimental design used in each experiment was randomized block with ten treatments and four replications. The treatments were disposed in 2x5 factorial scheme, represented by two cultivars (M-9144RR and TMG 1288RR) and five different doses of A. brasiliense (0, 100, 200, 300 and 400 ml of the commercial product per hectare). They were applied through the leaf at V2 and R1 stages of the crops. WUE determination was done through photosynthesis measurement (IRGA), through which the photosynthesis and transpiration values were obtained. There was no WUE difference between the cultivars. A. brasiliense doses had effect in relation to WUE, on stressed crops. A. brasiliense inoculation did not show any significant change in WUE in crops with favorable conditions.