Tratamento químico, uso de aditivos, Azospirillum brasilense e pH do solo na cultura do trigo

Abstract

The response to inoculation of wheat seeds with Azospirillum brasilense is variable and depends on factors related to the inoculation and the growing environment. The objective of this research was to evaluate the effect of soil pH, seed treatment, osmoprotective use and the presence of mineral nitrogen on the activity of A. brasilense and the effects of the bacteria on the physiological quality of seeds, growth and physiology of plants and wheat yield. For this, three experiments were carried out using the cultivar TBIO Toruk. The first, conducted in a completely randomized design and in the laboratory, had its treatments organized in a 2x8 bifatorial, with four replicates. The first factor was constituted in the pH levels of the imbibition solution (4.8 and 6.5) and the second, to the treatments applied by seed, being: control (without chemical treatment, additive osmoprotect and A. brasilense), inoculation with A. brasilense (A), chemical treatment (TS), additive osmoprotector (O), A + O, A + TS, O + TS and A + O + TS, where the response of the treatments on the physiological quality of seeds. To isolate the effects of the factors (phytosanitary treatment, osmoprotective additive, nitrogen in the solution, pH of the imbibition solution and A. brasilense) on seedling growth; The second study was subdivided into four substudies, conducted under a hydroponic system, under a completely randomized design, with treatments distributed in a 2x2 bifattal, with four replications. The third study characterized the effects of factors on plant physiological parameters and wheat yield. The experiment was conducted in a randomized complete block design and field conditions, with its treatments distributed in a 2x8 two-factorial, with four replications. The first factor was the soil pH and the second, to the treatments applied by seed, being: control, inoculation with A. brasilense (A), chemical treatment (TS), osmoprotective additive (O), A + O, A + TS, O + TS and A + O + TS. The number of normal seedlings is not influenced by the pH of the imbibition solution and by the treatments applied by seed, however, there is a reduction of seedling vigor with the use of the chemical treatment or osmoprotective additive (Study 1). The pH of the imbibition solution and the presence of nitrogen in the values tested did not influence the effects observed with the inoculation of A. brasilense. With the use of the chemical treatment and the osmoprotector there is no effect of A. brasilense on the growth of wheat seedlings (Study 2). Corrected soil pH and inoculation with A. brasilense increase the activity of the enzyme nitrate reductase. In soil with corrected acidity the inoculation with A. brasilense increases the grain yield of the wheat crop. The use of the chemical treatment has a negative effect on the response to inoculation in the wheat crop, where the use of the osmoprotectant does not attenuate its effects, which negatively influence the response to inoculation with A. brasilense (Study 3). Thus, inoculation with A. brasilense in the absence of chemical treatment and in conditions without soil acidity is justified as an efficient technology to increase wheat crop productivity.