ABSTRACT. The objective of this study was to evaluate the agronomic characteristics of corn seed inoculated with Azospirillum brasilense, grown on black oat and ryegrass straw, and managed under different grazing strategies and doses of nitrogen. The experiment was conducted in Santa Maria, Rio Grande do Sul State, Brazil, during two agricultural seasons (2012/2013 and 2013/2014) in a randomized, complete block design with three replications. In the winter period, black oat and ryegrass straw were managed at different grazing heights by sheep (0.30, 0.20, 0.10 m, conventional grazing, and no grazing) with three doses of nitrogen (0, 50, and 100 kg ha The height of corn plants was greater when they were grown on black oat and ryegrass straw, and the absence of grazing favored productivity. Under drought conditions, the application of nitrogen to the pasture favored corn development, increasing plant height, ear height, and stem diameter. Inoculation with A. brasilense had a positive effect on the characteristics of yield and productivity of corn, independent of growing season and hybrid used.

Increased grain yield can be obtained via an interaction between plants and growth-promoting microorganisms. The Bradyrhizobium spp. are capable of fixing atmospheric nitrogen in soybeans [Glycine max (L.) Merril], and Azospirillum spp. induce the synthesis of phytohormones. The aim of this study was to evaluate inoculation with Bradyrhizobium and co-inoculation with Bradyrhizobium + Azospirillum brasilense in soybeans in combination with the application a topdressing of 0, 75 or 150 kg of N ha -1 of urea during the reproductive stage. Three soybean cultivars (BMX Ativa, TEC 6029 and BMX Potência), were tested in field experiments in Santa Maria, RS, Brazil, during two agricultural years (2013/2014 and 2014/2015) and two sowing times. Morphological, nodulation and yield components were evaluated. Co-inoculation increased the grain yield by 240 kg ha -1 compared with conventional inoculation. When co-inoculated, cultivars BMX Ativa, TEC 6029 and BMX Potência showed increased grain yields of 6, 4 and 12%, respectively. The application of 150 kg ha -1 of N as a topdressing increased the grain yield by 300 kg ha -1 in the co-inoculated cultivars TEC 6029 and BMX Potência, but without a financial return. When inoculated only with Bradyrhizobium, the cultivars did not respond positively to the application of urea.Index terms: Azospirillum spp.; Bradyrhizobium spp.; Glicine max (L.) Merr.; nitrogen. RESUMOO incremento na produtividade de grãos pode ser obtido pela interação entre plantas e microrganismos promotores do crescimento vegetal. Bactérias do gênero Bradyrhizobium spp. são capazes de realizar a fixação do nitrogênio em soja [Glycine max (L.) Merril], enquanto as do gênero Azospirillum spp. induzem a síntese de hormônios vegetais. O objetivo do presente trabalho foi avaliar a inoculação com Bradyrhizobium e co-inoculação com Bradyrhizobium + Azospirillum brasilense em sementes de soja associado a aplicação de 0, 75 e 150 kg de N ha -1 de ureia aplicada em cobertura no estádio reprodutivo. Três cultivares de soja (BMX Ativa, TEC 6029 e BMX Potência) foram utilizadas nos experimentos em Santa Maria, RS, Brasil, durante dois anos agrícolas (2013/2014 e 2014/2015) e duas épocas de cultivo. Foram avaliadas as características morfológicas, de nodulação e componentes da produtividade. A co-inoculação proporcionou incremento de 240 kg de grãos ha -1 em relação a inoculação convencional. Quando co-inoculadas, as cultivares BMX Ativa, TEC 6029 e BMX Potência acresceram a produtividade de grãos em 6, 4 e 12% respectivamente. A aplicação de 150 kg de N ha -1 acresceu a produtividade em 300 kg de grãos ha -1 , com a co-inoculação das cultivares TEC 6029 e BMX Potência, porém, sem retorno econômico. Os cultivares testados quando inoculados somente com Bradyrhizobium não responderam positivamente à aplicação de ureia.Termos para indexação: Azospirillum spp.; Bradyrhizobium spp.; Glycine max (L.) Merr.; nitrogênio.

Seed treatment is a practice that helps the initial establishment of the crop without the effects caused by pests and diseases. The association of diazotrophic bacteria with grasses has been used in the supply of nitrogen to plants; however, these microorganisms produce growth-promoting substances, which promote benefits in the growth and development of the crops. Thus, the objective of this study was to evaluate the compatibility of Azospirillum brasilense associated with the fungicide difenoconazole and the insecticide thiamethoxam by observing the effects on the quality of seed emergence of three wheat cultivars (Triticum aestivum L.). Three wheat cultivars, arranged in a 4 x 2 factorial system with four replicates, were tested. The treatments were the control; difenoconazole (Spectro® at a dose of 150 mL per 100 kg of seed); thiamethoxam (Cruiser® FS 350 at a dose of 200 mL per 100 kg seed) and difenoconazole + thiamethoxam, applied on wheat cultivars TBIO Mestre, TBIO Itaipu and TBIO Sinuelo. Bacteria from the Azospirillum genus were used in the inoculation. The wheat seed retains its quality when it checks the germination, vigor and independent accelerated aging, whether or not fungicide, insecticide and A. brasilense were used. The insecticide thiamethoxam increased the length of shoots and roots and provided compatibility with A. brasilense, and fungicide inhibited the length of shoots and roots and was antagonistic to the bacterium A. brasilense.

The agronomic efficiency of the nitrogen-fixing inoculants or growth promoters depends on the growing conditions of the crops. One of the factors that may influence this response is the interaction between the bacteria present in the inoculant with the chemical treatment applied to the seeds. The objective of this study was to evaluate the influence of inoculation of wheat seeds with Azospirillum brasilense and its interaction with seed treatment on germination, vigor and initial growth of wheat plants of four cultivars. So, an experiment was carried out at the Federal University of Santa Maria, Santa Maria-RS. The experimental design was a completely randomized in a three-factorial (4x4x2), represented by the combinations between cultivar (FUNDACEP Bravo, OR/TBIO Quartzo, TBIO Itaipu e BRS 331), chemical treatment (1: Insecticide + Fungicide; 2: Insecticide; 3:Fungicide; 4: Witness without treatment) and Azospirillum brasilense inoculation (with and without inoculant). The determinations which were carried out were the following: emergence in beds, first germination test counting (vigor), germination, seedling length (root, aerial part and total), dry mass (root and aerial part). The responses to inoculants with Azospirillum brasilense are closely related to the cultivars used in the study. The treatment of seeds with fungicide and insecticide presented a phytotoxic effect, damaging the initial growth of the seedlings.

Soil temperature and humidity are the chief determinants for good nodule formation at the time of sowing and emergence. The aim of this study was to estimate the soil temperature and humidity range, at which the Bradyrhizobium spp., and Azospirillum brasilense may have the highest effect on root enhancement and development of nodulation in soybean. Two experiments were conducted, the first of which was done in the seed laboratory performing the treatments listed as non-inoculated; inoculation with Bradyrhizobium; root enhancers; inoculation with Bradyrhizobium + root enhancers; co-inoculation with Bradyrhizobium + Azospirillum brasilense; co-inoculation with Bradyrhizobium + Azospirillum brasilense + root enhancers, and assessed at temperatures of 15, 20, 25, 30 and 35ºC. The experimental design was completely randomized with distribution in a factorial. The second experiment was executed in a greenhouse, employing the same treatments affected in the seed laboratory experiment, but with the addition of non-inoculated control with mineral nitrogen. Tests were done at the soil moisture levels of 25, 50, 75 and 100% water retention capacity, forming a factorial 7 x 4 (only second experiment). All co-inoculated treatments induced the soybean root system to improve, in terms of length, volume, surface area and root diameter, exhibiting superiority to the uninoculated control in the 20 to 30ºC temperature range. The co-inoculation raised nodulation in the soybean crop, when soil water retention capacity was at the range of 56 - 96%, achieving higher means compared to the standard inoculation. The root planter added no improvement to either the root system or nodulation in soybean.