The aim of this study was to evaluate the effect of industrial seed treatments on the physiological potential of soybean seeds over storage. Four mixtures of agrochemical products in association with two fertilizers were tested. The agrochemical product mixtures were carbendazim/thiram + imidacloprid/thiodicarb; pyraclostrobin, thiophanate-methyl, and fipronil; thiophanate-methyl/fluazinam + bifenthrin/imidacloprid; and metalaxyl-m/fludioxonil + thiamethoxam. The two fertilizers were 7% N, 16% P2O5, 0.6% Co, and 2.5% Mo; and 1% Co, 10% Mo, and 7% P2 O5. The experiment was carried out in a completely randomized design in a split-plot arrangement in time, with four replications. The treatments were allocated in the plots, while the storage periods (0, 30, 60, 90, and 120 days) constituted the split-plots. The following tests were carried out in each period: first count of germination, germination, accelerated aging, emergence speed index in sand substrate, and final seedling emergence in sand substrate. Seed germination and vigor declined over the storage period, especially after industrial treatment. Pesticide mixtures of a carbendazim/thiram fungicide base and an imidacloprid/thiodicarb insecticide base most impaired seed physiological potential throughout storage, regardless of fertilizer use in the industrial treatment.

Although accelerated aging is one of the tests most used for evaluation of the physiological quality of soybean seeds, there are few studies that relate it to other physiological tests used for the crop. In this context, the objective of this study was to investigate the relationship of accelerated aging to the results of physiological performance obtained in the vigor tests most frequently used in the soybean quality control system (germination, first count, seedling vigor classification, accelerated aging, electrical conductivity, emergence speed index, final emergence in sand substrate, and field emergence). The experiment was conducted with seeds that had different vigor levels, adopting a completely randomized experimental design with four replications. Pearson simple correlation analysis (r) and simple linear regression analysis at both 1% and 5% probability were conducted on the data. The results showed that the seedling vigor classification test (r = 0.9160) and the field emergence test (r = 0.9198) were those that best correlated with accelerated aging, followed by the germination (r = 0.8690), first count of germination (r = 0.8460), and electrical conductivity (r = 0.8912) tests.

A B S T R A C TThis study aimed to evaluate the agronomic performance of different doses of Azospirillum brasilense in peat formulation on maize crop grown under limited N fertilization, using a completely randomized design with four replicates. The treatments tested consisted of absence of N fertilizer, the full N recommendation and a combination of the half of recommended N associated with the inoculation of three doses of A. brasilense in peat formulation (100, 150 or 200 g per 25 kg of seeds). The following variables were evaluated: insertion height of the first ear height, number of kernel per row, number of row per ear, shoot dry biomass, root dry biomass, chlorophyll content, thousand seed weight, grain N content, shoot N content and grain yield. Half the dose of N fertilizer combined with 150 g per 25 kg of seeds of A. brasilense in peat formulation provided significantly superior results in agronomic performance of maize, particularly regarding grain yield, thousand seed weight and dry biomass of both shoot and root.

R E S U M OO objetivo do presente trabalho foi avaliar a eficiência agronómica de diferentes dosagens e modos de aplicação (via sementes, aplicação foliar e no sulco de sementeira) da forma líquida de um inoculante à base de Azospirillum brasilense nos componentes da produtividade da cultura do trigo. As seguintes características agronómicas foram avaliadas: número de perfilhos por planta, número de grãos por espiga, massa seca da parte aérea, peso médio de mil grãos, peso do hectolitro, teor de N no grão, teor de N, P e K na massa seca da parte aérea e produtividade de grãos. Os resultados obtidos permitiram concluir que a utilização de metade da dose de N, associada à aplicação de A. brasilense na forma líquida, independentemente do método de inoculação, proporcionaram resultados benéficos ao rendimento da cultura, quando comparada com a aplicação isolada de metade da dose de N. A aplicação de A. brasilense via tratamento de sementes com a dose total de N em cobertura, no entanto, foi a combinação que proporcionou o maior incremento da produtividade de grãos. Palavras-chave: Triticum aestivum, Azospirillum brasilense, inoculação, rendimento. A B S T R A C TThe aim of this study was to evaluate the efficiency of inoculation techniques (seed treatment, in-furrow application and foliar spray) with Azospirillum brasilense on the agronomic performance and yield response of wheat. At the point of harvest, the number of seeds per ear, the thousand-seed mass, the hectoliter weight, the shoot dry matter, the N, P and K content of shoot dry matter, the grain N content, and the grain yield were evaluated. Regardless of the inoculation technique, at half the dose of N fertilizer combined with A. brasilense in liquid formulation, provided significantly superior results in agronomic performance compared to the treatment in which only the half the dose of N fertilizer was used. However, it is inferred that seed inoculation with A. brasilense associated with full nitrogen fertilization showed the highest increase in wheat development and grain yield.

The objective of this work was to evaluate the degree of linear association between field emergence with the results of germination and vigor of corn seeds belonging to different initial vigor and submitted to agrochemical treatment. Following seed treatments with (i) carbendazim/thiram + imidaclopride/tiodicarbe; (ii) piraclostrobine, methyl tiophanate and fipronil; (iii) methyl tiophanate/fluazinam + bifentrine/imidaclopride; and (iv) metalaxyl-m/fludioxonil + thiamethoxam, seeds belonging to four different corn cultivars were assessed for their physiological potential. The strength of the Pearson correlation between germination and vigor tests with field emergence decreased after the chemical treatment, to a degree depending on the slurry composition, initial vigor and the test’s substrate.

The continuous development of soybean cultivars aiming at higher yields can result in a demand of N supply higher than the standard inoculation with Bradyrhizobium species. In this context, Azospirillum species, a nitrogen-fixing microorganism found in the rhizosphere of various plant species, may be studied as a way of providing soybean crop with the part of the N it needs. Employing a completely randomized design with four replicates, this study aimed to evaluate the agronomic performance of two different methods of standard inoculation of Bradyrhizobium spp. associated with the co-inoculation with Azospirillum spp. The tested treatments consisted of the absence of N fertilizer and inoculant, full N recommendation, two single inoculations with Bradyrhizobium spp. (in-furrow and seed-applied) combined with an in-furrow application of Azospirillum spp. At R 2 growth stage, the nodule number, nodule dry weight, shoot dry biomass and shoot N content were the variables evaluated, whereas at R 8 the grain yield, thousand seed weight and grain N content were assessed. The results demonstrated that the co-inoculation of Bradyrhizobium spp. with Azospirillum brasilense is beneficial to soybean yield, mainly using the in-furrow method of application for Bradyrhizobium spp., associated to the infurrow co-inoculation with Azospirillum spp.

The present work aimed to evaluate the agronomic performance of wheat grown under no-tillage system and submitted to different doses and methods of inoculation with Azospirillum spp. Eight treatments were tested: 1) control; 2) half N dose; 3) full dose of N; 4) half N dose + standarded inoculation by seeds (200 mL ha-1); 5) half N dose + in-furrow inoculation (200 mL ha-1); 6) half N dose + in furrow inoculation (300 mL ha-1); 7) half N dose + inoculation by foliar spraying (200 m ha-1) and 8) half N dose + inoculation by foliar spraying (300 mL ha-1). The following parameters were evaluated: number of tillers per plant, number of grains per spike, shoot dry biomass, weight of thousand seed mass, hectoliter weight, nitrogen content in grains, nitrogen content in shoot dry matter as well as crop yield. Our results showed that the supply of the half dose of mineral N associated to foliar inoculation with Azospirillum at the dose of 300 mL ha-1 provided positive results on wheat yield, confirming the bacterial ability to fix N. However, only the full mineral N fertilization stood out as the best N fertilization management.

Corn has shown different degrees of positive response to inoculation with the nitrogen- fixing bacteria of the genera Azospirillum. Part of it has been attributed to the plant genotypic variation, including the root exudates, that are used by the bacteria as energy source. In this study, we grew two corn hybrids that differ for their response to Azospirillum, to investigate the effect of different exudates profiles on the bacteria growth and nitrogenase activity. Employing high performance liquid chromatography, we identified nine amino acids (asparagine, aspartic acid, serine, glutamic acid, valine, phenylalanine, threonine, tryptophan and alanine), six sugars (glucose, sucrose, xylose, arabinose, fructose and galactose) and four organic acids (citrate, malate, succinate and fumarate). The less responsive corn genotype showed reduced plant growth (root volume, shoot dry mass and shoot N content), a lower concentration of Azospirillum cells within the root tissues, a higher content of asparagine and glucose and a reduced amount of metabolites that serve as bacterial energy source (all organic acids + five sugars, excluding glucose). The genotypes did not interfere in the ability of Azospirillum to colonize the substrate, but the metabolites released by the less responsive one reduced the nitrogenase activity.