Lignin, elemental, and stable carbon isotope compositions are reported for local plants and for coarse (>63 pm) and fine (~63 pm) suspended particulate materials collected along a 1,950-km reach of the lower Amazon River during four contrasting stages of the 1982-1983 hydrograph.

More than one hundred years have passed since the development of the first microbial inoculant for plants. Nowadays, the use of microbial inoculants in agriculture is spread worldwide for different crops and carrying different microorganisms. In the last decades, impressive progress has been achieved in the production, commercialization and use of inoculants. Nowadays, farmers are more receptive to the use of inoculants mainly because high-quality products and multi-purpose elite strains are available at the market, improving yields at low cost in comparison to chemical fertilizers. In the context of a more sustainable agriculture, microbial inoculants also help to mitigate environmental impacts caused by agrochemicals. Challenges rely on the production of microbial inoculants for a broader range of crops, and the expansion of the inoculated area worldwide, in addition to the search for innovative microbial solutions in areas subjected to increasing episodes of environmental stresses. In this review, we explore the world market for inoculants, showing which bacteria are prominent as inoculants in different countries, and we discuss the main research strategies that might contribute to improve the use of microbial inoculants in agriculture.

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O rio Ivaí exerce importante papel para o estado do Paraná. Sua bacia hidrográfica abrange uma área de 35.845km 2 , sendo 70% dessa área situada na região noroeste do estado. Ao longo dos 685km do seu curso, drena as litologias Eo-Paleozóicas e Mesozóicas da bacia sedimentar do Paraná. O rio Ivaí desenvolve uma planície aluvial somente em seu curso inferior. Essa se estende desde sua foz no rio Paraná, no município de Icaraíma-PR, até cerca de 150km a montante, na corredeira do Ferro, município de Tapira-PR. Nessa região, de baixas declividades, o rio apresenta um padrão meândrico bastante encaixado e com um forte controle estrutural e litológico. O mapeamento geológico e geomorfológico, baseado em interpretação de imagens, em testemunhos de sondagem e em descrições de afloramento, permitiu dividir a planície em seis unidades morfoestratigráfias: Planície Paraná-Ivaí, Planície Ivaí, Terraço Paraná, Terraço Ivaí, Leque Aluvial e Canal Fluvial. As características morfológicas, estruturais e sedimentares de cada uma dessas unidades são discutidas nesse trabalho. O posicionamento estratigráfico das diferentes unidades possibilita um panorama da arquitetura e evolução da planície aluvial.

The inoculation of seeds with nitrogen-fixing and plant-growth promoting bacteria is a well-established agricultural practice that has been increasingly adopted worldwide, decreasing costs and environmental impacts of food production. Most of the globally commercialized inoculants are for the soybean crop, and a method for recovery of Bradyrhizobium cells from inoculated soybean seeds for subsequent counting has been adopted by several laboratories of South America, especially to investigate the bacterial survival on seeds treated with pesticides. However, the use of inoculants containing Azospirillum brasilense in cereal crops has exponentially increased, requiring investigation about the recovery and counting of cells from inoculated seeds. We first verified that the method used for recovery and counting of viable cells of Bradyrhizobium from soybean seeds was not applicable for maize seeds inoculated with A. brasilense. We then modified several steps of the method, aiming at succeeding in recovering Azospirillum viable cells. The main limitation was identified in the nature of the seed tegument, dry and poor in nutrients, resulting in A. brasilense cell aggregation. Pre-hydration of seeds for 2 h in sterile distilled water, followed by shaking for 30 min in sterile distilled water with Tween 80 allowed proper counting of A. brasilense cells recovered from maize seeds. The method was successfully applied to count Azospirillum cells recovered from pre-inoculated maize seeds, and to estimate the impact of seed treatment with pesticides on cell survival.

No abstract

Azospirillum brasilense strains Ab-V5 and Ab-V6 have been broadly and successfully used in commercial inoculants in Brazil, for both non-legumes and legumes, contributing to increases in grain yields with reduced applications of chemical fertilizers. Azospirillum survival, however, may be very low in liquid inoculant formulations and strategies such as the enrichment with polyhydroxybutyrate (PHB) and biofilm may help both bacterial survival and agronomic performance. The production was quantified for both PHB and biofilm by strains Ab-V5 and Ab-V6 in liquid inoculant formulations. Differences were observed between formulations, strains, and strain x formulation. Cellular PHB concentrations ranged from 7.9 to 40.2% of the cell dry weight after 96 h, and considerable amounts of biofilm were synthesized by both Ab-V5 and Ab-V6. Maximum accumulation of PHB and biofilm occurred with A. brasilense strain Ab-V6 in the formulation FORM2+P3, indicating that it is possible to enrich the inoculants on PHB and biofilm by improving the culture media. Field experiments will now be performed to confirm the agronomic efficiency of the improved inoculant.

Inoculants or biofertilizers aiming to partially or fully replace chemical fertilizers are becoming increasingly important in agriculture, as there is a global perception of the need to increase sustainability. In this review, we discuss some important results of inoculation of a variety of crops with rhizobia and other plant growth-promoting bacteria (PGPB). Important improvements in the quality of the inoculants and on the release of new strains and formulations have been achieved. However, agriculture will continue to demand chemical pesticides, and their low compatibility with inoculants, especially when applied to seeds, represents a major limitation to the success of inoculation. The differences in the compatibility between pesticides and inoculants depend on their active principle, formulation, time of application, and period of contact with living microorganisms; however, in general they have a high impact on cell survival and metabolism, affecting the microbial contribution to plant growth. New strategies to solve the incompatibility between pesticides and inoculants are needed, as those that have been proposed to date are still very modest in terms of demand.