ABSTRACT Inoculating corn with diazotrophic bacteria as growth promoters has been demonstrated to be an efficient agricultural practice in Brazil, mainly due to the root stimulation they provide to plants. This study investigates the corn (Zea mays L.) root architecture in a greenhouse assay where A. baldaniorum Sp245 and H. seropedicae ZAE94 strains were inoculated and evaluated for 22 days under two N levels: 0.6 and 6 mmol L-1 of N. Short-term bioassays were conducted to assess the plant’s response to the addition of indole-acetic acid, two bacterial populations, and two corn genotypes, utilizing image capture software WinRhizo Pro. The growth and distribution of tips, crossing, and length of fine roots were determined to be the most sensitive aspects to inoculation and indole-acetic acid induction. These responses were influenced by the genotype and the number of bacterial cells present. Biomass accumulation analyses quantified these modifications after a 22-day period. Additionally, the growth response was found to be more significant when applying the Hs-ZAE94 strain to plants fertilized with a higher dose of nitrogen (6.0 mmol L-1), and this response was positively correlated with bioassay data. Selected strains used as an inoculant can improve root architecture and, consequently, the N use efficiency.

RESUMO: Foram avaliados neste estudo novos sistemas de compostagem de mínimo impacto ambiental para o tratamento in loco de resíduos orgânicos. Dois tipos de composteiras e quatro formas de manejo foram testados. Focaram-se ainda duas composições de resíduos sólidos orgânicos com relação ao aproveitamento energético por aquecimento de água. Os resíduos mantiveram temperaturas termofílicas por mais de 20 dias, apresentaram produção desprezível de metano e não geraram chorume em condições de aeração passiva. Como aspectos de maior influência, podem ser considerados: a suspensão das composteiras sobre pallets, a composição dos resíduos, as condições de contorno das composteiras e o manejo adotado. No teste de recuperação energética, temperaturas de até 51ºC foram alcançadas após 24 horas de circulação de água no sistema, sugerindo que o processo pode ser uma fonte potencial de economia de energia. O modelo de compostagem proposto é ambientalmente adequado, porque minimiza emissões e geração de lixiviado se comparado a aterros sanitários e plantas de compostagem industrial, sendo indicado para cozinhas industriais, condomínios, shopping centers e outros geradores em pequena e média escalas.

ABSTRACT: This study comprehends the research of new composting systems for the organic solid waste treatment with low environmental impact. Two types of composting, four types of management and its economic feasibility were tested, as well as two compositions of organic solid waste focused at energy recovery by heating water. The composting maintained the thermophilic process for more than 20 days, showed a non-significant CH4 emission, maintained aerobic conditions by passive aeration, without leachate generation. The aspects with increase influence were: suspension of composters on pallets, waste composition, condition of composters, and adopted management. The test of energetic recovery showed that the water reached temperatures up to 51ºC after 24 hours of recirculation, demonstrating that this process can be a potential energy source. The proposed composting model is environmental feasible, because it minimizes gas emission and leachate generation compared to the landfill or industrial composting plants. Therefore, it is suggested to be used in industrial kitchens, condos, shopping malls, and other small and medium generators.