Inoculation of corn with diazotrophic bacteria reduces the need for nitrogen fertilization and mitigates environmental contamination risks due to the bacteria's biological nitrogen-fixation capacity. The aim of the present study was to evaluate the effect of corn seed inoculation with Azospirillum brasilense under different nitrogen levels and post-grazing residual heights. The experiment was performed in two growing seasons and conducted in an integrated crop-livestock system for the 2014/15 and 2015/16. A factorial randomized block experimental design with subdivided plots and three factors. The main plots varied in post-grazing residual height (0.10, 0.20, 0.30 m, continuous grazing, or no grazing), the subplots varied in inoculation (with or without seed inoculation), and the sub-subplots varied in nitrogen level (0, 75, 150, 225, or 300 kg ha-1 of N). The higher post-grazing residual height associated an A. brasilense and nitrogen fertilization resulted in increased corn biomass and production and yield. At the 300 kg dose of N, the highest grain yield was obtained under different post-grazing heights (10.15 Mg ha-1) and in the absence of the bacterium (10.00 Mg ha-1). Azospirillum brasilense helps plant growth and yield but does not replace the effect of N fertilization.
RESUMOO manejo adotado pode afetar negativamente a qualidade do solo, interferindo no funcionamento e na sustentabilidade do sistema. Objetivou-se com este trabalho avaliar as alterações na biomassa e atividade microbiana, e índices derivados em um Latossolo Vermelho, sob diferentes sistemas de manejo. Os sistemas avaliados compreenderam a lavouras sob manejo em Plantio Direto com rotação de culturas (RC), sucessão de cultura soja-trigo (SC), pastagem perene (PP), sistema integração lavoura-pecuária (ILP) e mata nativa (MN) utilizada como área referência. As coletas foram realizadas em trincheiras com dimensões de 50 x 50 x 40 cm, mensurando-se as camadas 0-5, 5-10 e 10-20 cm. Para determinação da biomassa e respiração basal do solo (RBS), as amostras foram acondicionadas sob refrigeração (4 ºC) até a realização das análises. Ainda por ocasião determinou-se o carbono da biomassa microbiana (C-Bmic) por amostras irradiadas e não irradiadas. Após as análises, realizou-se as relações para quociente metabólico (qCO 2 ) e os quocientes microbianos (qMIC). Os resultados foram submetidos à análise de variância e as médias comparadas pelo teste de Scott-knott, a 5% de probabilidade. O C-Bmic apresentou os maiores valores em RC e com menores valores médios nas áreas de SC, para a primeira camada mensurada. Na avaliação do qCO 2 , o menor valor foi obtido na área de RC e maior valor SC, na camada de 0-5 cm. Esses valores mostram que existem perturbação e com isso perdas de carbono do solo. Na relação de qMIC, todos resultados foram superiores a 1%, mas o maior quociente foi observado em RC, na camada de 0-5 cm. Os resultados demonstram a importância da rotação de culturas, na melhoria dos atributos biológicos do solo. PALAVRAS-CHAVE: Biomassa. Qualidade do solo. Respiração basal. ABSTRACTThe adopted management can adversely affect soil quality, interfering with the system functioning and sustainability. The aim of this study was to evaluate the alterations in biomass and microbial activity and derived indexes in a Red Oxisol under different management systems. The evaluated systems comprised the fields under management of no-tillage with crop rotation (RC), soybean-wheat succession (SC), perennial pasture (PP), integrated crop-livestock system (ILP) and native forest (MN) as reference area. The soil collections were performed in trenches with dimensions of 50 x 50 x 40 cm, measuring the layers of 0-5, 5-10 and 10-20 cm. For determination of biomass and basal soil respiration (RBS), samples were conditioned under refrigeration (4ºC) until analyzes were performed. In addition, the microbial biomass carbon (C-Bmic) was determined in irradiated and non-irradiated samples. After analysis, the relations for metabolic quotient (qCO 2 ) and microbial quotients (qMIC) were performed. The results were subjected to analysis of variance and the means were compared by the Scott-Knott test at 5% probability level. The C-Bmic presented the highest values in RC and lower mean values in the SC areas for the first measured layer. In the qCO...
Forage management in integrated crop-livestock system is a complex activity that increases profitability, when well performed, therefore consequently influencing future crop productivity. This study aimed to evaluate the agronomic performance of corn cultivation in the integrated crop-livestock system using the no-tillage system in different forage masses post-grazing. . In absolute terms, the winter pasture management of 0.2 m high presented the best results in terms of corn grain productivity.
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