Abstract

Population growth and improved gross domestic product may increase food consumption. Soybean is the main source of protein, lipids and mineral salts for human and domestic animals’ foods. Brazil is responsible of most of the soybeans produced in the world. However, soybean production in Tocantins/Brazil state caused a decrease in the Cerrado’s biome. Therefore, the aim of this study was to evaluate the anthropic impact of planting of soybean on microbial and physical-chemical properties of Cerrado’s soil. Soil samples were collected in three soybean farms (SF) of the Tocantins/Brazil state. They were collected in the soybean field, in native vegetation field, and in anthropogenic fragmentation area in the dry and wet seasons. The diversity of arbuscular mycorrhizal fungi (AMF) and nitrogen-fixing bacteria (NFB) were analyzed by denaturing gradient gel electrophoresis (DGGE). Regardless of the SF, physico-chemical indicators did not present significant differences between the seasons. The DGGE profiles of NFB and AMF genes were different between the soybean field and native vegetation field in both seasons. The viable cells counts and NFBs and AMFs diversity were influenced by the substitution of native vegetation for soybean. The increase of the agricultural production in Cerrado soil is worrisome, due to the endemic microorganisms that was observed in this study. In addition, anthropic action on the microbial community was more effective in the soybean field during the dry season, which showed the importance of maintaining an environmental reserve area within agricultural production units.

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