Abstract
The microbial biomass and activity are biological indicators sensitive to environmental changes caused by agricultural use and can provide important information for the planning of adequate land use. The objective of this research was to evaluate the nutrient recycling, persistence, and biological attributes of sorghum straw in Oxisol as a function of soil management systems. The experiment was carried out at the Federal Rural University of Amazonia in randomized block design with 3 x 2 factorial and four replicates. Three sorghum hybrids and two soil management systems were the factors used to assess straw decomposition. In order to evaluate the biological attributes, a 2 x 2 factorial experiment with four replicates was carried out using two soil management systems and two sampling dates. Total organic carbon (TOC), carbon in the soil microbial biomass (C-SMB), C-SMB/TOC ratio, basal respiration and metabolic quotient (qCO2) were investigated. The Qualimax hybrid presented the highest C/N ratio (55) and longer straw persistence in soil after 120 days of management (35%). The highest TOC, C-SMB, C-SMB/TOC ratio, and basal respiration and the smallest qCO2 were observed during the rainy season and in the no-till system.
Highlights
The Amazonian biome in Brazil has been intensely impacted by human use
Soil biological attributes such as microbial biomass, basal respiration and metabolic quotient are important soil quality indicators (KASCHUC; ALBERTON; HUNGRIA, 2011) and are very sensitive to changes due to soil management, being used for the monitoring of environmental changes resulting from agricultural use
The microbial biomass activity is related to the dynamic of soil organic matter, signaling changes in both short and long time periods (ARAÚJO; SANTOS; MONTEIRO, 2008)
Summary
The no-till soil management system can help to protect the soil biological resources because it allows for the crop straw to stay on soil surface longer, increasing soil organic matter. Sorghum plants can be used as cover crop in the no-till system because they present great dry mass production and regrowth capacity, and high C/N ratio and nutrient reserve (TORRES; PEREIRA, 2008). Soil biological attributes such as microbial biomass, basal respiration and metabolic quotient are important soil quality indicators (KASCHUC; ALBERTON; HUNGRIA, 2011) and are very sensitive to changes due to soil management, being used for the monitoring of environmental changes resulting from agricultural use. The microbial biomass provides a more efficient use of resources in the ecosystem: less CO is lost by respiration and a higher proportion of C is incorporated in the microbial tissues (FOLLET; SCHIMEL, 1989), which result in decreased metabolic quotient (qCO2)
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