The response of nitrogen fixers and phosphorus solubilizer microbes to soil coverage along depth

Abstract

Permanent soil coverage is one of the three proprieties of conservation agriculture to improve soil quality and crop production sustainability. To protect soils, the top cover can be performed by crop residues or cover crops, promoting the increase of soil organic matter, acting on the soil physical and chemical characteristics, and leading to shifts in microbial behavior. The soil microbial community interacts directly with the organic matter material present on the top of the soil, which serves as a substrate for microbial development. As most of soil coverages are characterized by high carbon:nitrogen ratio, it can be suggested that it imposes a selective pressure, stimulating some microbial groups, such as those involved in the biological nitrogen (N) fixation and phosphorus (P) solubilization processes. Therewith, it is proposed to quantify such effects by using two agricultural systems (sugarcane and coffee), where the response of total community, and also N fixers and P solubilizers will be monitored in front of contrasting situations of soil coverage, along soil six soil layers (up to 30 cm). Chemical characterization of soils will be determined, together with biological characteristics related to biological activity (enzymes ²-glucosidase and acid phosphatase), genes quantification (16S rRNA for Bacteria, nifH for biological nitrogen fixation and phoD for phosphorus solubilization), and microbial diversity (based on sequencing approaches). It is expected to highlight microbial community response to soil coverage, mainly remarking the effects of this management upon nitrogen fixers and phosphorus solubilizers, supporting more assertive propositions of soil managements in a conservation agriculture. (AU)