Microbiota associated with N2O emission in soil under energy cane cultivation

Abstract

The purpose of this proposal is to present a plan for a research internship abroad complementary to the ongoing postdoctoral project (Fapesp 2018/04992-1). The objective of this project is to measure N2O emissions and their associations with nirK, nirS, nosZI, nosZII, AOA, and AOB functional genes under controlled and field conditions. To meet this objective, the study related to the ongoing project in Brazil was developed under two different experimental conditions, conducted in parallel in an experimental field (Paulínia, SP) and greenhouse (Campinas, SP). The field experiment aims to evaluate the effect of different nitrogen (N) doses on energy cane and its implications on greenhouse gas (GHG) emissions and soil microbiology. The following treatments were tested: i) control without nitrogen fertilization; ii) 60 kg N ha1; iii) 120 kg N ha1; and iv) 180 kg N ha1. The experiment in a greenhouse also aims to evaluate the effect of different nitrogen doses, but on the initial growth of energy cane, as well as the efficiency of alternative fertilization, with addition of in natura vinasse and biochar produced from sugarcane biomass to soil, and investigate their possible effects on GHG emission dynamics and soil microbiota structure. Treatments evaluated in the greenhouse consisted of: i) control without nitrogen fertilization; ii) 60 kg N ha1; iii) 120 kg N ha1; iv) 180 kg N ha1; v) 120 kg N ha1 + vinasse (300 m3 ha1); vi) 120 kg N ha1 + biochar (5 g kg1 soil); and vii) 120 kg N ha1 + vinasse (300 m3 ha1) + biochar (5 g kg1 soil). Among the steps already completed are the determination of soil CO2, N2O, and CH4 emission (use of fixed chambers), soil temperature, and soil moisture, as well as soil chemical attributes and some soil microbiological attributes using techniques based on metagenomic studies. The steps to be carried out abroad at the laboratory of the National Institute of Agricultural Research (INRA) include quantifying nirK, nirS, nosZI, nosZII, AOA, and AOB functional genes according to the treatments described above under both field and greenhouse experimental conditions. This proposal will add a new dimension to the original ongoing project and a broader view of the relationships that have been hitherto observed. The proper data processing will be carried out using techniques in bioinformatics integrating soil chemical and physical properties with the microbiological data through network analysis, generated by Spearman correlation analysis through the software R and Gephi, for example. The scientific challenge of this project will be to obtain indicators, mainly microbiological, as a function of energy cane response to nitrogen fertilizer doses and application of the sugar-energy industry co-products (vinasse and biochar) to the mitigation of GHG of anthropogenic origin, aiming to reduce the contribution of agriculture to global warming. (AU)