Nitrification inhibitor as strategy to mitigate N2O emissions and its impacts on the active nitrifying and denitrifying soil microbial communities after concentrated vinasse and mineral N application

Abstract

Nitrogen fertilization has been one of the main sources of greenhouse gas (GHG) emissions to the atmosphere in sugarcane cultivation, mainly due to the emission of nitrous oxide (N2O). Recent studies indicate that the application of vinasse (concentrated-VC and in natura), a byproduct of ethanol production - especially with the addition of nitrogen (N) - results in significant increases in N2O emissions. Alternatives to reduce these emissions are necessary because the main destination of vinasse is the soil, where it recycles nutrients and improves fertility. One way to reduce this emission is to add nitrification inhibitors (IN), but little is known about the efficiency of INs when mineral N is mixed with vinasse and its effect on the soil microbial community. Therefore, the objective of this project is to evaluate the efficiency of IN, 3,4-dimethylpyrazole phosphate (DMPP) in reducing N2O emissions when mineral N is applied together with VC. In addition, the impact of the joint application of IN, VC and N mineral in the total microbial community of the soil (bacteria, archaea and fungus) and in the nitrifying community (bacteria and artery) and denitrifying (bacterium and fungus) will be determined. The strategy will be tested in field experiments setup at the beginning and end of the harvest season (dry and rainy season) and in laboratory experiments. The N and VC doses will be 120 kg ha-1 and 7 m3 ha-1, respectively. Gaseous (CO2, CH4 and N2O) will be intensively sampled, as well as soil sampling for NH4+, NO3-, pH and soil moisture determination. The DNA and RNA of the soil samples will be extracted with subsequent amplification and sequencing of the 16S rRNA genes (bacterium and total archaea) and ITS (total fungus). The genes linked to the N cycle (amoA, hao, nxr, nirK, nirS, norB and nosZ) will be amplified and quantified to determine the processes responsible for the production of N2O. The results obtained can be used to define sustainable management practices during the production of ethanol, as well as to improve the understanding of the microbial processes responsible for the production of N2O and the identification of such microorganisms, and specially to determine the participation of the denitrification fungi in the emissions of N2O in soils with sugarcane and straw on the soil surface.