Banca de DEFESA: JOYCE EUGENIO PERRUT

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : JOYCE EUGENIO PERRUT
DATE: 25/02/2026
TIME: 13:00
LOCAL: Embrapa Agrobiologia, auditório JD
TITLE:

Nutritional efficiency and nitrogen losses in sugarcane fertilized with a mixture of mineral fertilizers and digestate from the sugar–ethanol industry

KEY WORDS:

Vinasse; sugarcane; fertilization; anaerobic digestion; nitrogen use efficiency; 15N; N2O

PAGES: 54
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SPECIALTY: Fertilidade do Solo e Adubação
SUMMARY:

Sugarcane cultivation has a high nitrogen (N) demand, as this nutrient is essential for achieving high yields. Within the context of the energy transition and circular economy, the sugar–ethanol industry has gradually replaced raw vinasse with anaerobic digestate derived from biodigestion for biogas production. However, the chemical differences between these residues—particularly the acidic pH of vinasse and the alkaline pH of digestate—raise questions regarding how this substitution affects the efficiency of mineral fertilizers (such as urea and monoammonium phosphate, MAP) and the dynamics of N losses in the soil–plant system. In the first chapter, the study evaluated, under controlled conditions, the effects of organomineral mixtures associated with straw management. Using the 15N isotopic tracer technique, it was possible to accurately track the fate of fertilizer-derived nitrogen when applied in combination with organic residues. The main objective was to understand how the interaction between the organic source and straw cover regulates N availability to the plant and its retention in the soil. The results indicate that, during the initial growth stage, sugarcane biomass production was primarily determined by total N supply, with no significant differences between vinasse and digestate application. However, the fate of nitrogen within the system differed: vinasse promoted greater retention of fertilizer-derived N in the soil, whereas digestate favored greater N allocation to the plant. A key finding was the role of straw cover. Maintaining straw on the soil surface acted as both a physical and biological regulator, increasing plant recovery of urea-derived N by up to 30% and serving as a temporary N reservoir that reduced immediate losses. The study concludes that replacing vinasse with digestate is agronomically feasible in the initial stage, provided it is integrated with conservation management practices. Straw retention was identified as the main factor determining nitrogen use efficiency, playing a critical role in improving the utilization of mineral fertilizers and agro-industrial residues and enhancing the sustainability of the production system. The second chapter addresses how these by-products influence soil microbial processes, particularly nitrification and denitrification, with implications for both agronomic performance and environmental mitigation. Nitrous oxide (N2O) fluxes were measured using static chambers with thermal insulation. Gas concentrations were analyzed using a cavity ring-down spectroscopy (CRDS) system. Peak N₂O emissions occurred within the first days following fertilization, reflecting the high availability of mineral N in the soil. The organomineral treatment with digestate exhibited high initial emission peaks, comparable to mineral fertilization alone in terms of cumulative N2O emissions. Vinasse resulted in lower cumulative emissions, likely due to its acidic pH and the gradual mineralization of organic N. The results confirm that mineral N availability and its interaction with organic carbon regulate gaseous N losses. Digestate did not increase environmental impact relative to mineral fertilization, whereas vinasse showed greater potential for emission mitigation.

COMMITTEE MEMBERS:
Presidente - ***.282.827-** - BRUNO JOSÉ RODRIGUES ALVES - EMBRAPA
Interno - 2213075 - EVERALDO ZONTA
Externo à Instituição - EDNALDO DA SILVA ARAÚJO - EMBRAPA