Nitrogen fertilization (15N-fertilizer) and inoculation with Azospirillum brasilense and Bacillus velezensis in sugarcane: N balance in the soil-plant-atmosphere system

• Grant number: 24/20071-4
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: March 01, 2025
• End date: February 29, 2028
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: Thiago Assis Rodrigues Nogueira
• Grantee: Rodrigo Silva Alves
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil

Abstract

Nitrogen (N) fertilization plays a crucial role in the agronomic and industrial performance of sugarcane. In Brazil, due to external dependence and high acquisition costs of nitrogen fertilizers, aggravated by global geopolitical crises, it is essential to increase the efficiency of use and seek alternative N sources. Proper management of N fertilizers in sugarcane can mitigate the impacts caused by global climate change, by lowering greenhouse gases (GHG) emissions, especially nitrous oxide (N2O). Plant growth-promoting bacteria (PGPB) can be an alternative to minimize these problems since they are capable of making nutrients available, improving plant growth and development. Azospirillum spp. and Bacillus spp. are widely used in agriculture due to their benefits, which include the production of phytohormones, tolerance of plants to abiotic stresses, and increased nutrient availability, through engagement in biological nitrogen fixation (BNF). These above issues are fundamental to define the sustainability of sugarcane production, with repercussions on environmental sustainability. Conversely, there is still little information on the use of PGPB associated with nitrogen fertilization and its effects on sugarcane cultivation. Therefore, the objective of this study is to evaluate the N use efficiency and N balance in sugarcane cultivation, in response to N application rates associated with or without PGPB inoculation. The experiment will be conducted under field in the municipality of Sales Oliveira, SP, Brazil. A randomized complete block experimental design will be used, in a 4 × 4 factorial scheme, with four replications. The treatment will consist of four rates of 15N-ammonium nitrate (0, 80, 120, and 160 kg ha-1) and four inoculations of PGPB (i. without inoculation, ii. Azospirillum brasilense, iii. Bacillus velezensis, and iv. Azospirillum brasilense + Bacillus velezensis). In the 2024/25 and 2025/26 harvests, the following will be evaluated: nutritional status of the plant, morphological and production components, stalk productivity and technological quality of sugarcane, in addition to the N balance by isotopic techniques (15N), and BNF. In the 2025/26 harvest, will also be evaluated of N2O emissions. Soil samples will be collected at depths of 0-0.25 and 0.25-0.50 m, the concentration of total N, ammonium N, and nitrate N will be determined. This project is expected to understand the most efficient management of N use in the sugarcane cultivation system associated with PGPB inoculation in order to reduce dependence on nitrogen mineral fertilizers, resulting in reduced GHG emissions and increased crop productivity in a sustainable manner. These results have the potential to foster some research, innovation, and dissemination objectives aligned with the COP28, IPCC, and "Agenda 2030" initiatives of the United Nations to promote the "Sustainable Development Goals - SDGs 2, 7, 13, and 15".