Nitrogen doses (15N) and co-inoculation with growth-promoting bacteria in the wheat-soybean system in the Cerrado region: Nitrogen recovery from fertilizer and biological nitrogen fixation

• Grant number: 24/00819-4
• Support Opportunities: Regular Research Grants
• Start date: July 01, 2025
• End date: June 30, 2027
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: Marcelo Carvalho Minhoto Teixeira Filho
• Grantee: Marcelo Carvalho Minhoto Teixeira Filho
• Host Institution: Faculdade de Engenharia (FEIS). Universidade Estadual Paulista (UNESP). Campus de Ilha Solteira. Ilha Solteira , SP, Brazil
• Associated researchers: Arshad Jalal ; Bhim Bahadur Ghaley ; Edson Cabral da Silva ; Eduardo Mariano ; Eulogio de la Cruz Torres ; Fernando Shintate Galindo ; Mariangela Hungria da Cunha ; Takashi Muraoka

Abstract

Genetic improvement of wheat (Triticum aestivum L.) has made available cultivars adapted to Central Brazil, with high productivity and grain quality, being important for the diversification of crops in succession to soybean [Glycine max (L.) Merrill], in the no-tillage system (NTS). Soybeans, the successor to wheat, require large amounts of nitrogen (N), which is essential for high productivity, although most of it is obtained through biological N fixation (BNF). Developing techniques that minimize the application of mineral N and improve its use is essential for sustainable and low-carbon agriculture. The main objectives of this project will be to evaluate the effects of inoculation of Azospirillum brasilense, alone and combined with Bacillus subtilis or Pseudomonas fluorescens, in irrigated wheat, associated with doses of N (15N-urea) on grain nutrition, development and productivity; as well as the influence of the associated use of these BPCPs with Bradyrhizobium japonicum, on the agronomic performance of soybeans. In addition to estimating BNF in wheat and soybeans, using the 15N natural abundance technique, using three control species (reference). The experiments will be conducted under field conditions, for two harvests for each succession, in two areas with the same history of use and management, at UNESP, Selvíria-MS, in a dystroferric Oxisol, clayey, Cerrado phase, under NTS. The experimental design for wheat will be randomized blocks, in a 4 x 5 factorial scheme, with four replications. In wheat, in the first cycle, the treatments will be: i. Azospirillum brasilense; ii. A. brasilense + Pseudomonas fluorescens; iii. A. brasilense + Bacillus subtilis, and iv. Control (without inoculation), combined with five doses of N: 0, 30, 60, 120 and 180 kg ha-1 (15N-urea), applied as top dressing. In the second wheat cycle, the same BPCP inoculations will be used; however, the N doses will be: 0%, 25%, 50%, 75% and 100% of the N dose that provides maximum technical efficiency, preliminarily determined based on the response curve, in the first cycle. At the same time, an experiment with wheat will be conducted in another area in which the BNF will be estimated, using the 15N natural abundance technique and using three control species (rice, sorghum and guinea grass) cultivated in microplots next to the plots; therefore, in an area distant from that in which 15N-urea was used. For soybeans in succession to wheat, a randomized block experimental design will be used, with five treatments and four replications. The treatments will be: i. B. japonicum; ii. B. japonicum + A. brasilense (coinoculation); iii. B. japonicum + A. brasilense + B. subtilis (mixed co-inoculation 1); iv. B. japonicum + A. brasilense + Pseudomonas fluorescens (mixed co-inoculation 2), and v. control treatment (without inoculation), in which BNF will also be estimated using the 15N natural abundance technique, using three control species (non-nodulating soybean and common bean and rice) grown in microplots. We expected that plant growth promoting bacteria (PGPR) inoculations combined with N doses will optimize the efficiency of nutrient use, nutrition, vegetative and productive performance of plants, reducing the need for nitrogen fertilizer in wheat cultivation; as well as that the co-inoculations of PGPR associated with B. japonicum increase the FBN in soybeans, with synergistic effects resulting from multiple beneficial mechanisms (actions), in agronomic performance with positive reflections on grain productivity. (AU)