Nitrogen doses and co-inoculation with growth-promoting bacteria in the wheat-soybean system in the Cerrado region

• Grant number: 25/13618-0
• Support Opportunities: Scholarships in Brazil - Master
• Start date: September 01, 2025
• End date: February 28, 2027
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: Marcelo Carvalho Minhoto Teixeira Filho
• Grantee: Jeferson Silva de Souza
• Host Institution: Faculdade de Engenharia (FEIS). Universidade Estadual Paulista (UNESP). Campus de Ilha Solteira. Ilha Solteira , SP, Brazil
• Associated research grant: 24/00819-4 - 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, AP.R

Abstract

Nitrogen (N) is the nutrient required in the greatest quantity and represents one of the highest costs in production systems for non-legume crops such as wheat. However, soybean crops require large amounts of N to achieve high yields due to the high protein content of the grains, although most of the N in soybeans comes from biological nitrogen fixation (BNF). Developing management techniques that minimize the need for mineral N application and enable better use of this nutrient in production systems is essential for increasingly sustainable, productive, and less polluting agriculture, aiming for food security and low-carbon agriculture. In this context, the use of wheat and soybean cultivars with high production potential combined with technologies that promote greater resilience in production systems, and committed to the Sustainable Development Goals (SDGs), is fundamental to the success of modern agriculture. Research has demonstrated the potential of using plant growth-promoting bacteria (PGPBs) to improve plant development by acting on various mechanisms related to growth promotion, particularly the availability, absorption, and efficiency of nutrient use in production systems. However, knowledge on this subject is still insufficient and deserves further study under specific environmental conditions, such as in Cerrado regions. In this regard, the assumption is that the combined inoculation of two PGPBs, via seeds, associated with N doses, promotes additive effects of individual benefits, optimizing BNF and nutrient use efficiency, which positively impacts plant nutrition, vegetative and productive performance, and reduces the need for fertilizers in irrigated wheat cultivation. Although several studies have been conducted in recent years on the inoculation of PGPBs in different crops, most studies do not focus on the benefits of inoculations in optimizing nitrogen fertilization management in the wheat-soybean production system. Therefore, studies are needed that focus not only on the benefits of nitrogen fertilization management in wheat crops, but also on the recovery of fertilizer N (recycling) by soybean crops. The objectives will be to evaluate the effects of seed inoculation with Azospirillum brasilense applied alone and in combination with Bacillus subtilis or Pseudomonas fluorescens in wheat, combined with N rates, on nutrition, development, grain yield, nutrient accumulation, and nitrogen use efficiency (NUE) in irrigated wheat, as well as the effect of these treatments on soybean crops. The experiments will be conducted for two harvests per crop, in an experimental area of ¿¿the Ilha Solteira School of Engineering, UNESP, Selvíria, Mato Grosso do Sul, on a dystroferric Red Latosol, Cerrado phase, under a consolidated no-tillage system (> 15 years of adoption). The experimental design will be a randomized complete block design, in a 4x5 factorial arrangement, with four replications. The treatments will consist of three inoculations plus a control without inoculation: 1) Azospirillum brasilense; 2) A. brasilense+Pseudomonas fluorescens; 3) A. brasilense+Bacillus subtilis; and 4) Control, combined with five N rates: 0, 30, 60, 120, and 180 kg ha-1, applied as topdressing in the form of urea. Soil and plant chemical analyses will be performed at the UNESP (host institution) laboratories. Analyses will be performed on the nutritional status of wheat and soybean at flowering; biometric growth assessments; production components; grain yield; extraction (whole plant), export (grains), and return of macro and micronutrients to the soil (straw - crop residues); in addition to the C/N ratio, fiber, lignin, and polyphenols of the straw (crop residues).