Forms of nitrogen application and impact on nodulation, photosynthetic rate and biological nitrogen fixation in soybean

• Grant number: 17/14123-8
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: February 01, 2018
• End date: December 31, 2018
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: José Lavres Junior
• Grantee: Maria Clara Faria Chaves
• Host Institution: Centro de Energia Nuclear na Agricultura (CENA). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

Biological nitrogen fixation (BNF) is the main source of nitrogen (N) uptake and assimilation by soybean crop. The hypothesis to be verified is whether the mineral-N supply as fertilizer can halt nodulation and N-metabolism and reducing gains yield and shoot biomass. The objective of this work is to evaluate the effect of urea-N supply at sowing, flowering and at both times on nodulation efficiency, BNF, nitrogenase (EC 1.18.6.1) and nitrate reductase (EC 1.7 .1.1) activities, the rate of CO2 assimilation, the amount of N taken up in the shoot and in the grains, plant growth and the production of grains and plant dry mass. The fertilizer used (urea) will be enriched with the 15N isotope, at 5% excess atoms. The cultivar BMX Active RR with determined growth type will be used. The experiment will be carried out in pots containing 10 dm3 of soil from a LVAd, employing the experimental design of complete blocks, with treatments arranged in a 4 x 6 factorial scheme (four forms of N application x six times of evaluation - plant growth stage), with three blocks. In conclusion, starting from the fact that the farmers have tried to support the high yield by means of N-applications both at the sowing, and at the reproductive stages, mainly at the flowering, it is intended, with this work, to contribute to the studies of the nutritional physiology of the BNF in soybean, using genotype widely diffused in Brazil. (AU)