Agronomist, PhD (1982) in Soils and Plant Nutrition from the Luiz de Queiróz Higher School of Agriculture, Brazil, and post-doctorate (1994) from the University of London, UK. Credentialed Professor of the Graduate Program in Agronomy at the Federal Rural University of Rio de Janeiro. He is a technical consultant for the International Atomic Energy Agency, United Nations. He acts as a scientific consultant for the National Research Council (CNPq), the Rio de Janeiro Research Support Foundation and the São Paulo Research Support Foundation, Brazil. He published more than 200 articles and several book chapters and books on biological nitrogen fixation, sugarcane and pastures, grain production systems under zero tillage, agroenergy, use of stable isotopes (15N and 13C) in agriculture and sequestration of C soil and greenhouse gases in the agricultural systems of Brazil.