Advances in methodology for research on nitrogen transformations in soils

This chapter reviews the methodology employed in soil nitrogen (N) research, following the review by J. M. Bremner and R. D. Hauck. Advances in analytical instrumentation and techniques have played a key role in the proliferation of research since 1980 concerning the nature and transformations of soil N, particularly as regards agricultural productivity and environmental quality. The application of enzymatic assay techniques in soil N research has focused primarily on the role of nitrogenase in biological N₂ fixation and the hydrolysis of urea by soil urease. Environmental applications of molecular genetics have focused largely on xenobiotic degradation, but N-cycle processes also have been a subject of investigation, particularly N₂ fixation, nitrification, and denitrification. Limmer et al. have utilized a different form of isotope dilution to detect emission of N₂ generated during denitrification under field conditions.