Microbial Nitrate Elimination in Subsoils of an Agriculturally Used Water Catchment Area

Abstract

Depending on soil type and cropping system the NO ⁻₃ -impact on ground- and drinking water is increasing in areas of intensive agricultural production (Obermann, 1990). So far microbial N-transformation processes in the water unsaturated subsoil are poorly understood. There is indirect evidence suggesting that biological denitrification may play an important role in preventing groundwater contamination (Böttcher, 1990). Only very few measurements on the denitrifying capacity and on the population of denitrifying bacteria have been made in subsoils. In order to predict the nitrate respiring capacity of subsoil samples collected from an water catchment area, the actual denitrifying capacity (adc) of freshly taken samples was determined immediately using the acetylen inhibition technique. Simultaneously, the population density of denitrifying bacteria, as well as nitrate- and carbon-contents were quantified along several, selected soil profiles during 1989–1990.