Nitrogen Addition Decreases Dissimilatory Nitrate Reduction to Ammonium in Rice Paddies

Abstract

This study provides evidence that nitrogen addition reduces nitrogen retention through DNRA and increases nitrogen loss via denitrification in a paddy soil ecosystem. DNRA is one of the major NO 3 − reduction processes, and it can outcompete denitrification in NO 3 − consumption when rice paddies are low in nitrogen. A significant level of DNRA activity in paddy soils indicates that DNRA plays an important role in retaining nitrogen by reducing NO 3 − availability for denitrification and leaching. Our study shows that by reducing N addition to rice paddies, there is a positive effect from reduced nitrogen loss but, more importantly, from the conversion of NO 3 − to NH 4 + , which is the favored form of mineral nitrogen for plant uptake.