Quantification of denitrification in flooded soils as affected by rice establishment method

The Biogeochemistry of Submerged Soils

“…− reduction in submerged rice soils are born out by field observations. Buresh et al (1993b) found that from 60 to 75 % of 15 N-labelled NO 3 − applied on the surface of flooded ricefields was lost by denitrification over 2-3 weeks, as measured by the 15 N not recovered in the soil, floodwater and plants. The recovery of (N 2 + N 2 O)-15 N in chambers placed over the floodwater was less than the estimated denitrification loss because gas bubbles became entrapped in the soil.…”

Nitrogen Transformations in Submerged Soils

“…The quantity of N 2 O and N 2 formed by denitrifi cation but entrapped or dissolved in the soil-fl oodwater system rather than evolved and included in the measured fl ux of 15 N-labeled N 2 O and N 2 was relatively small (Samson et al, 1990). Rice plants can act as a conduit for the transport of N gases from soil to the overlying atmosphere (Reddy et al, 1989;Ni and Zhu, 2004), and the evolution of N 2 O and N 2 originating from added urea N is typically greater when gas collection chambers are placed over rather than between rice plants Buresh et al, 1993c;Chen et al, 1998a). However, even when accounting for entrapment of formed N 2 O and N 2 and preferential transport of formed N 2 O and N 2 through the rice canopy, the con-version of applied urea N to N 2 O and N 2 was small in puddled soils that remained saturated or submerged.…”

Denitrification in Wetlands

“…In paddy soils or soils grown with aquatic plants, an oxidized zone is also formed around their roots. In another study, from 60 to 75% of NO 3 Ϫ applied on the surface of flooded rice fields was lost by denitrification over 2-3 weeks [7]. The thickness of the oxidized zone depends on the oxygen consumption rate and can reach a few millimeters to a few centimeters.…”