Nitrous Oxide Production in an Eastern Corn Belt Soil: Sources and Redox Range


Nitrous oxide derived from soils is a main contributor to the greenhouse gas effect and a precursor to ozone-depleting substrates; however, the source processes and interacting controls are not well established. This study was conducted to estimate the magnitude and source (nitrification vs. denitrification) of N^sub 2^O production as affected by the form of N fertilizer, soil water content, and redox potential (Eh). Soils from continuous corn (Zea mays L.) experimental plots with a history of eight consecutive years of either side-dressed urea-NH^sub 4^NO^sub 3^ (UAN) or fall liquid swine manure (FM) were collected and N^sub 2^O evolution was traced in both aerobic and anaerobic incubations using ^sup 15^N labeling. Partitioning results were highly variable but suggested that enhanced denitrification occurred after an extreme increase in soil water content (from 45 to 90% water-filled pore space [WFPS]) while a more coupled nitrification-denitrification process drove N^sub 2^O evolution at moderate water content (55% WFPS). Manured soils at high water contents registered shorter duration peaks but with higher overall N^sub 2^O production rates than those observed at moderate water content (7-d weighted average of 0.61 vs. 0.09 μg N^sub 2^O kg^sup -1^ soil h^sup -1^). Under anoxic conditions, manured soils showed higher N^sub 2^O production rates than UAN soils (up to 336 and 145 μg N^sub 2^O kg^sup -1^ soil h^sup -1^, respectively) shortly after flooding, which coincided with a sharp drop in Eh (from 575 to 466 mV). Irrespective of the N source, a narrow, consistent Eh range for N^sub 2^O production occurred under moderate reducing conditions (420-575 mV). These results indicate that soils receiving repeated manure application that are subject to intensive, recurrent soil rewetting events may be prone to higher N^sub 2^O emissions. [PUBLICATION ABSTRACT]

Date of this Version










Link Out to Full Text