N2O emissions from wheat agro-ecosystems under elevated atmospheric CO2

Abstract

Fertilizer-derived nitrous oxide, N20, may cause an increase of tropospheric N20, which could contribute to the destruction of the ozone layer and enhance the "greenhouse effect". The impact of fertilizer on tropospheric N20 may be enhanced by increased carbon dioxide, CO2, which may alter soil N dynamics. The goal of this research was to measure N20 emissions from soil within a field of wheat grown under two levels of atmospheric CO2 (ambient and ambient plus 200 ppm), two irrigation levels (15 and 30% depletion of available water in the root zone), and two levels N-fertilizer (15 and 350 kg N/ha). Spring wheat (Triticum aestivum L. cv. Yecora Rojo) was planted at the University of Arizona Agricultural Center, Maricopa, Arizona, December 1996 and harvested May 1997 in conjunction with a Free Air CO2 Enrichment (FACE) experiment. Chamber measurements of N20 emissions were made five days during the season. The results showed that emissions were not different for the two different irrigation levels. There was, however, a positive correlation between emissions and air temperature. The elevated CO2 had no statistically significant effect on the N20 emissions.