Response of Nitrous Oxide and Corresponding Bacteria to Managements in an Agricultural Soil

Abstract

We investigated the linkages between composition and abundance of ammonia –oxidizing bacteria (AOB) and denitrifiers and emissions of N2O in a summer maize (Zea mays L.) field in a calcareous, intensively managed, agricultural soil. The treatments were zero‐N (control), NH4+–based fertilizer N (favoring nitrification), NO3−–based fertilizer N + glucose + soil compaction (NO3−+Glu+Com, favoring denitrification), and urea + straw (U+S, representing conventional farming practices). We observed a substantial period (approximately 1 wk) of high N2O emissions that commenced after N fertilization and irrigation. The highest emissions occurred in the NO3−+Glu+Com treatment. A significant positive relationship was observed between soil NH4+–N concentrations and N2O emissions in the NH4+ and U+S treatments. In general, a positive relationship between N2O emissions and soil water‐filled pore space (WFPS) existed when WFPS reached >55%. Community structure of AOB in the NH4+ treatment during the high N2O emission stage, based on terminal restriction fragment length polymorphism, was similar to that in the control treatment. There were no changes in the denitrifier community structure under NO3−+Glu+Com when 53 times higher N2O emissions occurred than in the control. High abundance of amoA gene copies for AOB and nir gene copies for denitrifiers were detected, however, during the high N2O emission period in the NH4+ and NO3−+Glu+Com treatments, respectively. The results indicate that N2O emissions were related to the abundance of AOB or denitrifiers. It remains unclear, however, whether their community composition can also have an effect on N2O emissions.