Nitrate Transformation and N 2 O Emission in a Typical Intensively Managed Calcareous Fluvaquent Soil: A 15-Nitrogen Tracer Incubation Study.

A 56-day aerobic incubation experiment was performed with 15-nitrogen (N) tracer techniques after application of wheat straw to investigate nitrate-N (NO3-N) immobilization in a typical intensively managed calcareous Fluvaquent soil. The dynamics of concentration and isotopic abundance of soil N pools and nitrous oxide (N2O) emission were determined. As the amount of straw increased, the concentration and isotopic abundance of total soil organic N and newly formed labeled particulate organic matter (POM-N) increased while NO3-N decreased. When15NO3-N was applied combined with a large amount of straw at 5000 mg carbon (C) kg−1only 1.1 ± 0.4 mg kg−1NO3-N remained on day 56. The soil microbial biomass N (SMBN) concentration and newly formed labeled SMBN increased significantly (P < 0.05) with increasing amount of straw. Total N2O-N emissions were at levels of only micrograms kg−1soil. The results indicate that application of straw can promote the immobilization of excessive nitrate with little emission of N2O. [ABSTRACT FROM PUBLISHER]