Denitrification from sandy soils treated with liquid or dry granular nitrogen form

The forms of nitrogen (N) in fertilizers and soil properties influence gaseous loss of N by denitrification. A laboratory incubation study was conducted to evaluate the denitrification losses from liquid or dry granular forms of ammonium nitrate (at 200 mg N kg(-1) soil) as nitrous oxide in acetylene-inhibited systems. Myakka fine sand (Spodosol), Parkwood sand (Alfisol), and Tavares fine sand (Entisol) sampled at 0 to 15 cm depths were used with or without the addition of a readily available carbon (C) source (200 mg C kg(-1), as glucose). The soils were incubated anaerobically for 96 h at field capacity moisture with 10% (vol/vol) acetylene atmosphere. Nitrous oxide emission was not detectable in the Parkwood sand throughout the study, despite its high organic C content and microbial activity, possibly because of incomplete inhibition of N2O reduction by acetylene in Parkwood soil as a result of its high clay content, which could have hindered the free diffusion of acetylene. In the Myakka fine sand and the Tavares fine sand, cumulative N2O production for 96 h was greater when ammonium nitrate was applied in the liquid form rather than the dry granular form. The difference was more pronounced in the Myakka sand (2.3-fold) than in the Tavares sand (1.9-fold). Denitrification was enhanced by the addition of readily available carbon in the form of glucose. The soil microbial population and soil organic carbon content seemed to play a major role in determining denitrification losses. Cumulative N2O emission was correlated significantly (r(2) = 0.92) with the microbial activity as measured by fluorescein diacetate hydrolytic activity.