Rakesh Awale, Department of Soil Science, North Dakota State University, Fargo, ND and Amitava Chatterjee, North Dakota State University, North Dakota State University, Fargo, ND
Denitrification from nitrogenous fertilizer like urea is the potential source of N2O flux from agroecosystem. Soil moisture content controls denitrification loss of mineralizable N. A lab incubation study was conducted to understand the relationship between N2O emissions of urea-N with and without additions of nitrification inhibitor, nitrapyrin (NP) and soil moisture content under silty clay soils. During lab incubation, we measured N2O emissions from urea-N- treatments consisting (1) control (0 kg N ha-1), (2) 150 kg urea-N ha-1 (3) 150 kg urea-N ha-1 with NP, (4) 250 kg urea-N ha-1, and (5) 250 kg urea-N ha-1 with NP from soils incubated at 30, 60 and 90% of soil water holding capacity. Soils, amended with urea-N across three moisture regimes, were incubated in an airtight 1 L mason jars at 25°C. Headspace samples are collected on days 1, 2, 4, 5, 7, 10, 12, 16, 20, 24, 30, 35, 45, and 60 from a sampling port (with butyl rubber septum) in a jar lid, using a 30 mL syringe fitted with a 21 gauge needle. Gas samples are analyzed for N2O concentration using a Dani Master gas chromatograph, equipped with electron capture detector. In addition, at the termination of the experiment, soils are analyzed for inorganic N (NH4+-N and NO3-- N) contents using an automated Timberline TL2800 Ammonia analyzer. The results will predict the moisture regulation of denitrification process as influenced by N management.