N2O and no emissions from poultry litter and urea applications to Bermuda grass

The objectives of the study were to quantify N2O and NO emissions from poultry litter and urea applications to Bermuda grass (Cynodaon dactylon L.) and examine the seasonal variations in emissions. Soil N2O and NO emissions were measured in a Bermuda grass pasture treated with two sources of poultry litter, composted poultry litter (CPL) and fresh poultry litter (FPL) and urea (URE). Nitrogen (N) was applied to supply 336 kg available N ha-1 in four split applications made during the period from April to August 1995. An automated closed chamber system was employed to monitor N2O and NO emissions. The seasonal N2O emission patterns were characterized by several peaks occurring in phase with intermittent rain events and increasing soil N and organic carbon (C) associated with fertilizer application. The cumulative N2O emissions over the season (May to mid September) from the various treatments were, 3.87 kg N ha-1 from FPL, 2.96 kg N ha-1 from URE, and 1.64 kg N ha-1 from CPL. These seasonal N2O losses accounted for 1.0, 0.73 and 0.32% of the added available N for the, FPL, URE and CPL treatments, respectively. Denitrification was suggested as the primary source of N2O following rain events when inorganic N and C soil concentrations were highest and soil water-filled-pore-space (WFPS) was elevated. Peaks in NO emissions were observed primarily immediately after the addition of N sources. The seasonal NO emissions were smaller and ranged from 1.36 kg N ha-1 for URE, and 0.97 kg N ha-1 for FPL, to 0.47 kg N ha-1 for CPL. The seasonal NO emissions accounted for 0.36, 0.24 and 0.09% of the added N for the URE, FPL, and CPL treatments, respectively.