Nitrous oxide, nitric oxide, and nitrogen dioxide fluxes from soils after manure and urea application

Nitrous oxide is a greenhouse gas, and NO and NO2 play a key role in atmospheric chemistry. Nitrous oxide, NO, and NO2 fluxes from fertilized soils were measured six times per day by an automated flux monitoring system for one year, beginning on 21 May 1998. Pac choi (Brassica spp.) was cultivated for two months, and the plots were left fallow the remainder of the year. Two types of manure, poultry manure (PM) and swine manure (SM), and a chemical fertilizer, urea, were applied to the soil. The total amount of nitrogen applied in each case was 15 g A m(-2). The total fluxes from PM, SM, and urea, for the year were 184, 61.3, and 44.8 mg N m(-2) for N2O, respectively; 9.95, 16.6, and 148 mg N m(-2) for NO, respectively; and -6.21, -7.23, and -7.84 mg N m(-2) for NO2, respectively. A negative correlation was found between the NO flux and the NO concentration of the chamber air just after the chamber I Was closed, when a flux from the atmosphere to soil was observed for 10 months. The mean gross NO production, the NO uptake rate constant, and the apparent compensation point for this period were 0.79 to 0.95 mug N m(-2) h(-1), 120 to 128 L MATERIALS AND-METHODS m(-2) h(-1), and 5.65 to 7.35 ppbv, respectively.