Nitrous oxide production and consumption in Calcaric Regosols as related to soil redox and texture

A b s t r a c t. The aim of this study was to investigate the effect of redox status on nitrous oxide (N 2 O) evolution and transformation in soils of various textures. Soils samples were collected from Calcaric Regosols (according to FAO/UNESCO) developed from sand, silt and loam across various regions in Poland and were incubated anaerobically for 35 days. The initial phase of N 2 O production, lasting 2-21 days, was followed by a gradual decrease indicating reducing of N 2 O. The total amount of N 2 O reached 13-44% of the initial nitrate-N (NO 3 - -N) content and was highest in the silty soils and lowest in the sandy soils. It was negatively correlated with the >0.05 mm fraction and positively with the 0.05-0.002 mm fraction. Average daily N 2 O production was negatively correlated with the >0.05 mm fraction and positively with finer fractions ie with the 0.05-0.002 mm and with the 0.05 mm fraction. N 2 O reduction to N 2 begins earlier in finely (eg loam) than in coarsely textured (eg sand) soils. Nitrous oxide content in the headspace existed in equilibrium with the nitrous oxide content in soil within a narrow redox potential interval +190-(+240) mV with maximum at about +200 mV. The redox potential about +200 mV is the limit value between the production of nitrous oxide and its consumption.