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NO fluxes from soils with a wide range of soil moistures, soil inorganic‐N concentrations, and soil temperatures were measured during the wet and the dry season at a Venezuelan savannah site. Maximum NO emissions (∼12 ngN m −2 s −1 ) were observed at soil gravimetric moistures between 10% and 18%. Deviation from this optimum range results in decreased NO fluxes; very low emissions ( 25% ) soil moistures. Both NO production in soil and its transport within the soil play important roles in the emission of NO to the atmosphere. Under most conditions no temperature effect was observed. NO emission was strongly stimulated by the addition of NO 3 − and only very weakly by the addition of NH 4 + ; at low and moderate soil moistures, soil nitrate and the NO flux were positively correlated. At low (natural) soil nitrate content and comparable soil moisture and temperature, NO emissions were greater during the dry season than during the rainy season, suggesting that other factors (i.e., soil physical structure) may also govern NO flux from savannah soil.
Cardenas et al. (Fri,) studied this question.