Nitrous oxide emissions from an irrigated sandy-clay loam cropped to maize and wheat

Nitrous oxide (N2O) emissions were measured from an irrigated sandy-clay loam cropped to maize and wheat, each receiving urea at 100 kg N ha(-1) During the maize season (24 August-26 October), N2O emissions ranged between -0.94 and 1.53 g N ha(-1) h(-1) with peaks during different irrigation cycles (four) ranging between 0.08 and 1.53 g N ha(-1) h(-1). N2O sink activity during the maize season was recorded on 10 of the 29 sampling occasions and ranged between 0.18 and 0.94 g N ha(-1) h(-1). N2O emissions during the wheat season (22 November-20 April) Varied between -0.85 and 3.27 g N ha(-1) h(-1), whereas peaks during different irrigation cycles (six) were in the range of 0.05 - 3.27 g N ha(-1) h(-1). N2O sink activity was recorded on 14 of the 41 samplings during the wheat season and ranged between 0.01 and 0.87 g N ha(-1) h(-1). Total N2O emissions were 0.16 and 0.49 kg N ha(-1), whereas the total N2O sink activity was 0.04 and 0.06 kg N ha(-1) during the maize and wheat seasons, respectively. N2O emissions under maize were significantly correlated with denitrification rate and soil NO3--N but not with soil NH4+- or soil temperature. Under wheat, however, N2O emissions showed a strong correlation with soil NH4+-N, soil NO3--N and soil temperature but not with the denitrification rate. Under either crop, N2O emissions did not shaw a significant relationship with water-filled pore space or soil respiration.