Resumen
Emissions of nitrous oxide (N2O) were measured in agricultural lands used for farming wheat and maize during 1998 in the states of Hidalgo and Tlaxcala in Mexico. In an irrigated wheat field (El Teñhé, Hidalgo), an average flux of -10.85 µg N2O-N m-2h-1 was obtained for the total cycle (155 days between December and May). There, high negative values were observed with Water Fill Porous Space (WFPS) close to 70%. The average flux of the complete cycle (269 days between March and December) in an irrigated maize field (El Progreso, Hidalgo) was 37.43 µg N2O-N m-2h-1. In this case, more significant negative fluxes were found with WFPS close to 45% or less. These last results may have been influenced by the strong ?El Niño?, which occurred in the middle of 1998. Twenty one percent of the measurements in the state of Hidalgo showed soil acting as a nitrous oxide sink. The samples from Tlaxcala showed that these fields acted as emitters. In the rain fed fields in the state of Tlaxcala, an average flux of 121 µg N2O-Nm-2h-1 was obtained for the wheat field. The farming season lasted 142 days, from July to December. In addition, for the maize field the averaged flux was 285.61 µg N2O-N m-2h-1. The farming season lasted 246 days, from April to December.