Effects of fertilizing nitrogen levels on soil respiration duringgrowing season in maize field

In order to explore effects of nitrogen (N) fertilization on soil respiration in maize （Zea mays） field during the growing season, the study, using EGM4 sealed soil respiration measurement system, was conducted to measure Soil respiration rate of the maize fieild with different N fertilizatian at Liangzhou, Gansu Province. Results obtained in the study indicated that the soil respiration rate of maize field was changed on a similar diurnal pattern with a single peak, and increased with soil temperature rising up. The minimum and maximum values occurred around 06:00 and 14:00, respectively. The seasonal change of soil respiration rate in maize land was significant, with a CO2 emission maximum value of 8.92 mol/(m2s) on July and a minimum value of 1.12 mol/(m2s) on May. The order of seasonal change of soil respiration rate in maize field was tasseling stagebigtrumpet stageelongation stagefilling stagemature stageseedling stage. Soil respiration rate increased with the increase of fertilizing nitrogen levels. Fertilized N with 450 kg/ha (N450), the CO2 emission from maize field was 5.72 mol/(m2s) on average; and fertilized N with 300 kg/ha (N300) and unfertilized N (N0), the CO2 emissions were 5.34 and 4.90 mol/(m2s) on average; whereas the soil respiration rate of N450 treatment was 7.12% and 16.73% higher than that of N300 and N0, respectively. However, the significant difference between treatments only occurred during the maize blooming stage.