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Using phytotron growth chambers, a short-term pot experiment under nonlimiting water condition was conducted to investigate the individual and interactive effects of elevated carbon dioxide (650 ± 10 lmol mol )1 vs. ambient), temperature (3°C above ambient vs. ambient) and different levels of urea-N (control, 100 % N and 200 % N of recommended dose) on growth and yields of wheat crop and changes in potential nitrogen mineralization (PNM), nitrification and denitrification activities, microbial biomass carbon (MBC), nitrogen (MBN), dissolved organic carbon (DOC), and nitrifying and denitrifying organisms in a semiarid Inceptisol. The plant parameters (root, shoot and grain) responded positively (10-23 %) to elevated CO 2 and negatively ()17 to )38 %) to higher temperature. Interactive effect of elevated CO 2 and temperature caused a negligible impact on root, shoot (%)5 %) and grain yields of wheat. Soil NH þ 4 -N content was not affected, but NO À 3 -N was reduced significantly. Nitrate reductase activity was decreased by 14-20 % at elevated CO 2 . There was positive effect of elevated temperature on PNM (+9-16 %), whereas negative effects were observed for potential nitrification activity (PNA), MBC, MBN and DOC. Elevation of atmospheric CO 2 or temperature did not affect the population of ammonia (AOB) and nitrite oxidizers (NOB), but elevation of CO 2 has decreased the population of denitrifiers by 4-14 %.

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