Effect of Elevated CO2 and Temperature on Nitrogen Dynamics and Microbial Activity During Wheat (Triticum aestivum L.) Growth on a Subtropical Inceptisol in India

Using phytotron growth chambers, a short‐term pot experiment under non‐limiting water condition was conducted to investigate the individual and interactive effects of elevated carbon dioxide (650 ± 10 μmol 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 CO₂ and negatively (?17 to ?38 %) to higher temperature. Interactive effect of elevated CO₂ and temperature caused a negligible impact on root, shoot (≈?5 %) and grain yields of wheat. Soil –N content was not affected, but –N was reduced significantly. Nitrate reductase activity was decreased by 14–20 % at elevated CO₂. 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 CO₂ or temperature did not affect the population of ammonia (AOB) and nitrite oxidizers (NOB), but elevation of CO₂ has decreased the population of denitrifiers by 4–14 %.