Elevated temperature and low nitrogen partially offset the yield, evapotranspiration, and water use efficiency of winter wheat under carbon dioxide enrichment

Atmospheric carbon dioxide (CO2) concentration, temperature and nitrogen (N) are the key regulators of productivity and water use of plants under the changing climate. However, field scale studies on the interactive effect of the three above critical inputs are limited. Hence, this field study was conducted with three climate treatments (ambient (AC), elevated CO2 (eC, similar to 550 mu mol mol(-1)) and co-elevation of both CO2 and temperature (eCeT, similar to 550 mu mol mol(-1) and temperature similar to 2 degrees C above ambient)) and four N treatments (0%, 50%, 100% and 150% of recommended N dose of 120 kg N ha(-1)). The experiment was carried out in open top field chambers to study the effects of climate and N application on grain yield, evapotranspiration (ET) and water use efficiency (WUE) in wheat crop. Crop ET was estimated by field water balance method and WUE by taking the ratio of grain yield to crop ET. Elevation of CO2 showed 9% yield gain over ambient (averaged across N levels), whereas, coelevation of temperature reduced the yield gain to 4%. Further, N application significantly altered the level of CO2 response. Under CO2 enriched environment, the yield gain was 15% with N-100 as compared to 2% and 4% under N-0 and N-50, respectively, indicating CO2 enrichment benefits in grain yield was N dependent. The three years' pooled data showed significant effect of climate, N and their interaction on profile water storage, evapotranspiration and WUE. Elevation of CO2 alone or with co-elevation of temperature resulted in significant decline in crop ET by 4-11 mm and significant increase in profile soil moisture and WUE. The WUE improved significantly, by 12% under eC and by 4% under eCeT, respectively, with the increase, more attributed to gain in grain yield. Quantitative derivation from the three years' field experimentation could establish that under elevated CO2 scenario (550 mu mol mol(-1)), an additional 1 degrees C rise in temperature would result in enhanced crop ET by 5 mm and yield loss of about 4%. This study thus revealed that limited N and increased temperature would potentially restrict the CO2 mediated benefits in wheat yield and water use under the changing climate.

Automated summary

The study found that under elevated CO2 concentration, proper nitrogen application can increase wheat yield, but excessive temperature rise may decrease this benefit. Nitrogen significantly influences the response to CO2, while CO2 enrichment and temperature increase can reduce crop evapotranspiration.