The present study was conducted to assess the impact of elevated levels of O3 and shifting of crop calendar practice, singly, and in combination on Triticum aestivum cv. HD 2967 on its growth, gas exchange parameters, and yield attributes in open-top chambers (OTCs). Two sowing dates were considered: timely sown and late sown. Late sowing was delayed by 20 days from the timely sowing date. The result revealed that wheat plants under elevated O3 and timely sown conditions (ET) showed reductions in growth parameters, while such effects were synergistic when plants were exposed to elevated O3 under late sown conditions (EL). Photosynthetic rate, stomatal conductance, and water use efficiency reduced significantly under EL followed by ET and AL as compared with AT (ambient O3 + timely sown) whereas transpiration rate showed maximum increment under EL. Grain yield reduced by 45.3% in EL as compared with AT and 16.2% in ET as compared with AT. The growth parameters and yield attributes obtained from the present experiment revealed that (i) O3 is affecting the growth and productivity of the wheat and (ii) late sowing practice has not proved to be a feasible adaptation strategy for the wheat cultivation against O3-induced production losses under the prevailing conditions of Indo-Gangetic Plain. This is the first report documenting the shifting of crop calendar practice at the present and future scenario of O3 concentration under agro-ecological conditions in the tropical region of India.
Keywords: AOT40; Late and timely sown; Open-top chambers; Ozone; Shifting crop calendar; Wheat; Yield attributes.