Interactive effect of elevated tropospheric ozone and carbon dioxide on radiation utilisation, growth and yield of chickpea (Cicer arietinum L.)

An experiment was conducted in the Free Air Ozone and Carbon dioxide Enrichment (FAOCE) facility to study the impact of elevated O₃, CO₂ and their interaction on chickpea crop (cv. Pusa-5023) in terms of phenology, biophysical parameters, yield components, radiation interception and use efficiency. The crop was exposed to elevated O₃ (EO:60ppb), CO₂ (EC:550 ppm) and their combined interactive treatment (ECO: EC+EO) during the entire growing season. Results revealed that the crop's total growth period was shortened by 10, 14 and 17 days under elevated CO₂, elevated O₃ and the combined treatment, respectively. Compared to ambient condition, the leaf area index (LAI) under elevated CO₂ was higher by 4 to 28%, whilst it is reduced by 7.3 to 23.8% under elevated O₃. The yield based radiation use efficiency (RUE_y) was highest under elevated CO₂ (0.48 g MJ^-1), followed by combined (0.41 g MJ^-1), ambient (0.38 g MJ^-1) and elevated O₃ (0.32 g MJ^-1) treatments. Elevated O₃ decreased RUE_y by 15.78% over ambient, and the interaction results in a 7.8% higher RUE_y. The yield was 31.7% more under elevated CO₂ and 21.9% lower in elevated O₃ treatment as compared to the ambient. The combined interactive treatment recorded a higher yield as compared to ambient by 9.7%. Harvest index (HI) was lowest under elevated O₃ (36.10%), followed by ambient (39.18%), combined (40.81%), and highest was under elevated CO₂ (44.18%). Chickpea showed a positive response to elevated CO₂ resulting a 5% increase in HI as compared to ambient condition. Our findings quantified the positive and negative impacts of elevated O₃, CO₂ and their interaction on chickpea and revealed that the negative impacts of elevated O₃ can be compensated by elevated CO₂ in chickpea. This work promotes the understanding of crop behaviour under elevated O₃, CO₂ and their interaction, which can be used as valuable inputs for radiation-based crop simulation models to simulate climate change impact on chickpea crop.