Interactive Effect of Elevated Carbon Dioxide and Elevated Temperature on Growth and Yield of Soybean

A field experiment was undertaken in the kharif season of 2016 in open-top chambers to study the individual and combined effects of elevated carbon dioxide and temperature on growth and yield parameters in soybean crop. The soybean (var. JS 20–29) crop was grown under two levels of CO₂ (ambient, 550 ppmv) in combination with two levels of air temperature (ambient, +2.0°C). The five different climate treatments were: open field (OF), ambient chamber (AC), elevated temperature (eT), elevated CO₂ (eC) and elevation of both temperature and CO₂ (eCeT). At the time of sowing, vermicompost @ 2.0 tonnes ha^–1 was applied along with 30 kg N ha^–1 (in the form of urea), 60 kg P₂O₅ ha^–1 (through single super phosphate) and 40 kg K₂O ha^–1 (through muriate of potash) to the soybean crop. Impact of the climate variables was studied in terms of selected plant attributes, viz. plant height, leaf area, biomass, number of pods, number of grains per pod, grain yield and seed index (100 seed weight). Results indicated significant positive effect of elevated CO₂ and temperature on plant growth parameters, pod attributes and grain yield. Compared to AC, leaf area at 50 days after sowing was higher by 143%, 281% and 259% and above-ground biomass at harvest was higher by 47%, 31% and 47% under eC, eT and eCeT treatments respectively. The difference in biomass under OF and AC was not significant. The increase in grain yield over ambient varied from 30% under eT to 51% and 65% under eC and eCeT treatments respectively. The seed index as measured through weight of 100 numbers of seeds, was significantly higher under elevated CO₂ and/or elevated temperature treatments than the ambient chamber and open field treatments.