| Abstract: | Rising carbon dioxide (CO2) concentration causes fertilization effects resulting in enhanced crop biomass and yields and thus likely enhances nutrient demand of plants. Hence, this field study was carried out to investigate the effects of elevated CO2 and N on biomass yield, nutrient partitioning, and uptake of major nutrients by soybean (Glycine max L.) using open‐top chambers (OTCs) of 4 m × 4 m size. Soybean was grown in OTCs under two CO2 ambient and elevated (535 ± 36.9 mg L?1)] and four N levels during July to October 2016. The four N levels were N0, N50, N100, and N150 referring to 0, 50, 100, and 150% recommended dose of N. Both CO2 and N significantly affected biomass and grain yield, though the interaction was non‐significant. CO2 enrichment produced 30–65% higher biomass and 26–59% higher grain yield under various N levels. As compared to the optimum N application (N100), the CO2‐mediated increment in biomass yield decreased with either lower or higher N application, with the response being lowest at N150. As compared to ambient concentration, elevated CO2 resulted in significant reduction of seed P concentration at all N application levels but at N150, an opposite trend was observed. The decrease in seed P was maximum at N0 and N50 (7–9%) and by 3% at N100, whereas there was a gain of 7.5% at N150. The seed N and K concentrations were not affected either by CO2 or N application. Total N, P, and K uptake at harvest were significantly affected by CO2 and N, but not by CO2 × N interaction. Elevated CO2 resulted higher uptake of N by 18–61%, P by 23–62%, and K by 22–62% under various N treatments. |
