Growth, Yield and Grain Mineral Nutrient Responses of Rice to Elevated Atmospheric CO_2 Concentration and Nitrogen Fertilization

The effects of combining atmospheric CO2 concentrations (360 vs. 700 μL L−1) and N fertilizer on the growth, yield and grain nutrients of a semi-dwarf, japonica rice (Oryza sativa L.) were examined by the use of artificially illuminated growth chambers. Throughout the growth period, elevated CO2 + high N promoted dry-matter production, and under elevated CO2, the optimum N level was even higher. Flowering occurred earlier under elevated CO2, but was delayed by higher N levels. The position of the flag leaf fell by one “slot” and the lengths of the culm and panicle decreased due to the elevated CO2. Elevated CO2 + high N enlarged the yield capacity in terms of the numbers of panicles and grains but higher yield did not necessarily occur, because of the decreased percentage of productive tillers. The effects of CO2 on the mineral content were complex, but under elevated CO2 + high N, two parameters (K + Mg, Mg/K) which indicate good rice quality were ameliorated.