Growth, Yield and Grain Mineral Nutrient Responses of Rice to Elevated Atmospheric CO₂ Concentration and Nitrogen Fertilization

Abstract

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.