Fertilizer N uptake of paddy rice in two soils with different fertility under experimental warming with elevated CO2

Background and aims

Only limited information is available in the research area on the effect of elevated CO₂ concentration ([CO₂]) and air temperature (T_air) on the fertilizer N uptake by rice. This study was conducted to investigate changes in rice uptake of N derived from fertilizer (NDFF) and soil (NDFS) as well as fertilizer N uptake efficiency (FUE) with elevated [CO₂] and T_air in two soils with different fertility.

Methods

Rice (Oryza sativa L.) plants were grown with ¹⁵N-urea for two growing seasons (2007 in the less fertile and 2008 in the more fertile soil) in temperature gradient chambers under two (ambient and elevated) levels of [CO₂] and T_air regimes. At harvest, dry matter (DM) and N uptake amount of rice compartments (root, shoot, and grain) were determined.

Results

The DM of whole rice increased (P?2] and T_air in both years (by 28.0 % in 2007 and by 27.4 % in 2008). The DM in 2008 was greater than that in 2007 by 48.1 to 63.1 % probably due to better soil fertility as well as longer sunshine hours (456 h vs. 568 h). Co-elevation of [CO₂] and T_air increased total N uptake, NDFF, and NDFS by 19.4 to 29.1 % in general compared to the ambient conditions. The FUE increased with co-elevation of [CO₂] and T_air from 46.5 to 59.5 % in 2007 and from 36.7 to 43.8 % in 2008.

Conclusions

The projected global warming with elevated [CO₂] is expected to increase FUE via enhanced DM accumulation with less increments in the soils that have higher indigenous soil N availabilities.