Seasonal changes in the effects of free-air CO₂ enrichment (FACE) on nitrogen (N) uptake and utilization of rice at three levels of N fertilization

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• 作者：Lianxin Yang ; Jianye Huang ; Hongjie Yang ; Guichun Dong ; Hongjiang Liu ; Gang Liu ; Jianguo Zhu ; Yulong Wang
• 关键词：Free-air CO₂ enrichment (FACE) ; Nitrogen concentration ; Nitrogen uptake ; Nitrogen allocation ; Nitrogen efficiency ; Rice
• 刊名：Field Crops Research
• 出版年：2007
• 期刊代码：44_03784290
• 类别：abs
• 出版时间：1 February 2007
• 卷：100
• 期：2-3
• 页码：189-199
• 文件大小：940 K

摘要

Over time, the relative effect of elevated [CO₂] on the photosynthesis and dry matter (DM) production of rice crops is likely to be changed with increasing duration of CO₂ exposure, but the resultant [CO₂] effects on rice N concentration, uptake, efficiency and allocation remain unclear, especially under different soil N availability. Therefore, we conducted a free-air CO₂ enrichment (FACE) experiment at Wuxi, Jiangsu, China, in 2001–2003. A japonica cultivar with large panicle was grown at ambient or elevated (ca. 200 μmol mol⁻¹ above ambient) [CO₂] under three levels of N: low (LN, 15 g N m²), medium (MN, 25 g N m²) and high N (HN, 35 g N m² (2002, 2003)). The MN level was similar to that recommended to local farmers. Averaged across all N levels and years, shoot N concentration (dry base) was lower under FACE by 1.8%, 6.1%, 12.2%, 14.3%, 12.1%, and 6.9%at early-tillering, mid-tillering, panicle initiation (PI), booting, heading and grain maturity, respectively. Shoot N uptake under FACE was enhanced by 46%, 38%, 6%and 16%on average during the growth periods from transplanting to early-tillering (period 1), early-tillering to mid-tillering (period 2), mid-tillering to PI (period 3) and heading to grain maturity (period 5), respectively, but slightly decreased by 2%in the period from PI to heading (period 4). Seasonal changes in crop response to FACE in ratio of shoot N uptake during a given growth period to that over the whole season followed a similar pattern to that of shoot N uptake, with average responses of 33%, 26%, −3%, −11%and 10%in periods 1–5 of the growth period, respectively. As a result, FACE increased final aboveground N uptake by 9%at maturity. FACE greatly reduced the ratio of leaf to shoot N content over the season, while allocation of N to stems and spikes showed an opposite trend. FACE treatment resulted in the significant increase in N use efficiency for biomass (NUEp) over the season except at early-tillering and in N use efficiency for grain yield (NUEg) at grain maturity. These results indicate that, in order to maximize grain output in a future high [CO₂] environment, the recommended rates, proportion and timing across the season of N application should be altered, in order to take full advantage of strong N uptake capacity during the early growth period and facilitate N uptake after that.