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Pedosphere 12(3): 207--218, 2002
ISSN 1002-0160/CN 32-1315/P
©2002 Soil Science Society of China
Published by Elsevier B.V. and Science Press

Effects of atmospheric CO₂ enrichment, applied nitrogen and soil moisture on dry matter accumulation and nitrogen uptake in spring wheat

LI Fu-Sheng¹ and KANG Shao-Zhong²

¹ Agricultural College, Guangxi University, Nanning 530005 (China);
² Key Laboratory of Agricultural Soil & Water Engineering in the Arid and Semiarid Areas, Ministry of Education, Northwest Sci-Tec University of Agriculture and Forestry, Shaanxi 712100 (China)

ABSTRACT

Spring wheat (Triticum aestivum L. cv. Dingxi No. 8654) was treated with two concentrations of atmospheric CO₂ (350 and 700 μmol mol^-1), two levels of soil moisture (well-watered and drought) and five rates of nitrogen fertilizer (0, 50, 100, 150, and 200 mg kg^-1 soil) to study the atmospheric CO₂ concentration effect on dry matter accumulation and N uptake of spring wheat. The effects of CO₂ enrichment on the shoot and total mass depended largely on soil nitrogen level, and the shoot and total mass increased significantly in the moderate to high N treatments but did not increase significantly in the low N treatment. Enriched CO₂ concentration did not increase more shoot and total mass in the drought treatment than in the well-watered treatment. Thus, elevated CO₂ did not ameliorate the depressive effects of drought and nitrogen stress. In addition, root mass decreased slightly and root/shoot ratio decreased significantly due to CO₂ enrichment in no N treatment under well-watered condition. Enriched CO₂ decreased shoot N content and shoot and total N uptake; but it reduced root N content and uptake slightly. Shoot critical N concentration was lower for spring wheat grown at 700 μmol mol^-1 CO₂ than at 350 μmol mol^-1 CO₂ in both well-watered and drought treatments. The critical N concentrations were 16 and 19 g kg^-1 for the well-watered treatment and drought treatment at elevated CO₂ and 21 and 26 g kg^-1 at ambient CO₂, respectively. The reductions in the movement of nutrients to the plant roots through mass flow due to the enhancement in WUE (water use efficiency) and the increase in N use efficiency at elevated CO₂ could elucidate the reduction of shoot and root N concentrations.

Key Words: CO₂ enrichment, critical N concentration, dry matter, nitrogen uptake, soil moisture

Citation: Li, F. S. and Kang, S. Z. 2002. Effects of atmospheric CO₂ enrichment, applied nitrogen and soil moisture on dry matter accumulation and nitrogen uptake in spring wheat. Pedosphere. 12(3): 207-218.

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