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Effects of Elevated CO2, Drought and Soil Nitrogen on Wheat Grain Quality
Reference
Kimball, B.A., Morris, C.F., Pinter Jr., P.J., Wall, G.W., Hunsaker, D.J., Adamsen, F.J., LaMorte, R.L., Leavitt, S.W., Thompson, T.L., Matthias, A.D. and Brooks, T.J.  2001.  Elevated CO2, drought and soil nitrogen effects on wheat grain quality.  New Phytologist 150: 295-303.

What was done
The authors grew spring wheat (Triticum aestivum) in FACE arrays maintained at atmospheric CO2 concentrations of 350 and 550 ppm for several years while utilizing both low and high soil nitrogen and water treatments to study the interactive effects of these parameters on wheat growth, yield and quality.  In this paper, they describe how these three variables (CO2, soil nitrogen and soil water) impacted wheat grain and flour quality.

What was learned
Overall, the authors observed 2 and 3% increases in grain protein content and bread loaf volume under low soil water conditions.  Under low soil nitrogen (N) conditions, on the other hand, these important grain and bread characteristics were reduced by 36 and 26%, respectively.

With ample soil water, atmospheric CO2 enrichment exacerbated the deleterious effects of low soil nitrogen, leading to 39 and 29% decreases in grain protein content and bread loaf volume, respectively.  However, the authors report that "grain and flour protein concentrations and the bread loaf volume were unaffected by elevated CO2 at High-N (with ample water)."  Consequently, as the authors note, "a 16% increase in grain yield with respect to Control [as reported by Pinter et al. (1997)] also resulted in a 16% increase in protein-N yield."

What it means
Low soil nitrogen contents are definitely detrimental to wheat grain and flour protein concentrations; and under such conditions, atmospheric CO2 enrichment could even make the situation a little worse.  When the soil is adequately fertilized with nitrogen, however, atmospheric CO2 enrichment appears to have no negative effect upon either grain quality or flour quality.  This latter observation is extremely important, for it indicates that greater quantities of equally nutritious wheat may be readily produced in a high-CO2 world of the future, as long as soils are adequately fertilized with nitrogen.

Reference
Pinter Jr., P.J., Kimball, B.A., Wall, G.W., LaMorte, R.L., Adamsen, F. and Hunsaker, D.J.  1997.  Effects of Elevated CO2 and Soil Nitrogen Fertilizer on Final Grain Yields of Spring Wheat.  Annual Research Report: Phoenix, USA. U.S. Water Conservation Laboratory, Agricultural Research Service, U.S. Department of Agriculture, pp. 71-74.


Reviewed 11 December 2002