|Wall, Gerard - Gary|
|Pinter Jr, Paul|
|Hunsaker, Douglas - Doug|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2004
Publication Date: 2/1/2005
Citation: Adamsen, F.J., Wechsung, G., Wechsung, F., Wall, G.W., Kimball, B.A., Pinter Jr, P.J., Lamorte, R.L., Garcia, R.L., Hunsaker, D.J., Leavitt, S.W. Temporal changes in soil and biomass niotrogen for irrigated wheat grown under free-air carbon dioxide enrichment (face). Agronomy Journal. 97:160-168 Interpretive Summary: Carbon dioxide levels are projected to increase 43 percent by 2050. An international group of 11 scientists, including seven from the Agricultural Research Service's (ARS) U.S. Water Conservation Laboratory, Phoenix, Ariz., are trying to determine whether this rise will increase the amount of nitrogen'a nutrient important to many crops'needed to grow wheat and other crops. In the January-February 2005 issue of Agronomy Journal, ARS soil scientist Floyd J. Adamsen explains that they found that wheat grown under elevated levels of CO2 needed slightly more nitrogen to grow, but not as much as predicted. At Arizona's Maricopa Agricultural Center, the team compared wheat grown under normal conditions to those grown with levels of CO2 that may appear in 45 years. A series of tubes injected CO2 in rings surrounding the fields to elevate CO2. This project, which was conducted in 1992 and 1993, is part of the larger Free-Air Carbon Dioxide Enrichment (FACE) program. Carbon dioxide speeds up the rate of photosynthesis and makes the plant grow bigger. But a bigger plant thus needs more nutrients such as nitrogen'in theory. The nitrogen concentrations of crops grown with elevated CO2 were not significantly lower than those of the control group. The researchers applied fertilizer four times, which spread out the uptake of the nutrients. The group believes that in the future, farmers may need to do that to successfully grow wheat. The scientists believe growers need to understand how the rising levels of CO2 effect their crops and to possibly change their farming practices, such as changing the timing and amounts of nitrogen fertilizer. Provided associated changes in climate are not too detrimental, the increase in carbon dioxide with slightly more nitrogen will likely bring more bountiful yields for farmers in the future. ARS is the U.S. Department of Agriculture's chief scientific research agency.
Technical Abstract: Increasing atmospheric CO2 concentrations are expected to increase plant productions and demand for N and other nutrients. The objectives of this investigation were to characterize and quantify the temporal trends in soil mineral N and aboveground biomass N during the growing season of wheat (Triticum aestivum L.) with adequate N, ambient and elevated CO2 and two levels of water stress. The free-air CO2 enrichment (FACE) technique was used to enrich the air from 370 to 550 umol mol-1 CO2. Spring wheat was planted in late December of 1992 and 1993 and harvested at the end of May. Each main plot (CO2 level) was split into two irrigation treatments to replace 100 and 50% of the potential evapotranspiration. Soil and plant samples were taken for N analysis six times each year. Elevated CO2 lowered soil mineral N concentrations in the top 0.3m of soil as much as 40% and increased aboveground biomass N by as much as 16% compared with the ambient treatment. Before anthesis, irrigation level had little effect on either soil mineral N or aboveground biomass N, but at harvest in 1992-1993 and at dough stage in 1993-1994 deficit-irrigated plots had higher soil mineral N(p greater than 0.05) and lower aboveground biomass N than plots that received adequate irrigation. There was little variation in the concentrations of N in the aboveground biomass among treatments within a sampling date. The data suggest eleveated CO2 may lead to rapid N uptake, which could result in increased early vegetative growth.