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Fluid Journal : Fluid Journal 2008-2009
to the amount of water used by the plant, offering a concept to characterize field variation in yield. Studies have described how soil management practices have affected WUE. Large variations have appeared in seasonal water use rates across production fields, varying almost 200 mm (8 inches) between a Webster soil having 4 to 5 percent organic matter and a Clarion soil having 1 to 2 percent SOM (Figure 2). The differences in Figure 2 are typical of what we have seen in fields and there is a relationship between water availability and crop water use rates. The seasonal differences in crop water use are related to the carbon dioxide (CO2) uptake rates across fields. In a comparison of water use (evapotranspiration) and CO2 uptake there was a large difference among the six fields of corn and five fields of soybean that were studied throughout the growing season. These differences in water use and CO2 uptake translate into crop production and yield differences. We typically observed yield variations between the Clarion and Webster soils of 50 to 75 bu/A. The differences in total biomass production are less because the major differences in water use occur during the grain-filling period rather than during vegetative growth (Figure 2). Continual removal of biomass from the field and reduction in SOM will exaggerate these differences within and among fields. Implications Removal of biomass for energy production should be planned and managed to protect and enhance the soil resource. Management for efficient production of both grain and biomass from our grain and grass crops needs to be carefully considered relative to the soil resource and climatic conditions. Integrating all of these components will produce a system that avoids potentially negative consequences and increases our production capacity for grains and biomass into the future. Dr. Hatfield is laboratory director and plant physiologist at the USDA-ARS National Soil Tilth Laborator y in Ames, Iowa. JOIN AN ORGANIZATION THAT BENEFITS YOUR BUSINESS The Fluid Fertilizer Foundation For Membership Information and Orders Contact: Fluid Fertilizer Foundation 2805 Claflin Road, Suite 200 Manhattan, KS 66502 785-776 -0273 E-mail: firstname.lastname@example.org Research and Education for Efficient Use of Fluids WE NEED YOU....to join hundreds of other dealers, fertilizer manufacturers, suppliers, laboratories, researchers and growers who help support the Fluid Fertilizer Foundation’s programs in research and education on the efficient and profitable use of fluid fertilizers. The Foundation is a non-profit 501(c) 3 organiza- tion committed to the development of applied research information and dissemina- tion of that information to Foundation members and the public. WINTER 2008 Fluid Journal 11
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