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Fluid Journal : Fluid Journal 1996-1998
2 Fluid Journal Spring 1998 looking at a corn field that would yield 377 bu/A! Warsaw's 10-year average was 275 hulA! Plants in narrow rows numbered 35,000 to 38,000. Leaves and residue littered the field. The soil was spongy because Warsaw meticulously built a deep fertile soil with a perfect balance of nutrients. After harvest, residue (almost 10 tons of stover) would be incorporated into the soil along with fertilizer to decompose organic matter. Warsaw's water-use efficiency (WUE) was over 11 bushels per inch of rain! What does all this have to do with global warming? Plenty. Corn absorbs large quantities of CO2, (believed to cause global warming) in its life span of approximately 100 days. In 1992, 9.2 billion bushels absorbed 815 million metric tons of CO2, (Figure 1)! Through the process of photosynthesis, sunlight energy plus chlorophyll from the green leaf transform CO2, into carbohydrates (Table 1). In this reaction, CO2, is absorbed from the air and converted to stover, grain, and roots. In 1992, CO2 was "fixed" or changed into 493 million metric tons of stover, shell corn and roots! Stover and grain, rich in carbohydrates and protein, are harvested to feed animals and humans. Let's see, more specifically, what this CO2 absorption has to do with global warming. Its many forms It is believed by many that burning fossil fuels (petroleum, gas, coal, trees, etc.), is producing CO2 that causes global warming. At the beginning of this century, atmosphere contained 290 parts per million (ppm) of CO2. Now it contains 360 ppm, with the reasonable estimate it will go to 600 ppm. Some of this increase, but not all, is due to Table 3. Total global emissions of carbon (as CO2). Natural emissions: (Volcanoes, vegetative decay, respiration of animals, humans, released from oceans, etc.) 550,000 mmt CO2 Human activities (Fossil fuels, etc.)* 26,069 mmt CO2 Total global CO2 emissions 576,069 mmt CO2 U.S. share of human activities: U.S. petroleum 2,279 mmt CO2 U.S. coal 1,923 mmt CO2 U.S. gas 1,167 mmt CO2 Agricultural share of emissions: Energy 92 mmt CO2 Fertilizer 40 mmt CO2 Chemical 40 mmt CO2 U.S. agricultural total 172 mmt CO2 U.S agricultural share 3.2% of U.S. *4.5% of total global emissions Figure 4. Estimated carbon (stated mmt of CO2) fixed by U.S. grain crop in 1996 and available for seqestering into organic matter. Crop Millions of metric tons of CO2 % of U.S. cropland Grain Stover Roots Total (approximate) Corn 326 326 163 815 22 Wheat 91 136 NE* 226 23 Soybeans 89 134 NE* 223 21 Sorghum 32 32 16 80 4 Other crops 332 NE* NE* 332 30** *Not estimated ** 19 other crops including hay, dry beans, potatoes, rice, sugarcane, beets, cotton, vegetables, and fruits. Figure 2. Growth in CO2 assimilated by U.S. corn between 1960 and 1995 in million metric tons.
Fluid Journal 1993-1995
Fluid Journal 1999-2001