Wednesday, 22 June 2005: 3:15 PM
North & Center Ballroom (Hilton DeSoto)
Patrick Guinan, Univ. of Missouri, Columbia, MO; and W. L. Decker and A. R. Lupo

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The objective of this research was to develop an index to project the likelihood of agricultural drought during the growing season in northwestern Missouri. The study examined historical seasonal and biweekly precipitation records and annual crop yield data for USDA crop reporting district one (CRD 1) in northwestern Missouri. Weekly precipitation data were collected for the period 1919-2002, and crop yield data for corn and soybeans were gathered between 1920-2003 and 1944-2003, respectively. Detrending methods using 1990's crop technology were applied to the corn and soybean yield data in order to eliminate yield bias. Seasonal precipitation periods for fall, winter, and spring and biweekly periods during the summer were analyzed each year and compared to the corn and soybean yields of that year. Frequency distributions of the precipitation periods were developed with a gamma distribution fit to them. Five probability classes were designated for the precipitation periods and compared to the crop yields. A combined weighting factor for two precipitation classes were calculated for each precipitation period according to an economic threshold yield for corn (°Ü100 bu/ac) and soybean (°Ü31 bu/ac) and was used to develop an agricultural drought projection index, or ADPI. Additionally, forecast products, such as the 30 and 90 day outlook from the Climate Prediction Center, were incorporated into the ADPI during these precipitation periods.
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