As of Sept. 27, nearly 91 percent of Iowa’s corn rates are “safe from frost” according to the USDA- NASS report indicating the majority of the crop isphysiologically mature (R6). The crop’s development is five days ahead of normal, 68 percent mature, and dramatically outpaces the 43 percent mature recorded in 2009 for the same week. Drydown remains as the last major in-field growing season process after the grain reaches physiological maturity – ‘black layer.’ The grain, although still connected to the cob, is disconnected physiologically from the plant because of the abscission or black layer - no further exchange of either nutrients or water between the cob and the kernel occurs.
Iowa State University
Elmore, Roger and Abendroth, Lori, "In-Field Drydown Rates and Harvest" (2010). Integrated Crop Management News. 361.
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