Drying Rates of Frosted Maturing Maize1

Freezing air temperatures sometimes occur in early autumn before maize (Zea mays L.) grain is physiologically mature. A study was conducted to determine maize grain, cob, and ear moisture profiles following certain treatments to simulate plant conditions which exist after a subfreezing temperature occurrence. Ears with husks and shanks attached were removed from plants and placed in a controlled temperature chamber for 0, 4, or 8 hours at −7 C. Three husk treatmeats-loosened, normal, or tied-were imposed on ears subjected to the three cold treatments. Treated ears weie taped onto plants in the normal ear position for field drying. Ears from these nine treatments and also ears from completely defoliated and control plants were sampled weekly from 19 Sept. to 23 Oct. 1974, to estimate drying rates of grain, cobs, and ears. Grain drying rates ranged from 0.83 to 1.16% moisture less⁄day. Drying rates of grain following leaf blade defoliation or moderate to severe cold treatments were not statistically different from the drying rate of normally maturing maize grain. Husk condition did not statisticslly affect grain drying rates, Defoliation and cold treatments caused grain moisture levels to be 2 to 6 percentage points greater than that of grain from control plants when grain from control plants was in the 22 to 30% harvest range. Grain from these treatments required 4 to 9 additional days of field drying to reach the 22 to 30% moisture range. Defoliation and cold treatments had little effect on the drying rates of cobs and ears. However both cob and ear moisture levels were greater than those of the control throughout the sampling period. Loose husks caused faster cob and ear drying compared to normal or tied husks which had similar cob and ear drying rates.