Harvest Methods for Estimated Ethanol Yields from Relative Fermentable Carbohydrate Accumulation in Maize Hybrids 1

Abstract Recurring energy shortages suggest the need for evaluation of alternate fuel energy sources. Conversion of plant carbohydrate to ethanol, as a fuel source, is considered a viable option with efficient energy‐producing crops such as maize, Zea mays L. Three maize hybrids (‘Coker 77’, ‘Pioneer 3369A’, and ‘Sokota Sugar Chop’) were grown in a Norfolk loamy sand (fine‐loamy, silicious Typic Paleudult) from 1981 to 1983 to evaluate four procedures for harvesting. The objective was to identify procedure(s) that maximize carbohydrate production potential, measured as estimated fermentable carbohydrate converted to ethanol. Ethanol yield estimates, calculated from grain or stalk sugars, or both, to make possible direct comparisons of harvest treatments, were analyzed as a split‐plot design with 10 replicates. Whole plots were hybrids, and subplots were harvest treatments. The treatments consisted of (i) covered ear shoots (EC); (ii) removed ear shoots (ER); (iii) grain and stalks harvested simultaneously (P‐SimH); and (iv) stalks harvested separately, 1 to 2 weeks after grain harvest (P‐ SepH). Coker 77 produced the least grain but significantly greater estimated ethanol yields than did the other hybrids in 2 of 3 yr because of greater stalk sugar yields. The P‐SepH and P‐SimH treatments of this hybrid produced less than twice as much estimated ethanol per plant, and other hybrids produced about three times as much as the EC and ER treatments of Coker 77. Differences between the P‐SimH and P‐SepH treatments were nonsignificant, and simultaneous harvest of grain and stalk sugar at physiological maturity proved an efficient procedure to produce high estimated ethanol yields.