Performance of commercial corn hybrids in Illinois, 1974- / 1108

DeKalb 7East North-Central Illinois: Elwood 10 above the ear were considered erect.Stand.In late June, plants in all plots on all fields were counted and the percent of stand was computed by comparing this number with the number of kernels planted.Plots with over 100-percent stand were thinned at this time.Stand differences may be caused by failure to germinate or by disease, insect injury, cultivation, or animal pest damage.Plants per acre.Plants per acre were calculated for each plot by using the percent stand obtained from plant counts.Differences in plants per acre and differ- ences in percent stand are caused by the same factors.Comparing hybrids.In any test of plant material, it is impossible to measure performance exactly.Samples may vary, soils may not be uniform, and many other conditions may produce variability.Results of repeated tests, like those reported in this circular, arc more reliable than those of a single year or a single strip test.In general, a yield difference of a few bushels per acre is not significant in these tests.When one hybrid consistently outyields another at several test locations and over several years of testing, the chances are good that this difference is real and should be a consideration in choosing a hybrid.But yield alone is not enough.Consider also the grain moisture content, per- centage of erect plants, percent stand, or plants per acre in comparing yields.As an aid in comparing hybrids, certain statistical tests have been devised.D. B. Duncan 1 has outlined an approach to the problem of multiple comparisons when only two means are compared among a set of hybrid means.Certain factors not accounted for in previous tests of this type are included in Fischer's L.S.D.This test is applied in the same manner as previous statistical tests used in these circulars.When two hybrids in a trial are compared, and the difference between them is 1 Duncan, D. B., "A Bayesian Approach to Multiple Com- parisons," Technometrics, 7:171-222, 1965.greater than the tabulated L.S.D. value, then the hy- brids are said to be "significantly different."Growing Conditions at 1974 Test Fields Extreme Northern Illinois: Woodstock.This test field represents the cool, humid area in northeastern Illinois.The test plot is on land operated by the Hughes Farms and Seed Company, Robert and Earl Hughes, Jr., cooperators.The soil is Proctor silt loam, a fertile, deep, well-drained, dark prairie soil.Very wet and cool weather in April and May slowed field work, and planting at this location was delayed until June.Some flooding in June decreased stands.A frost on September 14 hurt many varieties that had not matured.